This change defines the RA "6" (IPv6-Only) flag which routers
may advertise, kernel logic to check if all routers on a link
have the flag set and accordingly update a per-interface flag.
If all routers agree that it is an IPv6-only link, ether_output_frame(),
based on the interface flag, will filter out all ETHERTYPE_IP/ARP
frames, drop them, and return EAFNOSUPPORT to upper layers.
The change also updates ndp to show the "6" flag, ifconfig to
display the IPV6_ONLY nd6 flag if set, and rtadvd to allow
announcing the flag.
Further changes to tcpdump (contrib code) are availble and will
be upstreamed.
Tested the code (slightly earlier version) with 2 FreeBSD
IPv6 routers, a FreeBSD laptop on ethernet as well as wifi,
and with Win10 and OSX clients (which did not fall over with
the "6" flag set but not understood).
We may also want to (a) implement and RX filter, and (b) over
time enahnce user space to, say, stop dhclient from running
when the interface flag is set. Also we might want to start
IPv6 before IPv4 in the future.
All the code is hidden under the EXPERIMENTAL option and not
compiled by default as the draft is a work-in-progress and
we cannot rely on the fact that IANA will assign the bits
as requested by the draft and hence they may change.
Dear 6man, you have running code.
Discussed with: Bob Hinden, Brian E Carpenter
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.
that it is NUL terminated. Additional NUL padding is not required
for short names.
Use sizeof(destination) in a few places instead of IFNAMSIZ.
Cast afp->af_ridreq and afp->af_addreq to make the intent of
the code more obvious.
Reported by: Coverity
CID: 1009628, 1009630, 1009631, 1009632, 1009633, 1009635, 1009638
CID: 1009639, 1009640, 1009641, 1009642, 1009643, 1009644, 1009645
CID: 1009646, 1009647, 1010049, 1010050, 1010051, 1010052, 1010053
CID: 1010054, 1011293, 1011294, 1011295, 1011296, 1011297, 1011298
CID: 1011299, 1305821, 1351720, 1351721
MFC after: 1 week
- Add no_dad and ignoreloop per-IF knob. no_dad disables DAD completely,
and ignoreloop is to prevent infinite loop in loopback probing state when
loopback is permanently expected.
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.
Requested by: hrs
Reviewed by: IHANet folks including hrs
MFC after: 1 week
- 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.
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
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
