cnetlink: sync route cache on linkdown events #469
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Work around missing route removal notifications from kernel on link down with routes targeting nexthops on that link by forcing a cache resync on link down events to catch removed routes. When a link goes down, the kernel will delete all nexthops on that link without sending out netlink notifications. When a nexthop gets deleted, the kernel will delete all routes with the nexthop as destination without sending out netlink notifications. These two combined means that when using nexthop objects, like FRR does by default, deletion of routes on link loss are never seen by libnl, and consequently never seen by baseboxd. This causes flow table entries for routes to persist even though they were deleted in the kernel. To work around this, use nl_cache_resync_v2() to trigger a resync of all routes when a link goes down. Signed-off-by: Jonas Gorski <jonas.gorski@bisdn.de>
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jklare
approved these changes
Mar 24, 2025
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Work around missing route removal notifications from kernel on link down with routes targeting nexthops on that link by forcing a cache resync on link down events to catch removed routes.
When a link goes down, the kernel will delete all nexthops on that link without sending out netlink notifications.
When a nexthop gets deleted, the kernel will delete all routes with the nexthop as destination without sending out netlink notifications.
These two combined means that when using nexthop objects, like FRR does by default, deletion of routes on link loss are never seen by libnl, and consequently never seen by baseboxd.
This causes flow table entries for routes to persist even though they were deleted in the kernel.
To work around this,
use nl_cache_resync_v2()to trigger a resync of all routes when a link goes down.Motivation and Context
A customer reported routes still present in flow tables with EIGRP despite missing from kernel.
How Has This Been Tested?
Pipeline run with changes applied (87710 on cel-questone-2a).