ipv6: Update ip-sysctl.txt documentation for recent changes to accept_ra and forwarding

Documentation for recent changes to the tunables accept_ra and
forwarding.

Signed-off-by: Thomas Graf <tgraf@infradead.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 22 insertions, 5 deletions

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index f350c69b2bb4..c7165f4cb792 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -1014,6 +1014,12 @@ conf/interface/*:
 accept_ra - BOOLEAN
         Accept Router Advertisements; autoconfigure using them.
 
+        Possible values are:
+                0 Do not accept Router Advertisements.
+                1 Accept Router Advertisements if forwarding is disabled.
+                2 Overrule forwarding behaviour. Accept Router Advertisements
+                  even if forwarding is enabled.
+
         Functional default: enabled if local forwarding is disabled.
                             disabled if local forwarding is enabled.
 
@@ -1075,7 +1081,12 @@ forwarding - BOOLEAN
         Note: It is recommended to have the same setting on all
         interfaces; mixed router/host scenarios are rather uncommon.
 
-        FALSE:
+        Possible values are:
+                0 Forwarding disabled
+                1 Forwarding enabled
+                2 Forwarding enabled (Hybrid Mode)
+
+        FALSE (0):
 
         By default, Host behaviour is assumed.  This means:
 
@@ -1085,18 +1096,24 @@ forwarding - BOOLEAN
            Advertisements (and do autoconfiguration).
         4. If accept_redirects is TRUE (default), accept Redirects.
 
-        TRUE:
+        TRUE (1):
 
         If local forwarding is enabled, Router behaviour is assumed.
         This means exactly the reverse from the above:
 
         1. IsRouter flag is set in Neighbour Advertisements.
         2. Router Solicitations are not sent.
-        3. Router Advertisements are ignored.
+        3. Router Advertisements are ignored unless accept_ra is 2.
         4. Redirects are ignored.
 
-        Default: FALSE if global forwarding is disabled (default),
-                 otherwise TRUE.
+        TRUE (2):
+
+        Hybrid mode. Same behaviour as TRUE, except for:
+
+        2. Router Solicitations are being sent when necessary.
+
+        Default: 0 (disabled) if global forwarding is disabled (default),
+                 otherwise 1 (enabled).
 
 hop_limit - INTEGER
         Default Hop Limit to set.