Why the kamailio remove two route header?

Question

There is such a scenario:

u1(10.35.146.155) ---- kam proxy1(10.35.148.211) ---- kama proxy2 ---- u2(10.35.148.233, u2 is registered on kam proxy2)

The problem occurs in the forwarded ACK. After the ACK is forwarded, there is only one route header left. If such a message is forwarded to proxy2, it will not be routed. Why are two route headers removed at the same time? i don't understand.

kam proxy2 print error: kamailio[23404]: DEBUG: {1 20 ACK 20220407195255116117198@10.35.146.155} rr [loose.c:182]: find_next_route(): No next Route HF found

kamailio[23404]: DEBUG: {1 20 ACK 20220407195255116117198@10.35.146.155} rr [loose.c:623]: after_strict(): after_strict: No next URI found

Part of the sip message flow is as follows:

The reason why request uri is written is because proxy1 may be deployed on the public network, and proxy2 on the internal network.

u1 send INVITE:
Internet Protocol Version 4, Src: 10.35.146.155, Dst: 10.35.148.211
User Datagram Protocol, Src Port: 5060, Dst Port: 5060
Session Initiation Protocol (INVITE)
    Request-Line: INVITE sip:4594927728@10.35.148.211;user=phone SIP/2.0
    Message Header
        Via: SIP/2.0/UDP 10.35.146.155:5060;rport;branch=z9hG4bK325475974
        From: "elink11" <sip:11223344@10.35.146.155>;tag=264218750
        To: <sip:4594927728@10.35.148.211;user=phone>
        Call-ID: 20220407192539279786392@10.35.146.155
        [Generated Call-ID: 20220407192539279786392@10.35.146.155]
        CSeq: 20 INVITE
        Contact: <sip:11223344@10.35.146.155:5060>;video;audio
        Max-Forwards: 70
        User-Agent: Alaudae
        Subject: SIP/2.0
        Session-Expires: 1800
        Min-SE: 90
        Supported: timer,path,outbound,replaces
        Organization: localtest
        Allow: INVITE,ACK,BYE,CANCEL,UPDATE,INFO,SUBSCRIBE,NOTIFY,MESSAGE,OPTIONS
        Content-Type: application/sdp
        Content-Length:  1999
    Message Body

proxy1 send INVITE:
Internet Protocol Version 4, Src: 10.35.148.211, Dst: 10.35.148.233
User Datagram Protocol, Src Port: 5060, Dst Port: 5060
Session Initiation Protocol (INVITE)
    Request-Line: INVITE sip:4594927728@10.35.148.211;user=phone SIP/2.0
    Message Header
        Record-Route: <sip:10.35.148.211;lr;nat=yes>
        Via: SIP/2.0/UDP 10.35.148.211;branch=z9hG4bK4dc4.11c3814fdb0005a93b411d530dae0e9b.0
        Via: SIP/2.0/UDP 10.35.146.155:5060;received=10.35.146.155;rport=5060;branch=z9hG4bK325475974
        From: "elink11" <sip:11223344@10.35.146.155>;tag=264218750
        To: <sip:4594927728@10.35.148.211;user=phone>
        Call-ID: 20220407192539279786392@10.35.146.155
        [Generated Call-ID: 20220407192539279786392@10.35.146.155]
        CSeq: 20 INVITE
        Contact: <sip:11223344@10.35.146.155:5060;alias=10.35.146.155~5060~1>;video;audio
        Max-Forwards: 69
        User-Agent: Alaudae
        Subject: SIP/2.0
        Session-Expires: 1800
        Min-SE: 90
        Supported: timer,path,outbound,replaces
        Organization: localtest
        Allow: INVITE,ACK,BYE,CANCEL,UPDATE,INFO,SUBSCRIBE,NOTIFY,MESSAGE,OPTIONS
        Content-Type: application/sdp
        Content-Length:  2017
        P-hint: outbound


