[PATCH v2 bpf-next 10/11] bpf: Add BPF_SOCK_OPS_STATE_CB

[Lawrence Brakmo]

Adds support for calling sock_ops BPF program when there is a TCP state
change. Two arguments are used; one for the old state and another for
the new state.

New op: BPF_SOCK_OPS_STATE_CB.

Signed-off-by: Lawrence Brakmo <bra...@fb.com>
---
 include/uapi/linux/bpf.h | 4 ++++
 include/uapi/linux/tcp.h | 1 +
 net/ipv4/tcp.c           | 2 ++
 3 files changed, 7 insertions(+)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 415b951..14040e0 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1024,6 +1024,10 @@ enum {
                                         * Arg1: sequence number of 1st byte
                                         * Arg2: # segments
                                         */
+       BPF_SOCK_OPS_STATE_CB,          /* Called when TCP changes state.
+                                        * Arg1: old_state
+                                        * Arg2: new_state
+                                        */
 };
 
 #define TCP_BPF_IW             1001    /* Set TCP initial congestion window */
diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index dc36d3c..211322c 100644
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h
@@ -262,6 +262,7 @@ struct tcp_md5sig {
 /* Definitions for bpf_sock_ops_flags */
 #define BPF_SOCK_OPS_RTO_CB_FLAG       (1<<0)
 #define BPF_SOCK_OPS_RETRANS_CB_FLAG   (1<<1)
+#define BPF_SOCK_OPS_STATE_CB_FLAG     (1<<2)
 
 /* INET_DIAG_MD5SIG */
 struct tcp_diag_md5sig {
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 587d65c..f342f31 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2041,6 +2041,8 @@ void tcp_set_state(struct sock *sk, int state)
        int oldstate = sk->sk_state;
 
        trace_tcp_set_state(sk, oldstate, state);
+       if (BPF_SOCK_OPS_TEST_FLAG(tcp_sk(sk), BPF_SOCK_OPS_STATE_CB_FLAG))
+               tcp_call_bpf_2arg(sk, BPF_SOCK_OPS_STATE_CB, oldstate, state);
 
        switch (state) {
        case TCP_ESTABLISHED:
-- 
2.9.5