recent MFC of soreceive_dgram breaks kernels without INET6 option

[Josh Carroll]

Hello,

I just csup'd this morning and now I cannot build a kernel that does
not include INET6. I can send my KERNCONF, but it is sufficient to
create a kernel config with:

include GENERIC
nooption INET6

Here's the error during kernel compilation of a kernel config without
"options INET6" in the kernel config:

/usr/src/sys/netinet/udp_usrreq.c: In function 'udp_inpcb_init':
/usr/src/sys/netinet/udp_usrreq.c:170: error: 'udp6_usrreqs'
undeclared (first use in this function)
/usr/src/sys/netinet/udp_usrreq.c:170: error: (Each undeclared
identifier is reported only once
/usr/src/sys/netinet/udp_usrreq.c:170: error: for each function it appears in.)

It looks like the MFC for the new soreceive_dgram stuff is the culprit.

Can this can be fixed to not require IPv6? I have no desire to include
it in my kernel, but if that will be the requirement going forward,
perhaps a note in UPDATING is in order?

Thanks,
Josh