Pull up following revision(s) via patch (requested by knakahara in ticket #905):

sys/netinet/ip_mroute.c: revision 1.160
sys/netinet6/in6_l2tp.c: revision 1.16
sys/net/if.h: revision 1.263
sys/netinet/in_l2tp.c: revision 1.15
sys/netinet/ip_icmp.c: revision 1.172
sys/netinet/igmp.c: revision 1.68
sys/netinet/ip_encap.c: revision 1.69
sys/netinet6/ip6_mroute.c: revision 1.129

sbappendaddr() is required any lock. Currently, softnet_lock is appropriate.

When rip_input() is called as inetsw[].pr_input, rip_iput() is always called
with holding softnet_lock, that is, in case of !defined(NET_MPSAFE) it is
acquired in ipintr(), otherwise(defined(NET_MPSAFE)) it is acquire in
PR_WRAP_INPUT macro.

However, some function calls rip_input() directly without holding softnet_lock.
That causes assertion failure in sbappendaddr().
rip6_input() and icmp6_rip6_input() are also required softnet_lock for the same
reason.

(martin)