[asterisk-bugs] [JIRA] (ASTERISK-24889) Possible bug: PJSIP: stateless behavior when transport=tcp

[Anatoli (JIRA)]

Anatoli created ASTERISK-24889:
----------------------------------

             Summary: Possible bug: PJSIP: stateless behavior when transport=tcp
                 Key: ASTERISK-24889
                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-24889
             Project: Asterisk
          Issue Type: Bug
      Security Level: None
          Components: pjproject/pjsip
    Affects Versions: 13.2.0
         Environment: OS: Ubuntu 14.04, with all updates

Kernel: 3.13.0-44-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) 
            Reporter: Anatoli


When an endpoint registers via TCP, PJSIP processes everything as corresponds: the communication is via TCP, REGISTER/ACK pass OK, the endpoint can even establish calls. But, when another endpoint calls to the first one, PJSIP sends INVITE message in a new TCP session to the already opened port.

So if the registration was performed from TCP 55880 to 5060 and everything except INVITE flows in the same TCP session, INVITE is sent via a new TCP session from a random port on asterisk server (e.g. 32926) to the already opened 55880 port. With tcpdump I see a new SYN packet (and the already established TCP session was not closed/reset yet):

{noformat}
From: 10.101.10.1 (asterisk IP)
To: 10.101.100.100 (endpoint IP)
Source port: 32926
Destination port: 55880
Protocol: TCP
TCP Data: [SYN] Seq=0 Win=29200 Len=0 MSS=1460 SACK_PERM=1 TSval=9227246 TSecr=0 WS=128
{noformat}

Naturally, the endpoint responds with a RST,ACK.


The CLI shows the following:

{noformat}
ERROR[19352]: pjsip:0 <?>:    tcpc0x7fcdb404 TCP connect() error: Connection refused [code=120111]
WARNING[19352]: pjsip:0 <?>:  tsx0x7fcdb402e Failed to send Request msg INVITE/cseq=31054 (tdta0x7fcdb4034260)! err=120111 (Connection refused)
{noformat}


Investigating the code, I've found that to send the INVITE message PJSIP calls pjsip_endpt_send_request_stateless, which, as the name indicates, behaves statelessly, though using TCP.


Call trace:

{noformat}
sip_dialog.c at 1164 pjsip_dlg_send_request(INVITE) => @1214 call to pjsip_tsx_create_uac
sip_transaction.c at 1266 pjsip_tsx_create_uac  => call to pjsip_tsx_create_uac2
sip_transaction.c at 1273 pjsip_tsx_create_uac2  => @1367 tsx_on_state_null  callback assignment
sip_transaction.c at 2311 tsx_on_state_null => @2351 call to tsx_send_msg
sip_transaction.c at 2006 tsx_send_msg => @2120 call to pjsip_endpt_send_request_stateless
{noformat}

Asterisk 13.2.0, PJSIP 2.3, everything compiled from sources.

Config: same as in the examples except for one endpoint the transport=<tcp_transport> option is specified.

Client: a number of softphones, tested with latest Linphone on iPhone, SessionChat (freeware from AppStore), Jitsi on Windows.


Please let me know if additional information is required.

Regards,
Anatoli



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