amnapa created an issue (kamailio/kamailio#4205)

### Description

Using sCSCF sample found [here](https://github.com/kamailio/kamailio/blob/master/misc/examples/ims/scscf/kam...), after calling ims_www_challenge in REGISTER route block and sending a Diameter MAR request, the control is never passed to REG_MAR_REPLY route block and debug messages within REG_MAR_REPLY are not logged. This is not the case with REG_SAR_REPLY and PRE_REG_SAR_REPLY, those blocks are executed as expected.

``` ###################################################################### # Route for handling Registrations: ###################################################################### route[REGISTER] { xlog("ALGORITHM IS [$aa] and User-Agent is [$ua]\n"); $var(alg) = $aa; if ($aa == $null) { $var(alg) = "MD5"; #force to MD5 for zoiper.... non-ims } #!ifdef WITH_AUTH if (!ims_www_authenticate("$td")) { #!else if (($var(alg) == "MD5") && (!ims_www_authenticate("$td"))) { #!endif if ($? == -2) { send_reply("403", "Authentication Failed"); exit; } else if ($? == -3) { send_reply("400", "Bad Request"); exit; } else if ($? == -9) { xlog("L_DBG", "Authentication re-sync requested\n"); ims_www_resync_auth("REG_RESYNC_REPLY", "$td"); exit; } else { #user has not been authenticated. Lets send a challenge via 401 Unauthorized xlog("L_DBG", "About to challenge! auth_ims\n"); ims_www_challenge("REG_MAR_REPLY", "$td", "$var(alg)"); exit; } } else { xlog("L_DBG", "Auth succeeded\n"); # We need to check if this user is registered or not if (!impu_registered("location")) { xlog("L_ERR", "Not REGISTERED\n"); save("PRE_REG_SAR_REPLY", "location"); exit; } else { isc_match_filter_reg("1", "location"); save("REG_SAR_REPLY", "location"); exit; } } }

route[REG_MAR_REPLY] { #this is async so to know status we have to check the reply avp xlog("L_DBG", "maa_return code is $avp(s:maa_return_code)\n");

switch ($avp(s:maa_return_code)){ case 1: #success xlog("L_DBG", "MAR success - 401/407 response sent from module\n"); break; case -1: #failure xlog("L_ERR", "MAR failure - error response sent from module\n"); break; case -2: #error xlog("L_ERR", "MAR error - sending error response now\n"); send_reply("500", "MAR failed"); break; default: xlog("L_ERR", "Unknown return code from MAR, value is [$avp(s:maa_return_code)]\n"); send_reply("500", "Unknown response code from MAR"); break; } exit; } ```

### Troubleshooting

#### Reproduction

<!-- If the issue can be reproduced, describe how it can be done. -->

#### Debugging Data

