tcp: add OFO snmp counters

Add three SNMP TCP counters, to better track TCP behavior
at global stage (netstat -s), when packets are received
Out Of Order (OFO)

TCPOFOQueue : Number of packets queued in OFO queue

TCPOFODrop  : Number of packets meant to be queued in OFO
              but dropped because socket rcvbuf limit hit.

TCPOFOMerge : Number of packets in OFO that were merged with
              other packets.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 2 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 055ac49b8b4..cc4e12f1f2f 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4397,8 +4397,8 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
 
         TCP_ECN_check_ce(tp, skb);
 
-        if (tcp_try_rmem_schedule(sk, skb->truesize)) {
-                /* TODO: should increment a counter */
+        if (unlikely(tcp_try_rmem_schedule(sk, skb->truesize))) {
+                NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPOFODROP);
                 __kfree_skb(skb);
                 return;
         }
@@ -4407,6 +4407,7 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
         tp->pred_flags = 0;
         inet_csk_schedule_ack(sk);
 
+        NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPOFOQUEUE);
         SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n",
                    tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
 
@@ -4460,6 +4461,7 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
         if (skb1 && before(seq, TCP_SKB_CB(skb1)->end_seq)) {
                 if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
                         /* All the bits are present. Drop. */
+                        NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPOFOMERGE);
                         __kfree_skb(skb);
                         skb = NULL;
                         tcp_dsack_set(sk, seq, end_seq);
@@ -4498,6 +4500,7 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
                 __skb_unlink(skb1, &tp->out_of_order_queue);
                 tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
                                  TCP_SKB_CB(skb1)->end_seq);
+                NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPOFOMERGE);
                 __kfree_skb(skb1);
         }