Don't try to resolve all.dnsomatic.com if set as hostname

[RMerl]

Dnsomatic allows the use of the special "all.dnsomatic.com" hostname to instruct dnsomatic to update all supported hostname (in addition to the option of providing an empty hostname).

Reference: https://dnsomatic.com/wiki/faq (see "How do I update all my DNS-O-Matic services at once?")

I recommend implementing an exception (similar to what is being done for HE's tunnel) for that (non-resolvable) host to avoid generating an error message.

--- a/release/src/router/inadyn/src/cache.c
+++ b/release/src/router/inadyn/src/cache.c
@@ -85,7 +85,8 @@ static void read_one(ddns_alias_t *alias, int nonslookup)
        cache_file(alias->name, path, sizeof(path));
        fp = fopen(path, "r");
        if (!fp) {
-               if (nonslookup)
+               /* Exception for dnsomatic's special global hostname */
+               if (nonslookup || !strcmp(alias->address, "all.dnsomatic.com"))
                        return;
 
                /* Try a DNS lookup of our last known IP#. */

Not sure if this is the best way to implement this however, I haven't extensively studied the caching code.

[troglobit]

If the fix works, I'd very much appreciate a pull request! (A new release will be out very soon, so if you make a PR it will get merged :)

Sure the code can be made more generic, for other plugins to hook into, but no point to over-engineer it beforehand.

[RMerl]

I'll try to get a pull request done before the weekend (I first need to test the change myself in my own code base).

[RMerl]

The above patch doesn't work as-is, I still get "Failed resolving hostname all.dnsomatic.com" in the system log. I will need to do some digging to see if I missed another nslookup call somewhere else.

EDIT: my bad, I should be checking alias->name, not alias->address.