tcp: add TCPWinProbe and TCPKeepAlive SNMP counters

Diagnosing problems related to Window Probes has been hard because
we lack a counter.

TCPWinProbe counts the number of ACK packets a sender has to send
at regular intervals to make sure a reverse ACK packet opening back
a window had not been lost.

TCPKeepAlive counts the number of ACK packets sent to keep TCP
flows alive (SO_KEEPALIVE)

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Nandita Dukkipati <nanditad@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 7a2248a..b8ea128 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -527,7 +527,7 @@ int tcp_fragment(struct sock *, struct sk_buff *, u32, unsigned int, gfp_t);
 
 void tcp_send_probe0(struct sock *);
 void tcp_send_partial(struct sock *);
-int tcp_write_wakeup(struct sock *);
+int tcp_write_wakeup(struct sock *, int mib);
 void tcp_send_fin(struct sock *sk);
 void tcp_send_active_reset(struct sock *sk, gfp_t priority);
 int tcp_send_synack(struct sock *);

diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index 6a6fb74..eee8968 100644 (file)
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -276,6 +276,8 @@ enum
        LINUX_MIB_TCPACKSKIPPEDFINWAIT2,        /* TCPACKSkippedFinWait2 */
        LINUX_MIB_TCPACKSKIPPEDTIMEWAIT,        /* TCPACKSkippedTimeWait */
        LINUX_MIB_TCPACKSKIPPEDCHALLENGE,       /* TCPACKSkippedChallenge */
+       LINUX_MIB_TCPWINPROBE,                  /* TCPWinProbe */
+       LINUX_MIB_TCPKEEPALIVE,                 /* TCPKeepAlive */
        __LINUX_MIB_MAX
 };
 

diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index e1f3b91..da5d483 100644 (file)
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -298,6 +298,8 @@ static const struct snmp_mib snmp4_net_list[] = {
        SNMP_MIB_ITEM("TCPACKSkippedFinWait2", LINUX_MIB_TCPACKSKIPPEDFINWAIT2),
        SNMP_MIB_ITEM("TCPACKSkippedTimeWait", LINUX_MIB_TCPACKSKIPPEDTIMEWAIT),
        SNMP_MIB_ITEM("TCPACKSkippedChallenge", LINUX_MIB_TCPACKSKIPPEDCHALLENGE),
+       SNMP_MIB_ITEM("TCPWinProbe", LINUX_MIB_TCPWINPROBE),
+       SNMP_MIB_ITEM("TCPKeepAlive", LINUX_MIB_TCPKEEPALIVE),
        SNMP_MIB_SENTINEL
 };
 

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index b76c719..7386d32 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3382,7 +3382,7 @@ EXPORT_SYMBOL_GPL(tcp_send_ack);
  * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
  * out-of-date with SND.UNA-1 to probe window.
  */
-static int tcp_xmit_probe_skb(struct sock *sk, int urgent)
+static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
 {
        struct tcp_sock *tp = tcp_sk(sk);
        struct sk_buff *skb;
@@ -3400,6 +3400,7 @@ static int tcp_xmit_probe_skb(struct sock *sk, int urgent)
         */
        tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
        skb_mstamp_get(&skb->skb_mstamp);
+       NET_INC_STATS_BH(sock_net(sk), mib);
        return tcp_transmit_skb(sk, skb, 0, GFP_ATOMIC);
 }
 
@@ -3407,12 +3408,12 @@ void tcp_send_window_probe(struct sock *sk)
 {
        if (sk->sk_state == TCP_ESTABLISHED) {
                tcp_sk(sk)->snd_wl1 = tcp_sk(sk)->rcv_nxt - 1;
-               tcp_xmit_probe_skb(sk, 0);
+               tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE);
        }
 }
 
 /* Initiate keepalive or window probe from timer. */
-int tcp_write_wakeup(struct sock *sk)
+int tcp_write_wakeup(struct sock *sk, int mib)
 {
        struct tcp_sock *tp = tcp_sk(sk);
        struct sk_buff *skb;
@@ -3449,8 +3450,8 @@ int tcp_write_wakeup(struct sock *sk)
                return err;
        } else {
                if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
-                       tcp_xmit_probe_skb(sk, 1);
-               return tcp_xmit_probe_skb(sk, 0);
+                       tcp_xmit_probe_skb(sk, 1, mib);
+               return tcp_xmit_probe_skb(sk, 0, mib);
        }
 }
 
@@ -3464,7 +3465,7 @@ void tcp_send_probe0(struct sock *sk)
        unsigned long probe_max;
        int err;
 
-       err = tcp_write_wakeup(sk);
+       err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE);
 
        if (tp->packets_out || !tcp_send_head(sk)) {
                /* Cancel probe timer, if it is not required. */

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 8c65dc1..65bf670 100644 (file)
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -616,7 +616,7 @@ static void tcp_keepalive_timer (unsigned long data)
                        tcp_write_err(sk);
                        goto out;
                }
-               if (tcp_write_wakeup(sk) <= 0) {
+               if (tcp_write_wakeup(sk, LINUX_MIB_TCPKEEPALIVE) <= 0) {
                        icsk->icsk_probes_out++;
                        elapsed = keepalive_intvl_when(tp);
                } else {