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-rw-r--r--tcp.c77
-rw-r--r--tcp.h4
2 files changed, 65 insertions, 16 deletions
diff --git a/tcp.c b/tcp.c
index 05f0d8b..27db5f8 100644
--- a/tcp.c
+++ b/tcp.c
@@ -179,9 +179,11 @@
*
* Timeouts are implemented by means of timerfd timers, set based on flags:
*
- * - SYN_TIMEOUT: if no ACK is received from tap/guest during handshake (flag
- * ACK_FROM_TAP_DUE without ESTABLISHED event) within this time, reset the
- * connection
+ * - 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 TCP_MAX_RETRIES or (syn_retries + syn_linear_timeouts)
+ * times, then 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
@@ -340,7 +342,7 @@ enum {
#define WINDOW_DEFAULT 14600 /* RFC 6928 */
#define ACK_INTERVAL 10 /* ms */
-#define SYN_TIMEOUT 10 /* s */
+#define SYN_TIMEOUT_INIT 1 /* s, RFC 6928 */
#define ACK_TIMEOUT 2
#define FIN_TIMEOUT 60
#define ACT_TIMEOUT 7200
@@ -365,6 +367,13 @@ uint8_t tcp_migrate_rcv_queue [TCP_MIGRATE_RCV_QUEUE_MAX];
#define TCP_MIGRATE_RESTORE_CHUNK_MIN 1024 /* Try smaller when above this */
+#define SYN_RETRIES "/proc/sys/net/ipv4/tcp_syn_retries"
+#define SYN_LINEAR_TIMEOUTS "/proc/sys/net/ipv4/tcp_syn_linear_timeouts"
+
+#define SYN_RETRIES_DEFAULT 6
+#define SYN_LINEAR_TIMEOUTS_DEFAULT 4
+#define MAX_SYNCNT 127 /* derived from kernel's limit */
+
/* "Extended" data (not stored in the flow table) for TCP flow migration */
static struct tcp_tap_transfer_ext migrate_ext[FLOW_MAX];
@@ -543,11 +552,12 @@ static int tcp_epoll_ctl(const struct ctx *c, struct tcp_tap_conn *conn)
/**
* tcp_timer_ctl() - Set timerfd based on flags/events, create timerfd if needed
+ * @c: Execution context
* @conn: Connection pointer
*
* #syscalls timerfd_create timerfd_settime
*/
-static void tcp_timer_ctl(struct tcp_tap_conn *conn)
+static void tcp_timer_ctl(const struct ctx *c, struct tcp_tap_conn *conn)
{
struct itimerspec it = { { 0 }, { 0 } };
@@ -584,10 +594,13 @@ static void tcp_timer_ctl(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))
- it.it_value.tv_sec = SYN_TIMEOUT;
- else
+ if (!(conn->events & ESTABLISHED)) {
+ int exp;
+ exp = (int)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;
+ }
} else if (CONN_HAS(conn, SOCK_FIN_SENT | TAP_FIN_ACKED)) {
it.it_value.tv_sec = FIN_TIMEOUT;
} else {
@@ -631,7 +644,7 @@ void conn_flag_do(const struct ctx *c, struct tcp_tap_conn *conn,
* flags and factor this into the logic below.
