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Commit d5ac99a6 authored by David S. Miller's avatar David S. Miller Committed by David S. Miller
Browse files

[TCP]: skb pcount with MTU discovery 



The problem is that when doing MTU discovery, the too-large segments in
the write queue will be calculated as having a pcount of >1.  When
tcp_write_xmit() is trying to send, tcp_snd_test() fails the cwnd test
when pcount > cwnd.

The segments are eventually transmitted one at a time by keepalive, but
this can take a long time.

This patch checks if TSO is enabled when setting pcount.

Signed-off-by: default avatarJohn Heffner <jheffner@psc.edu>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 158a0e45

include/net/tcp.h

+6 −5
Original line number Diff line number Diff line
@@ -1417,19 +1417,20 @@ tcp_nagle_check(const struct tcp_sock *tp, const struct sk_buff *skb, 
		  tcp_minshall_check(tp))));

}



extern void tcp_set_skb_tso_segs(struct sk_buff *, unsigned int);

extern void tcp_set_skb_tso_segs(struct sock *, struct sk_buff *);



/* This checks if the data bearing packet SKB (usually sk->sk_send_head)

 * should be put on the wire right now.

 */

static __inline__ int tcp_snd_test(const struct tcp_sock *tp, 

static __inline__ int tcp_snd_test(struct sock *sk,

				   struct sk_buff *skb,

				   unsigned cur_mss, int nonagle)

{

	struct tcp_sock *tp = tcp_sk(sk);

	int pkts = tcp_skb_pcount(skb);



	if (!pkts) {

		tcp_set_skb_tso_segs(skb, tp->mss_cache_std);

		tcp_set_skb_tso_segs(sk, skb);

		pkts = tcp_skb_pcount(skb);

	}
@@ -1490,7 +1491,7 @@ static __inline__ void __tcp_push_pending_frames(struct sock *sk, 
	if (skb) {

		if (!tcp_skb_is_last(sk, skb))

			nonagle = TCP_NAGLE_PUSH;

		if (!tcp_snd_test(tp, skb, cur_mss, nonagle) ||

		if (!tcp_snd_test(sk, skb, cur_mss, nonagle) ||

		    tcp_write_xmit(sk, nonagle))

			tcp_check_probe_timer(sk, tp);

	}
@@ -1508,7 +1509,7 @@ static __inline__ int tcp_may_send_now(struct sock *sk, struct tcp_sock *tp) 
	struct sk_buff *skb = sk->sk_send_head;



	return (skb &&

		tcp_snd_test(tp, skb, tcp_current_mss(sk, 1),

		tcp_snd_test(sk, skb, tcp_current_mss(sk, 1),

			     tcp_skb_is_last(sk, skb) ? TCP_NAGLE_PUSH : tp->nonagle));

}

net/ipv4/tcp_output.c

+14 −11
Original line number Diff line number Diff line
@@ -427,7 +427,7 @@ void tcp_push_one(struct sock *sk, unsigned cur_mss) 
	struct tcp_sock *tp = tcp_sk(sk);

	struct sk_buff *skb = sk->sk_send_head;



	if (tcp_snd_test(tp, skb, cur_mss, TCP_NAGLE_PUSH)) {

	if (tcp_snd_test(sk, skb, cur_mss, TCP_NAGLE_PUSH)) {

		/* Send it out now. */

		TCP_SKB_CB(skb)->when = tcp_time_stamp;

		tcp_tso_set_push(skb);
@@ -440,9 +440,12 @@ void tcp_push_one(struct sock *sk, unsigned cur_mss) 
	}

}



void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_std)

void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb)

{

	if (skb->len <= mss_std) {

	struct tcp_sock *tp = tcp_sk(sk);



	if (skb->len <= tp->mss_cache_std ||

	    !(sk->sk_route_caps & NETIF_F_TSO)) {

		/* Avoid the costly divide in the normal

		 * non-TSO case.

		 */
@@ -451,10 +454,10 @@ void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_std) 
	} else {

		unsigned int factor;



		factor = skb->len + (mss_std - 1);

		factor /= mss_std;

		factor = skb->len + (tp->mss_cache_std - 1);

		factor /= tp->mss_cache_std;

		skb_shinfo(skb)->tso_segs = factor;

		skb_shinfo(skb)->tso_size = mss_std;

		skb_shinfo(skb)->tso_size = tp->mss_cache_std;

	}

}
@@ -525,8 +528,8 @@ static int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len) 
	}



	/* Fix up tso_factor for both original and new SKB.  */

	tcp_set_skb_tso_segs(skb, tp->mss_cache_std);

	tcp_set_skb_tso_segs(buff, tp->mss_cache_std);

	tcp_set_skb_tso_segs(sk, skb);

	tcp_set_skb_tso_segs(sk, buff);



	if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) {

		tp->lost_out += tcp_skb_pcount(skb);
@@ -601,7 +604,7 @@ int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len) 
	 * factor and mss.

	 */

	if (tcp_skb_pcount(skb) > 1)

		tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb));

		tcp_set_skb_tso_segs(sk, skb);



	return 0;

}
@@ -752,7 +755,7 @@ int tcp_write_xmit(struct sock *sk, int nonagle) 
		mss_now = tcp_current_mss(sk, 1);



		while ((skb = sk->sk_send_head) &&

		       tcp_snd_test(tp, skb, mss_now,

		       tcp_snd_test(sk, skb, mss_now,

			       	    tcp_skb_is_last(sk, skb) ? nonagle :

				    			       TCP_NAGLE_PUSH)) {

			if (skb->len > mss_now) {
@@ -1676,7 +1679,7 @@ int tcp_write_wakeup(struct sock *sk) 
					tp->mss_cache = tp->mss_cache_std;

				}

			} else if (!tcp_skb_pcount(skb))

				tcp_set_skb_tso_segs(skb, tp->mss_cache_std);

				tcp_set_skb_tso_segs(sk, skb);



			TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH;

			TCP_SKB_CB(skb)->when = tcp_time_stamp;