Slow responses to requests on 127.0.0.1 when DNSLink enabled

[gammazero]

When DNSLink is enabled in kubo (by default), queries to kubo on 127.0.0.1 take longer to respond to than the same queries to localhost.

The code in the gateway hostname handler, here, recognizes localhost in the Host header, but it does not recognize 127.0.0.1. This leads it all the way here after checking for DNSLink record.

The hostname handler code should recognize IP addresses (both IPv4 and IPv6) and avoid DNSLink lookup for these.

[gammazero]

completed