[Pdns-users] PowerDNS 2.9.16 + dnscache not working

[Matt Dainty]

On Thu, 2004-04-01 at 20:40, bert hubert wrote:
> is this problem still there?

Hmm, I decided to look at this, so I put some debug in dnsproxy.cc to
print out the id, d_xor, and id^d_xor result at the following places:

DNSProxy::sendPacket() after p->spoofID(id^d_xor);
Before and after the #ifdef'd byteswapping code in DNSProxy::mainloop()

I'm guessing the id's should match, so when it says reusing id 0 and
discarding id 7000-odd, something's gone wrong. Now, I get:

DNSProxy::sendPacket(): Sending packet with id=0, d_xor=45287,
id^d_xor=45287
DNSProxy::mainloop(): (BEFORE) Received packet with id=59312,
d_xor=45287,d.id^d_xor=22359
DNSProxy::mainloop(): (AFTER) Received packet with id=45031,
d_xor=45287, d.id^d_xor=7936
Discarding untracked packet from recursor backend with id 7936. Contrack
table size=1

So it's fairly obvious the WORDS_BIGENDIAN code *is* being coded in, but
the id is ending up 256 less than it should be for some reason. If I
make the byteswap code:

d.id = ( 256 * ( (u_int16_t)buffer[1] + 1 ) ) + (u_int16_t)buffer[0];

...then it works and queries via the recursor work, but I'm guessing the
id is getting messed up earlier on. Someone more familiar with the code
have an idea before I litter it with more print statements? :-)

Matt

> On Sat, Mar 13, 2004 at 12:55:52AM +0100, Roderick Groesbeek wrote:
> > Hello Matt,
> > 
> > > From: "Matt Dainty" <matt at bodgit-n-scarper.com>
> > >
> > > polymorph# env DNSCACHEIP=192.168.23.15 dnsqr a www.google.com
> > > Mar 12 22:42:50 polymorph pdns[108]: Recursive query for remote
> > 192.168.23.15 with internal id 1 was not answered by backend within timeout,
> > reusing id
> > > Mar 12 22:42:50 polymorph pdns[108]: Discarding untracked packet from
> > recursor backend with id 7937. Contrack table size=2
> > > Mar 12 22:42:53 polymorph pdns[108]: Discarding untracked packet from
> > recursor backend with id 7938. Contrack table size=3
> > >
> > > What's puzzling me is that in the dnscache logs, I can see dnscache get
> > > the query and return the answer immediately:
> > >
> > 
> > Probably you wanna check that the following code *DOES* get compiled in on
> > your
> > system.
> > 
> > ~~
> > #ifdef WORDS_BIGENDIAN
> >         // this is needed because spoof ID down below does not respect the
> > nativ
> > e byteorder
> >         d.id = ( 256 * (u_int16_t)buffer[1] ) + (u_int16_t)buffer[0];
> > #endif
> > "dnsproxy.cc" [Read only] line 176 of 216 --81%--
> > ~~
> > 
> > Or recompile your code with "CXXFLAGS=-DWORDS_BIGENDIAN ./configure" just to
> > be sure.
> > 
> > 
> > Vriendelijke Groet,
> > 
> > Roderick
> > --
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> > 
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