SV: [Users] Route-header DNS lookup? - sr-users

7 Jul 2006

hi
SRV records are all in place, but as I trace the DNS lookup queries sent
by the OpenSER host, it only asks for A records for "iptel1.ipatl.se" and
no NAPTR or SRV. the hostname that the NAPTR and SRV records points to is
"sip.iptel1.ipatl.se", but this is not resolved by OpenSER for the route-header
destination. 

but, for the initial INVITE, OpenSER correctly queries NAPTR and SRV rr to
resolv the hostname/IP of the server responsible for the domain
"iptel1.ipatl.se". 

i'm familiar with the rfc3263, and all is set up correctly and working just fine. 

best regards,
/staffan 

...
   -----Ursprungligt meddelande-----
  Från: users-bounces(a)openser.org 
  [mailto:users-bounces@openser.org] För Norman Brandinger
  Skickat: den 6 juli 2006 14:57
  Till: users(a)openser.org
  Ämne: Re: [Users] Route-header DNS lookup?

  Hi Kerker,

  Perhaps there needs to be SRV records in the DNS server that 
  manages iptel1.ipatl.se.

  Below are example SRV records.  If this is your first time 
  working with SRV records, I strongly suggest reading some of 
  the online doc that deals with them.

  _sip._tcp.iptel1.ipatl.se.             IN SRV 0 0 5060 
  sip.iptel1.ipatl.se.
  _sip._udp.iptel1.ipatl.se.             IN SRV 0 0 5060 
  sip.iptel1.ipatl.se.

  Regards,
  Norm

  Kerker Staffan wrote:
  hi
 i recently bounced into this problem, and i'm not sure here. 
 i'm running the openser-devel, with the cacheless    db_mode=3. (works 
  fine btw)

 the record-route header received by the proxy on the other side 
 (SNOM4S), inserts the domain name (iptel1.ipatl.se) and not the 
 hostname (sip.iptel1.ipatl.se) in the record-route header,    and uses the
maddr=<ip_of_server> with the actual server IP address.

 now, when my client (behind the OpenSER) replies with an    ACK to the 
  incomming OK, it uses the Route-header recieved
in the    RR-header, and 
  sends the ACK to OpenSER. i then get the
following errors    in OpenSER.

 ---
 /usr/local/sbin/openser[3583]: ERROR: mk_proxy: could not    resolve hostname:
"iptel1.ipatl.se"
  /usr/local/sbin/openser[3583]: ERROR: uri2proxy:
bad host    name in URI 

<sip:4ffec4ce755c218a72228c6643cb3b6b@iptel1.ipatl.se:5060;ma
  ddr=172.2
  8.248.66;transport=udp;lr>
 ---

 the ACK i sent look like this:

 ---
 Request-Line: ACK sip:2307@iptel1.ipatl.se;gruu=6fg9n6dl SIP/2.0
       Via: SIP/2.0/UDP    172.28.248.52:2051;branch=z9hG4bK-d96b1fvapkyn;rport
        Route:
<sip:172.28.248.10;lr=on;ftag=li9buf1i4p>
       Route:    <sip:4ffec4ce755c218a72228c6643cb3b6b@iptel1.ipatl.se:5060
  ;maddr=		172.28.248.66;transport=udp;lr>
        From: "Snom 2652"
<sip:2652@ipatl.se>;tag=li9buf1i4p
       To: <sip:2307@ipatl.se>;tag=hvseiz7kgb
       Call-ID: 3c269d83900b-xj3ild14y880@snom360
       CSeq: 1 ACK
       Max-Forwards: 70
       Contact: <sip:2652@172.28.248.52:2051;line=cp4a7ljd>
       Content-Length: 0
 ---

 as far as i understand, according the rfc 3263, the    route-header may 
  contain domain name that has to be resolved using
SRV.

 ---
 "6 Constructing SIP URIs

    In many cases, an element needs to construct a SIP URI    for inclusion
     in a Contact header in a REGISTER, or in a
Record-Route    header in an
     INVITE.  According to RFC 3261 [1], these URIs
have to have the
    property that they resolve to the specific element that inserted
    them.  However, if they are constructed with just an IP    address, for
     example:

    sip:1.2.3.4

    then should the element fail, there is no way to route    the request or
     response through a backup.

    SRV provides a way to fix this.  Instead of using an IP    address, a
     domain name that resolves to an SRV record can
be used:

    sip:server23.provider.com"
 ---

 now, OpenSER only asks DNS for an A record of the name    recieved in the 
  route header, and since that's a domain name,
it's    unresolvable, and so the ACK is never sent.

 any hints or clues? 

 best regards,
 /Staffan Kerker

 --
 Staffan Kerker
 Saab Communications, Växjö
 p. +46 470 42185
 c. +46 705 391365
 m. staffan.kerker(a)saabgroup.com

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