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 <rick.jones2@hp.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Stephen Hemminger <shemminger@vyatta.com>
CC: Yuchung Cheng <ycheng@google.com>
Tested-by: Rick Jones <rick.jones2@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index b886706..cb2b1c6 100644 (file)
--- 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
index a9db4b1..c4b8b09 100644 (file)
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1511,6 +1511,7 @@ exit:
        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
index 945efff..9dc146e 100644 (file)
--- 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);