1 files changed, 13 insertions, 0 deletions

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 7373115407e4..0d71fa962d8a 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -32,6 +32,19 @@ ip_no_pmtu_disc - INTEGER
 min_pmtu - INTEGER
         default 552 - minimum discovered Path MTU
 
+ip_forward_use_pmtu - BOOLEAN
+        By default we don't trust protocol path MTUs while forwarding
+        because they could be easily forged and can lead to unwanted
+        fragmentation by the router.
+        You only need to enable this if you have user-space software
+        which tries to discover path mtus by itself and depends on the
+        kernel honoring this information. This is normally not the
+        case.
+        Default: 0 (disabled)
+        Possible values:
+        0 - disabled
+        1 - enabled
+
 route/max_size - INTEGER
         Maximum number of routes allowed in the kernel.  Increase
         this when using large numbers of interfaces and/or routes.