| /* |
| * INET An implementation of the TCP/IP protocol suite for the LINUX |
| * operating system. INET is implemented using the BSD Socket |
| * interface as the means of communication with the user level. |
| * |
| * Implementation of the Transmission Control Protocol(TCP). |
| * |
| * Authors: Ross Biro |
| * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> |
| * Mark Evans, <evansmp@uhura.aston.ac.uk> |
| * Corey Minyard <wf-rch!minyard@relay.EU.net> |
| * Florian La Roche, <flla@stud.uni-sb.de> |
| * Charles Hedrick, <hedrick@klinzhai.rutgers.edu> |
| * Linus Torvalds, <torvalds@cs.helsinki.fi> |
| * Alan Cox, <gw4pts@gw4pts.ampr.org> |
| * Matthew Dillon, <dillon@apollo.west.oic.com> |
| * Arnt Gulbrandsen, <agulbra@nvg.unit.no> |
| * Jorge Cwik, <jorge@laser.satlink.net> |
| */ |
| |
| /* |
| * Changes: |
| * Pedro Roque : Fast Retransmit/Recovery. |
| * Two receive queues. |
| * Retransmit queue handled by TCP. |
| * Better retransmit timer handling. |
| * New congestion avoidance. |
| * Header prediction. |
| * Variable renaming. |
| * |
| * Eric : Fast Retransmit. |
| * Randy Scott : MSS option defines. |
| * Eric Schenk : Fixes to slow start algorithm. |
| * Eric Schenk : Yet another double ACK bug. |
| * Eric Schenk : Delayed ACK bug fixes. |
| * Eric Schenk : Floyd style fast retrans war avoidance. |
| * David S. Miller : Don't allow zero congestion window. |
| * Eric Schenk : Fix retransmitter so that it sends |
| * next packet on ack of previous packet. |
| * Andi Kleen : Moved open_request checking here |
| * and process RSTs for open_requests. |
| * Andi Kleen : Better prune_queue, and other fixes. |
| * Andrey Savochkin: Fix RTT measurements in the presence of |
| * timestamps. |
| * Andrey Savochkin: Check sequence numbers correctly when |
| * removing SACKs due to in sequence incoming |
| * data segments. |
| * Andi Kleen: Make sure we never ack data there is not |
| * enough room for. Also make this condition |
| * a fatal error if it might still happen. |
| * Andi Kleen: Add tcp_measure_rcv_mss to make |
| * connections with MSS<min(MTU,ann. MSS) |
| * work without delayed acks. |
| * Andi Kleen: Process packets with PSH set in the |
| * fast path. |
| * J Hadi Salim: ECN support |
| * Andrei Gurtov, |
| * Pasi Sarolahti, |
| * Panu Kuhlberg: Experimental audit of TCP (re)transmission |
| * engine. Lots of bugs are found. |
| * Pasi Sarolahti: F-RTO for dealing with spurious RTOs |
| */ |
| |
| #define pr_fmt(fmt) "TCP: " fmt |
| |
| #include <linux/mm.h> |
| #include <linux/slab.h> |
| #include <linux/module.h> |
| #include <linux/sysctl.h> |
| #include <linux/kernel.h> |
| #include <net/dst.h> |
| #include <net/tcp.h> |
| #include <net/inet_common.h> |
| #include <linux/ipsec.h> |
| #include <asm/unaligned.h> |
| #include <net/netdma.h> |
| |
| int sysctl_tcp_timestamps __read_mostly = 1; |
| int sysctl_tcp_window_scaling __read_mostly = 1; |
| int sysctl_tcp_sack __read_mostly = 1; |
| int sysctl_tcp_fack __read_mostly = 1; |
| int sysctl_tcp_reordering __read_mostly = TCP_FASTRETRANS_THRESH; |
| EXPORT_SYMBOL(sysctl_tcp_reordering); |
| int sysctl_tcp_dsack __read_mostly = 1; |
| int sysctl_tcp_app_win __read_mostly = 31; |
| int sysctl_tcp_adv_win_scale __read_mostly = 1; |
| EXPORT_SYMBOL(sysctl_tcp_adv_win_scale); |
| |
| /* rfc5961 challenge ack rate limiting */ |
| int sysctl_tcp_challenge_ack_limit = 100; |
| |
| int sysctl_tcp_stdurg __read_mostly; |
| int sysctl_tcp_rfc1337 __read_mostly; |
| int sysctl_tcp_max_orphans __read_mostly = NR_FILE; |
| int sysctl_tcp_frto __read_mostly = 2; |
| |
| int sysctl_tcp_thin_dupack __read_mostly; |
| |
| int sysctl_tcp_moderate_rcvbuf __read_mostly = 1; |
| int sysctl_tcp_early_retrans __read_mostly = 3; |
| int sysctl_tcp_default_init_rwnd __read_mostly = TCP_DEFAULT_INIT_RCVWND; |
| |
| #define FLAG_DATA 0x01 /* Incoming frame contained data. */ |
| #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */ |
| #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */ |
| #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */ |
| #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */ |
| #define FLAG_DATA_SACKED 0x20 /* New SACK. */ |
| #define FLAG_ECE 0x40 /* ECE in this ACK */ |
| #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/ |
| #define FLAG_ORIG_SACK_ACKED 0x200 /* Never retransmitted data are (s)acked */ |
| #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */ |
| #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */ |
| #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */ |
| #define FLAG_UPDATE_TS_RECENT 0x4000 /* tcp_replace_ts_recent() */ |
| |
| #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED) |
| #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED) |
| #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE) |
| #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED) |
| |
| #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH) |
| #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH)) |
| |
| /* Adapt the MSS value used to make delayed ack decision to the |
| * real world. |
| */ |
| static void tcp_measure_rcv_mss(struct sock *sk, const struct sk_buff *skb) |
| { |
| struct inet_connection_sock *icsk = inet_csk(sk); |
| const unsigned int lss = icsk->icsk_ack.last_seg_size; |
| unsigned int len; |
| |
| icsk->icsk_ack.last_seg_size = 0; |
| |
| /* skb->len may jitter because of SACKs, even if peer |
| * sends good full-sized frames. |
| */ |
| len = skb_shinfo(skb)->gso_size ? : skb->len; |
| if (len >= icsk->icsk_ack.rcv_mss) { |
| icsk->icsk_ack.rcv_mss = len; |
| } else { |
| /* Otherwise, we make more careful check taking into account, |
| * that SACKs block is variable. |
| * |
| * "len" is invariant segment length, including TCP header. |
| */ |
| len += skb->data - skb_transport_header(skb); |
| if (len >= TCP_MSS_DEFAULT + sizeof(struct tcphdr) || |
| /* If PSH is not set, packet should be |
| * full sized, provided peer TCP is not badly broken. |
| * This observation (if it is correct 8)) allows |
| * to handle super-low mtu links fairly. |
| */ |
| (len >= TCP_MIN_MSS + sizeof(struct tcphdr) && |
| !(tcp_flag_word(tcp_hdr(skb)) & TCP_REMNANT))) { |
| /* Subtract also invariant (if peer is RFC compliant), |
| * tcp header plus fixed timestamp option length. |
| * Resulting "len" is MSS free of SACK jitter. |
| */ |
| len -= tcp_sk(sk)->tcp_header_len; |
| icsk->icsk_ack.last_seg_size = len; |
| if (len == lss) { |
| icsk->icsk_ack.rcv_mss = len; |
| return; |
| } |
| } |
| if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED) |
| icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2; |
| icsk->icsk_ack.pending |= ICSK_ACK_PUSHED; |
| } |
| } |
| |
| static void tcp_incr_quickack(struct sock *sk) |
| { |
| struct inet_connection_sock *icsk = inet_csk(sk); |
| unsigned int quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss); |
| |
| if (quickacks == 0) |
| quickacks = 2; |
| if (quickacks > icsk->icsk_ack.quick) |
| icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS); |
| } |
| |
| static void tcp_enter_quickack_mode(struct sock *sk) |
| { |
| struct inet_connection_sock *icsk = inet_csk(sk); |
| tcp_incr_quickack(sk); |
| icsk->icsk_ack.pingpong = 0; |
| icsk->icsk_ack.ato = TCP_ATO_MIN; |
| } |
| |
| /* Send ACKs quickly, if "quick" count is not exhausted |
| * and the session is not interactive. |
| */ |
| |
| static inline bool tcp_in_quickack_mode(const struct sock *sk) |
| { |
| const struct inet_connection_sock *icsk = inet_csk(sk); |
| |
| return icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong; |
| } |
| |
| static inline void TCP_ECN_queue_cwr(struct tcp_sock *tp) |
| { |
| if (tp->ecn_flags & TCP_ECN_OK) |
| tp->ecn_flags |= TCP_ECN_QUEUE_CWR; |
| } |
| |
| static inline void TCP_ECN_accept_cwr(struct tcp_sock *tp, const struct sk_buff *skb) |
| { |
| if (tcp_hdr(skb)->cwr) |
| tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; |
| } |
| |
| static inline void TCP_ECN_withdraw_cwr(struct tcp_sock *tp) |
| { |
| tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; |
| } |
| |
| static inline void TCP_ECN_check_ce(struct tcp_sock *tp, const struct sk_buff *skb) |
| { |
| if (!(tp->ecn_flags & TCP_ECN_OK)) |
| return; |
| |
| switch (TCP_SKB_CB(skb)->ip_dsfield & INET_ECN_MASK) { |
| case INET_ECN_NOT_ECT: |
| /* Funny extension: if ECT is not set on a segment, |
| * and we already seen ECT on a previous segment, |
| * it is probably a retransmit. |
| */ |
| if (tp->ecn_flags & TCP_ECN_SEEN) |
| tcp_enter_quickack_mode((struct sock *)tp); |
| break; |
| case INET_ECN_CE: |
| if (!(tp->ecn_flags & TCP_ECN_DEMAND_CWR)) { |
| /* Better not delay acks, sender can have a very low cwnd */ |
| tcp_enter_quickack_mode((struct sock *)tp); |
| tp->ecn_flags |= TCP_ECN_DEMAND_CWR; |
| } |
| /* fallinto */ |
| default: |
| tp->ecn_flags |= TCP_ECN_SEEN; |
| } |
| } |
| |
| static inline void TCP_ECN_rcv_synack(struct tcp_sock *tp, const struct tcphdr *th) |
| { |
| if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || th->cwr)) |
| tp->ecn_flags &= ~TCP_ECN_OK; |
| } |
| |
| static inline void TCP_ECN_rcv_syn(struct tcp_sock *tp, const struct tcphdr *th) |
| { |
| if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || !th->cwr)) |
| tp->ecn_flags &= ~TCP_ECN_OK; |
| } |
| |
| static bool TCP_ECN_rcv_ecn_echo(const struct tcp_sock *tp, const struct tcphdr *th) |
| { |
| if (th->ece && !th->syn && (tp->ecn_flags & TCP_ECN_OK)) |
| return true; |
| return false; |
| } |
| |
| /* Buffer size and advertised window tuning. |
| * |
| * 1. Tuning sk->sk_sndbuf, when connection enters established state. |
| */ |
| |
| static void tcp_fixup_sndbuf(struct sock *sk) |
| { |
| int sndmem = SKB_TRUESIZE(tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER); |
| |
| sndmem *= TCP_INIT_CWND; |
| if (sk->sk_sndbuf < sndmem) |
| sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]); |
| } |
| |
| /* 2. Tuning advertised window (window_clamp, rcv_ssthresh) |
| * |
| * All tcp_full_space() is split to two parts: "network" buffer, allocated |
| * forward and advertised in receiver window (tp->rcv_wnd) and |
| * "application buffer", required to isolate scheduling/application |
| * latencies from network. |
| * window_clamp is maximal advertised window. It can be less than |
| * tcp_full_space(), in this case tcp_full_space() - window_clamp |
| * is reserved for "application" buffer. The less window_clamp is |
| * the smoother our behaviour from viewpoint of network, but the lower |
| * throughput and the higher sensitivity of the connection to losses. 8) |
| * |
| * rcv_ssthresh is more strict window_clamp used at "slow start" |
| * phase to predict further behaviour of this connection. |
| * It is used for two goals: |
| * - to enforce header prediction at sender, even when application |
| * requires some significant "application buffer". It is check #1. |
| * - to prevent pruning of receive queue because of misprediction |
| * of receiver window. Check #2. |
| * |
| * The scheme does not work when sender sends good segments opening |
| * window and then starts to feed us spaghetti. But it should work |
| * in common situations. Otherwise, we have to rely on queue collapsing. |
| */ |
| |
| /* Slow part of check#2. */ |
| static int __tcp_grow_window(const struct sock *sk, const struct sk_buff *skb) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| /* Optimize this! */ |
| int truesize = tcp_win_from_space(skb->truesize) >> 1; |
| int window = tcp_win_from_space(sysctl_tcp_rmem[2]) >> 1; |
| |
| while (tp->rcv_ssthresh <= window) { |
| if (truesize <= skb->len) |
| return 2 * inet_csk(sk)->icsk_ack.rcv_mss; |
| |
| truesize >>= 1; |
| window >>= 1; |
| } |
| return 0; |
| } |
| |
| static void tcp_grow_window(struct sock *sk, const struct sk_buff *skb) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| |
| /* Check #1 */ |
| if (tp->rcv_ssthresh < tp->window_clamp && |
| (int)tp->rcv_ssthresh < tcp_space(sk) && |
| !sk_under_memory_pressure(sk)) { |
| int incr; |
| |
| /* Check #2. Increase window, if skb with such overhead |
| * will fit to rcvbuf in future. |
| */ |
| if (tcp_win_from_space(skb->truesize) <= skb->len) |
| incr = 2 * tp->advmss; |
| else |
| incr = __tcp_grow_window(sk, skb); |
| |
| if (incr) { |
| incr = max_t(int, incr, 2 * skb->len); |
| tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, |
| tp->window_clamp); |
| inet_csk(sk)->icsk_ack.quick |= 1; |
| } |
| } |
| } |
| |
| /* 3. Tuning rcvbuf, when connection enters established state. */ |
| |
| static void tcp_fixup_rcvbuf(struct sock *sk) |
| { |
| u32 mss = tcp_sk(sk)->advmss; |
