[Dnsmasq-discuss] forward.c: fix handling of truncated response

[Geert Stappers]

On Mon, Sep 30, 2024 at 04:39:24AM +0000, Rahul Thakur via Dnsmasq-discuss wrote:
> Sent: 25 September 2024 15:29, From: Rahul Thakur <rahul.thakur at genexis.eu>
> > 
> > Hi Simon,
> > 
> > Thanks for responding to this patch, please find my justification
> > for this patch as follows:
> > 
> > I think rfc 2181 is defining the behaviour for DNS server and not
> > DNS proxy.
> > 
> > I am relying on and referring to rfc 5625 while making this change.
> > 
> > In section 4.4
> > (https://datatracker.ietf.org/doc/html/rfc5625#section-4.4), the
> > rfc 5625 states,
> > 
> >    If a proxy must unilaterally truncate a response, then the proxy MUST
> >    set the TC bit.  Similarly, proxies MUST NOT remove the TC bit from
> >    responses.
> > 
> > Dnsmasq is ofcourse complying to this behaviour
> > and not meddling with the TC bit while setting the
> > answers to 0. But, if I read further section 4.4.1
> > (https://datatracker.ietf.org/doc/html/rfc5625#section-4.4.1),
> > 
> >  Whilst TCP transport is not strictly mandatory, it is supported by
> >    the vast majority of stub resolvers and recursive servers.
> > 
> > So, this indicates that it is not mandatory that
> > the client ignores this truncated response. This
> > is further supported by section 6.1.3.2 of rfc 1123
> > (https://datatracker.ietf.org/doc/html/rfc1123#section-6.1.3.2). In
> > paragraph 3 of the DISCUSSION in section 6.1.3.2, it states,
> > 
> >                  Whether it is possible to use a truncated answer
> >                  depends on the application.
> > 
> > Hence, when dnsmasq explicitly deletes the answers, then it deprives
> > clients that do not fallback to TCP and are happy with the truncated
> > response to be able to resolve their queries.
> > 
> > To me, it sounds like a better strategy to forward the truncated
> > response as is to the client and let the client decide what it wants
> > to do rather than forcefully dropping the answers.
> > 
> > Best regards,
> > Rahul Thakur
> > 
> 
> Hi Simon,
> 
> So what do you think of my reasoning for this patch? Do you agree?

Review the feedback that was given by Simon.
Review the patch with the feedback in mind.
Submit a revisited patch and see what happens.
 

> Best regards,
> Rahul Thakur


Groeten
Geert Stappers
-- 
Silence is hard to parse