[lwip-users] DNS look-up of name that is already RFC 1035 encoded

[Craig McQueen]

DHCP option 120 provides SIP server address(es), which may be an IP address or 
a DNS name. If it's a DNS name, then it is already encoded in the encoding used 
for DNS look-ups (RFC 1035). See RFC 3361 section 3.1.

What is the best way to look up such a name via lwIP? Shall I convert it from 
the RFC 1035 encoding to the normal dotted string notation, and not fret about 
the perceived inefficiency that lwIP will just convert it back to RFC 1035 
encoding? (it's converted in dns_send().) Alternatively, core/dns.c could be 
modified to provide an API function that takes a hostname in the RFC 1035 
encoding.

RFC 3361 section 3.1 says "RFC 1035 encoding was chosen to accommodate future 
internationalized domain name mechanisms." I'm not sure what that means, 
because I've not really looked into DNS internationalization and Punycode. So 
I'm not sure if lwIP supporting DNS look-ups in RFC 1035 encoding would somehow 
help support internationalized DNS names.

-- 
Craig McQueen