| u32 icwnd = sysctl_tcp_default_init_rwnd; |
| int rcvmem; |
| |
| /* Limit to 10 segments if mss <= 1460, |
| * or 14600/mss segments, with a minimum of two segments. |
| */ |
| if (mss > 1460) |
| icwnd = max_t(u32, (1460 * icwnd) / mss, 2); |
| |
| rcvmem = SKB_TRUESIZE(mss + MAX_TCP_HEADER); |
| while (tcp_win_from_space(rcvmem) < mss) |
| rcvmem += 128; |
| |
| rcvmem *= icwnd; |
| |
| if (sk->sk_rcvbuf < rcvmem) |
| sk->sk_rcvbuf = min(rcvmem, sysctl_tcp_rmem[2]); |
| } |
| |
| /* 4. Try to fixup all. It is made immediately after connection enters |
| * established state. |
| */ |
| void tcp_init_buffer_space(struct sock *sk) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| int maxwin; |
| |
| if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) |
| tcp_fixup_rcvbuf(sk); |
| if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK)) |
| tcp_fixup_sndbuf(sk); |
| |
| tp->rcvq_space.space = tp->rcv_wnd; |
| |
| maxwin = tcp_full_space(sk); |
| |
| if (tp->window_clamp >= maxwin) { |
| tp->window_clamp = maxwin; |
| |
| if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss) |
| tp->window_clamp = max(maxwin - |
| (maxwin >> sysctl_tcp_app_win), |
| 4 * tp->advmss); |
| } |
| |
| /* Force reservation of one segment. */ |
| if (sysctl_tcp_app_win && |
| tp->window_clamp > 2 * tp->advmss && |
| tp->window_clamp + tp->advmss > maxwin) |
| tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss); |
| |
| tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp); |
| tp->snd_cwnd_stamp = tcp_time_stamp; |
| } |
| |
| /* 5. Recalculate window clamp after socket hit its memory bounds. */ |
| static void tcp_clamp_window(struct sock *sk) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| struct inet_connection_sock *icsk = inet_csk(sk); |
| |
| icsk->icsk_ack.quick = 0; |
| |
| if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] && |
| !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) && |
| !sk_under_memory_pressure(sk) && |
| sk_memory_allocated(sk) < sk_prot_mem_limits(sk, 0)) { |
| sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc), |
| sysctl_tcp_rmem[2]); |
| } |
| if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf) |
| tp->rcv_ssthresh = min(tp->window_clamp, 2U * tp->advmss); |
| } |
| |
| /* Initialize RCV_MSS value. |
| * RCV_MSS is an our guess about MSS used by the peer. |
| * We haven't any direct information about the MSS. |
| * It's better to underestimate the RCV_MSS rather than overestimate. |
| * Overestimations make us ACKing less frequently than needed. |
| * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss(). |
| */ |
| void tcp_initialize_rcv_mss(struct sock *sk) |
| { |
| const struct tcp_sock *tp = tcp_sk(sk); |
| unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache); |
| |
| hint = min(hint, tp->rcv_wnd / 2); |
| hint = min(hint, TCP_MSS_DEFAULT); |
| hint = max(hint, TCP_MIN_MSS); |
| |
| inet_csk(sk)->icsk_ack.rcv_mss = hint; |
| } |
| EXPORT_SYMBOL(tcp_initialize_rcv_mss); |
| |
| /* Receiver "autotuning" code. |
| * |
| * The algorithm for RTT estimation w/o timestamps is based on |
| * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL. |
| * <http://public.lanl.gov/radiant/pubs.html#DRS> |
| * |
| * More detail on this code can be found at |
| * <http://staff.psc.edu/jheffner/>, |
| * though this reference is out of date. A new paper |
| * is pending. |
| */ |
| static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep) |
| { |
| u32 new_sample = tp->rcv_rtt_est.rtt; |
| long m = sample; |
| |
| if (m == 0) |
| m = 1; |
| |
| if (new_sample != 0) { |
| /* If we sample in larger samples in the non-timestamp |
| * case, we could grossly overestimate the RTT especially |
| * with chatty applications or bulk transfer apps which |
| * are stalled on filesystem I/O. |
| * |
| * Also, since we are only going for a minimum in the |
| * non-timestamp case, we do not smooth things out |
| * else with timestamps disabled convergence takes too |
| * long. |
| */ |
| if (!win_dep) { |
| m -= (new_sample >> 3); |
| new_sample += m; |
| } else { |
| m <<= 3; |
| if (m < new_sample) |
| new_sample = m; |
| } |
| } else { |
| /* No previous measure. */ |
| new_sample = m << 3; |
| } |
| |
| if (tp->rcv_rtt_est.rtt != new_sample) |
| tp->rcv_rtt_est.rtt = new_sample; |
| } |
| |
| static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp) |
| { |
| if (tp->rcv_rtt_est.time == 0) |
| goto new_measure; |
| if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq)) |
| return; |
| tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rcv_rtt_est.time, 1); |
| |
| new_measure: |
| tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd; |
| tp->rcv_rtt_est.time = tcp_time_stamp; |
| } |
| |
| static inline void tcp_rcv_rtt_measure_ts(struct sock *sk, |
| const struct sk_buff *skb) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| if (tp->rx_opt.rcv_tsecr && |
| (TCP_SKB_CB(skb)->end_seq - |
| TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss)) |
| tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0); |
| } |
| |
| /* |
| * This function should be called every time data is copied to user space. |
| * It calculates the appropriate TCP receive buffer space. |
| */ |
| void tcp_rcv_space_adjust(struct sock *sk) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| int time; |
| int space; |
| |
| if (tp->rcvq_space.time == 0) |
| goto new_measure; |
| |
| time = tcp_time_stamp - tp->rcvq_space.time; |
| if (time < (tp->rcv_rtt_est.rtt >> 3) || tp->rcv_rtt_est.rtt == 0) |
| return; |
| |
| space = 2 * (tp->copied_seq - tp->rcvq_space.seq); |
| |
| space = max(tp->rcvq_space.space, space); |
| |
| if (tp->rcvq_space.space != space) { |
| int rcvmem; |
| |
| tp->rcvq_space.space = space; |
| |
| if (sysctl_tcp_moderate_rcvbuf && |
| !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) { |
| int new_clamp = space; |
| |
| /* Receive space grows, normalize in order to |
| * take into account packet headers and sk_buff |
| * structure overhead. |
| */ |
| space /= tp->advmss; |
| if (!space) |
| space = 1; |
| rcvmem = SKB_TRUESIZE(tp->advmss + MAX_TCP_HEADER); |
| while (tcp_win_from_space(rcvmem) < tp->advmss) |
| rcvmem += 128; |
| space *= rcvmem; |
| space = min(space, sysctl_tcp_rmem[2]); |
| if (space > sk->sk_rcvbuf) { |
| sk->sk_rcvbuf = space; |
| |
| /* Make the window clamp follow along. */ |
| tp->window_clamp = new_clamp; |
| } |
| } |
| } |
| |
| new_measure: |
| tp->rcvq_space.seq = tp->copied_seq; |
| tp->rcvq_space.time = tcp_time_stamp; |
| } |
| |
| /* There is something which you must keep in mind when you analyze the |
| * behavior of the tp->ato delayed ack timeout interval. When a |
| * connection starts up, we want to ack as quickly as possible. The |
| * problem is that "good" TCP's do slow start at the beginning of data |
| * transmission. The means that until we send the first few ACK's the |
| * sender will sit on his end and only queue most of his data, because |
| * he can only send snd_cwnd unacked packets at any given time. For |
| * each ACK we send, he increments snd_cwnd and transmits more of his |
| * queue. -DaveM |
| */ |
| static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| struct inet_connection_sock *icsk = inet_csk(sk); |
| u32 now; |
| |
| inet_csk_schedule_ack(sk); |
| |
| tcp_measure_rcv_mss(sk, skb); |
| |
| tcp_rcv_rtt_measure(tp); |
| |
| now = tcp_time_stamp; |
| |
| if (!icsk->icsk_ack.ato) { |
| /* The _first_ data packet received, initialize |
| * delayed ACK engine. |
| */ |
| tcp_incr_quickack(sk); |
| icsk->icsk_ack.ato = TCP_ATO_MIN; |
| } else { |
| int m = now - icsk->icsk_ack.lrcvtime; |
| |
| if (m <= TCP_ATO_MIN / 2) { |
| /* The fastest case is the first. */ |
| icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2; |
| } else if (m < icsk->icsk_ack.ato) { |
| icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m; |
| if (icsk->icsk_ack.ato > icsk->icsk_rto) |
| icsk->icsk_ack.ato = icsk->icsk_rto; |
| } else if (m > icsk->icsk_rto) { |
| /* Too long gap. Apparently sender failed to |
| * restart window, so that we send ACKs quickly. |
| */ |
| tcp_incr_quickack(sk); |
| sk_mem_reclaim(sk); |
| } |
| } |
| icsk->icsk_ack.lrcvtime = now; |
| |
| TCP_ECN_check_ce(tp, skb); |
| |
| if (skb->len >= 128) |
| tcp_grow_window(sk, skb); |
| } |
| |
| /* Called to compute a smoothed rtt estimate. The data fed to this |
| * routine either comes from timestamps, or from segments that were |
| * known _not_ to have been retransmitted [see Karn/Partridge |
| * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88 |
| * piece by Van Jacobson. |
| * NOTE: the next three routines used to be one big routine. |
| * To save cycles in the RFC 1323 implementation it was better to break |
| * it up into three procedures. -- erics |
| */ |
| static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| long m = mrtt; /* RTT */ |
| |
| /* The following amusing code comes from Jacobson's |
| * article in SIGCOMM '88. Note that rtt and mdev |
| * are scaled versions of rtt and mean deviation. |
| * This is designed to be as fast as possible |
| * m stands for "measurement". |
| * |
| * On a 1990 paper the rto value is changed to: |
| * RTO = rtt + 4 * mdev |
| * |
| * Funny. This algorithm seems to be very broken. |
| * These formulae increase RTO, when it should be decreased, increase |
| * too slowly, when it should be increased quickly, decrease too quickly |
| * etc. I guess in BSD RTO takes ONE value, so that it is absolutely |
| * does not matter how to _calculate_ it. Seems, it was trap |
| * that VJ failed to avoid. 8) |
| */ |
| if (m == 0) |
| m = 1; |
| if (tp->srtt != 0) { |
| m -= (tp->srtt >> 3); /* m is now error in rtt est */ |
| tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */ |
| if (m < 0) { |
| m = -m; /* m is now abs(error) */ |
| m -= (tp->mdev >> 2); /* similar update on mdev */ |
| /* This is similar to one of Eifel findings. |
| * Eifel blocks mdev updates when rtt decreases. |
| * This solution is a bit different: we use finer gain |
| * for mdev in this case (alpha*beta). |
| * Like Eifel it also prevents growth of rto, |
| * but also it limits too fast rto decreases, |
| * happening in pure Eifel. |
| */ |
| if (m > 0) |
| m >>= 3; |
| } else { |
| m -= (tp->mdev >> 2); /* similar update on mdev */ |
| } |
| tp->mdev += m; /* mdev = 3/4 mdev + 1/4 new */ |
| if (tp->mdev > tp->mdev_max) { |
| tp->mdev_max = tp->mdev; |
| if (tp->mdev_max > tp->rttvar) |
| tp->rttvar = tp->mdev_max; |
| } |
| if (after(tp->snd_una, tp->rtt_seq)) { |
| if (tp->mdev_max < tp->rttvar) |
| tp->rttvar -= (tp->rttvar - tp->mdev_max) >> 2; |
| tp->rtt_seq = tp->snd_nxt; |
| tp->mdev_max = tcp_rto_min(sk); |
| } |
| } else { |
| /* no previous measure. */ |
| tp->srtt = m << 3; /* take the measured time to be rtt */ |
| tp->mdev = m << 1; /* make sure rto = 3*rtt */ |
| tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk)); |
| tp->rtt_seq = tp->snd_nxt; |
| } |
| } |
| |
| /* Set the sk_pacing_rate to allow proper sizing of TSO packets. |
| * Note: TCP stack does not yet implement pacing. |
| * FQ packet scheduler can be used to implement cheap but effective |
| * TCP pacing, to smooth the burst on large writes when packets |
| * in flight is significantly lower than cwnd (or rwin) |
| */ |
| static void tcp_update_pacing_rate(struct sock *sk) |
| { |
| const struct tcp_sock *tp = tcp_sk(sk); |
| u64 rate; |
| |
| /* set sk_pacing_rate to 200 % of current rate (mss * cwnd / srtt) */ |
| rate = (u64)tp->mss_cache * 2 * (HZ << 3); |
| |
| rate *= max(tp->snd_cwnd, tp->packets_out); |
| |
| /* Correction for small srtt : minimum srtt being 8 (1 jiffy << 3), |
| * be conservative and assume srtt = 1 (125 us instead of 1.25 ms) |
| * We probably need usec resolution in the future. |
| * Note: This also takes care of possible srtt=0 case, |
| * when tcp_rtt_estimator() was not yet called. |
| */ |
| if (tp->srtt > 8 + 2) |
| do_div(rate, tp->srtt); |
| |
| sk->sk_pacing_rate = min_t(u64, rate, ~0U); |
| } |
| |
| /* Calculate rto without backoff. This is the second half of Van Jacobson's |
| * routine referred to above. |
| */ |
| void tcp_set_rto(struct sock *sk) |
| { |
| const struct tcp_sock *tp = tcp_sk(sk); |
| /* Old crap is replaced with new one. 8) |
| * |
| * More seriously: |
| * 1. If rtt variance happened to be less 50msec, it is hallucination. |
| * It cannot be less due to utterly erratic ACK generation made |
| * at least by solaris and freebsd. "Erratic ACKs" has _nothing_ |
| * to do with delayed acks, because at cwnd>2 true delack timeout |
| * is invisible. Actually, Linux-2.4 also generates erratic |
