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Commit 82ae9c60 authored by David S. Miller's avatar David S. Miller
Browse files

Merge branch 'tcp-more-reliable-window-probes' 



Eric Dumazet says:

====================
tcp: more reliable window probes

This series address a problem caused by small rto_min timers in DC,
leading to either timer storms or early flow terminations.

We also add two new SNMP counters for proper monitoring :
TCPWinProbe and TCPKeepAlive

v2: added TCPKeepAlive counter, as suggested by Yuchung & Neal
====================

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents b063bc5e e520af48

include/net/tcp.h

+23 −6
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 *);
@@ -1043,14 +1043,31 @@ static inline bool tcp_is_cwnd_limited(const struct sock *sk) 
	return tp->is_cwnd_limited;

}



static inline void tcp_check_probe_timer(struct sock *sk)

/* Something is really bad, we could not queue an additional packet,

 * because qdisc is full or receiver sent a 0 window.

 * We do not want to add fuel to the fire, or abort too early,

 * so make sure the timer we arm now is at least 200ms in the future,

 * regardless of current icsk_rto value (as it could be ~2ms)

 */

static inline unsigned long tcp_probe0_base(const struct sock *sk)

{

	const struct tcp_sock *tp = tcp_sk(sk);

	const struct inet_connection_sock *icsk = inet_csk(sk);

	return max_t(unsigned long, inet_csk(sk)->icsk_rto, TCP_RTO_MIN);

}



	if (!tp->packets_out && !icsk->icsk_pending)

/* Variant of inet_csk_rto_backoff() used for zero window probes */

static inline unsigned long tcp_probe0_when(const struct sock *sk,

					    unsigned long max_when)

{

	u64 when = (u64)tcp_probe0_base(sk) << inet_csk(sk)->icsk_backoff;



	return (unsigned long)min_t(u64, when, max_when);

}



static inline void tcp_check_probe_timer(struct sock *sk)

{

	if (!tcp_sk(sk)->packets_out && !inet_csk(sk)->icsk_pending)

		inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,

					  icsk->icsk_rto, TCP_RTO_MAX);

					  tcp_probe0_base(sk), TCP_RTO_MAX);

}



static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)

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_input.c

+1 −1
Original line number Diff line number Diff line
@@ -3233,7 +3233,7 @@ static void tcp_ack_probe(struct sock *sk) 
		 * This function is not for random using!

		 */

	} else {

		unsigned long when = inet_csk_rto_backoff(icsk, TCP_RTO_MAX);

		unsigned long when = tcp_probe0_when(sk, TCP_RTO_MAX);



		inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,

					  when, TCP_RTO_MAX);

net/ipv4/tcp_output.c

+8 −7
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. */
@@ -3490,7 +3491,7 @@ void tcp_send_probe0(struct sock *sk) 
		probe_max = TCP_RESOURCE_PROBE_INTERVAL;

	}

	inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,

				  inet_csk_rto_backoff(icsk, probe_max),

				  tcp_probe0_when(sk, probe_max),

				  TCP_RTO_MAX);

}