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authorJulian Anastasov <ja@ssi.bg>2009-10-19 10:03:58 +0000
committerDavid S. Miller <davem@davemloft.net>2009-10-19 19:19:03 -0700
commit0c3d79bce48034018e840468ac5a642894a521a3 (patch)
tree96a56d10d55173c032aa1adc2b47a7571e4055a2
parentd1b99ba41d6c5aa1ed2fc634323449dd656899e9 (diff)
tcp: reduce SYN-ACK retrans for TCP_DEFER_ACCEPT
Change SYN-ACK retransmitting code for the TCP_DEFER_ACCEPT users to not retransmit SYN-ACKs during the deferring period if ACK from client was received. The goal is to reduce traffic during the deferring period. When the period is finished we continue with sending SYN-ACKs (at least one) but this time any traffic from client will change the request to established socket allowing application to terminate it properly. Also, do not drop acked request if sending of SYN-ACK fails. Signed-off-by: Julian Anastasov <ja@ssi.bg> Acked-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/ipv4/inet_connection_sock.c34
1 files changed, 31 insertions, 3 deletions
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 4351ca2..537731b 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)