[Dnsmasq-discuss] dnsmasq, no RA being sent after RTR solicitation when interface has /128 prefix assigned

[Simon Kelley]

Looking at the code, a prefix is only advertised if and address with the
prefix exists on the interface AND the prefix length on the interface is
less than or equal to the prefix being advertised.

My IPv6 foo is not up to justifying that at the moment, but it certainly
explains what you are seeing.

Can you explain why what you're trying to do is sensible? If you're
advertising 2a06:8187:fbab:2:15::/64 wouldn't it make sense for router
advertising that prefix to have an address allowing it to reach other
on-link hosts with addresses in the prefix?


Cheers,

Simon.


On 03/07/17 05:44, Christof Schulze wrote:
> Hello everyone,
> 
> This is my first post to this list.
> Recently I have observed that dnsmasq sending Ras seems to depend on the
> ipv6 address that is assigned to the interface that dnsmasq is running
> on. This is a discrepancy to what uradvd is doing. Do I have a
> configuration issue or is this a missing feature and/or bug in dnsmasq?
> 
> This is my setup:
> ========================================================
> dnsmasq.conf
> 
> domain-needed
> localise-queries
> read-ethers
> expand-hosts
> cache-size=5000
> domain=client
> server=/lan/
> server=2a06:8187:fb00:53::53
> dhcp-leasefile=/tmp/dhcp.leases
> resolv-file=/tmp/resolv.conf.auto
> addn-hosts=/tmp/hosts
> user=dnsmasq
> group=dnsmasq
> 
> enable-ra
> dhcp-range=2a06:8187:fbab:0002::,ra-stateless,64,1h
> dhcp-option=option6:dns-server,[2a06:8187:fbab:2::1]
> 
> interface=local-node
> 
> no-dhcp-interface=br-wan
> ========================================================
> 
> 
> When the local-node interface is set up like this, then there will be
> RAs sent by dnsmasq
> 9: local-node at local-port: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500
> qdisc noqueue state UP group default qlen 1000
>    link/ether 16:41:95:40:f7:dc brd ff:ff:ff:ff:ff:ff
>    inet 10.126.0.1/16 brd 10.126.255.255 scope global local-node
>       valid_lft forever preferred_lft forever
>    inet6 2a06:8187:fbab:2:15::1/64 scope global       valid_lft forever
> preferred_lft forever
>    inet6 2a06:8187:fbab:2::1/128 scope global deprecated       valid_lft
> forever preferred_lft 0sec
>    inet6 fe80::1441:95ff:fe40:f7dc/64 scope link       valid_lft forever
> preferred_lft forever
> 
> While when local-node is set up like this, there will not be any RA sent
> by dnsmasq:
> 9: local-node at local-port: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500
> qdisc noqueue state UP group default qlen 1000
>    link/ether 16:41:95:40:f7:dc brd ff:ff:ff:ff:ff:ff
>    inet 10.126.0.1/16 brd 10.126.255.255 scope global local-node
>       valid_lft forever preferred_lft forever
>    inet6 2a06:8187:fbab:2::1/128 scope global deprecated       valid_lft
> forever preferred_lft 0sec
>    inet6 fe80::1441:95ff:fe40:f7dc/64 scope link       valid_lft forever
> preferred_lft forever
> 
> I would appreciate insights into how I could get dnsmasq to send Ras
> even in
> the second scenario, withouth the additional /64 address.
> 
> Regards
> 
> Christof
> 
> 
> _______________________________________________
> Dnsmasq-discuss mailing list
> Dnsmasq-discuss at lists.thekelleys.org.uk
> http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
> 


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