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authorStephen Hemminger <shemminger@vyatta.com>2009-02-20 11:25:36 +0300
committerDavid S. Miller <davem@davemloft.net>2009-02-23 06:54:45 +0300
commitc1cf8422f0512c2b14f0d66bce34abb0645c888a (patch)
treeb00499a8eb15d6613cfbce6d2770638b98cb2aae /Documentation/networking
parent6dac62d3888a34f5bccbe14222ba77e8877a2e54 (diff)
downloadlinux-c1cf8422f0512c2b14f0d66bce34abb0645c888a.tar.xz
ip: add loose reverse path filtering
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>
Diffstat (limited to 'Documentation/networking')
-rw-r--r--Documentation/networking/ip-sysctl.txt24
1 files changed, 15 insertions, 9 deletions
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index ff3f219ee4d7..71041c21af9b 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -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.
-
- conf/all/rp_filter must also be set to TRUE to do 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 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