| * ACKs in some circumstances. |
| */ |
| inet_csk(sk)->icsk_rto = __tcp_set_rto(tp); |
| |
| /* 2. Fixups made earlier cannot be right. |
| * If we do not estimate RTO correctly without them, |
| * all the algo is pure shit and should be replaced |
| * with correct one. It is exactly, which we pretend to do. |
| */ |
| |
| /* NOTE: clamping at TCP_RTO_MIN is not required, current algo |
| * guarantees that rto is higher. |
| */ |
| tcp_bound_rto(sk); |
| } |
| |
| __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst) |
| { |
| __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0); |
| |
| if (!cwnd) |
| cwnd = TCP_INIT_CWND; |
| return min_t(__u32, cwnd, tp->snd_cwnd_clamp); |
| } |
| |
| /* |
| * Packet counting of FACK is based on in-order assumptions, therefore TCP |
| * disables it when reordering is detected |
| */ |
| void tcp_disable_fack(struct tcp_sock *tp) |
| { |
| /* RFC3517 uses different metric in lost marker => reset on change */ |
| if (tcp_is_fack(tp)) |
| tp->lost_skb_hint = NULL; |
| tp->rx_opt.sack_ok &= ~TCP_FACK_ENABLED; |
| } |
| |
| /* Take a notice that peer is sending D-SACKs */ |
| static void tcp_dsack_seen(struct tcp_sock *tp) |
| { |
| tp->rx_opt.sack_ok |= TCP_DSACK_SEEN; |
| } |
| |
| static void tcp_update_reordering(struct sock *sk, const int metric, |
| const int ts) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| if (metric > tp->reordering) { |
| int mib_idx; |
| |
| tp->reordering = min(TCP_MAX_REORDERING, metric); |
| |
| /* This exciting event is worth to be remembered. 8) */ |
| if (ts) |
| mib_idx = LINUX_MIB_TCPTSREORDER; |
| else if (tcp_is_reno(tp)) |
| mib_idx = LINUX_MIB_TCPRENOREORDER; |
| else if (tcp_is_fack(tp)) |
| mib_idx = LINUX_MIB_TCPFACKREORDER; |
| else |
| mib_idx = LINUX_MIB_TCPSACKREORDER; |
| |
| NET_INC_STATS_BH(sock_net(sk), mib_idx); |
| #if FASTRETRANS_DEBUG > 1 |
| pr_debug("Disorder%d %d %u f%u s%u rr%d\n", |
| tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state, |
| tp->reordering, |
| tp->fackets_out, |
| tp->sacked_out, |
| tp->undo_marker ? tp->undo_retrans : 0); |
| #endif |
| tcp_disable_fack(tp); |
| } |
| |
| if (metric > 0) |
| tcp_disable_early_retrans(tp); |
| } |
| |
| /* This must be called before lost_out is incremented */ |
| static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb) |
| { |
| if ((tp->retransmit_skb_hint == NULL) || |
| before(TCP_SKB_CB(skb)->seq, |
| TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) |
| tp->retransmit_skb_hint = skb; |
| |
| if (!tp->lost_out || |
| after(TCP_SKB_CB(skb)->end_seq, tp->retransmit_high)) |
| tp->retransmit_high = TCP_SKB_CB(skb)->end_seq; |
| } |
| |
| static void tcp_skb_mark_lost(struct tcp_sock *tp, struct sk_buff *skb) |
| { |
| if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) { |
| tcp_verify_retransmit_hint(tp, skb); |
| |
| tp->lost_out += tcp_skb_pcount(skb); |
| TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; |
| } |
| } |
| |
| static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, |
| struct sk_buff *skb) |
| { |
| tcp_verify_retransmit_hint(tp, skb); |
| |
| if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) { |
| tp->lost_out += tcp_skb_pcount(skb); |
| TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; |
| } |
| } |
| |
| /* This procedure tags the retransmission queue when SACKs arrive. |
| * |
| * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L). |
| * Packets in queue with these bits set are counted in variables |
| * sacked_out, retrans_out and lost_out, correspondingly. |
| * |
| * Valid combinations are: |
| * Tag InFlight Description |
| * 0 1 - orig segment is in flight. |
| * S 0 - nothing flies, orig reached receiver. |
| * L 0 - nothing flies, orig lost by net. |
| * R 2 - both orig and retransmit are in flight. |
| * L|R 1 - orig is lost, retransmit is in flight. |
| * S|R 1 - orig reached receiver, retrans is still in flight. |
| * (L|S|R is logically valid, it could occur when L|R is sacked, |
| * but it is equivalent to plain S and code short-curcuits it to S. |
| * L|S is logically invalid, it would mean -1 packet in flight 8)) |
| * |
| * These 6 states form finite state machine, controlled by the following events: |
| * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue()) |
| * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue()) |
| * 3. Loss detection event of two flavors: |
| * A. Scoreboard estimator decided the packet is lost. |
| * A'. Reno "three dupacks" marks head of queue lost. |
| * A''. Its FACK modification, head until snd.fack is lost. |
| * B. SACK arrives sacking SND.NXT at the moment, when the |
| * segment was retransmitted. |
| * 4. D-SACK added new rule: D-SACK changes any tag to S. |
| * |
| * It is pleasant to note, that state diagram turns out to be commutative, |
| * so that we are allowed not to be bothered by order of our actions, |
| * when multiple events arrive simultaneously. (see the function below). |
| * |
| * Reordering detection. |
| * -------------------- |
| * Reordering metric is maximal distance, which a packet can be displaced |
| * in packet stream. With SACKs we can estimate it: |
| * |
| * 1. SACK fills old hole and the corresponding segment was not |
| * ever retransmitted -> reordering. Alas, we cannot use it |
| * when segment was retransmitted. |
| * 2. The last flaw is solved with D-SACK. D-SACK arrives |
| * for retransmitted and already SACKed segment -> reordering.. |
| * Both of these heuristics are not used in Loss state, when we cannot |
| * account for retransmits accurately. |
| * |
| * SACK block validation. |
| * ---------------------- |
| * |
| * SACK block range validation checks that the received SACK block fits to |
| * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT. |
| * Note that SND.UNA is not included to the range though being valid because |
| * it means that the receiver is rather inconsistent with itself reporting |
| * SACK reneging when it should advance SND.UNA. Such SACK block this is |
| * perfectly valid, however, in light of RFC2018 which explicitly states |
| * that "SACK block MUST reflect the newest segment. Even if the newest |
| * segment is going to be discarded ...", not that it looks very clever |
| * in case of head skb. Due to potentional receiver driven attacks, we |
| * choose to avoid immediate execution of a walk in write queue due to |
| * reneging and defer head skb's loss recovery to standard loss recovery |
| * procedure that will eventually trigger (nothing forbids us doing this). |
| * |
| * Implements also blockage to start_seq wrap-around. Problem lies in the |
| * fact that though start_seq (s) is before end_seq (i.e., not reversed), |
| * there's no guarantee that it will be before snd_nxt (n). The problem |
| * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt |
| * wrap (s_w): |
| * |
| * <- outs wnd -> <- wrapzone -> |
| * u e n u_w e_w s n_w |
| * | | | | | | | |
| * |<------------+------+----- TCP seqno space --------------+---------->| |
| * ...-- <2^31 ->| |<--------... |
| * ...---- >2^31 ------>| |<--------... |
| * |
| * Current code wouldn't be vulnerable but it's better still to discard such |
| * crazy SACK blocks. Doing this check for start_seq alone closes somewhat |
| * similar case (end_seq after snd_nxt wrap) as earlier reversed check in |
| * snd_nxt wrap -> snd_una region will then become "well defined", i.e., |
| * equal to the ideal case (infinite seqno space without wrap caused issues). |
| * |
| * With D-SACK the lower bound is extended to cover sequence space below |
| * SND.UNA down to undo_marker, which is the last point of interest. Yet |
| * again, D-SACK block must not to go across snd_una (for the same reason as |
| * for the normal SACK blocks, explained above). But there all simplicity |
| * ends, TCP might receive valid D-SACKs below that. As long as they reside |
| * fully below undo_marker they do not affect behavior in anyway and can |
| * therefore be safely ignored. In rare cases (which are more or less |
| * theoretical ones), the D-SACK will nicely cross that boundary due to skb |
| * fragmentation and packet reordering past skb's retransmission. To consider |
| * them correctly, the acceptable range must be extended even more though |
| * the exact amount is rather hard to quantify. However, tp->max_window can |
| * be used as an exaggerated estimate. |
| */ |
| static bool tcp_is_sackblock_valid(struct tcp_sock *tp, bool is_dsack, |
| u32 start_seq, u32 end_seq) |
| { |
| /* Too far in future, or reversed (interpretation is ambiguous) */ |
| if (after(end_seq, tp->snd_nxt) || !before(start_seq, end_seq)) |
| return false; |
| |
| /* Nasty start_seq wrap-around check (see comments above) */ |
| if (!before(start_seq, tp->snd_nxt)) |
| return false; |
| |
| /* In outstanding window? ...This is valid exit for D-SACKs too. |
| * start_seq == snd_una is non-sensical (see comments above) |
| */ |
| if (after(start_seq, tp->snd_una)) |
| return true; |
| |
| if (!is_dsack || !tp->undo_marker) |
| return false; |
| |
| /* ...Then it's D-SACK, and must reside below snd_una completely */ |
| if (after(end_seq, tp->snd_una)) |
| return false; |
| |
| if (!before(start_seq, tp->undo_marker)) |
| return true; |
| |
| /* Too old */ |
| if (!after(end_seq, tp->undo_marker)) |
| return false; |
| |
| /* Undo_marker boundary crossing (overestimates a lot). Known already: |
| * start_seq < undo_marker and end_seq >= undo_marker. |
| */ |
| return !before(start_seq, end_seq - tp->max_window); |
| } |
| |
| /* Check for lost retransmit. This superb idea is borrowed from "ratehalving". |
| * Event "B". Later note: FACK people cheated me again 8), we have to account |
| * for reordering! Ugly, but should help. |
| * |
| * Search retransmitted skbs from write_queue that were sent when snd_nxt was |
| * less than what is now known to be received by the other end (derived from |
| * highest SACK block). Also calculate the lowest snd_nxt among the remaining |
| * retransmitted skbs to avoid some costly processing per ACKs. |
| */ |
| static void tcp_mark_lost_retrans(struct sock *sk) |
| { |
| const struct inet_connection_sock *icsk = inet_csk(sk); |
| struct tcp_sock *tp = tcp_sk(sk); |
| struct sk_buff *skb; |
| int cnt = 0; |
| u32 new_low_seq = tp->snd_nxt; |
| u32 received_upto = tcp_highest_sack_seq(tp); |
| |
| if (!tcp_is_fack(tp) || !tp->retrans_out || |
| !after(received_upto, tp->lost_retrans_low) || |
| icsk->icsk_ca_state != TCP_CA_Recovery) |
| return; |
| |
| tcp_for_write_queue(skb, sk) { |
| u32 ack_seq = TCP_SKB_CB(skb)->ack_seq; |
| |
| if (skb == tcp_send_head(sk)) |
| break; |
| if (cnt == tp->retrans_out) |
| break; |
| if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) |
| continue; |
| |
| if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)) |
| continue; |
| |
| /* TODO: We would like to get rid of tcp_is_fack(tp) only |
| * constraint here (see above) but figuring out that at |
| * least tp->reordering SACK blocks reside between ack_seq |
| * and received_upto is not easy task to do cheaply with |
| * the available datastructures. |
| * |
| * Whether FACK should check here for tp->reordering segs |
| * in-between one could argue for either way (it would be |
| * rather simple to implement as we could count fack_count |
| * during the walk and do tp->fackets_out - fack_count). |
| */ |
| if (after(received_upto, ack_seq)) { |
| TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; |
| tp->retrans_out -= tcp_skb_pcount(skb); |
| |
| tcp_skb_mark_lost_uncond_verify(tp, skb); |
| NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSTRETRANSMIT); |
| } else { |
| if (before(ack_seq, new_low_seq)) |
| new_low_seq = ack_seq; |
| cnt += tcp_skb_pcount(skb); |
| } |
| } |
| |
| if (tp->retrans_out) |
| tp->lost_retrans_low = new_low_seq; |
| } |
| |
| static bool tcp_check_dsack(struct sock *sk, const struct sk_buff *ack_skb, |
| struct tcp_sack_block_wire *sp, int num_sacks, |
| u32 prior_snd_una) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| u32 start_seq_0 = get_unaligned_be32(&sp[0].start_seq); |
| u32 end_seq_0 = get_unaligned_be32(&sp[0].end_seq); |
| bool dup_sack = false; |
| |
| if (before(start_seq_0, TCP_SKB_CB(ack_skb)->ack_seq)) { |
| dup_sack = true; |
| tcp_dsack_seen(tp); |
| NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKRECV); |
| } else if (num_sacks > 1) { |
| u32 end_seq_1 = get_unaligned_be32(&sp[1].end_seq); |
| u32 start_seq_1 = get_unaligned_be32(&sp[1].start_seq); |
| |
| if (!after(end_seq_0, end_seq_1) && |
| !before(start_seq_0, start_seq_1)) { |
| dup_sack = true; |
| tcp_dsack_seen(tp); |
| NET_INC_STATS_BH(sock_net(sk), |
