| /* |
| * Copyright 2012 Daniel Drown |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| * |
| * clatd.c - tun interface setup and main event loop |
| */ |
| #include <arpa/inet.h> |
| #include <errno.h> |
| #include <fcntl.h> |
| #include <poll.h> |
| #include <signal.h> |
| #include <stdio.h> |
| #include <stdlib.h> |
| #include <string.h> |
| #include <sys/ioctl.h> |
| #include <sys/prctl.h> |
| #include <sys/stat.h> |
| #include <sys/types.h> |
| #include <time.h> |
| #include <unistd.h> |
| |
| #include <linux/filter.h> |
| #include <linux/if.h> |
| #include <linux/if_ether.h> |
| #include <linux/if_packet.h> |
| #include <linux/if_tun.h> |
| #include <net/if.h> |
| #include <sys/capability.h> |
| #include <sys/uio.h> |
| |
| #include <private/android_filesystem_config.h> |
| |
| #include "clatd.h" |
| #include "config.h" |
| #include "dump.h" |
| #include "getaddr.h" |
| #include "logging.h" |
| #include "mtu.h" |
| #include "resolv_netid.h" |
| #include "ring.h" |
| #include "setif.h" |
| #include "translate.h" |
| #include "tun.h" |
| |
| /* 40 bytes IPv6 header - 20 bytes IPv4 header + 8 bytes fragment header */ |
| #define MTU_DELTA 28 |
| |
| volatile sig_atomic_t running = 1; |
| |
| /* function: stop_loop |
| * signal handler: stop the event loop |
| */ |
| void stop_loop() { running = 0; } |
| |
| /* function: configure_packet_socket |
| * Binds the packet socket and attaches the receive filter to it. |
| * sock - the socket to configure |
| */ |
| int configure_packet_socket(int sock) { |
| struct sockaddr_ll sll = { |
| .sll_family = AF_PACKET, |
| .sll_protocol = htons(ETH_P_IPV6), |
| .sll_ifindex = if_nametoindex(Global_Clatd_Config.default_pdp_interface), |
| .sll_pkttype = PACKET_OTHERHOST, // The 464xlat IPv6 address is not assigned to the kernel. |
| }; |
| if (bind(sock, (struct sockaddr *)&sll, sizeof(sll))) { |
| logmsg(ANDROID_LOG_FATAL, "binding packet socket: %s", strerror(errno)); |
| return 0; |
| } |
| |
| uint32_t *ipv6 = Global_Clatd_Config.ipv6_local_subnet.s6_addr32; |
| |
| // clang-format off |
| struct sock_filter filter_code[] = { |
| // Load the first four bytes of the IPv6 destination address (starts 24 bytes in). |
| // Compare it against the first four bytes of our IPv6 address, in host byte order (BPF loads |
| // are always in host byte order). If it matches, continue with next instruction (JMP 0). If it |
| // doesn't match, jump ahead to statement that returns 0 (ignore packet). Repeat for the other |
| // three words of the IPv6 address, and if they all match, return PACKETLEN (accept packet). |
| BPF_STMT(BPF_LD | BPF_W | BPF_ABS, 24), |
| BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, htonl(ipv6[0]), 0, 7), |
| BPF_STMT(BPF_LD | BPF_W | BPF_ABS, 28), |
| BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, htonl(ipv6[1]), 0, 5), |
| BPF_STMT(BPF_LD | BPF_W | BPF_ABS, 32), |
| BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, htonl(ipv6[2]), 0, 3), |
| BPF_STMT(BPF_LD | BPF_W | BPF_ABS, 36), |
| BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, htonl(ipv6[3]), 0, 1), |
| BPF_STMT(BPF_RET | BPF_K, PACKETLEN), |
| BPF_STMT(BPF_RET | BPF_K, 0), |
| }; |
| // clang-format on |
| struct sock_fprog filter = { sizeof(filter_code) / sizeof(filter_code[0]), filter_code }; |
| |
| if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter))) { |
| logmsg(ANDROID_LOG_FATAL, "attach packet filter failed: %s", strerror(errno)); |