``` (paste your debugging data here) ```

#### Log Messages

``` ERROR: *** cfgtrace:request_route=[REGISTER] c=[/usr/local/etc/kamailio/kamailio.cfg] l=712 a=27 n=ims_www_challenge DEBUG: ims_auth [authorize.c:290]: challenge(): Looking for route block [REG_MAR_REPLY] INFO: ims_auth [cxdx_mar.c:76]: create_return_code(): created AVP successfully : [maa_return_code] - [-2] DEBUG: ims_auth [authorize.c:314]: challenge(): Need to challenge for realm [ims.mnc072.mcc432.3gppnetwork.org] DEBUG: ims_auth [authorize.c:321]: challenge(): Checking if REGISTER is authorized for realm [ims.mnc072.mcc432.3gppnetwork.org]... DEBUG: ims_auth [authorize.c:1446]: get_auth_userdata(): Searching auth_userdata for IMPU sip:bob@ims.mnc072.mcc432.3gppnetwork.org (Hash 295) DEBUG: ims_auth [authorize.c:1455]: get_auth_userdata(): Found auth_userdata DEBUG: ims_auth [authorize.c:1061]: get_auth_vector(): looping through AV status is 3 and were looking for 0 DEBUG: tm [t_lookup.c:1343]: t_newtran(): msg (0x7f8d3f410cb0) id=1/11 global id=1/11 T start=(nil) DEBUG: tm [t_lookup.c:498]: t_lookup_request(): start searching: hash=21555, isACK=0 DEBUG: tm [t_lookup.c:456]: matching_3261(): RFC3261 transaction matching failed - via branch [z9hG4bK3345.d6f2aff0d9192c2647aca3baea62cf94.1] DEBUG: tm [t_lookup.c:681]: t_lookup_request(): no transaction found DEBUG: tm [t_hooks.c:337]: run_reqin_callbacks_internal(): trans=0x7f8d2bff4520, callback type 1, id 0 entered DEBUG: ims_auth [authorize.c:457]: challenge(): Suspending SIP TM transaction DEBUG: ims_auth [authorize.c:1526]: multimedia_auth_request(): Sending MAR DEBUG: ims_auth [cxdx_mar.c:572]: cxdx_send_mar(): Successfully sent async diameter DEBUG: tm [t_lookup.c:1628]: t_lookup_ident_filter(): transaction found INFO: ims_auth [cxdx_avp.c:134]: cxdx_get_avp(): cxdx_get_experimental_result_code: Failed finding avp (avp_code = 297, vendor_id = 0) DEBUG: ims_auth [authorize.c:1557]: pack_challenge(): setting QOP str used is [, qop="auth"] DEBUG: ims_auth [authorize.c:1559]: pack_challenge(): QOP str used is [, qop="auth"] DEBUG: tm [t_reply.c:1660]: cleanup_uac_timers(): RETR/FR timers reset DEBUG: tm [t_reply.c:595]: _reply_light(): reply sent out. buf=0x7f8d3f4120b8: SIP/2.0 401 Unauthor..., shmem=0x7f8d2bff9288: SIP/2.0 401 Unauthor DEBUG: tm [t_reply.c:606]: _reply_light(): finished DEBUG: ims_auth [authorize.c:1446]: get_auth_userdata(): Searching auth_userdata for IMPU sip:bob@ims.mnc072.mcc432.3gppnetwork.org (Hash 295) DEBUG: ims_auth [authorize.c:1455]: get_auth_userdata(): Found auth_userdata DEBUG: ims_auth [authorize.c:1679]: add_auth_vector(): Adding auth_vector (status 1) for IMPU sip:bob@ims.mnc072.mcc432.3gppnetwork.org / IMPI bob@ims.mnc072.mcc432.3gppnetwork.org (Hash 295) DEBUG: ims_auth [cxdx_mar.c:483]: async_cdp_callback(): DBG:UAR Async CDP callback: ... Done resuming transaction INFO: ims_auth [cxdx_mar.c:76]: create_return_code(): created AVP successfully : [maa_return_code] - [1] DEBUG: ims_auth [cxdx_mar.c:495]: async_cdp_callback(): Destroying current transaction prevented! DEBUG: tm [t_lookup.c:1620]: t_lookup_ident_filter(): transaction in terminated phase - skipping ERROR: tm [t_suspend.c:196]: t_continue_helper(): active transaction not found DEBUG: ims_auth [cxdx_mar.c:84]: free_saved_transaction_data(): Freeing saved transaction data: async

```

#### SIP Traffic

``` (paste your sip traffic here) ```

### Possible Solutions

The issue is related to ims_auth module, in [cxdx_mar.c ](https://github.com/kamailio/kamailio/blob/master/src/modules/ims_auth/cxdx_m...). within async_cdp_callback function, if I replace: ``` tmb.t_continue(data->tindex, data->tlabel, data->act); ```` with the following: ``` tmb.t_continue_skip_timer(data->tindex, data->tlabel, data->act); ``` the issue will be fixed and the control will be passed to REG_MAR_REPLY route block. In fact, in ims_registrar_scscf module, in [cxdx_sar.c ](https://github.com/kamailio/kamailio/blob/master/src/modules/ims_registrar_s...) file, the t_continue_skip_timer is called instead of t_continue, if I replace it with t_continue the same issue happens for SAR callbacks.

### Additional Information

* **Kamailio Version** - output of `kamailio -v`

``` version: kamailio 6.1.0-dev0 (x86_64/linux) c858ce-dirty flags: USE_TCP, USE_TLS, USE_SCTP, TLS_HOOKS, USE_RAW_SOCKS, DISABLE_NAGLE, USE_MCAST, DNS_IP_HACK, SHM_MMAP, PKG_MALLOC, MEM_JOIN_FREE, Q_MALLOC, F_MALLOC, TLSF_MALLOC, DBG_SR_MEMORY, USE_FUTEX, FAST_LOCK-ADAPTIVE_WAIT, USE_DNS_CACHE, USE_DNS_FAILOVER, USE_NAPTR, USE_DST_BLOCKLIST, HAVE_RESOLV_RES, TLS_PTHREAD_MUTEX_SHARED ADAPTIVE_WAIT_LOOPS 1024, MAX_RECV_BUFFER_SIZE 262144, MAX_SEND_BUFFER_SIZE 262144, MAX_URI_SIZE 1024, BUF_SIZE 65535, DEFAULT PKG_SIZE 8MB poll method support: poll, epoll_lt, epoll_et, sigio_rt, select. id: c858ce -dirty compiled on 10:33:37 Apr 5 2025 with gcc 11.4.0 ```

* **Operating System**:

``` Distributor ID: Ubuntu Description: Ubuntu 22.04.5 LTS Release: 22.04 Codename: jammy

Linux kuber-worker 5.15.0-133-generic #144-Ubuntu SMP Fri Feb 7 20:47:38 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux ```