Commit e520af48 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

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: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarYuchung Cheng <ycheng@google.com>
Acked-by: default avatarNeal Cardwell <ncardwell@google.com>
Acked-by: default avatarNandita Dukkipati <nanditad@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 21c8fe99

include/net/tcp.h

+1 −1
Original line number Diff line number Diff line
@@ -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 *);

include/uapi/linux/snmp.h

+2 −0
Original line number Diff line number Diff line
@@ -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

};

net/ipv4/proc.c

+2 −0
Original line number Diff line number Diff line
@@ -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

};

net/ipv4/tcp_output.c

+7 −6
Original line number Diff line number Diff line
@@ -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 * out-of-date with SND.UNA-1 to probe window.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. */

net/ipv4/tcp_timer.c

+1 −1
Original line number Diff line number Diff line
@@ -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 {

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