[Blink] Blink Ubuntu DNS lookup deadlock?

g4-lisz at tonarchiv.ch g4-lisz at tonarchiv.ch
Wed Nov 30 18:17:19 CET 2022 

It's really strange, right now it's working but I don't know what has 
changed.

Again I did some network sniffing on port 53 and it seems a bit random 
how Blink is reacting to the DNS replies: Sometimes it simply ignores 
the CNAME answer to the NAPTR and doesn't send a request for 
ws1.voipgateway.org. Sometimes it sends a NAPTR request for 
ws1.voipgateway.org...

IMHO the same randomness decides if everything works or fails: If it 
interprets the NAPTR replies as "contains no answer", then the SRV 
requests are also sent and interpreted correctly.
If the first request is mistakenly handled like a timeout, all the other 
requests are not sent and the whole process seems to block somewhere.

Some timing issue in the DNS resolve threads?

Cheers
Till

On 30.11.22 15:42, g4-lisz at tonarchiv.ch wrote:
> Hi
>
> thank you for your replies.
>
> I'm a bit more familiar with DNS than with VOIP... If I get it right 
> the NAPTR is optional and SIP should work without it.
>
> CNAME can always be a reply to a DNS lookup, it just means: The name 
> you are looking for is an alias, i.e. guest1.voipgateway.org is a 
> virtual domain. IMHO Blink does the right thing and sends a second 
> request for ws1.voipgateway.org.
>
> But for ws1.voipgateway.org there's a NAPTR either. The SOA reply only 
> means that this an authoritative answer.
>
> IMHO the problem comes with the second DNS reply which contains only a 
> SOA. Blink seams not to handle this and runs into a timeout.
>
> Strangely enough the whole issue doesn't always appear and all works 
> fine sometimes. Then I get the same log lines like Timen de Mes:
>
> 2022-11-30 15:35:49.340913 [blink 2]: DNS lookup NAPTR 
> guest1.voipgateway.org failed: DNS response contains no answer
> 2022-11-30 15:35:49.405083 [blink 2]: DNS lookup SRV 
> _sip._udp.guest1.voipgateway.org failed: DNS record does not exist
> 2022-11-30 15:35:49.463001 [blink 2]: DNS lookup SRV 
> _sip._tcp.guest1.voipgateway.org failed: DNS record does not exist
> 2022-11-30 15:35:59.932458 [blink 2]: DNS lookup SRV 
> _sips._tcp.guest1.voipgateway.org failed: DNS record does not exist
> 2022-11-30 15:35:59.960770 [blink 2]: DNS lookup A 
> guest1.voipgateway.org succeeded, ttl=3600: 212.117.203.57
>
> Best regards
> Till
>
> On 30.11.22 12:10, Adrian Georgescu wrote:
>> $dig cname guest1.voipgateway.org
>>
>> ;; QUESTION SECTION:
>> ;guest1.voipgateway.org.        IN    CNAME
>>
>> ;; ANSWER SECTION:
>> guest1.voipgateway.org.    21600    IN    CNAME ws1.voipgateway.org.
>>
>> The CNAME should not be there for the domain name.
>>
>> —
>> Adrian
>>
>>
>>
>>
>>> On 30 Nov 2022, at 07:15, Tijmen de Mes <tijmen at ag-projects.com> wrote:
>>>
>>> Hi,
>>>
>>> I looked at it a bit more and the fact that a CNAME is returned 
>>> could happen.
>>>
>>> However in my Blink I can’t reproduce this fault, I used the domain 
>>> guest1.voipgateway.org and I could register(?), if I made a call I 
>>> got a prompt.
>>>
>>> This is how my logs look:
>>>
>>>    1 2022-11-30 10:59:46.901093 [blink 4977]: DNS lookup NAPTR 
>>> guest1.voipgateway.org failed: DNS response contains no answer
>>>    2 2022-11-30 10:59:46.901540 [blink 4977]: DNS lookup SRV 
>>> _sips._tcp.guest1.voipgateway.org failed: DNS record does not exist
>>>    3 2022-11-30 10:59:46.901950 [blink 4977]: DNS lookup SRV 