| LINUX_MIB_TCPDSACKOFORECV); |
| } |
| } |
| |
| /* D-SACK for already forgotten data... Do dumb counting. */ |
| if (dup_sack && tp->undo_marker && tp->undo_retrans && |
| !after(end_seq_0, prior_snd_una) && |
| after(end_seq_0, tp->undo_marker)) |
| tp->undo_retrans--; |
| |
| return dup_sack; |
| } |
| |
| struct tcp_sacktag_state { |
| int reord; |
| int fack_count; |
| int flag; |
| }; |
| |
| /* Check if skb is fully within the SACK block. In presence of GSO skbs, |
| * the incoming SACK may not exactly match but we can find smaller MSS |
| * aligned portion of it that matches. Therefore we might need to fragment |
| * which may fail and creates some hassle (caller must handle error case |
| * returns). |
| * |
| * FIXME: this could be merged to shift decision code |
| */ |
| static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb, |
| u32 start_seq, u32 end_seq) |
| { |
| int err; |
| bool in_sack; |
| unsigned int pkt_len; |
| unsigned int mss; |
| |
| in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && |
| !before(end_seq, TCP_SKB_CB(skb)->end_seq); |
| |
| if (tcp_skb_pcount(skb) > 1 && !in_sack && |
| after(TCP_SKB_CB(skb)->end_seq, start_seq)) { |
| mss = tcp_skb_mss(skb); |
| in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq); |
| |
| if (!in_sack) { |
| pkt_len = start_seq - TCP_SKB_CB(skb)->seq; |
| if (pkt_len < mss) |
| pkt_len = mss; |
| } else { |
| pkt_len = end_seq - TCP_SKB_CB(skb)->seq; |
| if (pkt_len < mss) |
| return -EINVAL; |
| } |
| |
| /* Round if necessary so that SACKs cover only full MSSes |
| * and/or the remaining small portion (if present) |
| */ |
| if (pkt_len > mss) { |
| unsigned int new_len = (pkt_len / mss) * mss; |
| if (!in_sack && new_len < pkt_len) { |
| new_len += mss; |
| if (new_len > skb->len) |
| return 0; |
| } |
| pkt_len = new_len; |
| } |
| err = tcp_fragment(sk, skb, pkt_len, mss); |
| if (err < 0) |
| return err; |
| } |
| |
| return in_sack; |
| } |
| |
| /* Mark the given newly-SACKed range as such, adjusting counters and hints. */ |
| static u8 tcp_sacktag_one(struct sock *sk, |
| struct tcp_sacktag_state *state, u8 sacked, |
| u32 start_seq, u32 end_seq, |
| bool dup_sack, int pcount) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| int fack_count = state->fack_count; |
| |
| /* Account D-SACK for retransmitted packet. */ |
| if (dup_sack && (sacked & TCPCB_RETRANS)) { |
| if (tp->undo_marker && tp->undo_retrans && |
| after(end_seq, tp->undo_marker)) |
| tp->undo_retrans--; |
| if (sacked & TCPCB_SACKED_ACKED) |
| state->reord = min(fack_count, state->reord); |
| } |
| |
| /* Nothing to do; acked frame is about to be dropped (was ACKed). */ |
| if (!after(end_seq, tp->snd_una)) |
| return sacked; |
| |
| if (!(sacked & TCPCB_SACKED_ACKED)) { |
| if (sacked & TCPCB_SACKED_RETRANS) { |
| /* If the segment is not tagged as lost, |
| * we do not clear RETRANS, believing |
| * that retransmission is still in flight. |
| */ |
| if (sacked & TCPCB_LOST) { |
| sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS); |
| tp->lost_out -= pcount; |
| tp->retrans_out -= pcount; |
| } |
| } else { |
| if (!(sacked & TCPCB_RETRANS)) { |
| /* New sack for not retransmitted frame, |
| * which was in hole. It is reordering. |
| */ |
| if (before(start_seq, |
| tcp_highest_sack_seq(tp))) |
| state->reord = min(fack_count, |
| state->reord); |
| if (!after(end_seq, tp->high_seq)) |
| state->flag |= FLAG_ORIG_SACK_ACKED; |
| } |
| |
| if (sacked & TCPCB_LOST) { |
| sacked &= ~TCPCB_LOST; |
| tp->lost_out -= pcount; |
| } |
| } |
| |
| sacked |= TCPCB_SACKED_ACKED; |
| state->flag |= FLAG_DATA_SACKED; |
| tp->sacked_out += pcount; |
| |
| fack_count += pcount; |
| |
| /* Lost marker hint past SACKed? Tweak RFC3517 cnt */ |
| if (!tcp_is_fack(tp) && (tp->lost_skb_hint != NULL) && |
| before(start_seq, TCP_SKB_CB(tp->lost_skb_hint)->seq)) |
| tp->lost_cnt_hint += pcount; |
| |
| if (fack_count > tp->fackets_out) |
| tp->fackets_out = fack_count; |
| } |
| |
| /* D-SACK. We can detect redundant retransmission in S|R and plain R |
| * frames and clear it. undo_retrans is decreased above, L|R frames |
| * are accounted above as well. |
| */ |
| if (dup_sack && (sacked & TCPCB_SACKED_RETRANS)) { |
| sacked &= ~TCPCB_SACKED_RETRANS; |
| tp->retrans_out -= pcount; |
| } |
| |
| return sacked; |
| } |
| |
| /* Shift newly-SACKed bytes from this skb to the immediately previous |
| * already-SACKed sk_buff. Mark the newly-SACKed bytes as such. |
| */ |
| static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *skb, |
| struct tcp_sacktag_state *state, |
| unsigned int pcount, int shifted, int mss, |
| bool dup_sack) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| struct sk_buff *prev = tcp_write_queue_prev(sk, skb); |
| u32 start_seq = TCP_SKB_CB(skb)->seq; /* start of newly-SACKed */ |
| u32 end_seq = start_seq + shifted; /* end of newly-SACKed */ |
| |
| BUG_ON(!pcount); |
| |
| /* Adjust counters and hints for the newly sacked sequence |
| * range but discard the return value since prev is already |
| * marked. We must tag the range first because the seq |
| * advancement below implicitly advances |
| * tcp_highest_sack_seq() when skb is highest_sack. |
| */ |
| tcp_sacktag_one(sk, state, TCP_SKB_CB(skb)->sacked, |
| start_seq, end_seq, dup_sack, pcount); |
| |
| if (skb == tp->lost_skb_hint) |
| tp->lost_cnt_hint += pcount; |
| |
| TCP_SKB_CB(prev)->end_seq += shifted; |
| TCP_SKB_CB(skb)->seq += shifted; |
| |
| skb_shinfo(prev)->gso_segs += pcount; |
| BUG_ON(skb_shinfo(skb)->gso_segs < pcount); |
| skb_shinfo(skb)->gso_segs -= pcount; |
| |
| /* When we're adding to gso_segs == 1, gso_size will be zero, |
| * in theory this shouldn't be necessary but as long as DSACK |
| * code can come after this skb later on it's better to keep |
| * setting gso_size to something. |
| */ |
| if (!skb_shinfo(prev)->gso_size) { |
| skb_shinfo(prev)->gso_size = mss; |
| skb_shinfo(prev)->gso_type = sk->sk_gso_type; |
| } |
| |
| /* CHECKME: To clear or not to clear? Mimics normal skb currently */ |
| if (skb_shinfo(skb)->gso_segs <= 1) { |
| skb_shinfo(skb)->gso_size = 0; |
| skb_shinfo(skb)->gso_type = 0; |
| } |
| |
| /* Difference in this won't matter, both ACKed by the same cumul. ACK */ |
| TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS); |
| |
| if (skb->len > 0) { |
| BUG_ON(!tcp_skb_pcount(skb)); |
| NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTED); |
| return false; |
| } |
| |
| /* Whole SKB was eaten :-) */ |
| |
| if (skb == tp->retransmit_skb_hint) |
| tp->retransmit_skb_hint = prev; |
| if (skb == tp->scoreboard_skb_hint) |
| tp->scoreboard_skb_hint = prev; |
| if (skb == tp->lost_skb_hint) { |
| tp->lost_skb_hint = prev; |
| tp->lost_cnt_hint -= tcp_skb_pcount(prev); |
| } |
| |
| TCP_SKB_CB(prev)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags; |
| if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) |
| TCP_SKB_CB(prev)->end_seq++; |
| |
| if (skb == tcp_highest_sack(sk)) |
| tcp_advance_highest_sack(sk, skb); |
| |
| tcp_unlink_write_queue(skb, sk); |
| sk_wmem_free_skb(sk, skb); |
| |
| NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKMERGED); |
| |
| return true; |
| } |
| |
| /* I wish gso_size would have a bit more sane initialization than |
| * something-or-zero which complicates things |
| */ |
| static int tcp_skb_seglen(const struct sk_buff *skb) |
| { |
| return tcp_skb_pcount(skb) == 1 ? skb->len : tcp_skb_mss(skb); |
| } |
| |
| /* Shifting pages past head area doesn't work */ |
| static int skb_can_shift(const struct sk_buff *skb) |
| { |
| return !skb_headlen(skb) && skb_is_nonlinear(skb); |
| } |
| |
| /* Try collapsing SACK blocks spanning across multiple skbs to a single |
| * skb. |
| */ |
| static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb, |
| struct tcp_sacktag_state *state, |
| u32 start_seq, u32 end_seq, |
| bool dup_sack) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| struct sk_buff *prev; |
| int mss; |
| int pcount = 0; |
| int len; |
| int in_sack; |
| |
| if (!sk_can_gso(sk)) |
| goto fallback; |
| |
| /* Normally R but no L won't result in plain S */ |
| if (!dup_sack && |
| (TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_RETRANS)) == TCPCB_SACKED_RETRANS) |
| goto fallback; |
| if (!skb_can_shift(skb)) |
| goto fallback; |
| /* This frame is about to be dropped (was ACKed). */ |
| if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) |
| goto fallback; |
| |
| /* Can only happen with delayed DSACK + discard craziness */ |
| if (unlikely(skb == tcp_write_queue_head(sk))) |
| goto fallback; |
| prev = tcp_write_queue_prev(sk, skb); |
| |
| if ((TCP_SKB_CB(prev)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) |
| goto fallback; |
| |
| in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && |
| !before(end_seq, TCP_SKB_CB(skb)->end_seq); |
| |
| if (in_sack) { |
| len = skb->len; |
| pcount = tcp_skb_pcount(skb); |
| mss = tcp_skb_seglen(skb); |
| |
| /* TODO: Fix DSACKs to not fragment already SACKed and we can |
| * drop this restriction as unnecessary |
| */ |
| if (mss != tcp_skb_seglen(prev)) |
| goto fallback; |
| } else { |
| if (!after(TCP_SKB_CB(skb)->end_seq, start_seq)) |
| goto noop; |
| /* CHECKME: This is non-MSS split case only?, this will |
| * cause skipped skbs due to advancing loop btw, original |
| * has that feature too |
| */ |
| if (tcp_skb_pcount(skb) <= 1) |
| goto noop; |
| |
| in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq); |
| if (!in_sack) { |
| /* TODO: head merge to next could be attempted here |
| * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)), |
| * though it might not be worth of the additional hassle |
| * |
| * ...we can probably just fallback to what was done |
| * previously. We could try merging non-SACKed ones |
| * as well but it probably isn't going to buy off |
| * because later SACKs might again split them, and |
| * it would make skb timestamp tracking considerably |
| * harder problem. |
| */ |
| goto fallback; |
| } |
| |
| len = end_seq - TCP_SKB_CB(skb)->seq; |
| BUG_ON(len < 0); |
| BUG_ON(len > skb->len); |
| |
| /* MSS boundaries should be honoured or else pcount will |
| * severely break even though it makes things bit trickier. |
| * Optimize common case to avoid most of the divides |
| */ |
| mss = tcp_skb_mss(skb); |
| |
| /* TODO: Fix DSACKs to not fragment already SACKed and we can |
| * drop this restriction as unnecessary |
| */ |
| if (mss != tcp_skb_seglen(prev)) |
| goto fallback; |
| |
| if (len == mss) { |
| pcount = 1; |
| } else if (len < mss) { |
| goto noop; |
| } else { |
| pcount = len / mss; |
| len = pcount * mss; |
| } |
| } |
| |
| /* tcp_sacktag_one() won't SACK-tag ranges below snd_una */ |
| if (!after(TCP_SKB_CB(skb)->seq + len, tp->snd_una)) |
| goto fallback; |
| |
| if (!skb_shift(prev, skb, len)) |
| goto fallback; |
| if (!tcp_shifted_skb(sk, skb, state, pcount, len, mss, dup_sack)) |
| goto out; |
| |
| /* Hole filled allows collapsing with the next as well, this is very |
| * useful when hole on every nth skb pattern happens |
| */ |
| if (prev == tcp_write_queue_tail(sk)) |
| goto out; |
| skb = tcp_write_queue_next(sk, prev); |
| |
| if (!skb_can_shift(skb) || |
| (skb == tcp_send_head(sk)) || |
| ((TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) || |
| (mss != tcp_skb_seglen(skb))) |
| goto out; |
| |
| len = skb->len; |
| if (skb_shift(prev, skb, len)) { |
| pcount += tcp_skb_pcount(skb); |
| tcp_shifted_skb(sk, skb, state, tcp_skb_pcount(skb), len, mss, 0); |
| } |
| |
| out: |
| state->fack_count += pcount; |
| return prev; |
| |
| noop: |
| return skb; |
| |
| fallback: |
| NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTFALLBACK); |
| return NULL; |
| } |
| |
| static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk, |
| struct tcp_sack_block *next_dup, |
| struct tcp_sacktag_state *state, |
| u32 start_seq, u32 end_seq, |
| bool dup_sack_in) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| struct sk_buff *tmp; |
| |
| tcp_for_write_queue_from(skb, sk) { |
| int in_sack = 0; |
| bool dup_sack = dup_sack_in; |
| |
| if (skb == tcp_send_head(sk)) |
| break; |
| |
| /* queue is in-order => we can short-circuit the walk early */ |
| if (!before(TCP_SKB_CB(skb)->seq, end_seq)) |
| break; |
| |
| if ((next_dup != NULL) && |
| before(TCP_SKB_CB(skb)->seq, next_dup->end_seq)) { |
| in_sack = tcp_match_skb_to_sack(sk, skb, |
| next_dup->start_seq, |
| next_dup->end_seq); |
| if (in_sack > 0) |
| dup_sack = true; |
| } |
| |
| /* skb reference here is a bit tricky to get right, since |
| * shifting can eat and free both this skb and the next, |
