MFC r326276:

various: general adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

No functional change intended.

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

mtest: Prevent access to uninitialized value.

case 'g' makes use of value n, which is initialized for case 'b'
and passe through to case 'g'. If case 'g' is called directly
value 'n' is not initialized.

Avoid the issue by initializing n before entering the switch.

CID: 1006375
Reviewed by: bms

Fix socket calls on error post-r243965.

Submitted by: Garrett Cooper

Don't die if either of INET or INET6 aren't in the running kernel.
Instead, report "protocol not supported" errors at runtime if a user
attempts to use a protocol that the kernel doesn't support.

Reviewed by: bz
MFC after: 1 week

Merge IPv6-capable mtest(8) from MLDv2 branch.

Add full SSM stack support to mtest(8) diagnostic tool.

Import rewrite of IPv4 socket multicast layer to support source-specific
and protocol-independent host mode multicast. The code is written to
accomodate IPv6, IGMPv3 and MLDv2 with only a little additional work.

This change only pertains to FreeBSD's use as a multicast end-station and
does not concern multicast routing; for an IGMPv3/MLDv2 router
implementation, consider the XORP project.

The work is based on Wilbert de Graaf's IGMPv3 code drop for FreeBSD 4.6,
which is available at: http://www.kloosterhof.com/wilbert/igmpv3.html

Summary
* IPv4 multicast socket processing is now moved out of ip_output.c
into a new module, in_mcast.c.
* The in_mcast.c module implements the IPv4 legacy any-source API in
terms of the protocol-independent source-specific API.
* Source filters are lazy allocated as the common case does not use them.
They are part of per inpcb state and are covered by the inpcb lock.
* struct ip_mreqn is now supported to allow applications to specify
multicast joins by interface index in the legacy IPv4 any-source API.
* In UDP, an incoming multicast datagram only requires that the source
port matches the 4-tuple if the socket was already bound by source port.
An unbound socket SHOULD be able to receive multicasts sent from an
ephemeral source port.
* The UDP socket multicast filter mode defaults to exclusive, that is,
sources present in the per-socket list will be blocked from delivery.
* The RFC 3678 userland functions have been added to libc: setsourcefilter,
getsourcefilter, setipv4sourcefilter, getipv4sourcefilter.
* Definitions for IGMPv3 are merged but not yet used.
* struct sockaddr_storage is now referenced from <netinet/in.h>. It
is therefore defined there if not already declared in the same way
as for the C99 types.
* The RFC 1724 hack (specify 0.0.0.0/8 addresses to IP_MULTICAST_IF
which are then interpreted as interface indexes) is now deprecated.
* A patch for the Rhyolite.com routed in the FreeBSD base system
is available in the -net archives. This only affects individuals
running RIPv1 or RIPv2 via point-to-point and/or unnumbered interfaces.
* Make IPv6 detach path similar to IPv4's in code flow; functionally same.
* Bump __FreeBSD_version to 700048; see UPDATING.

This work was financially supported by another FreeBSD committer.

Obtained from: p4://bms_netdev
Submitted by: Wilbert de Graaf (original work)
Reviewed by: rwatson (locking), silence from fenner,
net@ (but with encouragement)

Merge a slightly cleaner and SSM capable mtest(8).

Submitted by: Wilbert De Graaf
MFC after: 1 month

Use sizeof() for calculating the buffer size instead of hard-coded values.

add FBSDID

Include missing header files which define functions for which gcc has
builtints (e.g., exit, strcmp).

Use AF_LINK rather than AF_UNSPEC to set an ethernet multicast address.
This is obviously not a terribly used function as it's apparently been
broken forever.
It IS possible that this fix is wrong and that the KERNEL is wrong
(in which case you should fix if_ethersubr.c) either way it certainly has more hope of
working now than before. I'd take it to 2.2 except that obviously no-one cares :-)

Use err(3). -Wall cleaning.

Make mtest build. Write a makefile and a man page.

This commit was generated by cvs2svn to compensate for changes in r20529,
which included commits to RCS files with non-trunk default branches.

A multicast testing program, allowing you to join and leave both
IP and ethernet multicast groups.

Obtained from: Multicast release 3.5