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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Shuah Khan CC: "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-kselftest@vger.kernel.org" , Ido Schimmel Subject: [PATCH net-next v2 3/4] nexthop: Do not return invalid nexthop object during multipath selection Thread-Topic: [PATCH net-next v2 3/4] nexthop: Do not return invalid nexthop object during multipath selection Thread-Index: Adm6SPCTjLnm6ZDF2UuYdzGvm4mP9w== Date: Wed, 19 Jul 2023 13:57:22 +0000 Message-ID: <20230719-nh_select-v2-3-04383e89f868@nvidia.com> References: <20230719-nh_select-v2-0-04383e89f868@nvidia.com> In-Reply-To: <20230719-nh_select-v2-0-04383e89f868@nvidia.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-clientproxiedby: YQXP288CA0028.CANP288.PROD.OUTLOOK.COM (2603:10b6:c00:41::40) To MN2PR12MB4373.namprd12.prod.outlook.com (2603:10b6:208:261::8) x-mailer: b4 0.12.2 authentication-results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; 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OTOH, with nexthop objects, nexthop_select_path_hthr() may return a nexthop that failed the nexthop_is_good_nh() test even if there was one that passed. Refactor nexthop_select_path_hthr() to follow a selection logic more similar to fib_select_multipath(). The issue can be demonstrated with the following sequence of commands. The first block shows that things work as expected with legacy nexthops. The last sequence of `ip rou get` in the second block shows the problem case - some routes still use the .2 nexthop. sysctl net.ipv4.fib_multipath_use_neigh=1 ip link add dummy1 up type dummy ip rou add 198.51.100.0/24 nexthop via 192.0.2.1 dev dummy1 onlink nexthop via 192.0.2.2 dev dummy1 onlink for i in {10..19}; do ip -o rou get 198.51.100.$i; done ip neigh add 192.0.2.1 dev dummy1 nud failed echo ".1 failed:" # results should not use .1 for i in {10..19}; do ip -o rou get 198.51.100.$i; done ip neigh del 192.0.2.1 dev dummy1 ip neigh add 192.0.2.2 dev dummy1 nud failed echo ".2 failed:" # results should not use .2 for i in {10..19}; do ip -o rou get 198.51.100.$i; done ip link del dummy1 ip link add dummy1 up type dummy ip nexthop add id 1 via 192.0.2.1 dev dummy1 onlink ip nexthop add id 2 via 192.0.2.2 dev dummy1 onlink ip nexthop add id 1001 group 1/2 ip rou add 198.51.100.0/24 nhid 1001 for i in {10..19}; do ip -o rou get 198.51.100.$i; done ip neigh add 192.0.2.1 dev dummy1 nud failed echo ".1 failed:" # results should not use .1 for i in {10..19}; do ip -o rou get 198.51.100.$i; done ip neigh del 192.0.2.1 dev dummy1 ip neigh add 192.0.2.2 dev dummy1 nud failed echo ".2 failed:" # results should not use .2 for i in {10..19}; do ip -o rou get 198.51.100.$i; done ip link del dummy1 Signed-off-by: Ido Schimmel Signed-off-by: Benjamin Poirier Reviewed-by: David Ahern --- net/ipv4/nexthop.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/net/ipv4/nexthop.c b/net/ipv4/nexthop.c index c12acbf39659..93f14d39fef6 100644 --- a/net/ipv4/nexthop.c +++ b/net/ipv4/nexthop.c @@ -1194,20 +1194,22 @@ static struct nexthop *nexthop_select_path_hthr(struct nh_group *nhg, int hash) for (i = 0; i < nhg->num_nh; ++i) { struct nh_grp_entry *nhge = &nhg->nh_entries[i]; - if (hash > atomic_read(&nhge->hthr.upper_bound)) - continue; - /* nexthops always check if it is good and does * not rely on a sysctl for this behavior */ - if (nexthop_is_good_nh(nhge->nh)) - return nhge->nh; + if (!nexthop_is_good_nh(nhge->nh)) + continue; if (!rc) rc = nhge->nh; + + if (hash > atomic_read(&nhge->hthr.upper_bound)) + continue; + + return nhge->nh; } - return rc; + return rc ? : nhg->nh_entries[0].nh; } static struct nexthop *nexthop_select_path_res(struct nh_group *nhg, int hash)