Commit 1bede0a1 authored by Eric Dumazet's avatar Eric Dumazet Committed by Jakub Kicinski
Browse files

tcp: fix tcp_grow_skb() vs tstamps 



I forgot to call tcp_skb_collapse_tstamp() in the
case we consume the second skb in write queue.

Neal suggested to create a common helper used by tcp_mtu_probe()
and tcp_grow_skb().

Fixes: 8ee602c6 ("tcp: try to send bigger TSO packets")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Acked-by: default avatarNeal Cardwell <ncardwell@google.com>
Link: https://lore.kernel.org/r/20240425193450.411640-1-edumazet@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 8880e266

net/ipv4/tcp_output.c

+19 −14
Original line number Diff line number Diff line
@@ -2403,6 +2403,21 @@ static int tcp_clone_payload(struct sock *sk, struct sk_buff *to, 
	return 0;

}



/* tcp_mtu_probe() and tcp_grow_skb() can both eat an skb (src) if

 * all its payload was moved to another one (dst).

 * Make sure to transfer tcp_flags, eor, and tstamp.

 */

static void tcp_eat_one_skb(struct sock *sk,

			    struct sk_buff *dst,

			    struct sk_buff *src)

{

	TCP_SKB_CB(dst)->tcp_flags |= TCP_SKB_CB(src)->tcp_flags;

	TCP_SKB_CB(dst)->eor = TCP_SKB_CB(src)->eor;

	tcp_skb_collapse_tstamp(dst, src);

	tcp_unlink_write_queue(src, sk);

	tcp_wmem_free_skb(sk, src);

}



/* Create a new MTU probe if we are ready.

 * MTU probe is regularly attempting to increase the path MTU by

 * deliberately sending larger packets.  This discovers routing
@@ -2508,16 +2523,7 @@ static int tcp_mtu_probe(struct sock *sk) 
		copy = min_t(int, skb->len, probe_size - len);



		if (skb->len <= copy) {

			/* We've eaten all the data from this skb.

			 * Throw it away. */

			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;

			/* If this is the last SKB we copy and eor is set

			 * we need to propagate it to the new skb.

			 */

			TCP_SKB_CB(nskb)->eor = TCP_SKB_CB(skb)->eor;

			tcp_skb_collapse_tstamp(nskb, skb);

			tcp_unlink_write_queue(skb, sk);

			tcp_wmem_free_skb(sk, skb);

			tcp_eat_one_skb(sk, nskb, skb);

		} else {

			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &

						   ~(TCPHDR_FIN|TCPHDR_PSH);
@@ -2705,11 +2711,10 @@ static void tcp_grow_skb(struct sock *sk, struct sk_buff *skb, int amount) 
	TCP_SKB_CB(next_skb)->seq += nlen;



	if (!next_skb->len) {

		/* In case FIN is set, we need to update end_seq */

		TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;

		TCP_SKB_CB(skb)->eor = TCP_SKB_CB(next_skb)->eor;

		TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;

		tcp_unlink_write_queue(next_skb, sk);

		tcp_wmem_free_skb(sk, next_skb);



		tcp_eat_one_skb(sk, skb, next_skb);

	}

}