tcp: remove redundant code from tcp_mark_lost_retrans (d0af4160) · Commits · e / devices / android_kernel_fairphone_FP4

Arnd Hannemann <hannemann@nets.rwth-aachen.de> noticed and was puzzled by the fact that !tcp_is_fack(tp) leads to early return near the beginning and the later on tcp_is_fack(tp) was still used in an if condition. The later check was a left-over from RFC3517 SACK stuff (== !tcp_is_fack(tp) behavior nowadays) as there wasn't clear way how to handle this particular check cheaply in the spirit of RFC3517 (using only SACK blocks, not holes + SACK blocks as with FACK). I sort of left it there as a reminder but since it's confusing other people just remove it and comment the missing-feature stuff instead. Signed-off-by:

Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Cc: Arnd Hannemann <hannemann@nets.rwth-aachen.de> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/ipv4/tcp_input.c

+12 −4

Original line number	Diff line number	Diff line
		@@ -1178,10 +1178,18 @@ static void tcp_mark_lost_retrans(struct sock *sk)
		if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS))
		continue;

		if (after(received_upto, ack_seq) &&
		(tcp_is_fack(tp) \|\|
		!before(received_upto,
		ack_seq + tp->reordering * tp->mss_cache))) {
		/* TODO: We would like to get rid of tcp_is_fack(tp) only
		* constraint here (see above) but figuring out that at
		* least tp->reordering SACK blocks reside between ack_seq
		* and received_upto is not easy task to do cheaply with
		* the available datastructures.
		*
		* Whether FACK should check here for tp->reordering segs
		* in-between one could argue for either way (it would be
		* rather simple to implement as we could count fack_count
		* during the walk and do tp->fackets_out - fack_count).
		*/
		if (after(received_upto, ack_seq)) {
		TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
		tp->retrans_out -= tcp_skb_pcount(skb);