From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933297AbaHHVWV (ORCPT ); Fri, 8 Aug 2014 17:22:21 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:40929 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751977AbaHHUvD (ORCPT ); Fri, 8 Aug 2014 16:51:03 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Eric Dumazet , Shawn Bohrer , "David S. Miller" , Kamal Mostafa Subject: [PATCH 3.13 226/259] udp: ipv4: do not waste time in __udp4_lib_mcast_demux_lookup Date: Fri, 8 Aug 2014 13:40:49 -0700 Message-Id: <1407530482-4483-227-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1407530482-4483-1-git-send-email-kamal@canonical.com> References: <1407530482-4483-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.13 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.13.11.6 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit 63c6f81cdde58c41da62a8d8a209592e42a0203e ] Its too easy to add thousand of UDP sockets on a particular bucket, and slow down an innocent multicast receiver. Early demux is supposed to be an optimization, we should avoid spending too much time in it. It is interesting to note __udp4_lib_demux_lookup() only tries to match first socket in the chain. 10 is the threshold we already have in __udp4_lib_lookup() to switch to secondary hash. Fixes: 421b3885bf6d5 ("udp: ipv4: Add udp early demux") Signed-off-by: Eric Dumazet Reported-by: David Held Cc: Shawn Bohrer Signed-off-by: David S. Miller Signed-off-by: Kamal Mostafa --- net/ipv4/udp.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index a7e4729..98ea36d 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -1833,6 +1833,10 @@ static struct sock *__udp4_lib_mcast_demux_lookup(struct net *net, unsigned int count, slot = udp_hashfn(net, hnum, udp_table.mask); struct udp_hslot *hslot = &udp_table.hash[slot]; + /* Do not bother scanning a too big list */ + if (hslot->count > 10) + return NULL; + rcu_read_lock(); begin: count = 0; -- 1.9.1