[PATCH net-next 4/4] tcp: add TCPAckCompressed SNMP counter

[Eric Dumazet]

This counter tracks number of ACK packets that the host has not sent,
thanks to ACK compression.

Sample output :

$ nstat -n;sleep 1;nstat|egrep 
"IpInReceives|IpOutRequests|TcpInSegs|TcpOutSegs|TcpExtTCPAckCompressed"
IpInReceives                    123250             0.0
IpOutRequests                   3684               0.0
TcpInSegs                       123251             0.0
TcpOutSegs                      3684               0.0
TcpExtTCPAckCompressed          119252             0.0

Signed-off-by: Eric Dumazet <eduma...@google.com>
---
 include/uapi/linux/snmp.h | 1 +
 net/ipv4/proc.c           | 1 +
 net/ipv4/tcp_output.c     | 2 ++
 3 files changed, 4 insertions(+)

diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index 
d02e859301ff499dd72a1c0e1b56bed10a9397a6..750d89120335eb489f698191edb6c5110969fa8c
 100644
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -278,6 +278,7 @@ enum
        LINUX_MIB_TCPMTUPSUCCESS,               /* TCPMTUPSuccess */
        LINUX_MIB_TCPDELIVERED,                 /* TCPDelivered */
        LINUX_MIB_TCPDELIVEREDCE,               /* TCPDeliveredCE */
+       LINUX_MIB_TCPACKCOMPRESSED,             /* TCPAckCompressed */
        __LINUX_MIB_MAX
 };
 
diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 
261b71d0ccc5c17c6032bf67eb8f842006766e64..6c1ff89a60fa0a3485dcc71fafc799e798d5dc11
 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -298,6 +298,7 @@ static const struct snmp_mib snmp4_net_list[] = {
        SNMP_MIB_ITEM("TCPMTUPSuccess", LINUX_MIB_TCPMTUPSUCCESS),
        SNMP_MIB_ITEM("TCPDelivered", LINUX_MIB_TCPDELIVERED),
        SNMP_MIB_ITEM("TCPDeliveredCE", LINUX_MIB_TCPDELIVEREDCE),
+       SNMP_MIB_ITEM("TCPAckCompressed", LINUX_MIB_TCPACKCOMPRESSED),
        SNMP_MIB_SENTINEL
 };
 
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 
7ee98aad82b758674ca7f3e90bd3fc165e8fcd45..437bb7ceba7fd388abac1c12f2920b02be77bad9
 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -165,6 +165,8 @@ static inline void tcp_event_ack_sent(struct sock *sk, 
unsigned int pkts)
        struct tcp_sock *tp = tcp_sk(sk);
 
        if (unlikely(tp->compressed_ack)) {
+               NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPACKCOMPRESSED,
+                             tp->compressed_ack);
                tp->compressed_ack = 0;
                if (hrtimer_try_to_cancel(&tp->compressed_ack_timer) == 1)
                        __sock_put(sk);
-- 
2.17.0.441.gb46fe60e1d-goog