Commit 0c3d79bce48034018e840468ac5a642894a521a3 ("tcp: reduce SYN-ACK
retrans for TCP_DEFER_ACCEPT") introduces syn_ack_recalc() which decides
if a minisock is held and a SYN+ACK is retransmitted or not.
If rskq_defer_accept is not zero in syn_ack_recalc(), max_retries always
has the same value because max_retries is overwritten by rskq_defer_accept
in reqsk_timer_handler().
This commit adds two changes:
- remove max_retries from the arguments of syn_ack_recalc() and use
rskq_defer_accept instead.
- rename thresh to max_retries for readability.
Signed-off-by: Kuniyuki Iwashima <kun...@amazon.co.jp>
Reviewed-by: Benjamin Herrenschmidt <b...@amazon.com>
CC: Julian Anastasov <j...@ssi.bg>
---
net/ipv4/inet_connection_sock.c | 30 +++++++++++++-----------------
1 file changed, 13 insertions(+), 17 deletions(-)
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index afaf582a5aa9..323cdb8ce901 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -648,20 +648,22 @@ struct dst_entry *inet_csk_route_child_sock(const struct
sock *sk,
EXPORT_SYMBOL_GPL(inet_csk_route_child_sock);
/* 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,
+static inline void syn_ack_recalc(struct request_sock *req, const int
max_retries,
const u8 rskq_defer_accept,
int *expire, int *resend)
{
if (!rskq_defer_accept) {
- *expire = req->num_timeout >= thresh;
+ *expire = req->num_timeout >= max_retries;
*resend = 1;
return;
}
- *expire = req->num_timeout >= thresh &&
- (!inet_rsk(req)->acked || req->num_timeout >= max_retries);
- /*
- * Do not resend while waiting for data after ACK,
+ /* If a bare ACK has already been dropped, the client is alive, so
+ * do not free the request_sock to drop a bare ACK at most
+ * rskq_defer_accept times and wait for data.
+ */
+ *expire = req->num_timeout >= max_retries &&
+ (!inet_rsk(req)->acked || req->num_timeout >=
rskq_defer_accept);
+ /* 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.
*/
@@ -720,15 +722,12 @@ static void reqsk_timer_handler(struct timer_list *t)
struct net *net = sock_net(sk_listener);
struct inet_connection_sock *icsk = inet_csk(sk_listener);
struct request_sock_queue *queue = &icsk->icsk_accept_queue;
- int qlen, expire = 0, resend = 0;
- int max_retries, thresh;
- u8 defer_accept;
+ int max_retries, qlen, expire = 0, resend = 0;
if (inet_sk_state_load(sk_listener) != TCP_LISTEN)
goto drop;
max_retries = icsk->icsk_syn_retries ? :
net->ipv4.sysctl_tcp_synack_retries;
- thresh = max_retries;
/* Normally all the openreqs are young and become mature
* (i.e. converted to established socket) for first timeout.
* If synack was not acknowledged for 1 second, it means
@@ -750,17 +749,14 @@ static void reqsk_timer_handler(struct timer_list *t)
if ((qlen << 1) > max(8U, READ_ONCE(sk_listener->sk_max_ack_backlog))) {
int young = reqsk_queue_len_young(queue) << 1;
- while (thresh > 2) {
+ while (max_retries > 2) {
if (qlen < young)
break;
- thresh--;
+ max_retries--;
young <<= 1;
}
}
- defer_accept = READ_ONCE(queue->rskq_defer_accept);
- if (defer_accept)
- max_retries = defer_accept;
- syn_ack_recalc(req, thresh, max_retries, defer_accept,
+ syn_ack_recalc(req, max_retries, READ_ONCE(queue->rskq_defer_accept),
&expire, &resend);
req->rsk_ops->syn_ack_timeout(req);
if (!expire &&
--
2.17.2 (Apple Git-113)
