tcp: add LINUX_MIB_PAWS_OLD_ACK SNMP counter

Prior patch in the series added TCP_RFC7323_PAWS_ACK drop reason.

This patch adds the corresponding SNMP counter, for folks
using nstat instead of tracing for TCP diagnostics.

nstat -az | grep PAWSOldAck

Suggested-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Tested-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250113135558.3180360-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h
index 2855510..ed86493 100644 (file)
--- a/include/net/dropreason-core.h
+++ b/include/net/dropreason-core.h
@@ -262,6 +262,7 @@ enum skb_drop_reason {
        SKB_DROP_REASON_TCP_RFC7323_PAWS,
        /**
         * @SKB_DROP_REASON_TCP_RFC7323_PAWS_ACK: PAWS check, old ACK packet.
+        * Corresponds to LINUX_MIB_PAWS_OLD_ACK.
         */
        SKB_DROP_REASON_TCP_RFC7323_PAWS_ACK,
        /** @SKB_DROP_REASON_TCP_OLD_SEQUENCE: Old SEQ field (duplicate packet) */

diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index 2e75674..848c778 100644 (file)
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -186,6 +186,7 @@ enum
        LINUX_MIB_TIMEWAITKILLED,               /* TimeWaitKilled */
        LINUX_MIB_PAWSACTIVEREJECTED,           /* PAWSActiveRejected */
        LINUX_MIB_PAWSESTABREJECTED,            /* PAWSEstabRejected */
+       LINUX_MIB_PAWS_OLD_ACK,                 /* PAWSOldAck */
        LINUX_MIB_DELAYEDACKS,                  /* DelayedACKs */
        LINUX_MIB_DELAYEDACKLOCKED,             /* DelayedACKLocked */
        LINUX_MIB_DELAYEDACKLOST,               /* DelayedACKLost */

diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 40053a0..affd21a 100644 (file)
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -189,6 +189,7 @@ static const struct snmp_mib snmp4_net_list[] = {
        SNMP_MIB_ITEM("TWKilled", LINUX_MIB_TIMEWAITKILLED),
        SNMP_MIB_ITEM("PAWSActive", LINUX_MIB_PAWSACTIVEREJECTED),
        SNMP_MIB_ITEM("PAWSEstab", LINUX_MIB_PAWSESTABREJECTED),
+       SNMP_MIB_ITEM("PAWSOldAck", LINUX_MIB_PAWS_OLD_ACK),
        SNMP_MIB_ITEM("DelayedACKs", LINUX_MIB_DELAYEDACKS),
        SNMP_MIB_ITEM("DelayedACKLocked", LINUX_MIB_DELAYEDACKLOCKED),
        SNMP_MIB_ITEM("DelayedACKLost", LINUX_MIB_DELAYEDACKLOST),

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index dc0e88b..eb82e01 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5969,12 +5969,13 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
        if (unlikely(th->syn))
                goto syn_challenge;
 
-       /* Old ACK are common, do not change PAWSESTABREJECTED
+       /* Old ACK are common, increment PAWS_OLD_ACK
         * and do not send a dupack.
         */
-       if (reason == SKB_DROP_REASON_TCP_RFC7323_PAWS_ACK)
+       if (reason == SKB_DROP_REASON_TCP_RFC7323_PAWS_ACK) {
+               NET_INC_STATS(sock_net(sk), LINUX_MIB_PAWS_OLD_ACK);
                goto discard;
-
+       }
        NET_INC_STATS(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
        if (!tcp_oow_rate_limited(sock_net(sk), skb,
                                  LINUX_MIB_TCPACKSKIPPEDPAWS,