[PATCH] ip: update the description of rp_filter in ip-sysctl.txt

[Shan Wei <shanwei@cn.fujitsu.com>]

The commit 27fed4175acf81ddd91d9a4ee2fd298981f60295
（ip: fix logic of reverse path filter sysctl）has changed the logic of rp_filter.
The document about rp_filter is out of date. Now, setting conf/all/rp_filte with 0 
can also enable source validation.  

Update the document according to the commit.

Signed-off-by: Shan Wei <shanwei@cn.fujitsu.com>
---
 Documentation/networking/ip-sysctl.txt |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index fbe427a..5dcc067 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -738,8 +738,8 @@ rp_filter - INTEGER
 	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
+	The max value from conf/{all,interface}/rp_filter is used
+	when doing source validation on the {interface}.
 
 	Default value is 0. Note that some distributions enable it
 	in startup scripts.
-- 
1.6.3.3