*/
if (flag == ACK_FROM_TAP_DUE)
- tcp_timer_ctl(conn);
+ tcp_timer_ctl(c, conn);
return;
}
@@ -647,7 +660,7 @@ void conn_flag_do(const struct ctx *c, struct tcp_tap_conn *conn,
if (flag == ACK_FROM_TAP_DUE || flag == ACK_TO_TAP_DUE ||
(flag == ~ACK_FROM_TAP_DUE && (conn->flags & ACK_TO_TAP_DUE)) ||
(flag == ~ACK_TO_TAP_DUE && (conn->flags & ACK_FROM_TAP_DUE)))
- tcp_timer_ctl(conn);
+ tcp_timer_ctl(c, conn);
}
/**
@@ -703,7 +716,7 @@ void conn_event_do(const struct ctx *c, struct tcp_tap_conn *conn,
}
if (CONN_HAS(conn, SOCK_FIN_SENT | TAP_FIN_ACKED))
- tcp_timer_ctl(conn);
+ tcp_timer_ctl(c, conn);
}
/**
@@ -1771,7 +1784,7 @@ static int tcp_data_from_tap(const struct ctx *c, struct tcp_tap_conn *conn,
seq, conn->seq_from_tap);
tcp_send_flag(c, conn, ACK);
- tcp_timer_ctl(conn);
+ tcp_timer_ctl(c, conn);
if (p->count == 1) {
tcp_tap_window_update(c, conn,
@@ -2422,11 +2435,21 @@ void tcp_timer_handler(const struct ctx *c, union epoll_ref ref)
if (conn->flags & ACK_TO_TAP_DUE) {
tcp_send_flag(c, conn, ACK_IF_NEEDED);
- tcp_timer_ctl(conn);
+ tcp_timer_ctl(c, conn);
} else if (conn->flags & ACK_FROM_TAP_DUE) {
if (!(conn->events & ESTABLISHED)) {
- flow_dbg(conn, "handshake timeout");
- tcp_rst(c, conn);
+ int max;
+ max = c->tcp.syn_retries + c->tcp.syn_linear_timeouts;
+ max = MIN(TCP_MAX_RETRIES, max);
+ if (conn->retries >= max) {
+ flow_dbg(conn, "handshake timeout");
+ tcp_rst(c, conn);
+ } else {
+ flow_trace(conn, "SYN timeout, retry");
+ tcp_send_flag(c, conn, SYN);
+ conn->retries++;
+ tcp_timer_ctl(c, conn);
+ }
} else if (CONN_HAS(conn, SOCK_FIN_SENT | TAP_FIN_ACKED)) {
flow_dbg(conn, "FIN timeout");
tcp_rst(c, conn);
@@ -2444,7 +2467,7 @@ void tcp_timer_handler(const struct ctx *c, union epoll_ref ref)
return;
tcp_data_from_sock(c, conn);
- tcp_timer_ctl(conn);
+ tcp_timer_ctl(c, conn);
}
} else {
struct itimerspec new = { { 0 }, { ACT_TIMEOUT, 0 } };
@@ -2783,6 +2806,26 @@ static socklen_t tcp_probe_tcp_info(void)
}
/**
+ * tcp_get_rto_params() - Get host kernel RTO parameters
+ * @c: Execution context
+ */
+static void tcp_get_rto_params(struct ctx *c)
+{
+ intmax_t v;
+
+ v = read_file_integer(SYN_RETRIES, SYN_RETRIES_DEFAULT);
+ c->tcp.syn_retries = MIN(v, MAX_SYNCNT);
+
+ v = read_file_integer(SYN_LINEAR_TIMEOUTS, SYN_LINEAR_TIMEOUTS_DEFAULT);
+ c->tcp.syn_linear_timeouts = MIN(v, MAX_SYNCNT);
+
+ debug("Using TCP RTO parameters, syn_retries: %"PRIu8
+ ", syn_linear_timeouts: %"PRIu8,
+ c->tcp.syn_retries,
+ c->tcp.syn_linear_timeouts);
+}
+
+/**
* tcp_init() - Get initial sequence, hash secret, initialise per-socket data
* @c: Execution context
*
@@ -2792,6 +2835,8 @@ int tcp_init(struct ctx *c)
{
ASSERT(!c->no_tcp);
+ tcp_get_rto_params(c);
+
tcp_sock_iov_init(c);
memset(init_sock_pool4, 0xff, sizeof(init_sock_pool4));
diff --git a/tcp.h b/tcp.h
index 0082386..37d7758 100644
--- a/tcp.h
+++ b/tcp.h
@@ -60,12 +60,16 @@ union tcp_listen_epoll_ref {
* @fwd_out: Port forwarding configuration for outbound packets
* @timer_run: Timestamp of most recent timer run
* @pipe_size: Size of pipes for spliced connections
+ * @syn_retries: SYN retries using exponential backoff timeout
+ * @syn_linear_timeouts: SYN retries before using exponential backoff timeout
*/
struct tcp_ctx {
struct fwd_ports fwd_in;
struct fwd_ports fwd_out;
struct timespec timer_run;
size_t pipe_size;
+ uint8_t syn_retries;
+ uint8_t syn_linear_timeouts;
};
#endif /* TCP_H */
generated by cgit v1.2.3 (git 2.25.1) at 2025-12-08 08:35:55 +0000