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Summary:ASTERISK-24807: Missing mandatory field Max-Forwards
Reporter:Anatoli (anatoli)Labels:
Date Opened:2015-02-18 11:17:21.000-0600Date Closed:2015-03-11 10:26:08
Priority:CriticalRegression?
Status:Closed/CompleteComponents:pjproject/pjsip
Versions:13.2.0 Frequency of
Occurrence
Constant
Related
Issues:
is related toASTERISK-24945 Apply PJSIP global default values when no global configuration is present
Environment:OS: Ubuntu 12.04 inside VirtualBox, with all updates Kernel: 3.8.0-29-generic pjsip: 2.3 from http://www.pjsip.org/release/2.3/pjproject-2.3.tar.bz2 (./configure --prefix=/usr --enable-shared --enable-epoll; make; sudo make install) Asterisk: 13.2.0 from http://downloads.asterisk.org/pub/telephony/asterisk/asterisk-13.2.0.tar.gz (./configure --prefix=/usr --sysconfdir=/etc --localstatedir=/var; make; sudo make install)Attachments:
Description:While evaluating the latest Asterisk and PJSIP (both compiled from sources), when calling to/from softphones (in particular the latest Linphone v.3.7.0) the INVITE messages from Asterisk are rejected due to the specification violation.

Here are more people having the same problem: http://comments.gmane.org/gmane.comp.telephony.pbx.asterisk.user/281228 and http://lists.digium.com/pipermail/asterisk-dev/2003-July/001114.html.

Linphone has a debug option: {{linphone.exe --logfile "c:\Temp\logs.txt"}} and in the generated logfile one can see something like:

{code}[error] Missing mandatory header [Max-Forwards] for message [INVITE]{code}

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And this is what Asterisk sends to it:

{code}
INVITE sip:6002@192.168.56.102 SIP/2.0
Via: SIP/2.0/UDP 192.168.56.3:5060;rport;branch=z9hG4bKPjbf53c93c-a424-4b9e-9e6a-b50d0e606965
From: <sip:6001@192.168.56.3>;tag=deeff9b9-50ab-410e-b683-94fdeb9f87b3
To: <sip:6002@192.168.56.102>
Contact: <sip:9426fd27-7ccd-4e1e-ab7a-e6c27fc59a5c@192.168.56.3:5060>
Call-ID: 5b517cda-634b-4036-bb81-95a43379c09d
CSeq: 6848 INVITE
Allow: OPTIONS, SUBSCRIBE, NOTIFY, PUBLISH, INVITE, ACK, BYE, CANCEL, UPDATE, PRACK, REGISTER, MESSAGE, REFER
Supported: 100rel, timer, replaces, norefersub
Session-Expires: 1800
Min-SE: 90
Content-Type: application/sdp
Content-Length:   254
{code}

So indeed, there is no "Max-Forwards" header sent with the INVITE requests, but, according to the SIP RFC 3261: "A valid SIP request formulated by a UAC MUST, at a minimum, contain the following header fields: To, From, CSeq, Call-ID, Max-Forwards, and Via; all of these header fields are mandatory in all SIP requests."
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After researching a bit the source code of pjsip, I found that actually almost all messages originating from it don't have Max-Forwards fields.

I've tried to add the header manually and it solves the problem (this is not a definitive solution; it has some minor issues):

{code}
--- pjproject-2.3/pjsip/src/pjsip/sip_util.c.orig  2014-08-18 05:54:43.000000000 -0300
+++ pjproject-2.3/pjsip/src/pjsip/sip_util.c        2015-02-17 10:52:23.839673699 -0300
@@ -465,6 +465,8 @@ PJ_DEF(pj_status_t) pjsip_endpt_create_r
    }
    PJ_END;

+             pjsip_msg_add_hdr(tdata->msg, pjsip_max_fwd_hdr_create(tdata->pool, 70));
+
    *p_tdata = tdata;
    return PJ_SUCCESS;
{code}

But then I've discussed it with people at pjsip@lists.pjsip.org (here is the thread: http://lists.pjsip.org/pipermail/pjsip_lists.pjsip.org/2015-February/018120.html) and they suggest that the issue is actually within the code that integrates pjsip with asterisk (e.g. {{res/res_pjsip/config_global.c}}) and suggested filling an issue here.

