[TCP]: Maintain highest_sack accurately to the highest skb (0dde7b54) · Commits · 戴 / test

In general, it should not be necessary to call tcp_fragment for already SACKed skbs, but it's better to be safe than sorry. And indeed, it can be called from sacktag when a DSACK arrives or some ACK (with SACK) reordering occurs (sacktag could be made to avoid the call in the latter case though I'm not sure if it's worth of the trouble and added complexity to cover such marginal case). The collapse case has return for SACKED_ACKED case earlier, so just WARN_ON if internal inconsistency is detected for some reason. Signed-off-by:

Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/ipv4/tcp_output.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -692,6 +692,9 @@ int tcp_fragment(struct sock sk, struct sk_buff skb, u32 len, unsigned int mss
		TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
		TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;

		if (tp->sacked_out && (TCP_SKB_CB(skb)->seq == tp->highest_sack))
		tp->highest_sack = TCP_SKB_CB(buff)->seq;

		/* PSH and FIN should only be set in the second packet. */
		flags = TCP_SKB_CB(skb)->flags;
		TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN\|TCPCB_FLAG_PSH);
		@@ -1723,6 +1726,10 @@ static void tcp_retrans_try_collapse(struct sock sk, struct sk_buff skb, int m
		/* Update sequence range on original skb. */
		TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;

		if (WARN_ON(tp->sacked_out &&
		(TCP_SKB_CB(next_skb)->seq == tp->highest_sack)))
		return;

		/* Merge over control information. */
		flags \|= TCP_SKB_CB(next_skb)->flags; /* This moves PSH/FIN etc. over */
		TCP_SKB_CB(skb)->flags = flags;

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