socket-util: Elaborate inet_parse_active comment.
The function inet_parse_active() is an external API and used
as one stop shopping for parsing ip address and L4 port
combinations from many other modules.  Hence, the function
header is extended to describe the special cases that it
handles.
@@ -483,7 +483,9 @@ exit:
/* Parses 'target', which should be a string in the format "<host>[:<port>]".
* <host>, which is required, may be an IPv4 address or an IPv6 address
* enclosed in square brackets. If 'default_port' is nonnegative then <port>
- * is optional and defaults to 'default_port'.
+ * is optional and defaults to 'default_port' (use 0 to make the kernel choose
+ * an available port, although this isn't usually appropriate for active
+ * connections). If 'default_port' is negative, then <port> is required.
*
* On success, returns true and stores the parsed remote address into '*ss'.
* On failure, logs an error, stores zeros into '*ss', and returns false. */
