[Blink] Blink Ubuntu DNS lookup deadlock?

g4-lisz at tonarchiv.ch g4-lisz at tonarchiv.ch
Thu Jan 19 20:28:09 CET 2023 

It's really strange. It worked for quite a while. But now again it 
started to stall because of this DNS issue... Adding a static outbound 
proxy fixed it though - thanks again for this hint.

@Adrian: Can you elaborate a bit why in your opinion this CNAME is not 
allowed? It's for a subdomain, so it's totally legit... BTW this is a 
comercial SIP provider so I can't change anything in respect.

Cheers,
Till

On 01.12.22 03:56, g4-lisz at tonarchiv.ch wrote:
> I guess you mean voipgateway.org as root domain, not the '.' domain 
> above TLDs...
>
> I don't see an issue here. The idea of CNAME is to point to other 
> names. They don't have to be in the same zone file.
>
> guest1.voipgateway.org points to ws1.voipgateway.org so this is even 
> the same domain.
>
> Cheers
> Till
>
> On 30.11.22 23:50, GA Georgescu wrote:
>> CNAME on the root domain is not allowed in DNS. Each resolver may 
>> yield a different result when coping to this anomaly.
>>
>> As a start, just remove it and we can look at what happens afterwards.
>>
>> Adrian
>>
>>> On 30 Nov 2022, at 14:17, g4-lisz at tonarchiv.ch wrote:
>>>
>>> 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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