failed: read(/var/run/dovecot/dns-client)

[Laura Smith]

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Wednesday, April 10, 2019 9:14 PM, Aki Tuomi <aki.tuomi at open-xchange.com> wrote:

> > On 10 April 2019 23:13 Laura Smith via dovecot dovecot at dovecot.org wrote:
> > Sent with ProtonMail Secure Email.
> > ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> > On Wednesday, April 10, 2019 8:20 PM, Aki Tuomi aki.tuomi at open-xchange.com wrote:
> >
> > > > On 10 April 2019 22:13 Laura Smith via dovecot dovecot at dovecot.org wrote:
> > > > On Wednesday, April 10, 2019 7:57 PM, Aki Tuomi aki.tuomi at open-xchange.com wrote:
> > > >
> > > > > > On 10 April 2019 21:26 Laura Smith via dovecot dovecot at dovecot.org wrote:
> > > > > > ==========================================================================
> > > > > > dsync(foobar at example.com): Error: imapc(foobar.example.com:993): dns_lookup(foobar.example.com) failed: read(/var/run/dovecot/dns-client) failed: read(size=512) failed: Connection reset by peer
> > > > >
> > > > > This is dovecot's internal dns-client, and something goes wrong when talking to the service.
> > > > >
> > > > > > dsync(foobar at example.com): Error: Failed to initialize user: imapc: Login to foobar.example.com failed: Disconnected from server
> > > > >
> > > > > This is btw dsync service, not imap service.
> > > > >
> > > > > > ===
> > > > > > Initially I thought "oh no, not another AppArmor block".
> > > > > > But then surely the second message would not appear if the DNS lookup was not successful ?
> > > > > > Also "dig foobar.example.com" works fine.
> > > > > > How should I be troubleshooting this ? And if it is still likely to be AppArmor, what is calling it ? "doveadm" itself or something else ? What does "/var/run/dovecot/dns-client" do and why doesn't dovecot use standard OS calls like everyone else ?
> > > > >
> > > > > Because the "standard OS call" is blocking and we would prefer it to not block everything else.
> > > > >
> > > > > > So many questions !
> > > > >
> > > > > Aki
> > > >
> > > > Thanks for your reply, but both those message are generated from a simple :
> > > > doveadm -v -o mail_fsync=never backup -R -u foobar at example.com imapc:
> > > > So I don't know what you mean about dsync service failing ? Surely the DNS lookup succeeded if the 'dsync service' failed due to remote disconnect ?
> > > > I'm still none the wiser as to where to start looking for troubleshoting ?
> > >
> > > Did you check dovecot logs? Maybe there is something useful?
> > > Aki
> >
> > Only the same old cryptic message about dns-client ?
> > master: Fatal: execv(/usr/lib/dovecot/dns-client) failed: Permission denied
>
> Something prevents executing the dns-client binary.
>
> > master: Error: service(dns_client): command startup failed, throttling for 16 secs
> > dns_client: Fatal: master: service(dns_client): child 14293 returned error 84 (exec() failed)
>
> Aki


Yes but is it being called by doveadm directly or by some other dovecot program ?  If I'm going to have to go down the AppArmor route, then I would prefer if you told me what was calling it instead of me having to un-necessarily spend time doing straces !

Also, should I be able to call dns-client directly myself ? (or is there a way to do so to enable testing ?)

# /usr/lib/dovecot/dns-client
Panic: BUG: No IOs or timeouts set. Not waiting for infinity.
Error: Raw backtrace: /usr/lib64/dovecot/libdovecot.so.0(+0xd879e) [0x7f582c65f79e] -> /usr/lib64/dovecot/libdovecot.so.0(+0xd87e1) [0x7f582c65f7e1] -> /usr/lib64/dovecot/libdovecot.so.0(i_fatal+0) [0x7f582c5c9024] -> /usr/lib64/dovecot/libdovecot.so.0(+0xf045c) [0x7f582c67745c] -> /usr/lib64/dovecot/libdovecot.so.0(io_loop_handler_run_internal+0x36) [0x7f582c679e96] -> /usr/lib64/dovecot/libdovecot.so.0(io_loop_handler_run+0x4c) [0x7f582c6786ec] -> /usr/lib64/dovecot/libdovecot.so.0(io_loop_run+0x38) [0x7f582c678908] -> /usr/lib64/dovecot/libdovecot.so.0(master_service_run+0x13) [0x7f582c5ee203] -> /usr/lib/dovecot/dns-client(main+0x8d) [0x55866c96050d] -> /lib64/libc.so.6(__libc_start_main+0xea) [0x7f582c1edf4a] -> /usr/lib/dovecot/dns-client(_start+0x2a) [0x55866c96055a]