ipv6 addrconf: add accept_dad sysctl to control DAD operation.

- If 0, disable DAD.
- If 1, perform DAD (default).
- If >1, perform DAD and disable IPv6 operation if DAD for MAC-based
  link-local address has been failed (RFC4862 5.4.5).

We do not follow RFC4862 by default.  Refer to the netdev thread entitled
"Linux IPv6 DAD not full conform to RFC 4862 ?"
	http://www.spinics.net/lists/netdev/msg52027.html

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index dae980e8f1b9..72f6d52e52e6 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -1029,6 +1029,13 @@ disable_ipv6 - BOOLEAN
         Disable IPv6 operation.
         Default: FALSE (enable IPv6 operation)
 
+accept_dad - INTEGER
+        Whether to accept DAD (Duplicate Address Detection).
+        0: Disable DAD
+        1: Enable DAD (default)
+        2: Enable DAD, and disable IPv6 operation if MAC-based duplicate
+           link-local address has been found.
+
 icmp/*:
 ratelimit - INTEGER
         Limit the maximal rates for sending ICMPv6 packets.