| return 0; |
| } |
| |
| return 1; |
| } |
| |
| /* function: ipv4_address_generate |
| * picks a free IPv4 address from the local subnet or exits if there are no free addresses |
| * returns: the IPv4 address as an in_addr_t |
| */ |
| static in_addr_t ipv4_address_generate() { |
| // Pick an IPv4 address to use by finding a free address in the configured prefix. Technically, |
| // there is a race here - if another clatd calls config_select_ipv4_address after we do, but |
| // before we call add_address, it can end up having the same IP address as we do. But the time |
| // window in which this can happen is extremely small, and even if we end up with a duplicate |
| // address, the only damage is that IPv4 TCP connections won't be reset until both interfaces go |
| // down. |
| in_addr_t localaddr = config_select_ipv4_address(&Global_Clatd_Config.ipv4_local_subnet, |
| Global_Clatd_Config.ipv4_local_prefixlen); |
| if (localaddr == INADDR_NONE) { |
| logmsg(ANDROID_LOG_FATAL, "No free IPv4 address in %s/%d", |
| inet_ntoa(Global_Clatd_Config.ipv4_local_subnet), |
| Global_Clatd_Config.ipv4_local_prefixlen); |
| exit(1); |
| } |
| return localaddr; |
| } |
| |
| /* function: ipv4_address_from_cmdline |
| * configures the IPv4 address specified on the command line, or exits if the address is not valid |
| * v4_addr - a string, the IPv4 address |
| * returns: the IPv4 address as an in_addr_t |
| */ |
| static in_addr_t ipv4_address_from_cmdline(const char *v4_addr) { |
| in_addr_t localaddr; |
| if (!inet_pton(AF_INET, v4_addr, &localaddr)) { |
| logmsg(ANDROID_LOG_FATAL, "Invalid IPv4 address %s", v4_addr); |
| exit(1); |
| } |
| return localaddr; |
| } |
| |
| /* function: configure_tun_ip |
| * configures the ipv4 and ipv6 addresses on the tunnel interface |
| * tunnel - tun device data |
| */ |
| void configure_tun_ip(const struct tun_data *tunnel, const char *v4_addr) { |
| if (v4_addr) { |
| Global_Clatd_Config.ipv4_local_subnet.s_addr = ipv4_address_from_cmdline(v4_addr); |
| } else { |
| Global_Clatd_Config.ipv4_local_subnet.s_addr = ipv4_address_generate(); |
| } |
| |
| char addrstr[INET_ADDRSTRLEN]; |
| inet_ntop(AF_INET, &Global_Clatd_Config.ipv4_local_subnet, addrstr, sizeof(addrstr)); |
| logmsg(ANDROID_LOG_INFO, "Using IPv4 address %s on %s", addrstr, tunnel->device4); |
| |
| // Configure the interface before bringing it up. As soon as we bring the interface up, the |
| // framework will be notified and will assume the interface's configuration has been finalized. |
| int status = add_address(tunnel->device4, AF_INET, &Global_Clatd_Config.ipv4_local_subnet, 32, |
| &Global_Clatd_Config.ipv4_local_subnet); |
| if (status < 0) { |
| logmsg(ANDROID_LOG_FATAL, "configure_tun_ip/if_address(4) failed: %s", strerror(-status)); |
| exit(1); |
| } |
| |
| status = if_up(tunnel->device4, Global_Clatd_Config.ipv4mtu); |
| if (status < 0) { |
| logmsg(ANDROID_LOG_FATAL, "configure_tun_ip/if_up(4) failed: %s", strerror(-status)); |
| exit(1); |
| } |
| } |
| |
| /* function: set_capability |
| * set the permitted, effective and inheritable capabilities of the current |
| * thread |
| */ |
| void set_capability(uint64_t target_cap) { |
| struct __user_cap_header_struct header = { |
| .version = _LINUX_CAPABILITY_VERSION_3, |
| .pid = 0 // 0 = change myself |
| }; |
| struct __user_cap_data_struct cap[_LINUX_CAPABILITY_U32S_3] = {}; |
| |
