netdev - [PATCH bpf 10/11] bpf: Add BPF_SOCK_OPS_STATE

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Date:   Mon, 18 Dec 2017 22:21:59 -0800
From:   Lawrence Brakmo <brakmo@...com>
To:     netdev <netdev@...r.kernel.org>
CC:     Kernel Team <kernel-team@...com>, Blake Matheny <bmatheny@...com>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: [PATCH bpf 10/11] bpf: Add BPF_SOCK_OPS_STATE_CB

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 <brakmo@...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 7165619..b018d6f 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1018,6 +1018,10 @@ 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 817df3f..e70dd2f 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