### Description

I tried to set the `alias` configuration option using an ID set by `#!substdef` but this leads to `grep_sock_info()` to fail, falling back to `corex_check_self()` and failing altogether finally.

### Troubleshooting

#### Reproduction

The basic setup given `BASE_HOST=example.org`:

``` #!substdef "/BASE_HOST/$env(BASE_HOST)/"

alias="BASE_HOST"

listen=tcp:0.0.0.0:80

route[AUTH] { # ... if (from_uri!=myself && uri!=myself) { sl_send_reply("403","Not relaying"); exit; }

return; } ```

With this, any properly authenticated `REGISTER` call leads to a `403 Not Relaying`.

However, this works perfectly fine if I use a static value instead:

``` alias=example.org ```

#### Log Messages

``` kamailio_1 | 12(17) DEBUG: <core> [core/socket_info.c:628]: grep_sock_info(): checking if host==us: 11==7 && [example.org] == [0.0.0.0] kamailio_1 | 12(17) DEBUG: <core> [core/socket_info.c:635]: grep_sock_info(): checking if port 80 (advertise 0) matches port 5060 kamailio_1 | 12(17) DEBUG: <core> [core/forward.c:412]: check_self(): host != me kamailio_1 | 12(17) DEBUG: corex [corex_lib.c:200]: corex_check_self(): check self for: 0:example.org:5060 kamailio_1 | 12(17) DEBUG: corex [corex_lib.c:227]: corex_check_self(): no match found kamailio_1 | 12(17) DEBUG: <core> [core/socket_info.c:628]: grep_sock_info(): checking if host==us: 11==7 && [example.org] == [0.0.0.0] kamailio_1 | 12(17) DEBUG: <core> [core/socket_info.c:635]: grep_sock_info(): checking if port 80 (advertise 0) matches port 5060 kamailio_1 | 12(17) DEBUG: <core> [core/forward.c:412]: check_self(): host != me kamailio_1 | 12(17) DEBUG: corex [corex_lib.c:200]: corex_check_self(): check self for: 0:example.org:5060 kamailio_1 | 12(17) DEBUG: corex [corex_lib.c:227]: corex_check_self(): no match found ```

Output with the static value:

``` kamailio_1 | 11(16) DEBUG: <core> [core/socket_info.c:628]: grep_sock_info(): checking if host==us: 11==7 && [example.org] == [0.0.0.0] kamailio_1 | 11(16) DEBUG: <core> [core/socket_info.c:635]: grep_sock_info(): checking if port 80 (advertise 0) matches port 5060 kamailio_1 | 11(16) DEBUG: <core> [core/socket_info.c:628]: grep_sock_info(): checking if host==us: 11==7 && [example.org] == [0.0.0.0] kamailio_1 | 11(16) DEBUG: <core> [core/socket_info.c:635]: grep_sock_info(): checking if port 80 (advertise 0) matches port 5060 ```

### Possible Solutions

Right now I need to work around this issue by including a separate `kamailio-aliases.cfg` file which must then be provided in each environment.

### 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 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 5.3.1

```

* **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`) -->

Using the Docker image `kamailio/kamailio:5.3.3-xenial`. Info from the Docker host:

``` # uname -a Linux ubuntu-s-1vcpu-1gb-fra1-01-sip 4.4.0-177-generic #207-Ubuntu SMP Mon Mar 16 01:16:10 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux # lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 16.04.6 LTS Release: 16.04 Codename: xenial ```