routing: gracefully handle missing node IP during BGP announcements#871
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routing: gracefully handle missing node IP during BGP announcements#871
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In dual-stack or IPv6-enabled clusters, the agent can crash when it attempts
to announce or withdraw a BGP path for an IPv6 address, but the nodes does
not have a corresponding IPv6 address configured in HostMetadata.
Before this change, common.MakePath() returned a generic error ('no ip6
address for node'). That error was wrapped by the routing_server and
propagated back to tomb, causing the routing watcher to stop and the
main process to tear down (ending in a fatal gRPC server error).
Changes:
- Added sentinel errors ErrNoNodeIPv4 and ErrNoNodeIPv6 in common.go
- Added helper function IsMissingNodeIP() to detect these specific errors
- Updated MakePath() to return sentinel errors (including for SRv6 next-hop)
- Updated routing_server and prefix_watcher to treat missing-node-IP as a
non-fatal condition: log a warning indicating we skip announce/withdraw,
returning nil so tomb does not enter Dying state
This prevents the agent from crashing with a clear warning log for operators.
Signed-off-by: Aritra Basu <aritrbas@cisco.com>
Collaborator
|
There is probably a long discussion to be had on special case handling related to BGP, |
hedibouattour
approved these changes
Feb 5, 2026
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Problem
In dual-stack or IPv6-enabled clusters, the
agentcan crash when it attempts to announce or withdraw a BGP path for an IPv6 address, but the node does not have a corresponding IPv6 address configured inHostMetadata.RCA
common.MakePath()is called to construct a BGP path for announcement/withdrawal.nodeIPv6 == nil),MakePath()returns an error.routing_server.announceLocalAddress()orprefix_watcher.WatchPrefix().Go()wrapper passes the error to tomb, which enters theDyingstate, signaling all goroutines to stop.Impact
Solution
Implement graceful degradation by treating missing node IP as a non-fatal, recoverable condition.
The missing node IP is a transient or configuration condition, it does not mean the routing component is broken. Returning an error would stop the routing/prefix watchers and trigger the tomb to kill the whole agent.
By returning early, the routing/prefix watchers continue, and missing paths can be restored later. The logic keeps state in memory (
localAddressMap), so once the node IP becomes available,RestoreLocalAddresses()will re-announce.