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This problem is a show-stopper when there are softphones among the endpoints.
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*UPDATE*: Harald Radke pointed out in the discussion at pjsip at lists.pjsip.org:
{quote}having a quick look at res_pjsip.c of the asterisk res(ource?):
{noformat}
   /* PJSIP will automatically try to add a Max-Forwards header. Since we want to control that,
    * we need to stop PJSIP from doing it automatically
    */
   remove_request_headers(ast_pjsip_endpoint);
{noformat}
Thus this asterisk code clearly modifies the default behaviour of PJSIP thus it is up to either the user to configure it properly (maybe there is a Max-Forwards option in a config file which, if not set, will result in not putting in a max-forwards header field with a default value) or it is a bug in res-pjsip.
{quote}
So indeed, it looks like a bug in res_pjsip.
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----
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STEPS TO REPRODUCE

*extensions.conf*

{code}
[general]
language=en
static=yes
writeprotect=no
autofallthrough=yes

[internal]
exten => 6001,1,Dial(PJSIP/6001,20)
same => n,Hangup()

exten => 6002,1,Dial(PJSIP/6002,20)
same => n,Hangup()
{code}



*pjsip.conf*

{code}
[transport-udp]
type=transport
protocol=udp
bind=192.168.56.3


[6001]
type=endpoint
transport=transport-udp
context=internal
allow=ulaw
allow=gsm
auth=6001
aors=6001

device_state_busy_at=1
allow_subscribe=yes
sub_min_expiry=30

[6001]
type=auth
auth_type=userpass
password=6001
username=6001

[6001]
type=aor
max_contacts=1
contact=sip:6001@192.168.56.101


[6002]
type=endpoint
transport=transport-udp
context=internal
allow=ulaw
allow=gsm
auth=6002
aors=6002

device_state_busy_at=1
allow_subscribe=yes
sub_min_expiry=30

[6002]
type=auth
auth_type=userpass
password=6002
username=6002


[6002]
type=aor
max_contacts=1
contact=sip:6002@192.168.56.102
{code}


Start asterisk:
{{# /usr/sbin/asterisk}}


Then configure the extensions in 2 Linphones (in wizard: user/pass =
600x/600x and domain: 192.168.56.3) and try to make a call from one Linphone to another.
Comments:By: Mark Michelson (mmichelson) 2015-02-20 11:01:47.479-0600

The intent is for Max-Forwards to be added by default to outbound SIP requests. In res_pjsip/config_global.c, the Max-Forwards and User-Agent headers are configured to be added to outbound requests. Then the PJSIP module in res_pjsip/pjsip_global_headers.c is intended to send those headers out on each request.

My guess here is that this is another instance of that all-too-common config framework/sorcery mistake where the absence of a configuration section results in expected default values not being applied. As an experiment, in your pjsip.conf file, can you add the following:

{noformat}
[global]
type = global
{noformat}

Adding a global configuration section should result in the default Max-Forwards and User-agent headers being applied. If this fixes the problem, it should be easy to create a patch to fix this.

By: Rusty Newton (rnewton) 2015-02-20 12:21:09.093-0600

Be sure to use the Send Back or Enter Feedback buttons to get the issue back to us with your response.

By: Anatoli (anatoli) 2015-02-20 15:33:30.836-0600

Adding type global fixes the problem!

Without it {{pjsip set logger on}} shows no Max-Forwards header field and getting {{SIP/2.0 400 Bad request}} replies from the softphones. With this option there is {{Max-Forwards: 70}} header field and the softphones reach each other.

By: Rusty Newton (rnewton) 2015-02-20 15:58:24.127-0600

Thanks for the follow up Anatoli. We'll get this fixed.