[PATCH] net: add synsend and synrecv statistics

[lwk]

In some scenarios, it is necessary to know the count of syn
packages sent and syn packages received in order to assist in
troubleshooting issues.

Signed-off-by: lwk <lwk111111@xxxxxxx>

	modified:   include/uapi/linux/snmp.h
	modified:   net/ipv4/proc.c
	modified:   net/ipv4/tcp_input.c
	modified:   net/ipv4/tcp_output.c
---
 include/uapi/linux/snmp.h | 2 ++
 net/ipv4/proc.c           | 2 ++
 net/ipv4/tcp_input.c      | 1 +
 net/ipv4/tcp_output.c     | 1 +
 4 files changed, 6 insertions(+)

diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index 848c778..3ebf80d 100644
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -303,6 +303,8 @@ enum
 	LINUX_MIB_TCPAOKEYNOTFOUND,		/* TCPAOKeyNotFound */
 	LINUX_MIB_TCPAOGOOD,			/* TCPAOGood */
 	LINUX_MIB_TCPAODROPPEDICMPS,		/* TCPAODroppedIcmps */
+	LINUX_MIB_TCPSYNSEND,   /* TCPSynSend */
+	LINUX_MIB_TCPSYNRECV,   /* TCPSynRecv */
 	__LINUX_MIB_MAX
 };
 
diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index affd21a..1fb7755 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -306,6 +306,8 @@ static int sockstat_seq_show(struct seq_file *seq, void *v)
 	SNMP_MIB_ITEM("TCPAOKeyNotFound", LINUX_MIB_TCPAOKEYNOTFOUND),
 	SNMP_MIB_ITEM("TCPAOGood", LINUX_MIB_TCPAOGOOD),
 	SNMP_MIB_ITEM("TCPAODroppedIcmps", LINUX_MIB_TCPAODROPPEDICMPS),
+	SNMP_MIB_ITEM("TCPSynSend", LINUX_MIB_TCPSYNSEND),
+	SNMP_MIB_ITEM("TCPSynRecv", LINUX_MIB_TCPSYNRECV),
 	SNMP_MIB_SENTINEL
 };
 
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 0cbf81b..a77bf35 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6781,6 +6781,7 @@ enum skb_drop_reason
 			icsk->icsk_af_ops->conn_request(sk, skb);
 			local_bh_enable();
 			rcu_read_unlock();
+			NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRECV);
 
 			consume_skb(skb);
 			return 0;
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index bc95d2a..821aa63 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -4143,6 +4143,7 @@ int tcp_connect(struct sock *sk)
 	tcp_connect_queue_skb(sk, buff);
 	tcp_ecn_send_syn(sk, buff);
 	tcp_rbtree_insert(&sk->tcp_rtx_queue, buff);
+	NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNSEND);
 
 	/* Send off SYN; include data in Fast Open. */
 	err = tp->fastopen_req ? tcp_send_syn_data(sk, buff) :
-- 
1.8.3.1