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ip: add loose reverse path filtering

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Extend existing reverse path filter option to allow strict or loose
filtering. (See http://en.wikipedia.org/wiki/Reverse_path_filtering).

For compatibility with existing usage, the value 1 is chosen for strict mode
and 2 for loose mode.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Stephen Hemminger 2009-02-20 08:25:36 +00:00 committed by David S. Miller
parent 6dac62d388
commit c1cf8422f0
2 changed files with 15 additions and 9 deletions
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22
Documentation/networking/ip-sysctl.txt
View file

@ -699,16 +699,22 @@ accept_source_route - BOOLEAN
default TRUE (router)
FALSE (host)
rp_filter - BOOLEAN
1 - do source validation by reversed path, as specified in RFC1812
Recommended option for single homed hosts and stub network
routers. Could cause troubles for complicated (not loop free)
networks running a slow unreliable protocol (sort of RIP),
or using static routes.
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.
conf/all/rp_filter must also be set to TRUE to do source validation
Current recommended practice in RFC3704 is to enable strict mode
to prevent IP spoofin from DDos attacks. If using asymmetric routing
or other complicated routing,t hen 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

2
net/ipv4/fib_frontend.c
View file

@ -275,7 +275,7 @@ int fib_validate_source(__be32 src, __be32 dst, u8 tos, int oif,
fib_res_put(&res);
if (no_addr)
goto last_resort;
if (rpf)
if (rpf == 1)
goto e_inval;
fl.oif = dev->ifindex;