[PATCH net-next] tcp: add SNMP counter for the number of packets pruned from ofo queue

[Yafang Shao]

LINUX_MIB_OFOPRUNED is used to count how many times ofo queue is pruned,
but sometimes we want to know how many packets are pruned from this queue,
that could help us to track the dropped packets.

As LINUX_MIB_OFOPRUNED is a useful event for us, so I introduce a new
SNMP counter LINUX_MIB_OFOPRUNEDROP, which could be showed in netstat as
OfoPruneDrop.

Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
---
 include/uapi/linux/snmp.h | 1 +
 net/ipv4/proc.c           | 1 +
 net/ipv4/tcp_input.c      | 1 +
 3 files changed, 3 insertions(+)

diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index e5ebc83..c996fba 100644
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -172,6 +172,7 @@ enum
 	LINUX_MIB_PRUNECALLED,			/* PruneCalled */
 	LINUX_MIB_RCVPRUNED,			/* RcvPruned */
 	LINUX_MIB_OFOPRUNED,			/* OfoPruned */
+	LINUX_MIB_OFOPRUNEDROP,			/* OfoPruneDrop */
 	LINUX_MIB_OUTOFWINDOWICMPS,		/* OutOfWindowIcmps */
 	LINUX_MIB_LOCKDROPPEDICMPS,		/* LockDroppedIcmps */
 	LINUX_MIB_ARPFILTER,			/* ArpFilter */
diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index b46e4cf..c718295 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -180,6 +180,7 @@ static int sockstat_seq_show(struct seq_file *seq, void *v)
 	SNMP_MIB_ITEM("PruneCalled", LINUX_MIB_PRUNECALLED),
 	SNMP_MIB_ITEM("RcvPruned", LINUX_MIB_RCVPRUNED),
 	SNMP_MIB_ITEM("OfoPruned", LINUX_MIB_OFOPRUNED),
+	SNMP_MIB_ITEM("OfoPruneDrop", LINUX_MIB_OFOPRUNEDROP),
 	SNMP_MIB_ITEM("OutOfWindowIcmps", LINUX_MIB_OUTOFWINDOWICMPS),
 	SNMP_MIB_ITEM("LockDroppedIcmps", LINUX_MIB_LOCKDROPPEDICMPS),
 	SNMP_MIB_ITEM("ArpFilter", LINUX_MIB_ARPFILTER),
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 91dbb9a..5267121 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4980,6 +4980,7 @@ static bool tcp_prune_ofo_queue(struct sock *sk)
 	do {
 		prev = rb_prev(node);
 		rb_erase(node, &tp->out_of_order_queue);
+		NET_INC_STATS(sock_net(sk), LINUX_MIB_OFOPRUNEDROP);
 		tcp_drop(sk, rb_to_skb(node));
 		sk_mem_reclaim(sk);
 		if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf &&
-- 
1.8.3.1