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authorYuchung Cheng <ycheng@google.com>2017-01-13 09:11:41 +0300
committerDavid S. Miller <davem@davemloft.net>2017-01-14 06:37:16 +0300
commit4a7f6009441144783e5925551c72e3f2e1b0839b (patch)
tree41e521496a3c78abfcabb41f4a20f4f8c535887e /net/ipv4/tcp_input.c
parentac229dca7e4e582114e1ec9765fda0915aa58468 (diff)
downloadlinux-4a7f6009441144783e5925551c72e3f2e1b0839b.tar.xz
tcp: remove thin_dupack feature
Thin stream DUPACK is to start fast recovery on only one DUPACK provided the connection is a thin stream (i.e., low inflight). But this older feature is now subsumed with RACK. If a connection receives only a single DUPACK, RACK would arm a reordering timer and soon starts fast recovery instead of timeout if no further ACKs are received. The socket option (THIN_DUPACK) is kept as a nop for compatibility. Note that this patch does not change another thin-stream feature which enables linear RTO. Although it might be good to generalize that in the future (i.e., linear RTO for the first say 3 retries). Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp_input.c')
-rw-r--r--net/ipv4/tcp_input.c13
1 files changed, 0 insertions, 13 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 87315ab1ab1a..39ebc20ca1b2 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -95,9 +95,6 @@ int sysctl_tcp_rfc1337 __read_mostly;
int sysctl_tcp_max_orphans __read_mostly = NR_FILE;
int sysctl_tcp_frto __read_mostly = 2;
int sysctl_tcp_min_rtt_wlen __read_mostly = 300;
-
-int sysctl_tcp_thin_dupack __read_mostly;
-
int sysctl_tcp_moderate_rcvbuf __read_mostly = 1;
int sysctl_tcp_early_retrans __read_mostly = 3;
int sysctl_tcp_invalid_ratelimit __read_mostly = HZ/2;
@@ -2170,16 +2167,6 @@ static bool tcp_time_to_recover(struct sock *sk, int flag)
if (tcp_dupack_heuristics(tp) > tp->reordering)
return true;
- /* If a thin stream is detected, retransmit after first
- * received dupack. Employ only if SACK is supported in order
- * to avoid possible corner-case series of spurious retransmissions
- * Use only if there are no unsent data.
- */
- if ((tp->thin_dupack || sysctl_tcp_thin_dupack) &&
- tcp_stream_is_thin(tp) && tcp_dupack_heuristics(tp) > 1 &&
- tcp_is_sack(tp) && !tcp_send_head(sk))
- return true;
-
return false;
}