| * so not even _safe variant of the loop is enough. |
| */ |
| if (in_sack <= 0) { |
| tmp = tcp_shift_skb_data(sk, skb, state, |
| start_seq, end_seq, dup_sack); |
| if (tmp != NULL) { |
| if (tmp != skb) { |
| skb = tmp; |
| continue; |
| } |
| |
| in_sack = 0; |
| } else { |
| in_sack = tcp_match_skb_to_sack(sk, skb, |
| start_seq, |
| end_seq); |
| } |
| } |
| |
| if (unlikely(in_sack < 0)) |
| break; |
| |
| if (in_sack) { |
| TCP_SKB_CB(skb)->sacked = |
| tcp_sacktag_one(sk, |
| state, |
| TCP_SKB_CB(skb)->sacked, |
| TCP_SKB_CB(skb)->seq, |
| TCP_SKB_CB(skb)->end_seq, |
| dup_sack, |
| tcp_skb_pcount(skb)); |
| |
| if (!before(TCP_SKB_CB(skb)->seq, |
| tcp_highest_sack_seq(tp))) |
| tcp_advance_highest_sack(sk, skb); |
| } |
| |
| state->fack_count += tcp_skb_pcount(skb); |
| } |
| return skb; |
| } |
| |
| /* Avoid all extra work that is being done by sacktag while walking in |
| * a normal way |
| */ |
| static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk, |
| struct tcp_sacktag_state *state, |
| u32 skip_to_seq) |
| { |
| tcp_for_write_queue_from(skb, sk) { |
| if (skb == tcp_send_head(sk)) |
| break; |
| |
| if (after(TCP_SKB_CB(skb)->end_seq, skip_to_seq)) |
| break; |
| |
| state->fack_count += tcp_skb_pcount(skb); |
| } |
| return skb; |
| } |
| |
| static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb, |
| struct sock *sk, |
| struct tcp_sack_block *next_dup, |
| struct tcp_sacktag_state *state, |
| u32 skip_to_seq) |
| { |
| if (next_dup == NULL) |
| return skb; |
| |
| if (before(next_dup->start_seq, skip_to_seq)) { |
| skb = tcp_sacktag_skip(skb, sk, state, next_dup->start_seq); |
| skb = tcp_sacktag_walk(skb, sk, NULL, state, |
| next_dup->start_seq, next_dup->end_seq, |
| 1); |
| } |
| |
| return skb; |
| } |
| |
| static int tcp_sack_cache_ok(const struct tcp_sock *tp, const struct tcp_sack_block *cache) |
| { |
| return cache < tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache); |
| } |
| |
| static int |
| tcp_sacktag_write_queue(struct sock *sk, const struct sk_buff *ack_skb, |
| u32 prior_snd_una) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| const unsigned char *ptr = (skb_transport_header(ack_skb) + |
| TCP_SKB_CB(ack_skb)->sacked); |
| struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2); |
| struct tcp_sack_block sp[TCP_NUM_SACKS]; |
| struct tcp_sack_block *cache; |
| struct tcp_sacktag_state state; |
| struct sk_buff *skb; |
| int num_sacks = min(TCP_NUM_SACKS, (ptr[1] - TCPOLEN_SACK_BASE) >> 3); |
| int used_sacks; |
| bool found_dup_sack = false; |
| int i, j; |
| int first_sack_index; |
| |
| state.flag = 0; |
| state.reord = tp->packets_out; |
| |
| if (!tp->sacked_out) { |
| if (WARN_ON(tp->fackets_out)) |
| tp->fackets_out = 0; |
| tcp_highest_sack_reset(sk); |
| } |
| |
| found_dup_sack = tcp_check_dsack(sk, ack_skb, sp_wire, |
| num_sacks, prior_snd_una); |
| if (found_dup_sack) |
| state.flag |= FLAG_DSACKING_ACK; |
| |
| /* Eliminate too old ACKs, but take into |
| * account more or less fresh ones, they can |
| * contain valid SACK info. |
| */ |
| if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window)) |
| return 0; |
| |
| if (!tp->packets_out) |
| goto out; |
| |
| used_sacks = 0; |
| first_sack_index = 0; |
| for (i = 0; i < num_sacks; i++) { |
| bool dup_sack = !i && found_dup_sack; |
| |
| sp[used_sacks].start_seq = get_unaligned_be32(&sp_wire[i].start_seq); |
| sp[used_sacks].end_seq = get_unaligned_be32(&sp_wire[i].end_seq); |
| |
| if (!tcp_is_sackblock_valid(tp, dup_sack, |
| sp[used_sacks].start_seq, |
| sp[used_sacks].end_seq)) { |
| int mib_idx; |
| |
| if (dup_sack) { |
| if (!tp->undo_marker) |
| mib_idx = LINUX_MIB_TCPDSACKIGNOREDNOUNDO; |
| else |
| mib_idx = LINUX_MIB_TCPDSACKIGNOREDOLD; |
| } else { |
| /* Don't count olds caused by ACK reordering */ |
| if ((TCP_SKB_CB(ack_skb)->ack_seq != tp->snd_una) && |
| !after(sp[used_sacks].end_seq, tp->snd_una)) |
| continue; |
| mib_idx = LINUX_MIB_TCPSACKDISCARD; |
| } |
| |
| NET_INC_STATS_BH(sock_net(sk), mib_idx); |
| if (i == 0) |
| first_sack_index = -1; |
| continue; |
| } |
| |
| /* Ignore very old stuff early */ |
| if (!after(sp[used_sacks].end_seq, prior_snd_una)) |
| continue; |
| |
| used_sacks++; |
| } |
| |
| /* order SACK blocks to allow in order walk of the retrans queue */ |
| for (i = used_sacks - 1; i > 0; i--) { |
| for (j = 0; j < i; j++) { |
| if (after(sp[j].start_seq, sp[j + 1].start_seq)) { |
| swap(sp[j], sp[j + 1]); |
| |
| /* Track where the first SACK block goes to */ |
| if (j == first_sack_index) |
| first_sack_index = j + 1; |
| } |
| } |
| } |
| |
| skb = tcp_write_queue_head(sk); |
| state.fack_count = 0; |
| i = 0; |
| |
| if (!tp->sacked_out) { |
| /* It's already past, so skip checking against it */ |
| cache = tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache); |
| } else { |
| cache = tp->recv_sack_cache; |
| /* Skip empty blocks in at head of the cache */ |
| while (tcp_sack_cache_ok(tp, cache) && !cache->start_seq && |
| !cache->end_seq) |
| cache++; |
| } |
| |
| while (i < used_sacks) { |
| u32 start_seq = sp[i].start_seq; |
| u32 end_seq = sp[i].end_seq; |
| bool dup_sack = (found_dup_sack && (i == first_sack_index)); |
| struct tcp_sack_block *next_dup = NULL; |
| |
| if (found_dup_sack && ((i + 1) == first_sack_index)) |
| next_dup = &sp[i + 1]; |
| |
| /* Skip too early cached blocks */ |
| while (tcp_sack_cache_ok(tp, cache) && |
| !before(start_seq, cache->end_seq)) |
| cache++; |
| |
| /* Can skip some work by looking recv_sack_cache? */ |
| if (tcp_sack_cache_ok(tp, cache) && !dup_sack && |
| after(end_seq, cache->start_seq)) { |
| |
| /* Head todo? */ |
| if (before(start_seq, cache->start_seq)) { |
| skb = tcp_sacktag_skip(skb, sk, &state, |
| start_seq); |
| skb = tcp_sacktag_walk(skb, sk, next_dup, |
| &state, |
| start_seq, |
| cache->start_seq, |
| dup_sack); |
| } |
| |
| /* Rest of the block already fully processed? */ |
| if (!after(end_seq, cache->end_seq)) |
| goto advance_sp; |
| |
| skb = tcp_maybe_skipping_dsack(skb, sk, next_dup, |
| &state, |
| cache->end_seq); |
| |
| /* ...tail remains todo... */ |
| if (tcp_highest_sack_seq(tp) == cache->end_seq) { |
| /* ...but better entrypoint exists! */ |
| skb = tcp_highest_sack(sk); |
| if (skb == NULL) |
| break; |
| state.fack_count = tp->fackets_out; |
| cache++; |
| goto walk; |
| } |
| |
| skb = tcp_sacktag_skip(skb, sk, &state, cache->end_seq); |
| /* Check overlap against next cached too (past this one already) */ |
| cache++; |
| continue; |
| } |
| |
| if (!before(start_seq, tcp_highest_sack_seq(tp))) { |
| skb = tcp_highest_sack(sk); |
| if (skb == NULL) |
| break; |
| state.fack_count = tp->fackets_out; |
| } |
| skb = tcp_sacktag_skip(skb, sk, &state, start_seq); |
| |
| walk: |
| skb = tcp_sacktag_walk(skb, sk, next_dup, &state, |
| start_seq, end_seq, dup_sack); |
| |
| advance_sp: |
| i++; |
| } |
| |
| /* Clear the head of the cache sack blocks so we can skip it next time */ |
| for (i = 0; i < ARRAY_SIZE(tp->recv_sack_cache) - used_sacks; i++) { |
| tp->recv_sack_cache[i].start_seq = 0; |
| tp->recv_sack_cache[i].end_seq = 0; |
| } |
| for (j = 0; j < used_sacks; j++) |
| tp->recv_sack_cache[i++] = sp[j]; |
| |
| tcp_mark_lost_retrans(sk); |
| |
| tcp_verify_left_out(tp); |
| |
| if ((state.reord < tp->fackets_out) && |
| ((inet_csk(sk)->icsk_ca_state != TCP_CA_Loss) || tp->undo_marker)) |
| tcp_update_reordering(sk, tp->fackets_out - state.reord, 0); |
| |
| out: |
| |
| #if FASTRETRANS_DEBUG > 0 |
| WARN_ON((int)tp->sacked_out < 0); |
| WARN_ON((int)tp->lost_out < 0); |
| WARN_ON((int)tp->retrans_out < 0); |
| WARN_ON((int)tcp_packets_in_flight(tp) < 0); |
| #endif |
| return state.flag; |
| } |
| |
| /* Limits sacked_out so that sum with lost_out isn't ever larger than |
| * packets_out. Returns false if sacked_out adjustement wasn't necessary. |
| */ |
| static bool tcp_limit_reno_sacked(struct tcp_sock *tp) |
| { |
| u32 holes; |
| |
| holes = max(tp->lost_out, 1U); |
| holes = min(holes, tp->packets_out); |
| |
| if ((tp->sacked_out + holes) > tp->packets_out) { |
| tp->sacked_out = tp->packets_out - holes; |
| return true; |
| } |
| return false; |
| } |
| |
| /* If we receive more dupacks than we expected counting segments |
| * in assumption of absent reordering, interpret this as reordering. |
| * The only another reason could be bug in receiver TCP. |
| */ |
| static void tcp_check_reno_reordering(struct sock *sk, const int addend) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| if (tcp_limit_reno_sacked(tp)) |
| tcp_update_reordering(sk, tp->packets_out + addend, 0); |
| } |
| |
| /* Emulate SACKs for SACKless connection: account for a new dupack. */ |
| |
| static void tcp_add_reno_sack(struct sock *sk) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| tp->sacked_out++; |
| tcp_check_reno_reordering(sk, 0); |
| tcp_verify_left_out(tp); |
| } |
| |
| /* Account for ACK, ACKing some data in Reno Recovery phase. */ |
| |
| static void tcp_remove_reno_sacks(struct sock *sk, int acked) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| |
| if (acked > 0) { |
| /* One ACK acked hole. The rest eat duplicate ACKs. */ |
| if (acked - 1 >= tp->sacked_out) |
| tp->sacked_out = 0; |
| else |
| tp->sacked_out -= acked - 1; |
| } |
| tcp_check_reno_reordering(sk, acked); |
| tcp_verify_left_out(tp); |
| } |
| |
| static inline void tcp_reset_reno_sack(struct tcp_sock *tp) |
| { |
| tp->sacked_out = 0; |
| } |
| |
| static void tcp_clear_retrans_partial(struct tcp_sock *tp) |
| { |
| tp->retrans_out = 0; |
| tp->lost_out = 0; |
| |
| tp->undo_marker = 0; |
| tp->undo_retrans = 0; |
| } |
| |
| void tcp_clear_retrans(struct tcp_sock *tp) |
| { |
| tcp_clear_retrans_partial(tp); |
| |
| tp->fackets_out = 0; |
| tp->sacked_out = 0; |
| } |
| |
| /* Enter Loss state. If "how" is not zero, forget all SACK information |
| * and reset tags completely, otherwise preserve SACKs. If receiver |
| * dropped its ofo queue, we will know this due to reneging detection. |
| */ |
| void tcp_enter_loss(struct sock *sk, int how) |
| { |
| const struct inet_connection_sock *icsk = inet_csk(sk); |
| struct tcp_sock *tp = tcp_sk(sk); |
| struct sk_buff *skb; |
| bool new_recovery = false; |
| |
| /* Reduce ssthresh if it has not yet been made inside this window. */ |
| if (icsk->icsk_ca_state <= TCP_CA_Disorder || |
| !after(tp->high_seq, tp->snd_una) || |
| (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) { |
| new_recovery = true; |
| tp->prior_ssthresh = tcp_current_ssthresh(sk); |
| tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); |
| tcp_ca_event(sk, CA_EVENT_LOSS); |
| } |
| tp->snd_cwnd = 1; |
| tp->snd_cwnd_cnt = 0; |
| tp->snd_cwnd_stamp = tcp_time_stamp; |
| |
| tcp_clear_retrans_partial(tp); |
| |
| if (tcp_is_reno(tp)) |
| tcp_reset_reno_sack(tp); |
| |
| tp->undo_marker = tp->snd_una; |
| if (how) { |
| tp->sacked_out = 0; |
| tp->fackets_out = 0; |
| } |
| tcp_clear_all_retrans_hints(tp); |
| |
| tcp_for_write_queue(skb, sk) { |
| if (skb == tcp_send_head(sk)) |
| break; |
| |
| if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) |
| tp->undo_marker = 0; |
| TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED; |
| if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) { |
| TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED; |
| TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; |
| tp->lost_out += tcp_skb_pcount(skb); |
| tp->retransmit_high = TCP_SKB_CB(skb)->end_seq; |
| } |
| } |
| tcp_verify_left_out(tp); |
| |
| tp->reordering = min_t(unsigned int, tp->reordering, |
| sysctl_tcp_reordering); |
| tcp_set_ca_state(sk, TCP_CA_Loss); |
| tp->high_seq = tp->snd_nxt; |
| TCP_ECN_queue_cwr(tp); |
| |
| /* F-RTO RFC5682 sec 3.1 step 1: retransmit SND.UNA if no previous |
| * loss recovery is underway except recurring timeout(s) on |
| * the same SND.UNA (sec 3.2). Disable F-RTO on path MTU probing |
| */ |
| tp->frto = sysctl_tcp_frto && |
| (new_recovery || icsk->icsk_retransmits) && |
| !inet_csk(sk)->icsk_mtup.probe_size; |
| } |
| |
| /* If ACK arrived pointing to a remembered SACK, it means that our |
| * remembered SACKs do not reflect real state of receiver i.e. |
| * receiver _host_ is heavily congested (or buggy). |
| * |
| * Do processing similar to RTO timeout. |
| */ |
| static bool tcp_check_sack_reneging(struct sock *sk, int flag) |
| { |
| if (flag & FLAG_SACK_RENEGING) { |
| struct inet_connection_sock *icsk = inet_csk(sk); |
| NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSACKRENEGING); |
| |
| tcp_enter_loss(sk, 1); |
| icsk->icsk_retransmits++; |
| tcp_retransmit_skb(sk, tcp_write_queue_head(sk)); |
| inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, |
| icsk->icsk_rto, TCP_RTO_MAX); |
| return true; |
| } |
| return false; |
| } |
| |
| static inline int tcp_fackets_out(const struct tcp_sock *tp) |
| { |
| return tcp_is_reno(tp) ? tp->sacked_out + 1 : tp->fackets_out; |
| } |
| |
| /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs |
| * counter when SACK is enabled (without SACK, sacked_out is used for |
| * that purpose). |
| * |
| * Instead, with FACK TCP uses fackets_out that includes both SACKed |
| * segments up to the highest received SACK block so far and holes in |
| * between them. |
| * |
| * With reordering, holes may still be in flight, so RFC3517 recovery |
| * uses pure sacked_out (total number of SACKed segments) even though |
| * it violates the RFC that uses duplicate ACKs, often these are equal |
| * but when e.g. out-of-window ACKs or packet duplication occurs, |
| * they differ. Since neither occurs due to loss, TCP should really |
| * ignore them. |
| */ |
| static inline int tcp_dupack_heuristics(const struct tcp_sock *tp) |
| { |
| return tcp_is_fack(tp) ? tp->fackets_out : tp->sacked_out + 1; |
| } |
| |
| static bool tcp_pause_early_retransmit(struct sock *sk, int flag) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| unsigned long delay; |
| |
| /* Delay early retransmit and entering fast recovery for |
| * max(RTT/4, 2msec) unless ack has ECE mark, no RTT samples |
| * available, or RTO is scheduled to fire first. |
| */ |
| if (sysctl_tcp_early_retrans < 2 || sysctl_tcp_early_retrans > 3 || |
| (flag & FLAG_ECE) || !tp->srtt) |
| return false; |
| |
| delay = max_t(unsigned long, (tp->srtt >> 5), msecs_to_jiffies(2)); |
| if (!time_after(inet_csk(sk)->icsk_timeout, (jiffies + delay))) |
| return false; |
| |
| inet_csk_reset_xmit_timer(sk, ICSK_TIME_EARLY_RETRANS, delay, |
| TCP_RTO_MAX); |
| return true; |
| } |
| |
| static inline int tcp_skb_timedout(const struct sock *sk, |
| const struct sk_buff *skb) |
| { |
| return tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto; |
| } |
| |
| static inline int tcp_head_timedout(const struct sock *sk) |
| { |
| const struct tcp_sock *tp = tcp_sk(sk); |
| |
| return tp->packets_out && |
| tcp_skb_timedout(sk, tcp_write_queue_head(sk)); |
| } |
| |
| /* Linux NewReno/SACK/FACK/ECN state machine. |
| * -------------------------------------- |
| * |
| * "Open" Normal state, no dubious events, fast path. |
| * "Disorder" In all the respects it is "Open", |
| * but requires a bit more attention. It is entered when |
| * we see some SACKs or dupacks. It is split of "Open" |
| * mainly to move some processing from fast path to slow one. |
| * "CWR" CWND was reduced due to some Congestion Notification event. |
| * It can be ECN, ICMP source quench, local device congestion. |
| * "Recovery" CWND was reduced, we are fast-retransmitting. |
| * "Loss" CWND was reduced due to RTO timeout or SACK reneging. |
| * |
| * tcp_fastretrans_alert() is entered: |
| * - each incoming ACK, if state is not "Open" |
| * - when arrived ACK is unusual, namely: |
| * * SACK |
| * * Duplicate ACK. |
| * * ECN ECE. |
| * |
| * Counting packets in flight is pretty simple. |
| * |
| * in_flight = packets_out - left_out + retrans_out |
| * |
| * packets_out is SND.NXT-SND.UNA counted in packets. |
| * |
| * retrans_out is number of retransmitted segments. |
| * |
| * left_out is number of segments left network, but not ACKed yet. |
| * |
| * left_out = sacked_out + lost_out |
| * |
| * sacked_out: Packets, which arrived to receiver out of order |
| * and hence not ACKed. With SACKs this number is simply |
| * amount of SACKed data. Even without SACKs |
| * it is easy to give pretty reliable estimate of this number, |
| * counting duplicate ACKs. |
| * |
| * lost_out: Packets lost by network. TCP has no explicit |
| * "loss notification" feedback from network (for now). |
| * It means that this number can be only _guessed_. |
| * Actually, it is the heuristics to predict lossage that |
| * distinguishes different algorithms. |
| * |
| * F.e. after RTO, when all the queue is considered as lost, |
| * lost_out = packets_out and in_flight = retrans_out. |
| * |
| * Essentially, we have now two algorithms counting |
| * lost packets. |
| * |
| * FACK: It is the simplest heuristics. As soon as we decided |
| * that something is lost, we decide that _all_ not SACKed |
| * packets until the most forward SACK are lost. I.e. |
| * lost_out = fackets_out - sacked_out and left_out = fackets_out. |
| * It is absolutely correct estimate, if network does not reorder |
| * packets. And it loses any connection to reality when reordering |
| * takes place. We use FACK by default until reordering |
| * is suspected on the path to this destination. |
| * |
| * NewReno: when Recovery is entered, we assume that one segment |
| * is lost (classic Reno). While we are in Recovery and |
| * a partial ACK arrives, we assume that one more packet |
| * is lost (NewReno). This heuristics are the same in NewReno |
| * and SACK. |
| * |
| * Imagine, that's all! Forget about all this shamanism about CWND inflation |
| * deflation etc. CWND is real congestion window, never inflated, changes |
| * only according to classic VJ rules. |
| * |
| * Really tricky (and requiring careful tuning) part of algorithm |
| * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue(). |
| * The first determines the moment _when_ we should reduce CWND and, |
| * hence, slow down forward transmission. In fact, it determines the moment |
| * when we decide that hole is caused by loss, rather than by a reorder. |
| * |
| * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill |
| * holes, caused by lost packets. |
| * |
| * And the most logically complicated part of algorithm is undo |
| * heuristics. We detect false retransmits due to both too early |
| * fast retransmit (reordering) and underestimated RTO, analyzing |
| * timestamps and D-SACKs. When we detect that some segments were |
| * retransmitted by mistake and CWND reduction was wrong, we undo |
| * window reduction and abort recovery phase. This logic is hidden |
| * inside several functions named tcp_try_undo_<something>. |
| */ |
| |
| /* This function decides, when we should leave Disordered state |
| * and enter Recovery phase, reducing congestion window. |
| * |
| * Main question: may we further continue forward transmission |
| * with the same cwnd? |
| */ |
| static bool tcp_time_to_recover(struct sock *sk, int flag) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| __u32 packets_out; |
| |
| /* Trick#1: The loss is proven. */ |
| if (tp->lost_out) |
| return true; |
| |
| /* Not-A-Trick#2 : Classic rule... */ |
| if (tcp_dupack_heuristics(tp) > tp->reordering) |
| return true; |
| |
| /* Trick#3 : when we use RFC2988 timer restart, fast |
| * retransmit can be triggered by timeout of queue head. |
| */ |
| if (tcp_is_fack(tp) && tcp_head_timedout(sk)) |
| return true; |
| |
| /* Trick#4: It is still not OK... But will it be useful to delay |
| * recovery more? |
| */ |
| packets_out = tp->packets_out; |
| if (packets_out <= tp->reordering && |
| tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) && |
| !tcp_may_send_now(sk)) { |
| /* We have nothing to send. This connection is limited |
| * either by receiver window or by application. |
| */ |
| return true; |
| } |
| |
| /* If a thin stream is detected, retransmit after first |
| * received dupack. Employ only if SACK is supported in order |
| * to avoid possible corner-case series of spurious retransmissions |
| * Use only if there are no unsent data. |
| */ |
| if ((tp->thin_dupack || sysctl_tcp_thin_dupack) && |
| tcp_stream_is_thin(tp) && tcp_dupack_heuristics(tp) > 1 && |
| tcp_is_sack(tp) && !tcp_send_head(sk)) |
| return true; |
| |
| /* Trick#6: TCP early retransmit, per RFC5827. To avoid spurious |
| * retransmissions due to small network reorderings, we implement |
| * Mitigation A.3 in the RFC and delay the retransmission for a short |
| * interval if appropriate. |
| */ |
| if (tp->do_early_retrans && !tp->retrans_out && tp->sacked_out && |
| (tp->packets_out >= (tp->sacked_out + 1) && tp->packets_out < 4) && |
| !tcp_may_send_now(sk)) |
| return !tcp_pause_early_retransmit(sk, flag); |
| |
| return false; |
| } |
| |
| /* New heuristics: it is possible only after we switched to restart timer |
| * each time when something is ACKed. Hence, we can detect timed out packets |
| * during fast retransmit without falling to slow start. |
| * |
| * Usefulness of this as is very questionable, since we should know which of |
| * the segments is the next to timeout which is relatively expensive to find |
| * in general case unless we add some data structure just for that. The |
| * current approach certainly won't find the right one too often and when it |
| * finally does find _something_ it usually marks large part of the window |
| * right away (because a retransmission with a larger timestamp blocks the |
| * loop from advancing). -ij |
| */ |
| static void tcp_timeout_skbs(struct sock *sk) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| struct sk_buff *skb; |
| |
| if (!tcp_is_fack(tp) || !tcp_head_timedout(sk)) |
| return; |
| |
| skb = tp->scoreboard_skb_hint; |
| if (tp->scoreboard_skb_hint == NULL) |
| skb = tcp_write_queue_head(sk); |
| |
| tcp_for_write_queue_from(skb, sk) { |
| if (skb == tcp_send_head(sk)) |
| break; |
| if (!tcp_skb_timedout(sk, skb)) |
| break; |
| |
| tcp_skb_mark_lost(tp, skb); |
| } |
| |
| tp->scoreboard_skb_hint = skb; |
| |
| tcp_verify_left_out(tp); |
| } |
| |
| /* Detect loss in event "A" above by marking head of queue up as lost. |
| * For FACK or non-SACK(Reno) senders, the first "packets" number of segments |
| * are considered lost. For RFC3517 SACK, a segment is considered lost if it |
| * has at least tp->reordering SACKed seqments above it; "packets" refers to |
| * the maximum SACKed segments to pass before reaching this limit. |
| */ |
| static void tcp_mark_head_lost(struct sock *sk, int packets, int mark_head) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| struct sk_buff *skb; |
| int cnt, oldcnt; |
| int err; |
| unsigned int mss; |
| /* Use SACK to deduce losses of new sequences sent during recovery */ |
| const u32 loss_high = tcp_is_sack(tp) ? tp->snd_nxt : tp->high_seq; |
| |
| WARN_ON(packets > tp->packets_out); |
| if (tp->lost_skb_hint) { |
| skb = tp->lost_skb_hint; |
| cnt = tp->lost_cnt_hint; |
| /* Head already handled? */ |
| if (mark_head && skb != tcp_write_queue_head(sk)) |
| return; |
| } else { |
| skb = tcp_write_queue_head(sk); |
| cnt = 0; |
| } |
| |
| tcp_for_write_queue_from(skb, sk) { |
| if (skb == tcp_send_head(sk)) |
| break; |
| /* TODO: do this better */ |
| /* this is not the most efficient way to do this... */ |
| tp->lost_skb_hint = skb; |
| tp->lost_cnt_hint = cnt; |
| |
| if (after(TCP_SKB_CB(skb)->end_seq, loss_high)) |
| break; |
| |
| oldcnt = cnt; |
| if (tcp_is_fack(tp) || tcp_is_reno(tp) || |
| (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) |
| cnt += tcp_skb_pcount(skb); |
| |
| if (cnt > packets) { |
| if ((tcp_is_sack(tp) && !tcp_is_fack(tp)) || |
| (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) || |
| (oldcnt >= packets)) |
| break; |
| |
| mss = skb_shinfo(skb)->gso_size; |
| err = tcp_fragment(sk, skb, (packets - oldcnt) * mss, mss); |
| if (err < 0) |
| break; |
| cnt = packets; |
| } |
| |
| tcp_skb_mark_lost(tp, skb); |
| |
| if (mark_head) |
| break; |
| } |
| tcp_verify_left_out(tp); |
| } |
| |
| /* Account newly detected lost packet(s) */ |
| |
| static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| |
| if (tcp_is_reno(tp)) { |
| tcp_mark_head_lost(sk, 1, 1); |
| } else if (tcp_is_fack(tp)) { |
| int lost = tp->fackets_out - tp->reordering; |
| if (lost <= 0) |
| lost = 1; |
| tcp_mark_head_lost(sk, lost, 0); |
| } else { |
| int sacked_upto = tp->sacked_out - tp->reordering; |
| if (sacked_upto >= 0) |
| tcp_mark_head_lost(sk, sacked_upto, 0); |
| else if (fast_rexmit) |
| tcp_mark_head_lost(sk, 1, 1); |
| } |
| |
| tcp_timeout_skbs(sk); |
| } |
| |
| /* CWND moderation, preventing bursts due to too big ACKs |
| * in dubious situations. |
| */ |
| static inline void tcp_moderate_cwnd(struct tcp_sock *tp) |
| { |
| tp->snd_cwnd = min(tp->snd_cwnd, |
| tcp_packets_in_flight(tp) + tcp_max_burst(tp)); |
| tp->snd_cwnd_stamp = tcp_time_stamp; |
| } |
| |
| /* Nothing was retransmitted or returned timestamp is less |
| * than timestamp of the first retransmission. |
| */ |
| static inline bool tcp_packet_delayed(const struct tcp_sock *tp) |
| { |
