[sr-dev] [kamailio/kamailio] dns_int_match_ip is broken (#2645)

[Nathan]

### Description

`dns_int_match_ip` is broken on 5.3.0 and above

### Troubleshooting

#### Reproduction

Try this dialplan:

```
if (dns_int_match_ip('dns.google', '8.8.8.8')) {
   xlog("L_INFO", "OK dns-ip match with dns_int_match_ip");
} else {
   xlog("L_ERR", "FAIL dns-ip match with dns_int_match_ip");
}

if (dns_int_match_ip('100.100.100.100', '8.8.8.8')) {
   xlog("L_ERR", "FAIL dns_int_match_ip on 2 ip's");
} else {
   xlog("L_INFO", "OK dns_int_match_ip on 2 ip's");
}
```

On 5.2 releases, both checks succeed. On 5.3 and up, both fail.

#### Debugging Data

I've traced down the problem to `str2ip`.

In 5.2, this is a `static inline` function defined in the header file `resolve.h`. Therefore, the returned `ip` structure is allocated *once per compilation unit* - ie. `ipops_mod.c` and `dns_cache.c` both have their own versions of the variable.

Since fb75e90549a (5.3 and up) this function is defined in it's own compilation unit (`resolve.c`) and therefore shared by all callers.

See: https://stackoverflow.com/questions/185624/static-variables-in-an-inlined-function

#### Log Messages

n/a

#### SIP Traffic

n/a

### Possible Solutions

- Have `ki_dns_sys_match_ip` make a local copy of the return value of `str2ip`
- Move `str2ip` back to a header file
- Refactor `str2ip` to take a pointer to an output struct

### Additional Information

In 5.3, this is what happens:

```
# - ki_dns_int_match_ip will call str2ip on 8.8.8.8, filling the static variable
# - resolvehost will call dns_a_get_he, which calls str2ip on dns.google.com, zeroing out the static variable
# - (dns_cache_do_request will call str2ip on dns.google.com, zeroing out the static variable again)
# - resolvehost queries DNS
# - the resolved IP's will be compared to the zero'd out struct
dns_int_match_ip('dns.google', '8.8.8.8') == false

# - ki_dns_int_match_ip will call str2ip on 8.8.8.8, filling the static variable
# - resolvehost will call dns_a_get_he, which calls str2ip on 100.100.100.100, overwriting the static variable
# - the static variable will be compared to itself
dns_int_match_ip('100.100.100.100', '8.8.8.8') == true
```


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