When we are about to send down to the driver layer
we need to make sure that the m_nextpkt field is NULL
else the lower layers may do unwanted things.

Reviewed By: gallatin, melifaro
Differential Revision: https://reviews.freebsd.org/D28377
PR: 253587

(cherry picked from commit 24a8f6d369962f189ad808f538029179b1e7dc2f)

Git Hash: f974af4e59ee533906437b22a5b8b41219bde005
Git Author: rrs@FreeBSD.org

Revert r330897:

This was intended to be a non-functional change. It wasn't. The commit
message was thus wrong. In addition it broke arm, and merged crypto
related code.

Revert with prejudice.

This revert skips files touched in r316370 since that commit was since
MFCed. This revert also skips files that require $FreeBSD$ property
changes.

Thank you to those who helped me get out of this mess including but not
limited to gonzo, kevans, rgrimes.

Requested by: gjb (re)

Partial merge of the SPDX changes

These changes are incomplete but are making it difficult
to determine what other changes can/should be merged.

No objections from: pfg

MFC r328552

ND6: Set the correct state for new neighbor cache entries

Restore state 6. Many of the UNH tests end up exercising this
state, where we have a new neighbor cache entry and a new link-layer
entry is being created for it. The link-layer address is currently
unknown so the initial state of the "llentry" should remain initialized
to ND6_LLINFO_NOSTATE so that the ND code will send a solicitation.
Setting this to ND6_LLINFO_STALE implies that the link-level entry
is valid and can be used (but needs to be refreshed via the Neighbor
Unreachability state machine).

https://forums.freebsd.org/threads/64287/

Submitted by: Farrell Woods <Farrell_Woods@Dell.com>
Reviewed by: mjoras, dab, ae
Sponsored by: Dell EMC
Differential Revision: https://reviews.freebsd.org/D14059

MFC r313025, r313395, r314113, r314442, r315458, r315656

r313025:
Add tests for multi-fib IPv6 routing

PR: 196361
Submitted by: jhujhiti@adjectivism.org
Reported by: Jason Healy <jhealy@logn.net>
MFC after: 4 weeks
Sponsored by: Spectra Logic Corp

r313395:
Add fibs_test:udp_dontroute6, another IPv6 multi-FIB test

PR: 196361
MFC after: 3 weeks
Sponsored by: Spectra Logic Corp

r314113:
Remove tests/sys/netinet/fibs_tests's dependency on net/socat

Instead of bridging two tap interfaces with socat, just use an epair pair.

MFC after: 3 weeks
Sponsored by: Spectra Logic Corp

r314442:
Add an ATF test for IPv6 SLAAC with multiple fibs

Tests that an interface can get a SLAAC address and that it inserts its
routes into the correct fib. Does not test anything to do with NDP.

PR: 196361
Reviewed by: Erick Turnquist <jhujhiti@adjectivism.org>
MFC after: 3 weeks
Sponsored by: Spectra Logic Corp
Differential Revision: https://reviews.freebsd.org/D9776

r315458:
Constrain IPv6 routes to single FIBs when net.add_addr_allfibs=0

sys/netinet6/icmp6.c
Use the interface's FIB for source address selection in ICMPv6 error
responses.

sys/netinet6/in6.c
In in6_newaddrmsg, announce arrival of local addresses on the
interface's FIB only. In in6_lltable_rtcheck, use a per-fib ND6
cache instead of a single cache.

sys/netinet6/in6_src.c
In in6_selectsrc, use the caller's fib instead of the default fib.
In in6_selectsrc_socket, remove a superfluous check.

sys/netinet6/nd6.c
In nd6_lle_event, use the interface's fib for routing socket
messages. In nd6_is_new_addr_neighbor, check all FIBs when trying
to determine whether an address is a neighbor. Also, simplify the
code for point to point interfaces.

sys/netinet6/nd6.h
sys/netinet6/nd6.c
sys/netinet6/nd6_rtr.c
Make defrouter_select fib-aware, and make all of its callers pass in
the interface fib.

sys/netinet6/nd6_nbr.c
When inputting a Neighbor Solicitation packet, consider the
interface fib instead of the default fib for DAD. Output NS and
Neighbor Advertisement packets on the correct fib.

sys/netinet6/nd6_rtr.c
Allow installing the same host route on different interfaces in
different FIBs. If rt_add_addr_allfibs=0, only install or delete
the prefix route on the interface fib.

tests/sys/netinet/fibs_test.sh
Clear some expected failures, but add a skip for the newly revealed
BUG217871.

PR: 196361
Submitted by: Erick Turnquist <jhujhiti@adjectivism.org>
Reported by: Jason Healy <jhealy@logn.net>
Reviewed by: asomers
MFC after: 3 weeks
Sponsored by: Spectra Logic Corp
Differential Revision: https://reviews.freebsd.org/D9451

r315656:
Fix back-to-back runs of sys/netinet/fibs_test;slaac_on_nondefault_fib6

This test was failing if run twice because rtadvd takes too long to die.
The rtadvd process from the first run was still running when the
second run created its interfaces. The solution is to use SIGKILL during
the cleanup instead of SIGTERM so rtadvd will die faster.

While I'm here, randomize the addresses used for the test, which makes bugs
like this easier to spot, and fix the cleanup order to be the opposite of
the setup order

PR: 217871
MFC after: 18 days
X-MFC-With: 315458
Sponsored by: Spectra Logic Corp

MFC r306829, r310286, r311695:
Lock the ND prefix list and add refcounting for prefixes.

MFC r306792-r306795, r306826, r306828:
Miscellaneous ND6 code cleanups.

MFC r306285:
Rename ndpr_refcnt to ndpr_addrcnt.

MFC r303171: Fix per-connection L2 caching in fast path

r301217 re-added per-connection L2 caching from a previous change,
but it omitted caching in the fast path. Add it.

Reviewed By: gallatin
Approved by: gnn (mentor)
Approved by: re (kostikbel)
Differential Revision: https://reviews.freebsd.org/D7239