Bug#728374: freebsd-net-tools: /sbin/ifconfig is missing options for pfsync
On 31/10/13 19:53, Robert Millan wrote:
>> > +#ifndef INADDR_PFSYNC_GROUP
>> > +#define INADDR_PFSYNC_GROUP (uint32_t)0xf00000e0
>> > +#endif
> This is an IPv4 address right? Any idea what is it used for? What's
> special about packets sent to / received from this address?
In network byte order that's 224.0.0.240 (actually the FreeBSD header
shows this in a comment), which is a local multicast group address,
chosen for pfsync because 240 is also its IP protocol number. All hosts
running pfsync send and listen for shared state information there. Real
example:
> 20:50:56.486456 IP 192.168.11.1 > 224.0.0.240: ip-proto-240 360
> 20:50:56.486694 IP 192.168.11.3 > 224.0.0.240: ip-proto-240 412
> 20:50:56.488372 IP 192.168.11.1 > 224.0.0.240: ip-proto-240 1132
INADDR_CARP_GROUP does pretty much the same thing. It's using
224.0.0.18 although its protocol number is 112. These were chosen to
deliberately clobber what Cisco used for patent-encumbered VRRP :)
I'm surprised Linux doesn't define at least the first three groups; I'm
not familiar with the others.
Regards,
--
Steven Chamberlain
steven@pyro.eu.org
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