Re: [Dnsmasq-discuss] using dnsmasq with 4 upstream servers

[/dev/rob0]

On Fri, Sep 02, 2016 at 01:23:44PM +0200, Daniel Steglich wrote:
> I've got 4 upstream DNS Servers from my ISP (2 IPv4, 2 IPv6) and 
> use all of them in /etc/resolv.conf.

I think you'd be better off to simplify this.  Furthermore I am 
always leery of trusting ISP nameservers.  Sooner or later the ISP 
bosses get the idea to increase revenue with NXDOMAIN redirection.
Really, I'd trust Google before an ISP (but my own solution is to 
point dnsmasq at my own local caching resolver.)

> I start sending DNS SRV querys from a client to dnsmasq DNS relay 
> every 5 seconds.
> 
> Each request is sent to four DNS upstream servers (primary DNS v4, 
> secondary DNS v4, primary DNS v6, secondary DNS v6). The answer 
> from the fastest server is used.
> As the requests are DNS SRV records, the reply is not cached by 
> dnsmasq.

What?  Why not?  Caching is done based on TTL, not based on the 
RRtype.  If the upstream server gives you a zero TTL, then that 
record is not cached ... regardless of RRtype.

> During my tests the first IPv6 DNS server was always the fastest 
> replying server and for this reason the answer from this server
> is passed to the client always,

Do the answers from other upstream servers differ?

> After some time the dnsmasq relay is not forwarding the requests to 
> the four known DNS servers any more but only sends out the requests 
> to either the first IPv4 DNS server or the first IPv6 DNS server. 
> So only one server is used. After about 20 seconds (4 requests 
> later) the dnsmasq process falls back to the expected behaviour of 
> sending the request to all known DNS Servers.

I guess there is an implied "but the server fails to answer" in this, 
and it presents yet another reason why you might want to consider 
these ISP nameservers unreliable.

> does anybody knows the reason for this?

See --all-servers and --server in the manual.
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Re: [Dnsmasq-discuss] dnsmasq does crash

[e9hack]

Am 31.08.2016 um 11:51 schrieb Kevin Darbyshire-Bryant:
> 
> On 30/08/16 23:08, Simon Kelley wrote:
>> Sorry about this. Putative fix pushed to git.
> 
> Looks good.  It doesn't go bang anymore on my system :-)

The same for me.

Regards,
Hartmut


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[Dnsmasq-discuss] using dnsmasq with 4 upstream servers

[Daniel Steglich]

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Hi,

I've got 4 upstream DNS Servers from my ISP (2 IPv4, 2 IPv6) and use 
all of them in /etc/resolv.conf.
I start sending DNS SRV querys from a client to dnsmasq DNS relay every 
5 seconds.


Each request is sent to four DNS upstream servers (primary DNS v4, 
secondary DNS v4, primary DNS v6, secondary DNS v6). The answer from the 
fastest server is used.
As the requests are DNS SRV records, the reply is not cached by 
dnsmasq.


During my tests the first IPv6 DNS server was always the fastest 
replying server and for this reason the answer from this server is 
passed to the client always,
After some time the dnsmasq relay is not forwarding the requests to the 
four known DNS servers any more but only sends out the requests to 
either the first IPv4 DNS server or the first IPv6 DNS server. So only 
one server is used. After about 20 seconds (4 requests later) the 
dnsmasq process falls back to the expected behaviour of sending the 
request to all known DNS Servers.


does anybody knows the reason for this?

- ---
Mit freundlichen Grüßen

Daniel Steglich
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Re: [Dnsmasq-discuss] Dnsmasq doesn't reply to queries made over (link-local) IPv6

[Toke Høiland-Jørgensen]

Simon Kelley  writes:

> My first thought is that it's probably replying to the wrong
> interface: link local addresses can't be routed: you have to specify
> the interface they're connected to. This insight came late to me, and
> there's a chance that the dnsmasq code is still messing it up. I'll
> take a closer look in the next day or two.

Awesome, thanks! :)

-Toke

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Re: [Dnsmasq-discuss] Dnsmasq doesn't reply to queries made over (link-local) IPv6

[Simon Kelley]

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Hash: SHA256

My first thought is that it's probably replying to the wrong
interface: link local addresses can't be routed: you have to specify
the interface they're connected to. This insight came late to me, and
there's a chance that the dnsmasq code is still messing it up. I'll
take a closer look in the next day or two.

Cheers,

Simon.


On 01/09/16 22:29, Toke Høiland-Jørgensen wrote:
> Hi
> 
> I have this weird problem where my dnsmasq instance won't reply to 
> queries made over (link-local) IPv6. I can see the query coming in,
> it shows up in the logs (with log-queries) enabled and gets
> resolved, but no reply ever goes back out. Don't see any IPv6 DNS
> packets going out at all on that interface. Queries made over IPv4
> work fine.
> 
> I am stumped as to how to debug this. This is dnsmasq 2.76 running
> on LEDE nightlies.
> 
> -Toke
> 
> ___ Dnsmasq-discuss
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