Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756351AbbFSUki (ORCPT ); Fri, 19 Jun 2015 16:40:38 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:51546 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755998AbbFSUiy (ORCPT ); Fri, 19 Jun 2015 16:38:54 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Florian Westphal , Daniel Borkmann , Glenn Judd , Stephen Hemminger , Neal Cardwell , Eric Dumazet , Yuchung Cheng , Daniel Borkmann , "David S. Miller" Subject: [PATCH 4.0 024/105] tcp: fix child sockets to use system default congestion control if not set Date: Fri, 19 Jun 2015 13:35:14 -0700 Message-Id: <20150619203558.921739064@linuxfoundation.org> X-Mailer: git-send-email 2.4.4 In-Reply-To: <20150619203558.187802739@linuxfoundation.org> References: <20150619203558.187802739@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3826 Lines: 99 4.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Neal Cardwell [ Upstream commit 9f950415e4e28e7cfae2e416b43e862e8101d996 ] Linux 3.17 and earlier are explicitly engineered so that if the app doesn't specifically request a CC module on a listener before the SYN arrives, then the child gets the system default CC when the connection is established. See tcp_init_congestion_control() in 3.17 or earlier, which says "if no choice made yet assign the current value set as default". The change ("net: tcp: assign tcp cong_ops when tcp sk is created") altered these semantics, so that children got their parent listener's congestion control even if the system default had changed after the listener was created. This commit returns to those original semantics from 3.17 and earlier, since they are the original semantics from 2007 in 4d4d3d1e8 ("[TCP]: Congestion control initialization."), and some Linux congestion control workflows depend on that. In summary, if a listener socket specifically sets TCP_CONGESTION to "x", or the route locks the CC module to "x", then the child gets "x". Otherwise the child gets current system default from net.ipv4.tcp_congestion_control. That's the behavior in 3.17 and earlier, and this commit restores that. Fixes: 55d8694fa82c ("net: tcp: assign tcp cong_ops when tcp sk is created") Cc: Florian Westphal Cc: Daniel Borkmann Cc: Glenn Judd Cc: Stephen Hemminger Signed-off-by: Neal Cardwell Signed-off-by: Eric Dumazet Signed-off-by: Yuchung Cheng Acked-by: Daniel Borkmann Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- include/net/inet_connection_sock.h | 3 ++- net/ipv4/tcp_cong.c | 5 ++++- net/ipv4/tcp_minisocks.c | 5 ++++- 3 files changed, 10 insertions(+), 3 deletions(-) --- a/include/net/inet_connection_sock.h +++ b/include/net/inet_connection_sock.h @@ -98,7 +98,8 @@ struct inet_connection_sock { const struct tcp_congestion_ops *icsk_ca_ops; const struct inet_connection_sock_af_ops *icsk_af_ops; unsigned int (*icsk_sync_mss)(struct sock *sk, u32 pmtu); - __u8 icsk_ca_state:7, + __u8 icsk_ca_state:6, + icsk_ca_setsockopt:1, icsk_ca_dst_locked:1; __u8 icsk_retransmits; __u8 icsk_pending; --- a/net/ipv4/tcp_cong.c +++ b/net/ipv4/tcp_cong.c @@ -187,6 +187,7 @@ static void tcp_reinit_congestion_contro tcp_cleanup_congestion_control(sk); icsk->icsk_ca_ops = ca; + icsk->icsk_ca_setsockopt = 1; if (sk->sk_state != TCP_CLOSE && icsk->icsk_ca_ops->init) icsk->icsk_ca_ops->init(sk); @@ -335,8 +336,10 @@ int tcp_set_congestion_control(struct so rcu_read_lock(); ca = __tcp_ca_find_autoload(name); /* No change asking for existing value */ - if (ca == icsk->icsk_ca_ops) + if (ca == icsk->icsk_ca_ops) { + icsk->icsk_ca_setsockopt = 1; goto out; + } if (!ca) err = -ENOENT; else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) || --- a/net/ipv4/tcp_minisocks.c +++ b/net/ipv4/tcp_minisocks.c @@ -437,7 +437,10 @@ void tcp_ca_openreq_child(struct sock *s rcu_read_unlock(); } - if (!ca_got_dst && !try_module_get(icsk->icsk_ca_ops->owner)) + /* If no valid choice made yet, assign current system default ca. */ + if (!ca_got_dst && + (!icsk->icsk_ca_setsockopt || + !try_module_get(icsk->icsk_ca_ops->owner))) tcp_assign_congestion_control(sk); tcp_set_ca_state(sk, TCP_CA_Open); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in Please read the FAQ at http://www.tux.org/lkml/