tcp: inherit listener congestion control for passive cnx

Rick Jones reported that TCP_CONGESTION sockopt performed on a listener was ignored for its children sockets : right after accept() the congestion control for new socket is the system default one. This seems an oversight of the initial design (quoted from Stephen) Based on prior investigation and patch from Rick. Reported-by: Rick Jones <[email protected]> Signed-off-by: Eric Dumazet <[email protected]> CC: Stephen Hemminger <[email protected]> CC: Yuchung Cheng <[email protected]> Tested-by: Rick Jones <[email protected]> Signed-off-by: David S. Miller <[email protected]>
goeke · Nov 30, 2011 · d8a6e65 · d8a6e65
1 parent de56566
commit d8a6e65
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Showing 3 changed files with 7 additions and 1 deletion.
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
@@ -175,6 +175,9 @@ tcp_congestion_control - STRING
 	connections. The algorithm "reno" is always available, but
 	additional choices may be available based on kernel configuration.
 	Default is set as part of kernel configuration.
+	For passive connections, the listener congestion control choice
+	is inherited.
+	[see setsockopt(listenfd, SOL_TCP, TCP_CONGESTION, "name" ...) ]
 
 tcp_cookie_size - INTEGER
 	Default size of TCP Cookie Transactions (TCPCT) option, that may be

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
@@ -1511,6 +1511,7 @@ struct sock *tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
 	return NULL;
 put_and_exit:
 	tcp_clear_xmit_timers(newsk);
+	tcp_cleanup_congestion_control(newsk);
 	bh_unlock_sock(newsk);
 	sock_put(newsk);
 	goto exit;

diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
@@ -495,7 +495,9 @@ struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req,
 		newtp->frto_counter = 0;
 		newtp->frto_highmark = 0;
 
-		newicsk->icsk_ca_ops = &tcp_init_congestion_ops;
+		if (newicsk->icsk_ca_ops != &tcp_init_congestion_ops &&
+		    !try_module_get(newicsk->icsk_ca_ops->owner))
+			newicsk->icsk_ca_ops = &tcp_init_congestion_ops;
 
 		tcp_set_ca_state(newsk, TCP_CA_Open);
 		tcp_init_xmit_timers(newsk);