### Description

In following configuration :

UA -> KAMALIO PROXY -> REGISTRAR

In case if REGISTRAR answer 404 on first REGISTER kamailio just ignore it and reply not passed to onreply_route. ie 404 just dropped and not passed to UA. In case if REGISTRAR answer 401 on first REGISTER kamailio works like it have to be.

Grepped example :

``` 77.77.77.77 - UA 88.88.88.88 - Kamailio 10.34.64.2 - registrar

U 2020/04/02 10:47:02.345372 77.77.77.77:5060 -> 88.88.88.88:7060 #26887 REGISTER sip:proxy.domain.com:7060 SIP/2.0. Via: SIP/2.0/UDP 10.32.0.9:5060;branch=z9hG4bK4153798595. From: "999100044" sip:999100044@proxy.domain.com:7060;tag=3123330837. To: "999100044" sip:999100044@proxy.domain.com:7060. Call-ID: 2_912627073@10.32.0.9. CSeq: 1 REGISTER. Contact: sip:999100044@10.32.0.9:5060. Allow: INVITE, INFO, PRACK, ACK, BYE, CANCEL, OPTIONS, NOTIFY, REGISTER, SUBSCRIBE, REFER, PUBLISH, UPDATE, MESSAGE. Max-Forwards: 70. User-Agent: Yealink SIP-T46G 28.81.188.7 001565b577b2. Expires: 3600. Allow-Events: talk,hold,conference,refer,check-sync. Content-Length: 0. ..

U 2020/04/02 10:47:04.289850 88.88.88.88:7060 -> 10.34.64.2:5060 #26888 REGISTER sip:proxy.domain.com:7060 SIP/2.0. Record-Route: sip:88.88.88.88:7060;lr. Via: SIP/2.0/UDP 88.88.88.88:7060;branch=z9hG4bK0636.d927d7e86ebc02302d9ad6ae7d778817.0. Via: SIP/2.0/UDP 10.32.0.9:5060;received=77.77.77.77;branch=z9hG4bK4153798595. From: "999100044" sip:999100044@proxy.domain.com:7060;tag=3123330837. To: "999100044" sip:999100044@proxy.domain.com:7060. Call-ID: 2_912627073@10.32.0.9. CSeq: 1 REGISTER. Contact: sip:999100044@10.32.0.9:5060. Allow: INVITE, INFO, PRACK, ACK, BYE, CANCEL, OPTIONS, NOTIFY, REGISTER, SUBSCRIBE, REFER, PUBLISH, UPDATE, MESSAGE. Max-Forwards: 69. User-Agent: Yealink SIP-T46G 28.81.188.7 001565b577b2. Expires: 3600. Allow-Events: talk,hold,conference,refer,check-sync. Content-Length: 0. Path: sip:88.88.88.88:7060;lr;received=sip:77.77.77.77:5060. Supported: path. ..

U 2020/04/02 10:47:04.290295 10.34.64.2:5060 -> 88.88.88.88:7060 #26889 SIP/2.0 404 Not Found. Via: SIP/2.0/UDP 88.88.88.88:7060;branch=z9hG4bK0636.d927d7e86ebc02302d9ad6ae7d778817.0. Via: SIP/2.0/UDP 10.32.0.9:5060;received=77.77.77.77;branch=z9hG4bK4153798595. From: "999100044" sip:999100044@proxy.domain.com:7060;tag=3123330837. To: "999100044" sip:999100044@proxy.domain.com:7060;tag=1598650872. Call-ID: 2_912627073@10.32.0.9. CSeq: 1 REGISTER. Content-Length: 0. Date: Thu, 02 Apr 2020 10:47:03 GMT. Warning: Not maintaining bindings for domain. .. ```

### Troubleshooting

After checking RFC 3261 i found that ``` 5. The registrar extracts the address-of-record from the To header field of the request. If the address-of-record is not valid for the domain in the Request-URI, the registrar MUST send a 404 (Not Found) response and skip the remaining steps. ```

#### Reproduction following schema : UA -> KAMALIO PROXY -> REGISTRAR

modules related to issue: in kamailio.cfg

loadmodule "tm.so" loadmodule "tmx.so" loadmodule "sl.so" loadmodule "rr.so" loadmodule "db_mysql" loadmodule "domain" loadmodule "outbound" loadmodule "path"

simple conception route config which illustrate issue : ``` request_route {

# per request initial checks route(REQINIT);

route(CATCH_CANCEL);

route(RR_PARSE);

route(REGISTRATION);

xlog("L_INFO", "Initial relay packet\n"); $du = "sip:10.34.64.2:5060";

route(FORWARD);

# update $du to set the destination address for proxying exit; }

route[CATCH_CANCEL] { if (is_method("CANCEL") == true) { if (t_check_trans() == true) { route(FORWARD); } sl_reply("500", "Internal Server Error"); drop; } }

route[RR_PARSE] { if(loose_route() == true ) { xlog("L_INFO", "RR-enforced\n"); append_hf("P-hint: rr-enforced\r\n"); route(FORWARD);

} else { xlog("L_INFO", "RR simple\n"); record_route(); } }

route[REGISTRATION] { if(is_method("REGISTER") == true) { add_path_received(); append_hf("Supported: path\r\n"); xlog("L_INFO", "GOT REGISTER\n"); } }

route[FORWARD] { if(t_relay() == false) { sl_reply_error(); }

drop; }

onreply_route { xlog("Reply SIP message from $si:$sp\n"); if (t_check_trans() == false) { drop; } } ```

#### Debugging Data

#### Log Messages

``` Apr 2 11:05:26 fsinnosbc /usr/sbin/kamailio[16037]: INFO: {1 1 REGISTER 2_1386563412@10.32.0.9} <script>: RR simple Apr 2 11:05:26 fsinnosbc /usr/sbin/kamailio[16037]: INFO: {1 1 REGISTER 2_1386563412@10.32.0.9} <script>: GOT REGISTER Apr 2 11:05:26 fsinnosbc /usr/sbin/kamailio[16037]: INFO: {1 1 REGISTER 2_1386563412@10.32.0.9} <script>: Initial relay packet ```

#### SIP Traffic

<!-- If the issue is exposed by processing specific SIP messages, grab them with ngrep or save in a pcap file, then add them next, or attach to issue, or provide a link to download them (e.g., to a pastebin site). -->

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

### Possible Solutions

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### Additional Information

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

``` version: kamailio 5.3.3 (x86_64/linux) flags: USE_TCP, USE_TLS, USE_SCTP, TLS_HOOKS, USE_RAW_SOCKS, DISABLE_NAGLE, USE_MCAST, DNS_IP_HACK, SHM_MMAP, PKG_MALLOC, 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_BLACKLIST, HAVE_RESOLV_RES, TLS_PTHREAD_MUTEX_SHARED ADAPTIVE_WAIT_LOOPS 1024, MAX_RECV_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: unknown compiled with gcc 8.3.0 ```

* **Operating System**:

<!-- Details about the operating system, the type: Linux (e.g.,: Debian 8.4, Ubuntu 16.04, CentOS 7.1, ...), MacOS, xBSD, Solaris, ...; Kernel details (output of `uname -a`) -->

``` root@fsinnosbc:~# lsb_release -a No LSB modules are available. Distributor ID: Debian Description: Debian GNU/Linux 10 (buster) Release: 10 Codename: buster root@fsinnosbc:~# ```