| cap[0].permitted = cap[0].effective = cap[0].inheritable = target_cap; |
| cap[1].permitted = cap[1].effective = cap[1].inheritable = target_cap >> 32; |
| |
| if (capset(&header, cap) < 0) { |
| logmsg(ANDROID_LOG_FATAL, "capset failed: %s", strerror(errno)); |
| exit(1); |
| } |
| } |
| |
| /* function: drop_root_but_keep_caps |
| * drops root privs but keeps the needed capabilities |
| */ |
| void drop_root_but_keep_caps() { |
| gid_t groups[] = { AID_INET, AID_VPN }; |
| if (setgroups(sizeof(groups) / sizeof(groups[0]), groups) < 0) { |
| logmsg(ANDROID_LOG_FATAL, "setgroups failed: %s", strerror(errno)); |
| exit(1); |
| } |
| |
| prctl(PR_SET_KEEPCAPS, 1); |
| |
| if (setresgid(AID_CLAT, AID_CLAT, AID_CLAT) < 0) { |
| logmsg(ANDROID_LOG_FATAL, "setresgid failed: %s", strerror(errno)); |
| exit(1); |
| } |
| if (setresuid(AID_CLAT, AID_CLAT, AID_CLAT) < 0) { |
| logmsg(ANDROID_LOG_FATAL, "setresuid failed: %s", strerror(errno)); |
| exit(1); |
| } |
| |
| // keep CAP_NET_RAW capability to open raw socket, and CAP_IPC_LOCK for mmap |
| // to lock memory. |
| set_capability((1 << CAP_NET_ADMIN) | |
| (1 << CAP_NET_RAW) | |
| (1 << CAP_IPC_LOCK)); |
| } |
| |
| /* function: open_sockets |
| * opens a packet socket to receive IPv6 packets and a raw socket to send them |
| * tunnel - tun device data |
| * mark - the socket mark to use for the sending raw socket |
| */ |
| void open_sockets(struct tun_data *tunnel, uint32_t mark) { |
| int rawsock = socket(AF_INET6, SOCK_RAW | SOCK_NONBLOCK | SOCK_CLOEXEC, IPPROTO_RAW); |
| if (rawsock < 0) { |
| logmsg(ANDROID_LOG_FATAL, "raw socket failed: %s", strerror(errno)); |
| exit(1); |
| } |
| |
| int off = 0; |
| if (setsockopt(rawsock, SOL_IPV6, IPV6_CHECKSUM, &off, sizeof(off)) < 0) { |
| logmsg(ANDROID_LOG_WARN, "could not disable checksum on raw socket: %s", strerror(errno)); |
| } |
| if (mark != MARK_UNSET && setsockopt(rawsock, SOL_SOCKET, SO_MARK, &mark, sizeof(mark)) < 0) { |
| logmsg(ANDROID_LOG_ERROR, "could not set mark on raw socket: %s", strerror(errno)); |
| } |
| |
| tunnel->write_fd6 = rawsock; |
| |
| tunnel->read_fd6 = ring_create(tunnel); |
| if (tunnel->read_fd6 < 0) { |
| exit(1); |
| } |
| } |
| |
| int ipv6_address_changed(const char *interface) { |
| union anyip *interface_ip; |
| |
| interface_ip = getinterface_ip(interface, AF_INET6); |
| if (!interface_ip) { |
| logmsg(ANDROID_LOG_ERROR, "Unable to find an IPv6 address on interface %s", interface); |
| return 1; |
| } |
| |
| if (!ipv6_prefix_equal(&interface_ip->ip6, &Global_Clatd_Config.ipv6_local_subnet)) { |
| char oldstr[INET6_ADDRSTRLEN]; |
| char newstr[INET6_ADDRSTRLEN]; |
| inet_ntop(AF_INET6, &Global_Clatd_Config.ipv6_local_subnet, oldstr, sizeof(oldstr)); |
| inet_ntop(AF_INET6, &interface_ip->ip6, newstr, sizeof(newstr)); |
| logmsg(ANDROID_LOG_INFO, "IPv6 prefix on %s changed: %s -> %s", interface, oldstr, newstr); |
| free(interface_ip); |
| return 1; |
| } else { |
| free(interface_ip); |
| return 0; |
| } |
| } |
| |
| /* function: clat_ipv6_address_from_interface |
| * picks the clat IPv6 address based on the interface address |
| * interface - uplink interface name |
| * returns: 1 on success, 0 on failure |
| */ |
| static int clat_ipv6_address_from_interface(const char *interface) { |
| union anyip *interface_ip; |
| |
| // TODO: check that the prefix length is /64. |
| interface_ip = getinterface_ip(interface, AF_INET6); |
