[PATCH docs-next] sysctl -- rp_format completed description with filter criteria

[PATCH docs-next] sysctl -- rp_format completed description with filter criteria

[Stephen Satchell]

---
  Documentation/networking/ip-sysctl.rst | 7 +++++++
  1 file changed, 7 insertions(+)

diff --git a/Documentation/networking/ip-sysctl.rst 
b/Documentation/networking/ip-sysctl.rst
index c2ecc98..0ab017b 100644
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -1443,6 +1443,13 @@ rp_filter - INTEGER
  	  and if the source address is not reachable via any interface
  	  the packet check will fail.

+	rp_filter will examine the source address of an incoming IP
+	packet by performing an FIB lookup.  In loose mode (value 2),
+	the packet is rejected if the source address is neither
+	UNICAST nor LOCAL(when interface allows) nor IPSEC.  For
+	strict mode (value 1) the interface indicated by the FIB table
+	entry must also match the interface on which the packet arrived.
+
  	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.
-- 
1.8.3.1