1 files changed, 31 insertions, 3 deletions

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 4351ca2cf0b..537731b3bcb 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -446,6 +446,28 @@ extern int sysctl_tcp_synack_retries;
 
 EXPORT_SYMBOL_GPL(inet_csk_reqsk_queue_hash_add);
 
+/* Decide when to expire the request and when to resend SYN-ACK */
+static inline void syn_ack_recalc(struct request_sock *req, const int thresh,
+                                  const int max_retries,
+                                  const u8 rskq_defer_accept,
+                                  int *expire, int *resend)
+{
+        if (!rskq_defer_accept) {
+                *expire = req->retrans >= thresh;
+                *resend = 1;
+                return;
+        }
+        *expire = req->retrans >= thresh &&
+                  (!inet_rsk(req)->acked || req->retrans >= max_retries);
+        /*
+         * Do not resend while waiting for data after ACK,
+         * start to resend on end of deferring period to give
+         * last chance for data or ACK to create established socket.
+         */
+        *resend = !inet_rsk(req)->acked ||
+                  req->retrans >= rskq_defer_accept - 1;
+}
+
 void inet_csk_reqsk_queue_prune(struct sock *parent,
                                 const unsigned long interval,
                                 const unsigned long timeout,
@@ -501,9 +523,15 @@ void inet_csk_reqsk_queue_prune(struct sock *parent,
                 reqp=&lopt->syn_table[i];
                 while ((req = *reqp) != NULL) {
                         if (time_after_eq(now, req->expires)) {
-                                if ((req->retrans < thresh ||
-                                     (inet_rsk(req)->acked && req->retrans < max_retries))
-                                    && !req->rsk_ops->rtx_syn_ack(parent, req)) {
+                                int expire = 0, resend = 0;
+
+                                syn_ack_recalc(req, thresh, max_retries,
+                                               queue->rskq_defer_accept,
+                                               &expire, &resend);
+                                if (!expire &&
+                                    (!resend ||
+                                     !req->rsk_ops->rtx_syn_ack(parent, req) ||
+                                     inet_rsk(req)->acked)) {
                                         unsigned long timeo;
 
                                         if (req->retrans++ == 0)