On 06/06/2011 06:53 AM, Mr Dash Four wrote: > >> That bit above is particularly helpful and puts it, quite simply, in a >> nutshell. If details of this are going to be made public tomorrow, >> would you post what is published (or at least point to a link where >> this is done)? I am fairly interested to see what the actual issue is! > Related to this - what does "routefilter[=2]" option in interfaces > actually does in terms of iptables statements?
From Documentation/networking/ip_sysctl.txt:
rp_filter - INTEGER
0 - No source validation.
1 - Strict mode as defined in RFC3704 Strict Reverse Path
Each incoming packet is tested against the FIB and if the
interface is not the best reverse path the packet check
will fail.
By default failed packets are discarded.
2 - Loose mode as defined in RFC3704 Loose Reverse Path
Each incoming packet's source address is also tested
against the FIB and if the source address is not reachable
via any interface the packet check will fail.
Current recommended practice in RFC3704 is to enable strict mode
to prevent IP spoofing from DDos attacks. If using asymmetric
routing or other complicated routing, then loose mode is
recommended.
conf/all/rp_filter must also be set to non-zero to do source
validation on the interface
Default value is 0. Note that some distributions enable it
in startup scripts.
-Tom
--
Tom Eastep \ When I die, I want to go like my Grandfather who
Shoreline, \ died peacefully in his sleep. Not screaming like
Washington, USA \ all of the passengers in his car
http://shorewall.net \________________________________________________
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