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For IPv4, neighbour lookup is ARP, no? >> It is but it is not the only way. A device may not do ARP by itself but it relies on the rest of the stack like vrf or ip vlan mode to resolve. >> A user may also set manual entry without explicit ARP. > I think it was just a mistake to use NOARP this way in RDMA, I looked > in the git history and there was no justification. That or it was > right in the 2.x days and netdev moved on to the current schem. > > I expect to just call the neighbor functions and if they can't work > for some reason they should fail? > > Jason Right. This is the patch does, to rely on the neighbour functions to resolve without depending on the NOARP.