| return !tp->retrans_stamp || |
| (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && |
| before(tp->rx_opt.rcv_tsecr, tp->retrans_stamp)); |
| } |
| |
| /* Undo procedures. */ |
| |
| #if FASTRETRANS_DEBUG > 1 |
| static void DBGUNDO(struct sock *sk, const char *msg) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| struct inet_sock *inet = inet_sk(sk); |
| |
| if (sk->sk_family == AF_INET) { |
| pr_debug("Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n", |
| msg, |
| &inet->inet_daddr, ntohs(inet->inet_dport), |
| tp->snd_cwnd, tcp_left_out(tp), |
| tp->snd_ssthresh, tp->prior_ssthresh, |
| tp->packets_out); |
| } |
| #if IS_ENABLED(CONFIG_IPV6) |
| else if (sk->sk_family == AF_INET6) { |
| struct ipv6_pinfo *np = inet6_sk(sk); |
| pr_debug("Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n", |
| msg, |
| &np->daddr, ntohs(inet->inet_dport), |
| tp->snd_cwnd, tcp_left_out(tp), |
| tp->snd_ssthresh, tp->prior_ssthresh, |
| tp->packets_out); |
| } |
| #endif |
| } |
| #else |
| #define DBGUNDO(x...) do { } while (0) |
| #endif |
| |
| static void tcp_undo_cwr(struct sock *sk, const bool undo_ssthresh) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| |
| if (tp->prior_ssthresh) { |
| const struct inet_connection_sock *icsk = inet_csk(sk); |
| |
| if (icsk->icsk_ca_ops->undo_cwnd) |
| tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk); |
| else |
| tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh << 1); |
| |
| if (undo_ssthresh && tp->prior_ssthresh > tp->snd_ssthresh) { |
| tp->snd_ssthresh = tp->prior_ssthresh; |
| TCP_ECN_withdraw_cwr(tp); |
| } |
| } else { |
| tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh); |
| } |
| tp->snd_cwnd_stamp = tcp_time_stamp; |
| } |
| |
| static inline bool tcp_may_undo(const struct tcp_sock *tp) |
| { |
| return tp->undo_marker && (!tp->undo_retrans || tcp_packet_delayed(tp)); |
| } |
| |
| /* People celebrate: "We love our President!" */ |
| static bool tcp_try_undo_recovery(struct sock *sk) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| |
| if (tcp_may_undo(tp)) { |
| int mib_idx; |
| |
| /* Happy end! We did not retransmit anything |
| * or our original transmission succeeded. |
| */ |
| DBGUNDO(sk, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans"); |
| tcp_undo_cwr(sk, true); |
| if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss) |
| mib_idx = LINUX_MIB_TCPLOSSUNDO; |
| else |
| mib_idx = LINUX_MIB_TCPFULLUNDO; |
| |
| NET_INC_STATS_BH(sock_net(sk), mib_idx); |
| tp->undo_marker = 0; |
| } |
| if (tp->snd_una == tp->high_seq && tcp_is_reno(tp)) { |
| /* Hold old state until something *above* high_seq |
| * is ACKed. For Reno it is MUST to prevent false |
| * fast retransmits (RFC2582). SACK TCP is safe. */ |
| tcp_moderate_cwnd(tp); |
| return true; |
| } |
| tcp_set_ca_state(sk, TCP_CA_Open); |
| return false; |
| } |
| |
| /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */ |
| static void tcp_try_undo_dsack(struct sock *sk) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| |
| if (tp->undo_marker && !tp->undo_retrans) { |
| DBGUNDO(sk, "D-SACK"); |
| tcp_undo_cwr(sk, true); |
| tp->undo_marker = 0; |
| NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKUNDO); |
| } |
| } |
| |
| /* We can clear retrans_stamp when there are no retransmissions in the |
| * window. It would seem that it is trivially available for us in |
| * tp->retrans_out, however, that kind of assumptions doesn't consider |
| * what will happen if errors occur when sending retransmission for the |
| * second time. ...It could the that such segment has only |
| * TCPCB_EVER_RETRANS set at the present time. It seems that checking |
| * the head skb is enough except for some reneging corner cases that |
| * are not worth the effort. |
| * |
| * Main reason for all this complexity is the fact that connection dying |
| * time now depends on the validity of the retrans_stamp, in particular, |
| * that successive retransmissions of a segment must not advance |
| * retrans_stamp under any conditions. |
| */ |
| static bool tcp_any_retrans_done(const struct sock *sk) |
| { |
| const struct tcp_sock *tp = tcp_sk(sk); |
| struct sk_buff *skb; |
| |
| if (tp->retrans_out) |
| return true; |
| |
| skb = tcp_write_queue_head(sk); |
| if (unlikely(skb && TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS)) |
| return true; |
| |
| return false; |
| } |
| |
| /* Undo during fast recovery after partial ACK. */ |
| |
| static int tcp_try_undo_partial(struct sock *sk, int acked) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| /* Partial ACK arrived. Force Hoe's retransmit. */ |
| int failed = tcp_is_reno(tp) || (tcp_fackets_out(tp) > tp->reordering); |
| |
| if (tcp_may_undo(tp)) { |
| /* Plain luck! Hole if filled with delayed |
| * packet, rather than with a retransmit. |
| */ |
| if (!tcp_any_retrans_done(sk)) |
| tp->retrans_stamp = 0; |
| |
| tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1); |
| |
| DBGUNDO(sk, "Hoe"); |
| tcp_undo_cwr(sk, false); |
| NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPARTIALUNDO); |
| |
| /* So... Do not make Hoe's retransmit yet. |
| * If the first packet was delayed, the rest |
| * ones are most probably delayed as well. |
| */ |
| failed = 0; |
| } |
| return failed; |
| } |
| |
| /* Undo during loss recovery after partial ACK or using F-RTO. */ |
| static bool tcp_try_undo_loss(struct sock *sk, bool frto_undo) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| |
| if (frto_undo || tcp_may_undo(tp)) { |
| struct sk_buff *skb; |
| tcp_for_write_queue(skb, sk) { |
| if (skb == tcp_send_head(sk)) |
| break; |
| TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; |
| } |
| |
| tcp_clear_all_retrans_hints(tp); |
| |
| DBGUNDO(sk, "partial loss"); |
| tp->lost_out = 0; |
| tcp_undo_cwr(sk, true); |
| NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSSUNDO); |
| if (frto_undo) |
| NET_INC_STATS_BH(sock_net(sk), |
| LINUX_MIB_TCPSPURIOUSRTOS); |
| inet_csk(sk)->icsk_retransmits = 0; |
| tp->undo_marker = 0; |
| if (frto_undo || tcp_is_sack(tp)) |
| tcp_set_ca_state(sk, TCP_CA_Open); |
| return true; |
| } |
| return false; |
| } |
| |
| /* The cwnd reduction in CWR and Recovery use the PRR algorithm |
| * https://datatracker.ietf.org/doc/draft-ietf-tcpm-proportional-rate-reduction/ |
| * It computes the number of packets to send (sndcnt) based on packets newly |
| * delivered: |
| * 1) If the packets in flight is larger than ssthresh, PRR spreads the |
| * cwnd reductions across a full RTT. |
| * 2) If packets in flight is lower than ssthresh (such as due to excess |
| * losses and/or application stalls), do not perform any further cwnd |
| * reductions, but instead slow start up to ssthresh. |
| */ |
| static void tcp_init_cwnd_reduction(struct sock *sk, const bool set_ssthresh) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| |
| tp->high_seq = tp->snd_nxt; |
| tp->tlp_high_seq = 0; |
| tp->snd_cwnd_cnt = 0; |
| tp->prior_cwnd = tp->snd_cwnd; |
| tp->prr_delivered = 0; |
| tp->prr_out = 0; |
| if (set_ssthresh) |
| tp->snd_ssthresh = inet_csk(sk)->icsk_ca_ops->ssthresh(sk); |
| TCP_ECN_queue_cwr(tp); |
| } |
| |
| static void tcp_cwnd_reduction(struct sock *sk, int newly_acked_sacked, |
| int fast_rexmit) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| int sndcnt = 0; |
| int delta = tp->snd_ssthresh - tcp_packets_in_flight(tp); |
| |
| tp->prr_delivered += newly_acked_sacked; |
| if (tcp_packets_in_flight(tp) > tp->snd_ssthresh) { |
| u64 dividend = (u64)tp->snd_ssthresh * tp->prr_delivered + |
| tp->prior_cwnd - 1; |
| sndcnt = div_u64(dividend, tp->prior_cwnd) - tp->prr_out; |
| } else { |
| sndcnt = min_t(int, delta, |
| max_t(int, tp->prr_delivered - tp->prr_out, |
| newly_acked_sacked) + 1); |
| } |
| |
| sndcnt = max(sndcnt, (fast_rexmit ? 1 : 0)); |
| tp->snd_cwnd = tcp_packets_in_flight(tp) + sndcnt; |
| } |
| |
| static inline void tcp_end_cwnd_reduction(struct sock *sk) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| |
| /* Reset cwnd to ssthresh in CWR or Recovery (unless it's undone) */ |
| if (inet_csk(sk)->icsk_ca_state == TCP_CA_CWR || |
| (tp->undo_marker && tp->snd_ssthresh < TCP_INFINITE_SSTHRESH)) { |
| tp->snd_cwnd = tp->snd_ssthresh; |
| tp->snd_cwnd_stamp = tcp_time_stamp; |
| } |
| tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR); |
| } |
| |
| /* Enter CWR state. Disable cwnd undo since congestion is proven with ECN */ |
| void tcp_enter_cwr(struct sock *sk, const int set_ssthresh) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| |
| tp->prior_ssthresh = 0; |
| if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) { |
| tp->undo_marker = 0; |
| tcp_init_cwnd_reduction(sk, set_ssthresh); |
| tcp_set_ca_state(sk, TCP_CA_CWR); |
| } |
| } |
| |
| static void tcp_try_keep_open(struct sock *sk) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| int state = TCP_CA_Open; |
| |
| if (tcp_left_out(tp) || tcp_any_retrans_done(sk)) |
| state = TCP_CA_Disorder; |
| |
| if (inet_csk(sk)->icsk_ca_state != state) { |
| tcp_set_ca_state(sk, state); |
| tp->high_seq = tp->snd_nxt; |
| } |
| } |
| |
| static void tcp_try_to_open(struct sock *sk, int flag, int newly_acked_sacked) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| |
| tcp_verify_left_out(tp); |
| |
| if (!tcp_any_retrans_done(sk)) |
| tp->retrans_stamp = 0; |
| |
| if (flag & FLAG_ECE) |
| tcp_enter_cwr(sk, 1); |
| |
| if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) { |
| tcp_try_keep_open(sk); |
| if (inet_csk(sk)->icsk_ca_state != TCP_CA_Open) |
| tcp_moderate_cwnd(tp); |
| } else { |
| tcp_cwnd_reduction(sk, newly_acked_sacked, 0); |
| } |
| } |
| |
| static void tcp_mtup_probe_failed(struct sock *sk) |
| { |
| struct inet_connection_sock *icsk = inet_csk(sk); |
| |
| icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1; |
| icsk->icsk_mtup.probe_size = 0; |
| } |
| |
| static void tcp_mtup_probe_success(struct sock *sk) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| struct inet_connection_sock *icsk = inet_csk(sk); |
| |
| /* FIXME: breaks with very large cwnd */ |
| tp->prior_ssthresh = tcp_current_ssthresh(sk); |
| tp->snd_cwnd = tp->snd_cwnd * |
| tcp_mss_to_mtu(sk, tp->mss_cache) / |
| icsk->icsk_mtup.probe_size; |
| tp->snd_cwnd_cnt = 0; |
| tp->snd_cwnd_stamp = tcp_time_stamp; |
| tp->snd_ssthresh = tcp_current_ssthresh(sk); |
| |
| icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size; |
| icsk->icsk_mtup.probe_size = 0; |
| tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); |
| } |
| |
| /* Do a simple retransmit without using the backoff mechanisms in |
| * tcp_timer. This is used for path mtu discovery. |
| * The socket is already locked here. |
| */ |
| void tcp_simple_retransmit(struct sock *sk) |
| { |
| const struct inet_connection_sock *icsk = inet_csk(sk); |
| struct tcp_sock *tp = tcp_sk(sk); |
| struct sk_buff *skb; |
| unsigned int mss = tcp_current_mss(sk); |
| u32 prior_lost = tp->lost_out; |
| |
| tcp_for_write_queue(skb, sk) { |
| if (skb == tcp_send_head(sk)) |
| break; |
| if (tcp_skb_seglen(skb) > mss && |
| !(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) { |
| if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) { |
| TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; |
| tp->retrans_out -= tcp_skb_pcount(skb); |
| } |
| tcp_skb_mark_lost_uncond_verify(tp, skb); |
| } |
| } |
| |
| tcp_clear_retrans_hints_partial(tp); |
| |
| if (prior_lost == tp->lost_out) |
| return; |
| |
| if (tcp_is_reno(tp)) |
| tcp_limit_reno_sacked(tp); |
| |
| tcp_verify_left_out(tp); |
| |
| /* Don't muck with the congestion window here. |
| * Reason is that we do not increase amount of _data_ |
| * in network, but units changed and effective |
| * cwnd/ssthresh really reduced now. |
| */ |
| if (icsk->icsk_ca_state != TCP_CA_Loss) { |
| tp->high_seq = tp->snd_nxt; |
| tp->snd_ssthresh = tcp_current_ssthresh(sk); |
| tp->prior_ssthresh = 0; |
| tp->undo_marker = 0; |
| tcp_set_ca_state(sk, TCP_CA_Loss); |
| } |
| tcp_xmit_retransmit_queue(sk); |
| } |
| EXPORT_SYMBOL(tcp_simple_retransmit); |
| |
| static void tcp_enter_recovery(struct sock *sk, bool ece_ack) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| int mib_idx; |
| |
| if (tcp_is_reno(tp)) |
| mib_idx = LINUX_MIB_TCPRENORECOVERY; |
| else |
| mib_idx = LINUX_MIB_TCPSACKRECOVERY; |
| |
| NET_INC_STATS_BH(sock_net(sk), mib_idx); |
| |
| tp->prior_ssthresh = 0; |
| tp->undo_marker = tp->snd_una; |
| tp->undo_retrans = tp->retrans_out; |
| |
| if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) { |
| if (!ece_ack) |
| tp->prior_ssthresh = tcp_current_ssthresh(sk); |
| tcp_init_cwnd_reduction(sk, true); |
