tcp: Increase timeout for SYN segments
Commit 9ad7c049 ("tcp: RFC2988bis + taking RTT sample from 3WHS for
the passive open side") changed the initRTO from 3secs to 1sec in
accordance to RFC6298 (former RFC2988bis). This reduced the time till
the last SYN retransmission packet gets sent from 93secs to 31secs.
RFC1122 is stating that the retransmission should be done for at least 3
minutes, but this seems to be quite high.
"However, the values of R1 and R2 may be different for SYN
and data segments. In particular, R2 for a SYN segment MUST
be set large enough to provide retransmission of the segment
for at least 3 minutes. The application can close the
connection (i.e., give up on the open attempt) sooner, of
course."
This patch increases the value of TCP_SYN_RETRIES to the value of 6,
providing a retransmission window of 63secs.
The comments for SYN and SYNACK retries have also been updated to
describe the current settings. The same goes for the documentation file
"Documentation/networking/ip-sysctl.txt".
Signed-off-by: Alexander Bergmann <alex@linlab.net>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 9a0021d..0fca06f 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -98,11 +98,21 @@
* 15 is ~13-30min depending on RTO.
*/
-#define TCP_SYN_RETRIES 5 /* number of times to retry active opening a
- * connection: ~180sec is RFC minimum */
+#define TCP_SYN_RETRIES 6 /* This is how many retries are done
+ * when active opening a connection.
+ * RFC1122 says the minimum retry MUST
+ * be at least 180secs. Nevertheless
+ * this value is corresponding to
+ * 63secs of retransmission with the
+ * current initial RTO.
+ */
-#define TCP_SYNACK_RETRIES 5 /* number of times to retry passive opening a
- * connection: ~180sec is RFC minimum */
+#define TCP_SYNACK_RETRIES 5 /* This is how may retries are done
+ * when passive opening a connection.
+ * This is corresponding to 31secs of
+ * retransmission with the current
+ * initial RTO.
+ */
#define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy TIME-WAIT
* state, about 60 seconds */
