[TCP]: Maintain highest_sack accurately to the highest skb
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>
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index d65d17b..9df5b2a 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -692,6 +692,9 @@
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 @@
/* 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;