proxy1 recv 200 OK:
Internet Protocol Version 4, Src: 10.35.148.233, Dst: 10.35.148.211
User Datagram Protocol, Src Port: 5060, Dst Port: 5060
Session Initiation Protocol (200)
    Status-Line: SIP/2.0 200 OK
    Message Header
        Via: SIP/2.0/UDP 10.35.148.211;branch=z9hG4bK4dc4.11c3814fdb0005a93b411d530dae0e9b.0
        Via: SIP/2.0/UDP 10.35.146.155:5060;received=10.35.146.155;rport=5060;branch=z9hG4bK325475974
        From: "elink11" <sip:11223344@10.35.146.155>;tag=264218750
        To: "PVS2803841713" <sip:4594927728@10.35.148.211;user=phone>;tag=211199AF-D02E39DC
        CSeq: 20 INVITE
        Call-ID: 20220407192539279786392@10.35.146.155
        [Generated Call-ID: 20220407192539279786392@10.35.146.155]
        Contact: <sip:4594927728@10.35.148.211:5060;transport=tcp>;+sip.instance="<urn:uuid:cea31ad7-d73c-4e2c-b9e6-d2530239f3dd>"
        Record-Route: <sip:10.35.148.233;transport=tcp;r2=on;lr>, <sip:10.35.148.233;r2=on;lr>, <sip:10.35.148.211;lr;nat=yes>
        Allow: INVITE,ACK,BYE,CANCEL,OPTIONS,INFO,MESSAGE,SUBSCRIBE,NOTIFY,PRACK,UPDATE,REFER
        MRD: MRE; MRC-V=1.0.1
        Multiplexing: EP
        User-Agent: Polycom RealPresence Desktop for Windows (3.10.0.71107)
        Session-Expires: 1800;refresher=uac
        Content-Type: application/sdp
        Content-Length: 3126
        SrcAddr: 10.34.80.132-64999

u1 recv 200 OK:
Frame 61: 1115 bytes on wire (8920 bits), 1115 bytes captured (8920 bits)
Ethernet II, Src: IntelCor_00:b2:eb (a4:bf:01:00:b2:eb), Dst: NewH3CTe_dd:b6:71 (b0:44:14:dd:b6:71)
Internet Protocol Version 4, Src: 10.35.148.211, Dst: 10.35.146.155
User Datagram Protocol, Src Port: 5060, Dst Port: 5060
Session Initiation Protocol (200)
    Status-Line: SIP/2.0 200 OK
    Message Header
        Via: SIP/2.0/UDP 10.35.146.155:5060;received=10.35.146.155;rport=5060;branch=z9hG4bK325475974
        From: "elink11" <sip:11223344@10.35.146.155>;tag=264218750
        To: "PVS2803841713" <sip:4594927728@10.35.148.211;user=phone>;tag=211199AF-D02E39DC
        CSeq: 20 INVITE
        Call-ID: 20220407192539279786392@10.35.146.155
        [Generated Call-ID: 20220407192539279786392@10.35.146.155]
        Contact: <sip:4594927728@10.35.148.211:5060;transport=tcp>;+sip.instance="<urn:uuid:cea31ad7-d73c-4e2c-b9e6-d2530239f3dd>"
        Record-Route: <sip:10.35.148.233;transport=tcp;r2=on;lr>, <sip:10.35.148.233;r2=on;lr>, <sip:10.35.148.211;lr;nat=yes>
        Allow: INVITE,ACK,BYE,CANCEL,OPTIONS,INFO,MESSAGE,SUBSCRIBE,NOTIFY,PRACK,UPDATE,REFER
        MRD: MRE; MRC-V=1.0.1
        Multiplexing: EP
        User-Agent: Polycom RealPresence Desktop for Windows (3.10.0.71107)
        Session-Expires: 1800;refresher=uac
        Content-Type: application/sdp
        Content-Length: 3150


