Commits on Mar 6, 2024

1. Downgrade L2 Neighbor Discovery failure log to Debug …

   Suppress the "Unable to determine next hop address" logs. While it shows
   the L2 neighbor resolution failure, it does not always indicate a
   datapath connectivity issue.
   
   For example, when "devices=eth+" is specified and the device
   naming/purposing is not consistent across the nodes in the cluster, in
   some nodes "eth1" is a device reachable to other nodes, but in some
   nodes, it is not. As a result, L2 Discovery generates an "Unable to
   determine next hop address".
   
   Another example is ENI mode with automatic device detection. When
   secondary interfaces are added, they are used for L2 Neighbor Discovery
   as well. However, nodes can only be reached via the primary interface
   through the default route in the main routing table. Thus, L2 Neighbor
   Discovery generates "Unable to determine next hop address" for secondary
   interfaces.
   
   In both cases, it does not always mean the datapath has an issue for KPR
   functionality. However, the logs appear repeatedly, are noisy, and the
   message is error-ish, causing confusion.
   
   This log started to appear for some users who did not see it before from
   v1.14.3 (cilium#28858) and v1.15.0 (in theory). For v1.14.3, it affects KPR +
   Tunnel users because of f2dcc86. Before the commit, we did not perform
   L2 Neighbor Discovery in tunnel mode, so even if users had an interface
   unreachable to other nodes, the log did not appear.
   
   For v1.15.0, it affects to the users who used to have the unreachable
   interface. 2058ed6 made it visible. Before the commit, some kind of the
   errors like EHOSTUNREACH and ENETUNREACH were not caught because
   FIBMatch option didn't specified. After v1.15.0, users started to see
   the log.
   
   Fixes: cilium#28858
   
   Signed-off-by: Yutaro Hayakawa <yutaro.hayakawa@isovalent.com>

   

   YutaroHayakawa committed Mar 6, 2024
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