>>> _sip._tcp.guest1.voipgateway.org failed: DNS record does not exist
>>>    4 2022-11-30 10:59:46.902359 [blink 4977]: DNS lookup SRV 
>>> _sip._udp.guest1.voipgateway.org failed: DNS record does not exist
>>>    5 2022-11-30 10:59:46.902618 [blink 4977]: DNS lookup A 
>>> guest1.voipgateway.org succeeded, ttl=2675: 212.117.203.57
>>>
>>> I don’t have the flatpack so I can’t tell you if something is wrong 
>>> in there. The lookups are handled by python3-sipsimple.
>>>
>>> Best regards,
>>>
>>> Timen de Mes
>>> —
>>> AG Projects
>>>
>>>> Op 30 nov. 2022, om 10:35 heeft Tijmen de Mes 
>>>> <tijmen at ag-projects.com> het volgende geschreven:
>>>>
>>>> Hi,
>>>>
>>>> The fact that you see the timeouts could be a bug.
>>>>
>>>> The problem is that a NAPTR does exist and is a CNAME? I’ve never 
>>>> seen this and I am not sure this is even valid in DNS.
>>>>
>>>> AFAIK a NAPTR in this case should return something like:
>>>>
>>>> 20 100 "s" "SIP+D2U" "" _sip._udp.sip2sip.info.
>>>> 10 100 "s" "SIP+D2T" "" _sip._tcp.sip2sip.info.
>>>> 25 100 "s" "SIPS+D2T" "" _sips._tcp.sip2sip.info.
>>>>
>>>> After this a SRV lookup would be done.
>>>>
>>>> Are you able to register your account?
>>>>
>>>>
>>>> Best regards,
>>>>
>>>> Tijmen de Mes
>>>> —
>>>> AG Projects
>>>>
>>>>> Op 29 nov. 2022, om 17:44 heeft g4-lisz at tonarchiv.ch het volgende 
>>>>> geschreven:
>>>>>
>>>>> Hi there
>>>>>
>>>>> A few days ago I updated my OS to Pop! OS / Ubuntu 22.04 LTS with 
>>>>> the Blink flatpack V5.5.0
>>>>>
>>>>> A few times it worked flawlessly, but most of the time, starting a 
>>>>> call lags a lot and it simply fails with a beep after a few 
>>>>> minutes without any further message.
>>>>>
>>>>> The logs shows issues with DNS:
>>>>>
>>>>> 2022-11-29 15:22:37.533993 [blink 2]: DNS lookup NAPTR 
>>>>> guest1.voipgateway.org failed: no DNS response received, the query 
>>>>> has timed out
>>>>> 2022-11-29 15:22:37.534465 [blink 2]: DNS lookup SRV 
>>>>> _sip._udp.guest1.voipgateway.org failed: no DNS response received, 
>>>>> the query has timed out
>>>>> 2022-11-29 15:22:37.534699 [blink 2]: DNS lookup SRV 
>>>>> _sip._tcp.guest1.voipgateway.org failed: no DNS response received, 
>>>>> the query has timed out
>>>>> 2022-11-29 15:22:37.534909 [blink 2]: DNS lookup SRV 
>>>>> _sips._tcp.guest1.voipgateway.org failed: no DNS response 
>>>>> received, the query has timed out
>>>>> 2022-11-29 15:22:37.535100 [blink 2]: DNS lookup A 
>>>>> guest1.voipgateway.org failed: no DNS response received, the query 
>>>>> has timed out
>>>>> 2022-11-29 15:22:37.637499 [blink 2]: DNS lookup TXT 
>>>>> xcap.guest1.voipgateway.org failed: DNS record does not exist
>>>>> 2022-11-29 15:23:08.049049 [blink 2]: DNS lookup NAPTR 
>>>>> guest1.voipgateway.org failed: no DNS response received, the query 
>>>>> has timed out
>>>>> 2022-11-29 15:23:08.049976 [blink 2]: DNS lookup SRV 
>>>>> _sips._tcp.guest1.voipgateway.org failed: no DNS response 
>>>>> received, the query has timed out
>>>>> 2022-11-29 15:23:08.050817 [blink 2]: DNS lookup SRV 
>>>>> _sip._tcp.guest1.voipgateway.org failed: no DNS response received, 
>>>>> the query has timed out
>>>>> 2022-11-29 15:23:08.051510 [blink 2]: DNS lookup SRV 
>>>>> _sip._udp.guest1.voipgateway.org failed: no DNS response received, 
>>>>> the query has timed out
>>>>> 2022-11-29 15:23:08.052161 [blink 2]: DNS lookup A 
>>>>> guest1.voipgateway.org failed: no DNS response received, the query 
>>>>> has timed out