u1 send ACK:
Internet Protocol Version 4, Src: 10.35.146.155, Dst: 10.35.148.211
User Datagram Protocol, Src Port: 5060, Dst Port: 5060
Session Initiation Protocol (ACK)
    Request-Line: ACK sip:4594927728@10.35.148.211:5060;transport=tcp SIP/2.0
    Message Header
        Via: SIP/2.0/UDP 10.35.146.155:5060;rport;branch=z9hG4bK2104083668
        Route: <sip:10.35.148.211;lr;nat=yes>
        Route: <sip:10.35.148.233;r2=on;lr>
        Route: <sip:10.35.148.233;transport=tcp;r2=on;lr>
        From: "elink11" <sip:11223344@10.35.146.155>;tag=264218750
        To: "PVS2803841713" <sip:4594927728@10.35.148.211;user=phone>;tag=211199AF-D02E39DC
        Call-ID: 20220407192539279786392@10.35.146.155
        [Generated Call-ID: 20220407192539279786392@10.35.146.155]
        CSeq: 20 ACK
        Contact: <sip:11223344@10.35.146.155:5060>;video;audio
        Max-Forwards: 70
        User-Agent: Alaudae
        Supported: timer,path,outbound,replaces
        Allow: INVITE,ACK,BYE,CANCEL,UPDATE,INFO,SUBSCRIBE,NOTIFY,MESSAGE,OPTIONS
        Content-Length: 0

proxy2 send ACK:
Frame 63: 878 bytes on wire (7024 bits), 878 bytes captured (7024 bits)
Ethernet II, Src: IntelCor_00:b2:eb (a4:bf:01:00:b2:eb), Dst: AdlinkTe_4c:b1:3d (00:30:64:4c:b1:3d)
Internet Protocol Version 4, Src: 10.35.148.211, Dst: 10.35.148.233
User Datagram Protocol, Src Port: 5060, Dst Port: 5060
Session Initiation Protocol (ACK)
    Request-Line: ACK sip:10.35.148.233;transport=tcp;r2=on;lr SIP/2.0
    Message Header
        Via: SIP/2.0/UDP 10.35.148.211;branch=z9hG4bK4dc4.bf03454b05da12787ff6071b3c44764c.0
        Via: SIP/2.0/UDP 10.35.148.211;rport=5060;branch=z9hG4bK4dc4.bc5eb8ce444f77bbeb7254c2f131e5e4.0
        Via: SIP/2.0/UDP 10.35.146.155:5060;received=10.35.146.155;rport=5060;branch=z9hG4bK2104083668
        Route: <sip:10.35.148.233;r2=on;lr>
        From: "elink11" <sip:11223344@10.35.146.155>;tag=264218750
        To: "PVS2803841713" <sip:4594927728@10.35.148.211;user=phone>;tag=211199AF-D02E39DC
        Call-ID: 20220407192539279786392@10.35.146.155
        [Generated Call-ID: 20220407192539279786392@10.35.146.155]
        CSeq: 20 ACK
        Contact: <sip:11223344@10.35.146.155:5060;alias=10.35.146.155~5060~1>;video;audio
        Max-Forwards: 68
        User-Agent: Alaudae
        Supported: timer,path,outbound,replaces
        Allow: INVITE,ACK,BYE,CANCEL,UPDATE,INFO,SUBSCRIBE,NOTIFY,MESSAGE,OPTIONS
        Content-Length: 0

Maybe, you have not catch the purpose of my answer. The problem is not the routing itself but somewhere else; the messages do not match the diagram. — tomrtc, Apr 13 '22 at 13:30

score 0 · Answer 1 · answered Apr 10 '22 at 09:59

0

It is a normal behavior for SIP: The route-set is :

    Route: <sip:10.35.148.211;lr;nat=yes>
    Route: <sip:10.35.148.233;r2=on;lr>
    Route: <sip:10.35.148.233;transport=tcp;r2=on;lr>

So when the router bound to sip:10.35.148.233 receives the ACK, it removes the two route entries where it is it very own address. There is an invisible loop routing on 10.35.148.233.

answered Apr 10 '22 at 09:59

tomrtc

517
6
10

To clarify, r2=on indicates double record routing, i.e. one proxy is adding two records. The reason in this case is that the transport is TCP on one side and UDP on the other. When the proxy receives this message, it automatically knows which interface and transport it needs to use to relay the message onwards so it doesn't have to figure it out based on next hop. – vaizki Aug 04 '22 at 10:58

Why the kamailio remove two route header?

1 Answers1