Use an exponential backoff timeout for data retransmission according
to RFC 2988 and RFC 6298. Set the initial RTO to one second as discussed
in Appendix A of RFC 6298.
Also combine the macros defining the initial RTO for both SYN and ACK.
Signed-off-by: Yumei Huang
Reviewed-by: David Gibson
---
tcp.c | 31 ++++++++++++-------------------
1 file changed, 12 insertions(+), 19 deletions(-)
diff --git a/tcp.c b/tcp.c
index da40a99..ee111e0 100644
--- a/tcp.c
+++ b/tcp.c
@@ -179,16 +179,13 @@
*
* Timeouts are implemented by means of timerfd timers, set based on flags:
*
- * - SYN_TIMEOUT_INIT: if no SYN,ACK is received from tap/guest during
- * handshake (flag ACK_FROM_TAP_DUE without ESTABLISHED event) within
- * this time, resend SYN. It's the starting timeout for the first SYN
- * retry. Retry for TCP_MAX_RETRIES or (syn_retries + syn_linear_timeouts)
- * times, reset the connection
- *
- * - ACK_TIMEOUT: if no ACK segment was received from tap/guest, after sending
- * data (flag ACK_FROM_TAP_DUE with ESTABLISHED event), re-send data from the
- * socket and reset sequence to what was acknowledged. If this persists for
- * more than TCP_MAX_RETRIES times in a row, reset the connection
+ * - RTO_INIT: if no ACK segment was received from tap/guest, either during
+ * handshake (flag ACK_FROM_TAP_DUE without ESTABLISHED event) or after
+ * sending data (flag ACK_FROM_TAP_DUE with ESTABLISHED event), re-send data
+ * from the socket and reset sequence to what was acknowledged. This is the
+ * timeout for the first retry, in seconds. Retry for TCP_MAX_RETRIES times
+ * for established connections, or (syn_retries + syn_linear_timeouts) times
+ * during the handshake, reset the connection
*
* - FIN_TIMEOUT: if a FIN segment was sent to tap/guest (flag ACK_FROM_TAP_DUE
* with TAP_FIN_SENT event), and no ACK is received within this time, reset
@@ -342,8 +339,7 @@ enum {
#define WINDOW_DEFAULT 14600 /* RFC 6928 */
#define ACK_INTERVAL 10 /* ms */
-#define SYN_TIMEOUT_INIT 1 /* s, RFC 6928 */
-#define ACK_TIMEOUT 2
+#define RTO_INIT 1 /* s, RFC 6298 */
#define FIN_TIMEOUT 60
#define ACT_TIMEOUT 7200
@@ -594,13 +590,10 @@ static void tcp_timer_ctl(const struct ctx *c, struct tcp_tap_conn *conn)
if (conn->flags & ACK_TO_TAP_DUE) {
it.it_value.tv_nsec = (long)ACK_INTERVAL * 1000 * 1000;
} else if (conn->flags & ACK_FROM_TAP_DUE) {
- if (!(conn->events & ESTABLISHED)) {
- int exp = conn->retries - c->tcp.syn_linear_timeouts;
- it.it_value.tv_sec = SYN_TIMEOUT_INIT << MAX(exp, 0);
- }
- else {
- it.it_value.tv_sec = ACK_TIMEOUT;
- }
+ int exp = conn->retries;
+ if (!(conn->events & ESTABLISHED))
+ exp -= c->tcp.syn_linear_timeouts;
+ it.it_value.tv_sec = RTO_INIT << MAX(exp, 0);
} else if (CONN_HAS(conn, SOCK_FIN_SENT | TAP_FIN_ACKED)) {
it.it_value.tv_sec = FIN_TIMEOUT;
} else {
--
2.51.0