Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

MFC r245230: Add no_prefer_iface option.
It stops treating the address on the interface as special by source
address selection rule even when the interface is outgoing interface.
This is desired in some situation.

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

If compiling RESCUE always ignore feature_present(3) calls so that
a /rescue/ifconfig more modern than the kernel could still configure
IPv4 or IPv6 addresses.

Reported by: Andrzej Tobola (ato iem.pw.edu.pl)
Reported by: gcooper
MFC after: 1 day
X-MFC: will not MFC any time soon, just reminder for r222527

- Accept Router Advertisement messages even when net.inet6.ip6.forwarding=1.

- A new per-interface knob IFF_ND6_NO_RADR and sysctl IPV6CTL_NO_RADR.
This controls if accepting a route in an RA message as the default route.
The default value for each interface can be set by net.inet6.ip6.no_radr.
The system wide default value is 0.

- A new sysctl: net.inet6.ip6.norbit_raif. This controls if setting R-bit in
NA on RA accepting interfaces. The default is 0 (R-bit is set based on
net.inet6.ip6.forwarding).

Background:

IPv6 host/router model suggests a router sends an RA and a host accepts it for
router discovery. Because of that, KAME implementation does not allow
accepting RAs when net.inet6.ip6.forwarding=1. Accepting RAs on a router can
make the routing table confused since it can change the default router
unintentionally.

However, in practice there are cases where we cannot distinguish a host from
a router clearly. For example, a customer edge router often works as a host
against the ISP, and as a router against the LAN at the same time. Another
example is a complex network configurations like an L2TP tunnel for IPv6
connection to Internet over an Ethernet link with another native IPv6 subnet.
In this case, the physical interface for the native IPv6 subnet works as a
host, and the pseudo-interface for L2TP works as the default IP forwarding
route.

Problem:

Disabling processing RA messages when net.inet6.ip6.forwarding=1 and
accepting them when net.inet6.ip6.forward=0 cause the following practical
issues:

- A router cannot perform SLAAC. It becomes a problem if a box has
multiple interfaces and you want to use SLAAC on some of them, for
example. A customer edge router for IPv6 Internet access service
using an IPv6-over-IPv6 tunnel sometimes needs SLAAC on the
physical interface for administration purpose; updating firmware
and so on (link-local addresses can be used there, but GUAs by
SLAAC are often used for scalability).

- When a host has multiple IPv6 interfaces and it receives multiple RAs on
them, controlling the default route is difficult. Router preferences
defined in RFC 4191 works only when the routers on the links are
under your control.

Details of Implementation Changes:

Router Advertisement messages will be accepted even when
net.inet6.ip6.forwarding=1. More precisely, the conditions are as
follow:

(ACCEPT_RTADV && !NO_RADR && !ip6.forwarding)
=> Normal RA processing on that interface. (as IPv6 host)

(ACCEPT_RTADV && (NO_RADR || ip6.forwarding))
=> Accept RA but add the router to the defroute list with
rtlifetime=0 unconditionally. This effectively prevents
from setting the received router address as the box's
default route.

(!ACCEPT_RTADV)
=> No RA processing on that interface.

ACCEPT_RTADV and NO_RADR are per-interface knob. In short, all interface
are classified as "RA-accepting" or not. An RA-accepting interface always
processes RA messages regardless of ip6.forwarding. The difference caused by
NO_RADR or ip6.forwarding is whether the RA source address is considered as
the default router or not.

R-bit in NA on the RA accepting interfaces is set based on
net.inet6.ip6.forwarding. While RFC 6204 W-1 rule (for CPE case) suggests
a router should disable the R-bit completely even when the box has
net.inet6.ip6.forwarding=1, I believe there is no technical reason with
doing so. This behavior can be set by a new sysctl net.inet6.ip6.norbit_raif
(the default is 0).

Usage:

# ifconfig fxp0 inet6 accept_rtadv
=> accept RA on fxp0
# ifconfig fxp0 inet6 accept_rtadv no_radr
=> accept RA on fxp0 but ignore default route information in it.
# sysctl net.inet6.ip6.norbit_no_radr=1
=> R-bit in NAs on RA accepting interfaces will always be set to 0.

Add the "nd6 options" line handler as af_other_status() of AF_INET6, not as an
own address family.

Reviewed by: bz

Conditionally compile in the af_inet and af_inet6, af_nd6 modules.
If compiled in for dual-stack use, test with feature_present(3)
to see if we should register the IPv4/IPv6 address family related
options.

In case there is no "inet" support we would love to go with the
usage() and make the address family mandatory (as it is for anything
but inet in theory). Unfortunately people are used to
ifconfig IF up/down
etc. as well, so use a fallback of "link". Adjust the man page
to reflect these minor details.

Improve error handling printing a warning in addition to the usage
telling that we do not know the given address family in two places.

Reviewed by: hrs, rwatson
Sponsored by: The FreeBSD Foundation
Sponsored by: iXsystems
MFC after: 2 weeks

Improve flexibility of receiving Router Advertisement and
automatic link-local address configuration:

- Convert a sysctl net.inet6.ip6.accept_rtadv to one for the
default value of a per-IF flag ND6_IFF_ACCEPT_RTADV, not a
global knob. The default value of the sysctl is 0.

- Add a new per-IF flag ND6_IFF_AUTO_LINKLOCAL and convert a
sysctl net.inet6.ip6.auto_linklocal to one for its default
value. The default value of the sysctl is 1.

- Make ND6_IFF_IFDISABLED more robust. It can be used to disable
IPv6 functionality of an interface now.

- Receiving RA is allowed if ip6_forwarding==0 *and*
ND6_IFF_ACCEPT_RTADV is set on that interface. The former
condition will be revisited later to support a "host + router" box
like IPv6 CPE router. The current behavior is compatible with
the older releases of FreeBSD.

- The ifconfig(8) now supports these ND6 flags as well as "nud",
"prefer_source", and "disabled" in ndp(8). The ndp(8) now
supports "auto_linklocal".

Discussed with: bz and jinmei
Reviewed by: bz
MFC after: 3 days

- Use size_t instead of int when appropriate;
- Use C99 sparse initialization.

With these changes ifconfig(8) is WARNS=2 clean.

use getifaddrs from libc instead of private code

Reviewed by: bms
MFC after: 1 month

Backout revision 1.4; it is not verified as the correct fix for the PR.
A more correct fix has been committed to ifconfig(8).

Submitted by: bz
PR: 102701

Fix a typo in af_inet6.c such that IPv6 addresses may be deleted
from interfaces.

PR: bin/102701
Submitted by: George Mitchell
MFC after: 3 days

only show a tunnel information of an adequate address family.

Approved by: re (dwhite)

NI_WITHSCOPEID cleanup. Neither RFC 2553 nor RFC 3493 defines
NI_WITHSCOPEID, and our getaddrinfo(3) does nothing special
for it, now.

Overhaul to cleanup some of the tangled logic that's grown over the years.

o break per-address family support out into separate files
o modularize per-address family and functional operations using
a registration mechanism; this permits configuration according
to which files you include (but beware that order of the files
is important to insure backwards compatibility)
o many cleanups to eliminate incestuous behaviour, global variables,
and poor coding practices (still much more to fix)

The original motivation of this work was to support dynamic addition
of functionality based on the interface so we can eliminate the various
little control programs and so that vendors can distribute ifconfig
plugins that support their in-kernel code. That work is still to be
completed.

o Update 802.11 support for all the new net80211 functionality; some
of these operations (e.g. list *) may be better suited in a different
program