[Dnsmasq-discuss] IPv6 Router Advertisements not working

Erik Nordmark nordmark at sonic.net
Tue Jan 23 16:51:24 GMT 2018


On 01/22/2018 02:27 AM, Andy Hawkins wrote:
> Hi,
> In article <8534ac3c-30d0-095a-8bde-179bdbe8f988 at thekelleys.org.uk>,
>             Simon Kelley<simon at thekelleys.org.uk> wrote:
>> Do you have an interface configured with an address in fd01::/64 ?
> 
> Is this a requirement? radvd is able to send advertisements out on an
> interface that has no IPv6 address configured (indeed, I have been using
> this facility to automatically configure the interface that router
> advertisements are being sent on).
> 
> Would be nice to be able to do the same with dnsmasq without having to
> manually configure the IPv6 address of the interface.

Andy,

I've run into this limitation as well, due to using the "no on-link 
prefixes" option in neighbor discovery (meaning that I use dhcpv6 for 
address assignment, and radvd doesn't advertise any onlink prefix).

This means I don't have a /64 prefix configured on any interface which 
matches the range from which dnsmasq assigns IPv6 addresses.

My workaround is to remove the /64 check from dnsmasq (see below). I've 
been meaning to discuss this on the list.

    Erik


diff -r -u ../dnsmasq-orig/dnsmasq-2.75/src/option.c src/option.c
--- ../dnsmasq-orig/dnsmasq-2.75/src/option.c	2015-07-30 
12:59:07.000000000 -0
700
+++ src/option.c	2017-06-13 15:14:58.109166818 -0700
@@ -2734,9 +2734,6 @@
  		  ret_err(_("prefix length must be exactly 64 for subnet constru
ctors"));
  	      }

-	    if (new->prefix < 64)
-	      ret_err(_("prefix length must be at least 64"));
-	
  	    if (!is_same_net6(&new->start6, &new->end6, new->prefix))
  	      ret_err(_("inconsistent DHCPv6 range"));




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