[PATCH net-next] tcp: replace LINUX_MIB_TCPOFODROP with LINUX_MIB_TCPRMEMFULLDROP for drops due to receive buffer full

[Yafang Shao]

When sk_rmem_alloc is larger than the receive buffer and we can't
schedule more memory for it, the skb will be dropped.

In above situation, if this skb is put into the ofo queue,
LINUX_MIB_TCPOFODROP is incremented to track it,
while if this skb is put into the receive queue, there's no record.

So LINUX_MIB_TCPOFODROP is replaced with LINUX_MIB_TCPRMEMFULLDROP to track
this behavior.

Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
---
 include/uapi/linux/snmp.h |  2 +-
 net/ipv4/proc.c           |  2 +-
 net/ipv4/tcp_input.c      | 10 +++++++---
 3 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index 97517f3..3a83322 100644
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -243,7 +243,6 @@ enum
 	LINUX_MIB_TCPRETRANSFAIL,		/* TCPRetransFail */
 	LINUX_MIB_TCPRCVCOALESCE,		/* TCPRcvCoalesce */
 	LINUX_MIB_TCPOFOQUEUE,			/* TCPOFOQueue */
-	LINUX_MIB_TCPOFODROP,			/* TCPOFODrop */
 	LINUX_MIB_TCPOFOMERGE,			/* TCPOFOMerge */
 	LINUX_MIB_TCPCHALLENGEACK,		/* TCPChallengeACK */
 	LINUX_MIB_TCPSYNCHALLENGE,		/* TCPSYNChallenge */
@@ -280,6 +279,7 @@ enum
 	LINUX_MIB_TCPDELIVEREDCE,		/* TCPDeliveredCE */
 	LINUX_MIB_TCPACKCOMPRESSED,		/* TCPAckCompressed */
 	LINUX_MIB_TCPZEROWINDOWDROP,		/* TCPZeroWindowDrop */
+	LINUX_MIB_TCPRMEMFULLDROP,              /* TCPRmemFullDrop */
 	__LINUX_MIB_MAX
 };
 
diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 225ef34..43ee02d 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -251,7 +251,6 @@ static int sockstat_seq_show(struct seq_file *seq, void *v)
 	SNMP_MIB_ITEM("TCPRetransFail", LINUX_MIB_TCPRETRANSFAIL),
 	SNMP_MIB_ITEM("TCPRcvCoalesce", LINUX_MIB_TCPRCVCOALESCE),
 	SNMP_MIB_ITEM("TCPOFOQueue", LINUX_MIB_TCPOFOQUEUE),
-	SNMP_MIB_ITEM("TCPOFODrop", LINUX_MIB_TCPOFODROP),
 	SNMP_MIB_ITEM("TCPOFOMerge", LINUX_MIB_TCPOFOMERGE),
 	SNMP_MIB_ITEM("TCPChallengeACK", LINUX_MIB_TCPCHALLENGEACK),
 	SNMP_MIB_ITEM("TCPSYNChallenge", LINUX_MIB_TCPSYNCHALLENGE),
@@ -288,6 +287,7 @@ static int sockstat_seq_show(struct seq_file *seq, void *v)
 	SNMP_MIB_ITEM("TCPDeliveredCE", LINUX_MIB_TCPDELIVEREDCE),
 	SNMP_MIB_ITEM("TCPAckCompressed", LINUX_MIB_TCPACKCOMPRESSED),
 	SNMP_MIB_ITEM("TCPZeroWindowDrop", LINUX_MIB_TCPZEROWINDOWDROP),
+	SNMP_MIB_ITEM("TCPRmemFullDrop", LINUX_MIB_TCPRMEMFULLDROP),
 	SNMP_MIB_SENTINEL
 };
 
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 9c5b341..d11abb8 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4442,7 +4442,7 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
 	tcp_ecn_check_ce(sk, skb);
 
 	if (unlikely(tcp_try_rmem_schedule(sk, skb, skb->truesize))) {
-		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPOFODROP);
+		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRMEMFULLDROP);
 		tcp_drop(sk, skb);
 		return;
 	}
@@ -4611,8 +4611,10 @@ int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size)
 	skb->data_len = data_len;
 	skb->len = size;
 
-	if (tcp_try_rmem_schedule(sk, skb, skb->truesize))
+	if (tcp_try_rmem_schedule(sk, skb, skb->truesize)) {
+		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRMEMFULLDROP);
 		goto err_free;
+	}
 
 	err = skb_copy_datagram_from_iter(skb, 0, &msg->msg_iter, size);
 	if (err)
@@ -4677,8 +4679,10 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
 queue_and_out:
 		if (skb_queue_len(&sk->sk_receive_queue) == 0)
 			sk_forced_mem_schedule(sk, skb->truesize);
-		else if (tcp_try_rmem_schedule(sk, skb, skb->truesize))
+		else if (tcp_try_rmem_schedule(sk, skb, skb->truesize)) {
+			NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRMEMFULLDROP);
 			goto drop;
+		}
 
 		eaten = tcp_queue_rcv(sk, skb, 0, &fragstolen);
 		tcp_rcv_nxt_update(tp, TCP_SKB_CB(skb)->end_seq);
-- 
1.8.3.1