ipv6: add sysctl_mld_qrv to configure query robustness variable

This patch adds a new sysctl_mld_qrv knob to configure the mldv1/v2 query
robustness variable. It specifies how many retransmit of unsolicited mld
retransmit should happen. Admins might want to tune this on lossy links.

Also reset mld state on interface down/up, so we pick up new sysctl
settings during interface up event.

IPv6 certification requests this knob to be available.

I didn't make this knob netns specific, as it is mostly a setting in a
physical environment and should be per host.

Cc: Flavio Leitner <fbl@redhat.com>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: Flavio Leitner <fbl@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 0 deletions

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 3cce8ea6b139..cfc71ac0f764 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -1152,6 +1152,11 @@ anycast_src_echo_reply - BOOLEAN
         FALSE: disabled
         Default: FALSE
 
+mld_qrv - INTEGER
+        Controls the MLD query robustness variable (see RFC3810 9.1).
+        Default: 2 (as specified by RFC3810 9.1)
+        Minimum: 1 (as specified by RFC6636 4.5)
+
 IPv6 Fragmentation:
 
 ip6frag_high_thresh - INTEGER