Unexpected BYE, 408 "Session timeout" with Aastra 400

[BrianMiller793]

Version: FreeSWITCH version: 1.10.12-release+git~20240802T210227Z~a88d069d6f~64bit (git a88d069 2024-08-02 21:02:27Z 64bit)
Sofia: sofia-sip-1.13.17

An Aastra 400 calls FreeSWITCH as a client. Less than 120 seconds later, FreeSWITCH hangs up with an unexpected BYE, and "Session timeout" for the reason. The problem only occurs when the UAC is outside the local network.

I have reproduced this using a test script, and the error happens only when the NAT is in use from an external address. To reproduce the error under test, I connect a Raspberry PI through my cell phone, and then run a Python Behave script against my test server. The error will not reproduce when the UAC is on the same network as the server.

From fs_cli: nua_session.c:1564 nua_session_usage_refresh() nua(0x7a56ec0509a0): session almost expired, sending BYE before timeout.

In mod_sofia.c, I found that commenting out the check for Aastra in sofia_receive_message() (line 2071) allows the call to complete normally.

What sets off the unexpected action is a 200 OK to an UPDATE, with "Session-Expires: 1800;refresher=uas". If Session-Expires does not have the "refresher", then the premature BYE does not occur.

Session Initiation Protocol (200)
Status-Line: SIP/2.0 200 OK
Message Header
    Via: SIP/2.0/TCP 64.19.65.25:5080;rport=5080;branch=z9hG4bKe3UKBgKt3Bm8K;received=64.19.65.25
    To: "Osthoff" <sip:wunderbaum@littletrees>;tag=AI1E037B1410C9A99B
    From: <sip:7253@littletrees>;tag=yXt8Dy3e1QB9H
    Call-ID: AI15C12F081C97F2D2_00:08:5d:97:7d:12
    CSeq: 90289035 UPDATE
    Contact: <sip:[email protected]:5060;transport=tcp>
    Allow-Events: presence,dialog,message-summary,refer
    Allow: ACK,BYE,CANCEL,INVITE,NOTIFY,OPTIONS,PUBLISH,UPDATE,REFER
    User-Agent: Aastra 400
    P-Preferred-Identity: "Osthoff" <sip:[email protected]>
    Require: timer
    Session-Expires: 1800;refresher=uas
    Supported: timer
    Content-Type: application/sdp
    Content-Length: 234
Message Body
    Session Description Protocol
        Session Description Protocol Version (v): 0
        Owner/Creator, Session Id (o): aastra400 48971799 48971800 IN IP4 192.168.1.225
        Session Name (s): call
        Connection Information (c): IN IP4 192.168.1.225
        Time Description, active time (t): 0 0
        Media Description, name and address (m): audio 5004 RTP/AVP 8 0 101
        Media Attribute (a): rtpmap:8 PCMA/8000
        Media Attribute (a): rtpmap:0 PCMU/8000
        Media Attribute (a): rtpmap:101 telephone-event/8000
        Media Attribute (a): fmtp:101 0-15
        Media Attribute (a): ptime:20

[BrianMiller793]

I have attached console logs and captures of the problem.

BehaveVanillaReproConsole.txt.gz
BehaveVanillaRepro.pcapng.gz
AastraFail.pcap.gz

[BrianMiller793]

From my investigation, it looks like the session timer parameters may not be set correctly during initialization:

nua_session.c:1545 nua_session_usage_refresh() nh=0x7521e00032d0, ss=0x75223c02ba50, callstate=ready
nua_session.c:1546 nua_session_usage_refresh() ss_timer: interval=120, refresher=1, timer_set=1
nua_session.c:1548 nua_session_usage_refresh() local: expires=90, defaults=0, min_se=120, refresher=1, supported=1, require=0
nua_session.c:1550 nua_session_usage_refresh() remote: expires=120, defaults=0, min_se=0, refresher=1, supported=1, require=0

and

nua_session.c:1545 nua_session_usage_refresh() nh=0x75223c028da0, ss=0x75223c025be0, callstate=ready
nua_session.c:1546 nua_session_usage_refresh() ss_timer: interval=120, refresher=2, timer_set=1
nua_session.c:1548 nua_session_usage_refresh() local: expires=90, defaults=0, min_se=120, refresher=2, supported=1, require=0
nua_session.c:1550 nua_session_usage_refresh() remote: expires=1800, defaults=0, min_se=0, refresher=2, supported=1, require=1
nua_session.c:1574 nua_session_usage_refresh() nua(0x75223c028da0): session almost expired, sending BYE before timeout.

The 200 OK response doesn't have a Min-SE header, so that seems to affect timer behavior. I added code to set the Min-SE value from Session-Expires if Min-SE isn't present.

diff --git a/libsofia-sip-ua/nua/nua_session.c b/libsofia-sip-ua/nua/nua_session.c
index b9bd1ee..214d135 100644
--- a/libsofia-sip-ua/nua/nua_session.c
+++ b/libsofia-sip-ua/nua/nua_session.c
@@ -4427,6 +4427,8 @@ void session_timer_store(struct session_timer *t,
 
   if (sip->sip_min_se)
     t->remote.min_se = sip->sip_min_se->min_delta;
+  else if (x)
+    t->remote.min_se = x->x_delta;
 }
 
 /** Add timer feature and Session-Expires/Min-SE headers to request/response

The issue seems to be fixed with that change.

nua_session.c:1545 nua_session_usage_refresh() nh=0x7ce048000dd0, ss=0x7ce0a002b7a0, callstate=ready
nua_session.c:1546 nua_session_usage_refresh() ss_timer: interval=120, refresher=1, timer_set=1
nua_session.c:1548 nua_session_usage_refresh() local: expires=90, defaults=0, min_se=120, refresher=1, supported=1, require=0
nua_session.c:1550 nua_session_usage_refresh() remote: expires=120, defaults=0, min_se=120, refresher=1, supported=1, require=0

I'm doing further testing now.