[asterisk-users] PJSIP trunk is down when DNS was not available during the Asterisk start.

[Leonid Fainshtein]

I see that pjsip_resolver.c tries unsuccessfuly to resolve the
hostname each 10 seconds:

[Aug 27 07:51:36] DEBUG[595] res_pjsip.c: 0x7f75282eb150: Wrapper created
[Aug 27 07:51:36] DEBUG[595] res_pjsip.c: 0x7f75282eb150: Set timer to 2000
msec
[Aug 27 07:51:36] DEBUG[595] res_pjsip/pjsip_resolver.c: Performing SIP DNS
resolution of target 'rpi6.in.xorcom.com'
[Aug 27 07:51:36] DEBUG[595] res_pjsip/pjsip_resolver.c: Transport type for
target 'rpi6.in.xorcom.com' is 'Unspecified'
[Aug 27 07:51:36] DEBUG[595] res_pjsip/pjsip_resolver.c: [0x7f75282fe7f8]
Created resolution tracking for target 'rpi6.in.xorcom.com'
[Aug 27 07:51:36] DEBUG[595] res_pjsip/pjsip_resolver.c: [0x7f75282fe7f8]
Added target 'rpi6.in.xorcom.com' with record type '35', transport
'Unspecified', and port '0'
[Aug 27 07:51:36] DEBUG[595] res_pjsip/pjsip_resolver.c: [0x7f75282fe7f8]
Added target '_sips._tcp.rpi6.in.xorcom.com' with record type '33',
transport 'TLS', and port '5061'
[Aug 27 07:51:36] DEBUG[595] res_pjsip/pjsip_resolver.c: [0x7f75282fe7f8]
Added target '_sip._tcp.rpi6.in.xorcom.com' with record type '33',
transport 'TCP', and port '5060'
[Aug 27 07:51:36] DEBUG[595] res_pjsip/pjsip_resolver.c: [0x7f75282fe7f8]
Added target '_sip._udp.rpi6.in.xorcom.com' with record type '33',
transport 'UDP', and port '5060'
[Aug 27 07:51:36] DEBUG[595] res_pjsip/pjsip_resolver.c: [0x7f75282fe7f8]
Added target 'rpi6.in.xorcom.com' with record type '1', transport 'UDP',
and port '5060'
[Aug 27 07:51:36] DEBUG[595] res_pjsip/pjsip_resolver.c: [0x7f75282fe7f8]
Starting initial resolution using parallel queries for target '
rpi6.in.xorcom.com'
[Aug 27 07:51:36] DEBUG[605] res_pjsip/pjsip_resolver.c: [0x7f75282fe7f8]
All parallel queries completed
[Aug 27 07:51:36] DEBUG[605] res_pjsip/pjsip_resolver.c: [0x7f75282fe7f8]
Resolution completed - 0 viable targets
[Aug 27 07:51:36] DEBUG[595] res_pjsip/pjsip_resolver.c: [0x7f75282fe7f8]
Invoking user callback with '0' addresses
[Aug 27 07:51:36] DEBUG[595] res_pjsip.c: 0x7f75282eb150: PJSIP tsx
response received
[Aug 27 07:51:36] DEBUG[595] res_pjsip.c: 0x7f75282eb150: Cancelling timer
[Aug 27 07:51:36] DEBUG[595] res_pjsip.c: 0x7f75282eb150: Timer cancelled
[Aug 27 07:51:36] DEBUG[595] res_pjsip.c: 0x7f75282eb150: Callbacks
executed
[Aug 27 07:51:36] DEBUG[595] res_pjsip.c: 0x7f75282eb150: wrapper destroyed
[Aug 27 07:51:36] DEBUG[595] res_pjsip/pjsip_options.c: Contact g145/sip:
rpi6.in.xorcom.com status didn't change: Unreachable, RTT: 0.000 msec
[Aug 27 07:51:36] DEBUG[595] res_pjsip/pjsip_options.c: AOR 'g145' now has
0 available contacts

But a DNS server is available at this time:
# host rpi6.in.xorcom.com
rpi6.in.xorcom.com has address 192.168.0.175

# ping rpi6.in.xorcom.com
PING rpi6.in.xorcom.com (192.168.0.175) 56(84) bytes of data.
64 bytes from rpi6.in.xorcom.com (192.168.0.175): icmp_seq=1 ttl=64
time=0.990 ms

Thank you,
Leonid Fainshtein



On Thu, Aug 27, 2020 at 1:52 PM Joshua C. Colp <jcolp at sangoma.com> wrote:

> On Thu, Aug 27, 2020 at 7:48 AM Leonid Fainshtein <
> leonid.fainshtein at xorcom.com> wrote:
>
>> Hi,
>> I have Asterisk 16.x with a trunk configured with a hostname in PJSIP AOR.
>> The registration is not required for this trunk.
>> I paid attention that Asterisk performs DNS resolving of the hostname
>> that is configured in the AOR 'contact' parameter only upon the Asterisk
>> start only.
>> Thus, if Asterisk is started when the DNS server is unreachable due to
>> the Internet connection failure then the 'contact' will be not resolvable
>> forever even when the Internet connection is returned. As a result of that,
>> the 'qualify' procedure is not performed and the trunk status is 'Unavail'.
>> The only way to revive the trunk is to restart Asterisk. Even 'pjsip
>> reload' doesn't solve the problem.
>> Is it the 'by design' Asterisk behavior or I have missed something?
>>
>
> PJSIP in Asterisk uses asynchronous DNS, so it should resolve at the time
> the request is actually made and should work afterwards. Not doing so would
> be a bug, and collecting a debug level log (debug to a file in logger.conf
> with core set debug 9) would explicitly show what is going on for DNS.
>
> --
> Joshua C. Colp
> Asterisk Technical Lead
> Sangoma Technologies
> Check us out at www.sangoma.com and www.asterisk.org
> --
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