Pull up following revision(s) (requested by ozaki-r in ticket #353):
sys/net/if_llatbl.c: 1.22
sys/net/if_llatbl.h: 1.13
sys/netinet/if_arp.c: 1.254
sys/netinet/in.c: 1.208-1.209
sys/netinet6/in6.c: 1.249-1.250
sys/netinet6/nd6.c: 1.237
Remove redundant KASSERTMSG
The function is static, has just one caller and the caller does the same check.
--
Fix a deadlock between a route update and lltable
It happens because rtalloc1 is called from lltable with holding
IF_AFDATA_WLOCK.
If a route update is in action, rtalloc1 would wait for its completion with
holding IF_AFDATA_WLOCK. At the same moment, a softint (e.g., arpintr) may try
to take IF_AFDATA_WLOCK and get stuck on it. Unfortunately the stuck softint
prevents the route update from progressing because the route update calls
psref_target_destroy that needs the softint to complete.
A resource allocation graph of the senario looks like this:
    route update =(psref_target_destroy)=> softint => IF_AFDATA_WLOCK
    =(rt_update_wait)=> route update
Fix the deadlock by pulling rtalloc1 out of the lltable codes inside
IF_AFDATA_WLOCK.
Note that the deadlock happens only if NET_MPSAFE is enabled.

(snj)