Hi, It's not OK to modify the method in that way. That will cause problems with standard implementation. As you cat see function returns explicitly the first via for REQUESTs and the last via for RESPONSEs. You should extend the method with parameters or modify it in another way.

BR, Aleksandar Yosifov

On Wed, Sep 29, 2021 at 1:08 AM ErhanOnur notifications@github.com wrote:

Description

I put a dispatcher between PCSCF and UE. When I tried to register, Pcscf's save function saved dispatcher's via IP and via port instead of UE's via IP and via port.

When I checked save function of ims_registrar_pcscf module , I saw that cscf_get_ue_via function is used for that. And It gives wrong via value. Instead of giving last via , it gives the first via in the via list.

Here is the function:

https://github.com/kamailio/kamailio/blob/master/src/lib/ims/ims_getters.c

/**

• Looks for the UE Via in First Via header if its a request
• or in the last if its a response and returns its body
• @param msg - the SIP message
• @returns the via of the UE

*/ struct via_body* cscf_get_ue_via(struct sip_msg *msg) { struct via_body *vb=0;

if (msg->first_line.type==SIP_REQUEST) vb = cscf_get_first_via(msg,0); else vb = cscf_get_last_via(msg);

if (!vb) return 0;

if (vb->port == 0) vb->port=5060; return vb; }

Troubleshooting

I corrected the code as below:

/**

• Looks for the UE Via in Last Via header and returns its body
• @param msg - the SIP message
• @returns the via of the UE

*/ struct via_body* cscf_get_ue_via(struct sip_msg *msg) { struct via_body *vb=0;

vb = cscf_get_last_via(msg);

if (!vb) return 0;

if (vb->port == 0) vb->port=5060; return vb; }

Reproduction

Try to put a dispatcher between PCSCF and UE. save function of ims_registrar_pcscf module saves dispatcher's IP and port as UE's IP and port. Debugging Data

(paste your debugging data here)

Log Messages

(paste your log messages here)

SIP Traffic

(paste your sip traffic here)

Possible Solutions Additional Information

• *Kamailio Version* - output of kamailio -v

(paste your output here)

• *Operating System*:

(paste your output here)

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Hello @henningw,

I checked usage of cscf_get_ue_via function. And I saw ims_ipsec_pcscf, ims_qos, ims_registrar_pcscf module are using this function.

All of them are pcscf modules.

ims_usrloc_pcscf keeps a hashtable to keep the pcscf contacts. And hash code is calculated with UE's IP address. To get UE's IP address we are currently using cscf_get_ue_via function.

In pull request , we will change the cscf_get_ue_via with cscf_get_ue_last_via in ims_registrar_pcscf_registrar module only. So contact will be saved into hash table with the return value of cscf_get_ue_last_via.

Since we will not change ims_ipsec_pcscf and ims_qos modules, they will query hash table with the return value of cscf_get_ue_via. Since these module will not use the same function to get UE's IP adress, they may get a different value and may not reach the contact in the hash table. because calculated hash code will be different.

Closed #2864 as not planned.