neigh: Init new neighbor for older kernel with NUD_STALE
neigh: Init new neighbor for older kernel with NUD_STALE

NUD_STALE reuses the NUD_PERMANENT's prior lladdr for its stale state if the
entry existed before, and subsequently triggers a new resolution via NTF_USE
given it's none of NUD_CONNECTED, NUD_DELAY or NUD_PROBE. NUD_NONE is less
ideal for agent restarts where the agent is not aware of the already existing
entry given this would incur a tiny window where lladdr is unavailable.

Signed-off-by: Daniel Borkmann <3d0f3b9ddcacec30c4008c5e030e6c13a478cb4f@iogearbox.net>

michi-covalent/cilium,michi-covalent/cilium,cilium/cilium,michi-covalent/cilium,michi-covalent/cilium,michi-covalent/cilium,cilium/cilium,cilium/cilium,cilium/cilium,cilium/cilium