bpf: Add bpf_get_listener_sock(struct bpf_sock *sk) helper
Add a new helper "struct bpf_sock *bpf_get_listener_sock(struct bpf_sock *sk)"
which returns a bpf_sock in TCP_LISTEN state. It will trace back to
the listener sk from a request_sock if possible. It returns NULL
for all other cases.
No reference is taken because the helper ensures the sk is
in SOCK_RCU_FREE (where the TCP_LISTEN sock should be in).
Hence, bpf_sk_release() is unnecessary and the verifier does not
allow bpf_sk_release(listen_sk) to be called either.
The following is also allowed because the bpf_prog is run under
rcu_read_lock():
sk = bpf_sk_lookup_tcp();
/* if (!sk) { ... } */
listen_sk = bpf_get_listener_sock(sk);
/* if (!listen_sk) { ... } */
bpf_sk_release(sk);
src_port = listen_sk->src_port; /* Allowed */
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 3c38ac9..983b25c 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -2366,6 +2366,14 @@
* current value is ect (ECN capable). Works with IPv6 and IPv4.
* Return
* 1 if set, 0 if not set.
+ *
+ * struct bpf_sock *bpf_get_listener_sock(struct bpf_sock *sk)
+ * Description
+ * Return a **struct bpf_sock** pointer in TCP_LISTEN state.
+ * bpf_sk_release() is unnecessary and not allowed.
+ * Return
+ * A **struct bpf_sock** pointer on success, or NULL in
+ * case of failure.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -2465,7 +2473,8 @@
FN(spin_unlock), \
FN(sk_fullsock), \
FN(tcp_sock), \
- FN(skb_ecn_set_ce),
+ FN(skb_ecn_set_ce), \
+ FN(get_listener_sock),
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
* function eBPF program intends to call
diff --git a/net/core/filter.c b/net/core/filter.c
index 36b6afa..647c63a 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5418,6 +5418,23 @@
.arg1_type = ARG_PTR_TO_SOCK_COMMON,
};
+BPF_CALL_1(bpf_get_listener_sock, struct sock *, sk)
+{
+ sk = sk_to_full_sk(sk);
+
+ if (sk->sk_state == TCP_LISTEN && sock_flag(sk, SOCK_RCU_FREE))
+ return (unsigned long)sk;
+
+ return (unsigned long)NULL;
+}
+
+static const struct bpf_func_proto bpf_get_listener_sock_proto = {
+ .func = bpf_get_listener_sock,
+ .gpl_only = false,
+ .ret_type = RET_PTR_TO_SOCKET_OR_NULL,
+ .arg1_type = ARG_PTR_TO_SOCK_COMMON,
+};
+
BPF_CALL_1(bpf_skb_ecn_set_ce, struct sk_buff *, skb)
{
unsigned int iphdr_len;
@@ -5603,6 +5620,8 @@
#ifdef CONFIG_INET
case BPF_FUNC_tcp_sock:
return &bpf_tcp_sock_proto;
+ case BPF_FUNC_get_listener_sock:
+ return &bpf_get_listener_sock_proto;
case BPF_FUNC_skb_ecn_set_ce:
return &bpf_skb_ecn_set_ce_proto;
#endif
@@ -5698,6 +5717,8 @@
return &bpf_sk_release_proto;
case BPF_FUNC_tcp_sock:
return &bpf_tcp_sock_proto;
+ case BPF_FUNC_get_listener_sock:
+ return &bpf_get_listener_sock_proto;
#endif
default:
return bpf_base_func_proto(func_id);