| if (!interface_ip) { |
| logmsg(ANDROID_LOG_ERROR, "Unable to find an IPv6 address on interface %s", interface); |
| return 0; |
| } |
| |
| // Generate an interface ID. |
| config_generate_local_ipv6_subnet(&interface_ip->ip6); |
| |
| Global_Clatd_Config.ipv6_local_subnet = interface_ip->ip6; |
| free(interface_ip); |
| return 1; |
| } |
| |
| /* function: clat_ipv6_address_from_cmdline |
| * parses the clat IPv6 address from the command line |
| * v4_addr - a string, the IPv6 address |
| * returns: 1 on success, 0 on failure |
| */ |
| static int clat_ipv6_address_from_cmdline(const char *v6_addr) { |
| if (!inet_pton(AF_INET6, v6_addr, &Global_Clatd_Config.ipv6_local_subnet)) { |
| logmsg(ANDROID_LOG_FATAL, "Invalid source address %s", v6_addr); |
| return 0; |
| } |
| |
| return 1; |
| } |
| |
| /* function: configure_clat_ipv6_address |
| * picks the clat IPv6 address and configures packet translation to use it. |
| * tunnel - tun device data |
| * interface - uplink interface name |
| * returns: 1 on success, 0 on failure |
| */ |
| int configure_clat_ipv6_address(const struct tun_data *tunnel, const char *interface, |
| const char *v6_addr) { |
| int ret; |
| if (v6_addr) { |
| ret = clat_ipv6_address_from_cmdline(v6_addr); |
| } else { |
| ret = clat_ipv6_address_from_interface(interface); |
| } |
| if (!ret) return 0; |
| |
| char addrstr[INET6_ADDRSTRLEN]; |
| inet_ntop(AF_INET6, &Global_Clatd_Config.ipv6_local_subnet, addrstr, sizeof(addrstr)); |
| logmsg(ANDROID_LOG_INFO, "Using IPv6 address %s on %s", addrstr, interface); |
| |
| // Start translating packets to the new prefix. |
| add_anycast_address(tunnel->write_fd6, &Global_Clatd_Config.ipv6_local_subnet, interface); |
| |
| // Update our packet socket filter to reflect the new 464xlat IP address. |
| if (!configure_packet_socket(tunnel->read_fd6)) { |
| // Things aren't going to work. Bail out and hope we have better luck next time. |
| // We don't log an error here because configure_packet_socket has already done so. |
| return 0; |
| } |
| |
| return 1; |
| } |
| |
| /* function: configure_interface |
| * reads the configuration and applies it to the interface |
| * uplink_interface - network interface to use to reach the ipv6 internet |
| * plat_prefix - PLAT prefix to use |
| * tunnel - tun device data |
| * net_id - NetID to use, NETID_UNSET indicates use of default network |
| */ |
| void configure_interface(const char *uplink_interface, const char *plat_prefix, const char *v4_addr, |
| const char *v6_addr, struct tun_data *tunnel, unsigned net_id) { |
| |
| if (!read_config("/system/etc/clatd.conf", uplink_interface, plat_prefix, net_id)) { |
| logmsg(ANDROID_LOG_FATAL, "read_config failed"); |
| exit(1); |
| } |
| |
| if (Global_Clatd_Config.mtu > MAXMTU) { |
| logmsg(ANDROID_LOG_WARN, "Max MTU is %d, requested %d", MAXMTU, Global_Clatd_Config.mtu); |
| Global_Clatd_Config.mtu = MAXMTU; |
| } |
| if (Global_Clatd_Config.mtu <= 0) { |
| Global_Clatd_Config.mtu = getifmtu(Global_Clatd_Config.default_pdp_interface); |
| logmsg(ANDROID_LOG_WARN, "ifmtu=%d", Global_Clatd_Config.mtu); |
| } |
| if (Global_Clatd_Config.mtu < 1280) { |
| logmsg(ANDROID_LOG_WARN, "mtu too small = %d", Global_Clatd_Config.mtu); |
| Global_Clatd_Config.mtu = 1280; |
| } |
| |
| if (Global_Clatd_Config.ipv4mtu <= 0 || |
| Global_Clatd_Config.ipv4mtu > Global_Clatd_Config.mtu - MTU_DELTA) { |
