ip: add loose reverse path filtering

[net-next-2.6.git] / Documentation / networking / ip-sysctl.txt

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index ff3f219ee4d7bc590ecea9a9144c094f78f07dbd..71041c21af9bf620da6583e921e9b39b427a0cba 100644 (file)
--- 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