| } |
| tcp_set_ca_state(sk, TCP_CA_Recovery); |
| } |
| |
| /* Process an ACK in CA_Loss state. Move to CA_Open if lost data are |
| * recovered or spurious. Otherwise retransmits more on partial ACKs. |
| */ |
| static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack) |
| { |
| struct inet_connection_sock *icsk = inet_csk(sk); |
| struct tcp_sock *tp = tcp_sk(sk); |
| bool recovered = !before(tp->snd_una, tp->high_seq); |
| |
| if (tp->frto) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */ |
| /* Step 3.b. A timeout is spurious if not all data are |
| * lost, i.e., never-retransmitted data are (s)acked. |
| */ |
| if (tcp_try_undo_loss(sk, flag & FLAG_ORIG_SACK_ACKED)) |
| return; |
| |
| if (after(tp->snd_nxt, tp->high_seq) && |
| (flag & FLAG_DATA_SACKED || is_dupack)) { |
| tp->frto = 0; /* Loss was real: 2nd part of step 3.a */ |
| } else if (flag & FLAG_SND_UNA_ADVANCED && !recovered) { |
| tp->high_seq = tp->snd_nxt; |
| __tcp_push_pending_frames(sk, tcp_current_mss(sk), |
| TCP_NAGLE_OFF); |
| if (after(tp->snd_nxt, tp->high_seq)) |
| return; /* Step 2.b */ |
| tp->frto = 0; |
| } |
| } |
| |
| if (recovered) { |
| /* F-RTO RFC5682 sec 3.1 step 2.a and 1st part of step 3.a */ |
| icsk->icsk_retransmits = 0; |
| tcp_try_undo_recovery(sk); |
| return; |
| } |
| if (flag & FLAG_DATA_ACKED) |
| icsk->icsk_retransmits = 0; |
| if (tcp_is_reno(tp)) { |
| /* A Reno DUPACK means new data in F-RTO step 2.b above are |
| * delivered. Lower inflight to clock out (re)tranmissions. |
| */ |
| if (after(tp->snd_nxt, tp->high_seq) && is_dupack) |
| tcp_add_reno_sack(sk); |
| else if (flag & FLAG_SND_UNA_ADVANCED) |
| tcp_reset_reno_sack(tp); |
| } |
| if (tcp_try_undo_loss(sk, false)) |
| return; |
| tcp_xmit_retransmit_queue(sk); |
| } |
| |
| /* Process an event, which can update packets-in-flight not trivially. |
| * Main goal of this function is to calculate new estimate for left_out, |
| * taking into account both packets sitting in receiver's buffer and |
| * packets lost by network. |
| * |
| * Besides that it does CWND reduction, when packet loss is detected |
| * and changes state of machine. |
| * |
| * It does _not_ decide what to send, it is made in function |
| * tcp_xmit_retransmit_queue(). |
| */ |
| static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked, |
| int prior_sacked, int prior_packets, |
| bool is_dupack, int flag) |
| { |
| struct inet_connection_sock *icsk = inet_csk(sk); |
| struct tcp_sock *tp = tcp_sk(sk); |
| int do_lost = is_dupack || ((flag & FLAG_DATA_SACKED) && |
| (tcp_fackets_out(tp) > tp->reordering)); |
| int newly_acked_sacked = 0; |
| int fast_rexmit = 0; |
| |
| if (WARN_ON(!tp->packets_out && tp->sacked_out)) |
| tp->sacked_out = 0; |
| if (WARN_ON(!tp->sacked_out && tp->fackets_out)) |
| tp->fackets_out = 0; |
| |
| /* Now state machine starts. |
| * A. ECE, hence prohibit cwnd undoing, the reduction is required. */ |
| if (flag & FLAG_ECE) |
| tp->prior_ssthresh = 0; |
| |
| /* B. In all the states check for reneging SACKs. */ |
| if (tcp_check_sack_reneging(sk, flag)) |
| return; |
| |
| /* C. Check consistency of the current state. */ |
| tcp_verify_left_out(tp); |
| |
| /* D. Check state exit conditions. State can be terminated |
| * when high_seq is ACKed. */ |
| if (icsk->icsk_ca_state == TCP_CA_Open) { |
| WARN_ON(tp->retrans_out != 0); |
| tp->retrans_stamp = 0; |
| } else if (!before(tp->snd_una, tp->high_seq)) { |
| switch (icsk->icsk_ca_state) { |
| case TCP_CA_CWR: |
| /* CWR is to be held something *above* high_seq |
| * is ACKed for CWR bit to reach receiver. */ |
| if (tp->snd_una != tp->high_seq) { |
| tcp_end_cwnd_reduction(sk); |
| tcp_set_ca_state(sk, TCP_CA_Open); |
| } |
| break; |
| |
| case TCP_CA_Recovery: |
| if (tcp_is_reno(tp)) |
| tcp_reset_reno_sack(tp); |
| if (tcp_try_undo_recovery(sk)) |
| return; |
| tcp_end_cwnd_reduction(sk); |
| break; |
| } |
| } |
| |
| /* E. Process state. */ |
| switch (icsk->icsk_ca_state) { |
| case TCP_CA_Recovery: |
| if (!(flag & FLAG_SND_UNA_ADVANCED)) { |
| if (tcp_is_reno(tp) && is_dupack) |
| tcp_add_reno_sack(sk); |
| } else |
| do_lost = tcp_try_undo_partial(sk, pkts_acked); |
| newly_acked_sacked = prior_packets - tp->packets_out + |
| tp->sacked_out - prior_sacked; |
| break; |
| case TCP_CA_Loss: |
| tcp_process_loss(sk, flag, is_dupack); |
| if (icsk->icsk_ca_state != TCP_CA_Open) |
| return; |
| /* Fall through to processing in Open state. */ |
| default: |
| if (tcp_is_reno(tp)) { |
| if (flag & FLAG_SND_UNA_ADVANCED) |
| tcp_reset_reno_sack(tp); |
| if (is_dupack) |
| tcp_add_reno_sack(sk); |
| } |
| newly_acked_sacked = prior_packets - tp->packets_out + |
| tp->sacked_out - prior_sacked; |
| |
| if (icsk->icsk_ca_state <= TCP_CA_Disorder) |
| tcp_try_undo_dsack(sk); |
| |
| if (!tcp_time_to_recover(sk, flag)) { |
| tcp_try_to_open(sk, flag, newly_acked_sacked); |
| return; |
| } |
| |
| /* MTU probe failure: don't reduce cwnd */ |
| if (icsk->icsk_ca_state < TCP_CA_CWR && |
| icsk->icsk_mtup.probe_size && |
| tp->snd_una == tp->mtu_probe.probe_seq_start) { |
| tcp_mtup_probe_failed(sk); |
| /* Restores the reduction we did in tcp_mtup_probe() */ |
| tp->snd_cwnd++; |
| tcp_simple_retransmit(sk); |
| return; |
| } |
| |
| /* Otherwise enter Recovery state */ |
| tcp_enter_recovery(sk, (flag & FLAG_ECE)); |
| fast_rexmit = 1; |
| } |
| |
| if (do_lost || (tcp_is_fack(tp) && tcp_head_timedout(sk))) |
| tcp_update_scoreboard(sk, fast_rexmit); |
| tcp_cwnd_reduction(sk, newly_acked_sacked, fast_rexmit); |
| tcp_xmit_retransmit_queue(sk); |
| } |
| |
| void tcp_valid_rtt_meas(struct sock *sk, u32 seq_rtt) |
| { |
| tcp_rtt_estimator(sk, seq_rtt); |
| tcp_set_rto(sk); |
| inet_csk(sk)->icsk_backoff = 0; |
| } |
| EXPORT_SYMBOL(tcp_valid_rtt_meas); |
| |
| /* Read draft-ietf-tcplw-high-performance before mucking |
| * with this code. (Supersedes RFC1323) |
| */ |
| static void tcp_ack_saw_tstamp(struct sock *sk, int flag) |
| { |
| /* RTTM Rule: A TSecr value received in a segment is used to |
| * update the averaged RTT measurement only if the segment |
| * acknowledges some new data, i.e., only if it advances the |
| * left edge of the send window. |
| * |
| * See draft-ietf-tcplw-high-performance-00, section 3.3. |
| * 1998/04/10 Andrey V. Savochkin <saw@msu.ru> |
| * |
| * Changed: reset backoff as soon as we see the first valid sample. |
| * If we do not, we get strongly overestimated rto. With timestamps |
| * samples are accepted even from very old segments: f.e., when rtt=1 |
| * increases to 8, we retransmit 5 times and after 8 seconds delayed |
| * answer arrives rto becomes 120 seconds! If at least one of segments |
| * in window is lost... Voila. --ANK (010210) |
| */ |
| struct tcp_sock *tp = tcp_sk(sk); |
| |
| tcp_valid_rtt_meas(sk, tcp_time_stamp - tp->rx_opt.rcv_tsecr); |
| } |
| |
| static void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag) |
| { |
| /* We don't have a timestamp. Can only use |
| * packets that are not retransmitted to determine |
| * rtt estimates. Also, we must not reset the |
| * backoff for rto until we get a non-retransmitted |
| * packet. This allows us to deal with a situation |
| * where the network delay has increased suddenly. |
| * I.e. Karn's algorithm. (SIGCOMM '87, p5.) |
| */ |
| |
| if (flag & FLAG_RETRANS_DATA_ACKED) |
| return; |
| |
| tcp_valid_rtt_meas(sk, seq_rtt); |
| } |
| |
| static inline void tcp_ack_update_rtt(struct sock *sk, const int flag, |
| const s32 seq_rtt) |
| { |
| const struct tcp_sock *tp = tcp_sk(sk); |
| /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */ |
| if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr) |
| tcp_ack_saw_tstamp(sk, flag); |
| else if (seq_rtt >= 0) |
| tcp_ack_no_tstamp(sk, seq_rtt, flag); |
| } |
| |
| static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 in_flight) |
| { |
| const struct inet_connection_sock *icsk = inet_csk(sk); |
| icsk->icsk_ca_ops->cong_avoid(sk, ack, in_flight); |
| tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp; |
| } |
| |
| /* Restart timer after forward progress on connection. |
| * RFC2988 recommends to restart timer to now+rto. |
| */ |
| void tcp_rearm_rto(struct sock *sk) |
| { |
| const struct inet_connection_sock *icsk = inet_csk(sk); |
| struct tcp_sock *tp = tcp_sk(sk); |
| |
| /* If the retrans timer is currently being used by Fast Open |
| * for SYN-ACK retrans purpose, stay put. |
| */ |
| if (tp->fastopen_rsk) |
| return; |
| |
| if (!tp->packets_out) { |
| inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS); |
| } else { |
| u32 rto = inet_csk(sk)->icsk_rto; |
| /* Offset the time elapsed after installing regular RTO */ |
| if (icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS || |
| icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) { |
| struct sk_buff *skb = tcp_write_queue_head(sk); |
| const u32 rto_time_stamp = TCP_SKB_CB(skb)->when + rto; |
| s32 delta = (s32)(rto_time_stamp - tcp_time_stamp); |
| /* delta may not be positive if the socket is locked |
| * when the retrans timer fires and is rescheduled. |
| */ |
| if (delta > 0) |
| rto = delta; |
| } |
| inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, rto, |
| TCP_RTO_MAX); |
| } |
| } |
| |
| /* This function is called when the delayed ER timer fires. TCP enters |
| * fast recovery and performs fast-retransmit. |
| */ |
| void tcp_resume_early_retransmit(struct sock *sk) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| |
| tcp_rearm_rto(sk); |
| |
| /* Stop if ER is disabled after the delayed ER timer is scheduled */ |
| if (!tp->do_early_retrans) |
| return; |
| |
| tcp_enter_recovery(sk, false); |
| tcp_update_scoreboard(sk, 1); |
| tcp_xmit_retransmit_queue(sk); |
| } |
| |
| /* If we get here, the whole TSO packet has not been acked. */ |
| static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| u32 packets_acked; |
| |
| BUG_ON(!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)); |
| |
| packets_acked = tcp_skb_pcount(skb); |
| if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq)) |
| return 0; |
| packets_acked -= tcp_skb_pcount(skb); |
| |
| if (packets_acked) { |
| BUG_ON(tcp_skb_pcount(skb) == 0); |
| BUG_ON(!before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)); |
| } |
| |
| return packets_acked; |
| } |
| |
| /* Remove acknowledged frames from the retransmission queue. If our packet |
| * is before the ack sequence we can discard it as it's confirmed to have |
| * arrived at the other end. |
| */ |
| static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets, |
| u32 prior_snd_una) |
| { |
| struct tcp_sock *tp = tcp_sk(sk); |
| const struct inet_connection_sock *icsk = inet_csk(sk); |
| struct sk_buff *skb; |
| u32 now = tcp_time_stamp; |
| int fully_acked = true; |
| int flag = 0; |
| u32 pkts_acked = 0; |
| u32 reord = tp->packets_out; |
| u32 prior_sacked = tp->sacked_out; |
| s32 seq_rtt = -1; |
| s32 ca_seq_rtt = -1; |
| ktime_t last_ackt = net_invalid_timestamp(); |
| |
| while ((skb = tcp_write_queue_head(sk)) && skb != tcp_send_head(sk)) { |
| struct tcp_skb_cb *scb = TCP_SKB_CB(skb); |
| u32 acked_pcount; |
| u8 sacked = scb->sacked; |
| |
| /* Determine how many packets and what bytes were acked, tso and else */ |
| if (after(scb->end_seq, tp->snd_una)) { |
| if (tcp_skb_pcount(skb) == 1 || |
| !after(tp->snd_una, scb->seq)) |
| break; |
| |
| acked_pcount = tcp_tso_acked(sk, skb); |
| if (!acked_pcount) |
| break; |
| |
| fully_acked = false; |
| } else { |
| acked_pcount = tcp_skb_pcount(skb); |
| } |
| |
| if (sacked & TCPCB_RETRANS) { |
| if (sacked & TCPCB_SACKED_RETRANS) |
| tp->retrans_out -= acked_pcount; |
| flag |= FLAG_RETRANS_DATA_ACKED; |
| ca_seq_rtt = -1; |
| seq_rtt = -1; |
| } else { |
| ca_seq_rtt = now - scb->when; |
| last_ackt = skb->tstamp; |
| if (seq_rtt < 0) { |
| seq_rtt = ca_seq_rtt; |
| } |
| if (!(sacked & TCPCB_SACKED_ACKED)) |
| reord = min(pkts_acked, reord); |
| if (!after(scb->end_seq, tp->high_seq)) |
| flag |= FLAG_ORIG_SACK_ACKED; |
| } |
| |
| if (sacked & TCPCB_SACKED_ACKED) |
| tp->sacked_out -= acked_pcount; |
| if (sacked & TCPCB_LOST) |
| tp->lost_out -= acked_pcount; |
| |
| tp->packets_out -= acked_pcount; |
| pkts_acked += acked_pcount; |
| |
| /* Initial outgoing SYN's get put onto the write_queue |
| * just like anything else we transmit. It is not |
| * true data, and if we misinform our callers that |
| * this ACK acks real data, we will erroneously exit |
| * connection startup slow start one packet too |
| * quickly. This is severely frowned upon behavior. |
| */ |
| if (!(scb->tcp_flags & TCPHDR_SYN)) { |
| flag |= FLAG_DATA_ACKED; |
| } else { |
|