[sr-dev] [kamailio/kamailio] fix_nated_contact() and remove_hf malform packet (#977)

Jared Hull notifications at github.com
Tue Feb 7 17:33:52 CET 2017


### Description
fix_nated_contact() and removing and appending a contact will malform the SIP packet.
I read somewhere that all of the *_hf functions are applied only when the packet is sent out again. Perhaps things are working as intended and I am just asking too much of these functions. 

#### Reproduction
In my onreply_route for 200 OK with SDP:

fix_nated_contact();
#dlg_setflag(1); # I want the contact in the dialog table to be the fixed one
#Then I want to replace that contact with a contact to Kamailio's public IP and route it to Asterisk
#for ACK response. This contact must be here for Asterisk to relay this back to me.
remove_hf("Contact"); 
append_hf("Contact: <sip:$sel(cfg_get.global.publicIP):5060>\r\n"); # insert_hf same problem

### Troubleshooting
This results in two contacts, but does not malform. remove_hf after the nat_fix_contact is the issue.
fix_nated_contact();
insert_hf("Contact: <sip:$sel(cfg_get.global.publicIP):5060>\r\n");

#### SIP Traffic
The inbound 200 OK
CSeq: 9865 INVITE
Contact: <sip:424242143 at devicePrivateIP:5060>
Content-Type: application/sdp

After fix_nated_contact(); remove_hf("Contact"); append_hf("Contact: <sip:serverIP:5060>\r\n");
CSeq: 9865 INVITE
sip:424242143 at devicePublicIP:1026Content-Type: application/sdp

### Possible Solutions

I managed to get the functionality I wanted with either of these, but they result in two contact headers.
I have also noticed that a remove->append->remove->append ignores the remove between appends.

Workaround 1
remove_hf("Contact");
insert_hf("Contact: <sip:$tU@$si:$sp>\r\n");
dlg_setflag(1);
insert_hf("Contact: <sip:$sel(cfg_get.global.publicIP):5060>\r\n");

Workaround 2
fix_nated_contact();
dlg_setflag(1);
insert_hf("Contact: <sip:$sel(cfg_get.global.publicIP):5060>\r\n");

### Additional Information

  * **Kamailio Version**: kamailio 4.4.5 (x86_64/linux) f98162

* **Operating System**: Linux 3.10.0-514.2.2.el7.x86_64 # 1 SMP Tue Dec 6 23:06:41 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

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https://github.com/kamailio/kamailio/issues/977
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