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 | 27 ++++++++++++---------------
1 file changed, 12 insertions(+), 15 deletions(-)
diff --git a/tcp.c b/tcp.c
index 71e2da0..31bba6f 100644
--- a/tcp.c
+++ b/tcp.c
@@ -179,16 +179,14 @@
*
* Timeouts are implemented by means of timerfd timers, set based on flags:
*
- * - SYN_TIMEOUT_INIT: if no 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. If this persists
- * for more than TCP_MAX_RETRIES or (tcp_syn_retries +
- * tcp_syn_linear_timeouts) times in a row, 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. If this persists too many times
+ * in a row, reset the connection: TCP_MAX_RETRIES for established
+ * connections, or (tcp_syn_retries + tcp_syn_linear_timeouts) during the
+ * handshake.
*
* - 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 +340,7 @@ enum {
#define WINDOW_DEFAULT 14600 /* RFC 6928 */
#define ACK_INTERVAL 10 /* ms */
-#define SYN_TIMEOUT_INIT 1 /* s */
-#define ACK_TIMEOUT 2
+#define RTO_INIT 1 /* s, RFC 6298 */
#define FIN_TIMEOUT 60
#define ACT_TIMEOUT 7200
@@ -588,13 +585,13 @@ static void tcp_timer_ctl(const struct ctx *c, struct tcp_tap_conn *conn)
} else if (conn->flags & ACK_FROM_TAP_DUE) {
if (!(conn->events & ESTABLISHED)) {
if (conn->retries < c->tcp.syn_linear_timeouts)
- it.it_value.tv_sec = SYN_TIMEOUT_INIT;
+ it.it_value.tv_sec = RTO_INIT;
else
- it.it_value.tv_sec = SYN_TIMEOUT_INIT <<
+ it.it_value.tv_sec = RTO_INIT <<
(conn->retries - c->tcp.syn_linear_timeouts);
}
else
- it.it_value.tv_sec = ACK_TIMEOUT;
+ it.it_value.tv_sec = RTO_INIT << conn->retries;
} else if (CONN_HAS(conn, SOCK_FIN_SENT | TAP_FIN_ACKED)) {
it.it_value.tv_sec = FIN_TIMEOUT;
} else {
--
2.47.0