>>>>> 2022-11-29 15:23:38.498519 [blink 2]: DNS lookup NAPTR 
>>>>> guest1.voipgateway.org failed: no DNS response received, the query 
>>>>> has timed out
>>>>> 2022-11-29 15:23:38.498998 [blink 2]: DNS lookup SRV 
>>>>> _sip._udp.guest1.voipgateway.org failed: no DNS response received, 
>>>>> the query has timed out
>>>>> 2022-11-29 15:23:38.499612 [blink 2]: DNS lookup SRV 
>>>>> _sip._tcp.guest1.voipgateway.org failed: no DNS response received, 
>>>>> the query has timed out
>>>>> 2022-11-29 15:23:38.500547 [blink 2]: DNS lookup SRV 
>>>>> _sips._tcp.guest1.voipgateway.org failed: no DNS response 
>>>>> received, the query has timed out
>>>>> 2022-11-29 15:23:38.501826 [blink 2]: DNS lookup A 
>>>>> guest1.voipgateway.org failed: no DNS response received, the query 
>>>>> has timed out
>>>>> 2022-11-29 15:24:08.946267 [blink 2]: DNS lookup NAPTR 
>>>>> guest1.voipgateway.org failed: no DNS response received, the query 
>>>>> has timed out
>>>>>
>>>>> and so on.
>>>>>
>>>>> But in reality there are no DNS timeouts. IMHO the issue is that 
>>>>> Blink doesn't handle the DNS answers right and then somehow 
>>>>> deadlocks on the first NATPR request.
>>>>>
>>>>> I did some sniffing on port 53 and there are no DNS requests for SRV:
>>>>>
>>>>> 192.168.178.23        192.168.178.1         DNS      82 Standard 
>>>>> query 0x1eab NAPTR guest1.voipgateway.org
>>>>> 192.168.178.1         192.168.178.23        DNS      162 Standard 
>>>>> query response 0x1eab NAPTR guest1.voipgateway.org CNAME 
>>>>> ws1.voipgateway.org SOA ns1.backbone.ch
>>>>> 192.168.178.23        192.168.178.1         DNS      79 Standard 
>>>>> query 0x3a0b NAPTR ws1.voipgateway.org
>>>>> 192.168.178.1         192.168.178.23        DNS      141 Standard 
>>>>> query response 0x3a0b NAPTR ws1.voipgateway.org SOA ns1.backbone.ch
>>>>> [ ..nothing concerning VOIP...]
>>>>> 192.168.178.23        192.168.178.1         DNS      82 Standard 
>>>>> query 0xb5c0 NAPTR guest1.voipgateway.org
>>>>> 192.168.178.1         192.168.178.23        DNS      162 Standard 
>>>>> query response 0xb5c0 NAPTR guest1.voipgateway.org CNAME 
>>>>> ws1.voipgateway.org SOA ns1.backbone.ch
>>>>> 192.168.178.23        192.168.178.1         DNS      79 Standard 
>>>>> query 0x5cba NAPTR ws1.voipgateway.org
>>>>> 192.168.178.1         192.168.178.23        DNS      141 Standard 
>>>>> query response 0x5cba NAPTR ws1.voipgateway.org SOA ns1.backbone.ch
>>>>> [ ..nothing concerning VOIP...]
>>>>> 192.168.178.23        192.168.178.1         DNS      82 Standard 
>>>>> query 0x63b5 NAPTR guest1.voipgateway.org
>>>>> 192.168.178.1         192.168.178.23        DNS      162 Standard 
>>>>> query response 0x63b5 NAPTR guest1.voipgateway.org CNAME 
>>>>> ws1.voipgateway.org SOA ns1.backbone.ch
>>>>> 192.168.178.23        192.168.178.1         DNS      79 Standard 
>>>>> query 0x6dce NAPTR ws1.voipgateway.org
>>>>>
>>>>> The queries timeout occurs because Blink does not issue the 
>>>>> requests. IMHO Blink does not handle the SOA replies and somehow 
>>>>> deadlocks, so other requests are never sent.
>>>>>
>>>>> Instead it should simply return: NAPTR record does not exist. Go 
>>>>> on...
>>>>>
>>>>> Cheers
>>>>> Till
>>>>>
>>>>> _______________________________________________
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>>>>> Blink at lists.ag-projects.com
>>>>> https://lists.ag-projects.com/mailman/listinfo/blink
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