route: treat nhid changes as full route replacements #449
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When updating a route targeting a nexthoup group with id changing its nexthop to a single nexthop, we treat this as an update and instead add that nexthop to the group instead of replacing the route in the cache. So e.g. with nexthop id 10 fe80::1 dev eth1 nexthop id 11 fe80::2 dev eth2 nexthop id 12 fe80::3 dev eth3 nexthop id 20 grp 10/11 adding a route dst 2001:db8:1:/64 nhid 20 libnl will store this as 2001:db8:1:/64 via fe80::1, fe80::2 if we now update the route with dst 2001:db8:1:/64 nhid 12 libnl will see a new route with a single nexthop. Since the existing route for dst 2001:db8:1:/64 is a multipath route, and the new route has a single nexthop, libnl assumes this is a new nexthop for the route, and merges it to 2001:db8:1:/64 via fe80::1, fe80::2, fe80::3 instead of replacing it. Fix this by checking the nhid of the routes, and only merge if they match. Fixes: 29b7137 ("route cache: Fix handling of ipv6 multipath routes") Signed-off-by: Jonas Gorski <[email protected]>
thom311
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Dec 23, 2025
When updating a route targeting a nexthoup group with id changing its nexthop to a single nexthop, we treat this as an update and instead add that nexthop to the group instead of replacing the route in the cache. So e.g. with nexthop id 10 fe80::1 dev eth1 nexthop id 11 fe80::2 dev eth2 nexthop id 12 fe80::3 dev eth3 nexthop id 20 grp 10/11 adding a route dst 2001:db8:1:/64 nhid 20 libnl will store this as 2001:db8:1:/64 via fe80::1, fe80::2 if we now update the route with dst 2001:db8:1:/64 nhid 12 libnl will see a new route with a single nexthop. Since the existing route for dst 2001:db8:1:/64 is a multipath route, and the new route has a single nexthop, libnl assumes this is a new nexthop for the route, and merges it to 2001:db8:1:/64 via fe80::1, fe80::2, fe80::3 instead of replacing it. Fix this by checking the nhid of the routes, and only merge if they match. Fixes: 29b7137 ("route cache: Fix handling of ipv6 multipath routes") Signed-off-by: Jonas Gorski <[email protected]> #449
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merged. Thank you for the patch!! |
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When updating a route targeting a nexthoup group with id changing its nexthop to a single nexthop, we treat this as an update and instead add that nexthop to the group instead of replacing the route in the cache.
So e.g. with
adding a route
libnl will store this as 2001:db8:1:/64 via fe80::1, fe80::2
if we now update the route with
libnl will see a new route with a single nexthop. Since the existing route for dst
2001:db8:1:/64is a multipath route, and the new route has a single nexthop, libnl assumes this is a new nexthop for the route, and merges it to2001:db8:1:/64 via fe80::1, fe80::2, fe80::3instead of replacing it.Fix this by checking the nhid of the routes, and only merge if they match.
Fixes: 29b7137 ("route cache: Fix handling of ipv6 multipath routes")