| Message ID | 20230719-nh_select-v2-3-04383e89f868@nvidia.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 75f5f04c7bd2163044f80d5f7bea6b79edc288fa |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | nexthop: Refactor and fix nexthop selection for multipath routes | expand |
On 7/19/23 7:57 AM, Benjamin Poirier wrote: > With legacy nexthops, when net.ipv4.fib_multipath_use_neigh is set, > fib_select_multipath() will never set res->nhc to a nexthop that is not > good (as per fib_good_nh()). 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 <idosch@nvidia.com> > Signed-off-by: Benjamin Poirier <bpoirier@nvidia.com> > --- > net/ipv4/nexthop.c | 14 ++++++++------ > 1 file changed, 8 insertions(+), 6 deletions(-) > Reviewed-by: David Ahern <dsahern@kernel.org>
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)
With legacy nexthops, when net.ipv4.fib_multipath_use_neigh is set, fib_select_multipath() will never set res->nhc to a nexthop that is not good (as per fib_good_nh()). 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 <idosch@nvidia.com> Signed-off-by: Benjamin Poirier <bpoirier@nvidia.com> --- net/ipv4/nexthop.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-)