1 files changed, 12 insertions, 0 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 3fddc69ccccc..788851ca8c5d 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -89,6 +89,8 @@ int sysctl_tcp_frto __read_mostly = 2;
 int sysctl_tcp_frto_response __read_mostly;
 int sysctl_tcp_nometrics_save __read_mostly;
 
+int sysctl_tcp_thin_dupack __read_mostly;
+
 int sysctl_tcp_moderate_rcvbuf __read_mostly = 1;
 int sysctl_tcp_abc __read_mostly;
 
@@ -2447,6 +2449,16 @@ static int tcp_time_to_recover(struct sock *sk)
                 return 1;
         }
 
+        /* 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 1;
+
         return 0;
 }