| Global_Clatd_Config.ipv4mtu = Global_Clatd_Config.mtu - MTU_DELTA; |
| logmsg(ANDROID_LOG_WARN, "ipv4mtu now set to = %d", Global_Clatd_Config.ipv4mtu); |
| } |
| |
| configure_tun_ip(tunnel, v4_addr); |
| |
| if (!configure_clat_ipv6_address(tunnel, uplink_interface, v6_addr)) { |
| exit(1); |
| } |
| } |
| |
| /* function: read_packet |
| * reads a packet from the tunnel fd and translates it |
| * read_fd - file descriptor to read original packet from |
| * write_fd - file descriptor to write translated packet to |
| * to_ipv6 - whether the packet is to be translated to ipv6 or ipv4 |
| */ |
| void read_packet(int read_fd, int write_fd, int to_ipv6) { |
| ssize_t readlen; |
| uint8_t buf[PACKETLEN], *packet; |
| |
| readlen = read(read_fd, buf, PACKETLEN); |
| |
| if (readlen < 0) { |
| if (errno != EAGAIN) { |
| logmsg(ANDROID_LOG_WARN, "read_packet/read error: %s", strerror(errno)); |
| } |
| return; |
| } else if (readlen == 0) { |
| logmsg(ANDROID_LOG_WARN, "read_packet/tun interface removed"); |
| running = 0; |
| return; |
| } |
| |
| struct tun_pi *tun_header = (struct tun_pi *)buf; |
| if (readlen < (ssize_t)sizeof(*tun_header)) { |
| logmsg(ANDROID_LOG_WARN, "read_packet/short read: got %ld bytes", readlen); |
| return; |
| } |
| |
| uint16_t proto = ntohs(tun_header->proto); |
| if (proto != ETH_P_IP) { |
| logmsg(ANDROID_LOG_WARN, "%s: unknown packet type = 0x%x", __func__, proto); |
| return; |
| } |
| |
| if (tun_header->flags != 0) { |
| logmsg(ANDROID_LOG_WARN, "%s: unexpected flags = %d", __func__, tun_header->flags); |
| } |
| |
| packet = (uint8_t *)(tun_header + 1); |
| readlen -= sizeof(*tun_header); |
| translate_packet(write_fd, to_ipv6, packet, readlen); |
| } |
| |
| /* function: event_loop |
| * reads packets from the tun network interface and passes them down the stack |
| * tunnel - tun device data |
| */ |
| void event_loop(struct tun_data *tunnel) { |
| time_t last_interface_poll; |
| struct pollfd wait_fd[] = { |
| { tunnel->read_fd6, POLLIN, 0 }, |
| { tunnel->fd4, POLLIN, 0 }, |
| }; |
| |
| // start the poll timer |
| last_interface_poll = time(NULL); |
| |
| while (running) { |
| if (poll(wait_fd, ARRAY_SIZE(wait_fd), NO_TRAFFIC_INTERFACE_POLL_FREQUENCY * 1000) == -1) { |
| if (errno != EINTR) { |
| logmsg(ANDROID_LOG_WARN, "event_loop/poll returned an error: %s", strerror(errno)); |
| } |
| } else { |
| if (wait_fd[0].revents & POLLIN) { |
| ring_read(&tunnel->ring, tunnel->fd4, 0 /* to_ipv6 */); |
| } |
| // If any other bit is set, assume it's due to an error (i.e. POLLERR). |
| if (wait_fd[0].revents & ~POLLIN) { |
| // ring_read doesn't clear the error indication on the socket. |
| recv(tunnel->read_fd6, NULL, 0, MSG_PEEK); |
| logmsg(ANDROID_LOG_WARN, "event_loop: clearing error on read_fd6: %s", strerror(errno)); |
| } |
| |
| // Call read_packet if the socket has data to be read, but also if an |
| // error is waiting. If we don't call read() after getting POLLERR, a |
| // subsequent poll() will return immediately with POLLERR again, |
| // causing this code to spin in a loop. Calling read() will clear the |
| // socket error flag instead. |
| if (wait_fd[1].revents) { |
| read_packet(tunnel->fd4, tunnel->write_fd6, 1 /* to_ipv6 */); |
| } |
| } |
| |
| time_t now = time(NULL); |
| if (last_interface_poll < (now - INTERFACE_POLL_FREQUENCY)) { |
| if (ipv6_address_changed(Global_Clatd_Config.default_pdp_interface)) { |
| break; |
| } |
| } |
| } |
| } |