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
* Constify rtpref_str declaration
* Remove unused h_errno declaration
* Use time_t type for expire
* Use strlcpy to set static "?" value to ifname
* Rename local variable 's' to stop shadowing global definition
* Close socket used in pfx_flush()
* Use local variables for sock() in setdefif() and getdefif()
* Increase WARNS to 3
Reviewed by: allanjude, kevans
Approved by: allanjude
Sponsored by: Rubicon Communications, LLC (Netgate)
Differential Revision: https://reviews.freebsd.org/D11118
present in ndp(8).
The vendor branch import uses a _U_ macro to apply the GCC 'unused' attribute
to the rcs ids embedded in each source file. Teach ndp about this.
