From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AF50B4EB879; Wed, 30 Sep 2026 16:27:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790785667; cv=none; b=Ba1xoPBCnK+l+wG7ZBYKOyVdJq7CXR+XqExZHXgEQfLq5u2gb0n2iVbWh7LpwFsL+7P5iTE3qpBb7jrJhKxhnN+9O00lbG+uDB20UgVTT/3H020oMiAGfwNY9ClYjyON0VWA7tOgm0bonZ9vgrQzwJnShrkuKGLZBgBRSsLCpSA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790785667; c=relaxed/simple; bh=mA0CWExp+Br/ui7kInjYupn+OrFpREIGUokHUl9asno=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=LHCbhVM8GRKN6wDtWniA2jt/qvIdPOQDSfB5Zp0BmY8iRNDf+SGKnsuVm8oYvW5o/yIEewSJJLoYU5dwhxzGjfRB2iqzflz4DJUHrz6i4TYI0AMNhk80lCiRAp9QciLg46VEm4NTkWygZ+gm8iY72Tf6sqnILqy1iYZ2II1dW3U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=wx0zmens; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="wx0zmens" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D928F1F000FF; Wed, 30 Sep 2026 16:27:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790785665; bh=ZnpvVIDprfdSSLhYrSp0FTrL6qUIcOA1b72kMVvHMLM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=wx0zmensu0JHMiBEaAbaSFUKVPdpjy01h8pnyqT0ZYTGK72E0uHlEzzzDoRLzJI02 oTzvL0V4g7qtKoB1iv5xqNdqmW7c+D04z12FvN2qoqwy5Q4VWxPaUn6zueGUgG4WQm KVv0Ni8lew+vFbUaEnj8s7YAPdfrRhcrfioxOhcM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Ido Schimmel , David Ahern , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.1 587/982] ipv6: Select best matching nexthop object in fib6_table_lookup() Date: Wed, 30 Sep 2026 17:22:03 +0200 Message-ID: <20260930152429.390970122@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152416.775402466@linuxfoundation.org> References: <20260930152416.775402466@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ido Schimmel [ Upstream commit 484bb9d164df397a53e0f533b262b27b1590efcb ] Currently, when using multipath routes without nexthop objects, fib6_table_lookup() selects the nexthop with the highest score. This means that when both a source address and an oif are specified, the nexthop that is chosen is the one that matches in terms of oif: # sysctl -wq net.ipv6.conf.all.forwarding=1 # ip address add 2001:db8:2::1/64 dev lo # ip route add 2001:db8:10::/64 nexthop via fe80::1 dev dummy1 nexthop via fe80::2 dev dummy2 # perf record -e fib6:fib6_table_lookup -- bash -c "for i in {1..100}; do ip route get 2001:db8:10::${i} from 2001:db8:2::1 oif dummy1; done > /dev/null" # perf script | grep -o dummy[0-9] | sort | uniq -c 100 dummy1 # perf record -e fib6:fib6_table_lookup -- bash -c "for i in {1..100}; do ip route get 2001:db8:10::${i} from 2001:db8:2::1 oif dummy2; done > /dev/null" # perf script | grep -o dummy[0-9] | sort | uniq -c 100 dummy2 When using nexthop objects, fib6_table_lookup() selects the first matching nexthop and not necessarily the one with the highest score: # ip nexthop add id 1 via fe80::1 dev dummy1 # ip nexthop add id 2 via fe80::2 dev dummy2 # ip nexthop add id 3 group 1/2 # ip route add 2001:db8:20::/64 nhid 3 # perf record -e fib6:fib6_table_lookup -- bash -c "for i in {1..100}; do ip route get 2001:db8:20::${i} from 2001:db8:2::1 oif dummy1; done > /dev/null" # perf script | grep -o dummy[0-9] | sort | uniq -c 100 dummy1 # perf record -e fib6:fib6_table_lookup -- bash -c "for i in {1..100}; do ip route get 2001:db8:20::${i} from 2001:db8:2::1 oif dummy2; done > /dev/null" # perf script | grep -o dummy[0-9] | sort | uniq -c 100 dummy1 This is not very significant right now because the nexthop is later overwritten during path selection in fib6_select_path(). However, the next patch is going to skip path selection when we have an oif match during output route lookup. As a preparation for this change, align the nexthop object behavior with the legacy one and make sure that fib6_table_lookup() always selects the best matching nexthop. Do that by always returning 0 from rt6_nh_find_match() in order not to terminate the loop in nexthop_for_each_fib6_nh() and storing in arg->nh the best matching nexthop so far. Behavior after the change: # perf record -e fib6:fib6_table_lookup -- bash -c "for i in {1..100}; do ip route get 2001:db8:20::${i} from 2001:db8:2::1 oif dummy1; done > /dev/null" # perf script | grep -o dummy[0-9] | sort | uniq -c 100 dummy1 # perf record -e fib6:fib6_table_lookup -- bash -c "for i in {1..100}; do ip route get 2001:db8:20::${i} from 2001:db8:2::1 oif dummy2; done > /dev/null" # perf script | grep -o dummy[0-9] | sort | uniq -c 100 dummy2 Signed-off-by: Ido Schimmel Reviewed-by: David Ahern Link: https://patch.msgid.link/20260611154605.992528-2-idosch@nvidia.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/ipv6/route.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/net/ipv6/route.c b/net/ipv6/route.c index b1de7c6f895a2..be3e36162d059 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -823,9 +823,11 @@ static int rt6_nh_find_match(struct fib6_nh *nh, void *_arg) { struct fib6_nh_frl_arg *arg = _arg; - arg->nh = nh; - return find_match(nh, arg->flags, arg->oif, arg->strict, - arg->mpri, arg->do_rr); + if (find_match(nh, arg->flags, arg->oif, arg->strict, arg->mpri, + arg->do_rr)) + arg->nh = nh; + + return 0; } static void __find_rr_leaf(struct fib6_info *f6i_start, @@ -865,11 +867,10 @@ static void __find_rr_leaf(struct fib6_info *f6i_start, res->nh = nexthop_fib6_nh(f6i->nh); return; } - if (nexthop_for_each_fib6_nh(f6i->nh, rt6_nh_find_match, - &arg)) { - matched = true; - nh = arg.nh; - } + nexthop_for_each_fib6_nh(f6i->nh, rt6_nh_find_match, + &arg); + matched = !!arg.nh; + nh = arg.nh; } else { nh = f6i->fib6_nh; if (find_match(nh, f6i->fib6_flags, oif, strict, -- 2.53.0