No functional changes.
Signed-off-by: Ilpo Järvinen <ilpo.jarvi...@helsinki.fi>
---
net/ipv4/tcp_input.c | 21 +++++++++++++++++----
1 file changed, 17 insertions(+), 4 deletions(-)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 1a33752..e20f9ad 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2211,6 +2211,19 @@ static void tcp_update_scoreboard(struct sock *sk, int
fast_rexmit)
}
}
+/* False fast retransmits may occur when SACK is not in use under certain
+ * conditions (RFC6582). The sender MUST hold old state until something
+ * *above* high_seq is ACKed to prevent triggering such false fast
+ * retransmits. SACK TCP is safe.
+ */
+static bool tcp_false_fast_retrans_possible(const struct sock *sk,
+ const u32 snd_una)
+{
+ const struct tcp_sock *tp = tcp_sk(sk);
+
+ return ((snd_una == tp->high_seq) && tcp_is_reno(tp));
+}
+
static bool tcp_tsopt_ecr_before(const struct tcp_sock *tp, u32 when)
{
return tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
@@ -2350,10 +2363,10 @@ static bool tcp_try_undo_recovery(struct sock *sk)
} else if (tp->rack.reo_wnd_persist) {
tp->rack.reo_wnd_persist--;
}
- if (tp->snd_una == tp->high_seq && tcp_is_reno(tp)) {
- /* Hold old state until something *above* high_seq
- * is ACKed. For Reno it is MUST to prevent false
- * fast retransmits (RFC2582). SACK TCP is safe. */
+ if (tcp_false_fast_retrans_possible(sk, tp->snd_una)) {
+ /* Hold old state until something *above* high_seq is ACKed
+ * if false fast retransmit is possible.
+ */
if (!tcp_any_retrans_done(sk))
tp->retrans_stamp = 0;
return true;
--
2.7.4
