Commit 48611c47 authored Oct 07, 2007 by Ilpo Järvinen Committed by David S. Miller Oct 07, 2007

[TCP]: Fix fastpath_cnt_hint when GSO skb is partially ACKed



When only GSO skb was partially ACKed, no hints are reset,
therefore fastpath_cnt_hint must be tweaked too or else it can
corrupt fackets_out. The corruption to occur, one must have
non-trivial ACK/SACK sequence, so this bug is not very often
that harmful. There's a fackets_out state reset in TCP because
fackets_out is known to be inaccurate and that fixes the issue
eventually anyway.

In case there was also at least one skb that got fully ACKed,
the fastpath_skb_hint is set to NULL which causes a recount for
fastpath_cnt_hint (the old value won't be accessed anymore),
thus it can safely be decremented without additional checking.

Reported by Cedric Le Goater <clg@fr.ibm.com>

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 3eb215de

net/ipv4/tcp_input.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -2420,6 +2420,9 @@ static int tcp_tso_acked(struct sock sk, struct sk_buff skb,
		__u32 dval = min(tp->fackets_out, packets_acked);
		tp->fackets_out -= dval;
		}
		/* hint's skb might be NULL but we don't need to care */
		tp->fastpath_cnt_hint -= min_t(u32, packets_acked,
		tp->fastpath_cnt_hint);
		tp->packets_out -= packets_acked;

		BUG_ON(tcp_skb_pcount(skb) == 0);

Admin message