diff options
| author | Ido Schimmel <idosch@nvidia.com> | 2025-04-30 13:02:40 +0300 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2025-05-03 21:52:38 +0100 |
| commit | 836b313a14a316290886dcc2ce7e78bf5ecc8658 (patch) | |
| tree | c558ac606f84935ced53b5a91a24988f1dea6853 /net | |
| parent | 586ceac9acb71c4caf84552bd29b36c799c102a0 (diff) | |
ipv4: Honor "ignore_routes_with_linkdown" sysctl in nexthop selection
Commit 32607a332cfe ("ipv4: prefer multipath nexthop that matches source
address") changed IPv4 nexthop selection to prefer a nexthop whose
nexthop device is assigned the specified source address for locally
generated traffic.
While the selection honors the "fib_multipath_use_neigh" sysctl and will
not choose a nexthop with an invalid neighbour, it does not honor the
"ignore_routes_with_linkdown" sysctl and can choose a nexthop without a
carrier:
$ sysctl net.ipv4.conf.all.ignore_routes_with_linkdown
net.ipv4.conf.all.ignore_routes_with_linkdown = 1
$ ip route show 198.51.100.0/24
198.51.100.0/24
nexthop via 192.0.2.2 dev dummy1 weight 1
nexthop via 192.0.2.18 dev dummy2 weight 1 dead linkdown
$ ip route get 198.51.100.1 from 192.0.2.17
198.51.100.1 from 192.0.2.17 via 192.0.2.18 dev dummy2 uid 0
Solve this by skipping over nexthops whose assigned hash upper bound is
minus one, which is the value assigned to nexthops that do not have a
carrier when the "ignore_routes_with_linkdown" sysctl is set.
In practice, this probably does not matter a lot as the initial route
lookup for the source address would not choose a nexthop that does not
have a carrier in the first place, but the change does make the code
clearer.
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
| -rw-r--r-- | net/ipv4/fib_semantics.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c index 03959c60d128..dabe2b7044ab 100644 --- a/net/ipv4/fib_semantics.c +++ b/net/ipv4/fib_semantics.c @@ -2188,7 +2188,14 @@ void fib_select_multipath(struct fib_result *res, int hash, saddr = fl4 ? fl4->saddr : 0; change_nexthops(fi) { - if (use_neigh && !fib_good_nh(nexthop_nh)) + int nh_upper_bound; + + /* Nexthops without a carrier are assigned an upper bound of + * minus one when "ignore_routes_with_linkdown" is set. + */ + nh_upper_bound = atomic_read(&nexthop_nh->fib_nh_upper_bound); + if (nh_upper_bound == -1 || + (use_neigh && !fib_good_nh(nexthop_nh))) continue; if (!found) { @@ -2197,7 +2204,7 @@ void fib_select_multipath(struct fib_result *res, int hash, found = !saddr || nexthop_nh->nh_saddr == saddr; } - if (hash > atomic_read(&nexthop_nh->fib_nh_upper_bound)) + if (hash > nh_upper_bound) continue; if (!saddr || nexthop_nh->nh_saddr == saddr) { |