[TCP]: Reduce sacked_out with reno when purging write_queue

Previously TCP had a transitional state during which reno
counted segments that are already below the current window into
sacked_out, which is now prevented. In addition, re-try now
the unconditional S+L skb catching.

This approach conservatively calls just remove_sack and leaves
reset_sack() calls alone. The best solution to the whole problem
would be to first calculate the new sacked_out fully (this patch
does not move reno_sack_reset calls from original sites and thus
does not implement this). However, that would require very
invasive change to fastretrans_alert (perhaps even slicing it to
two halves). Alternatively, all callers of tcp_packets_in_flight
(i.e., users that depend on sacked_out) should be postponed
until the new sacked_out has been calculated but it isn't any
simpler alternative.

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

1 files changed, 1 insertions, 2 deletions

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 7042c32085f5..064c92fe00d2 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -759,8 +759,7 @@ static inline __u32 tcp_current_ssthresh(const struct sock *sk)
 }
 
 /* Use define here intentionally to get BUG_ON location shown at the caller */
-#define tcp_verify_left_out(tp) \
-        BUG_ON(tp->rx_opt.sack_ok && (tcp_left_out(tp) > tp->packets_out))
+#define tcp_verify_left_out(tp) BUG_ON(tcp_left_out(tp) > tp->packets_out)
 
 extern void tcp_enter_cwr(struct sock *sk, const int set_ssthresh);
 extern __u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst);