link-local IPv6 addresses are rejected

[Valery Ushakov]

getaddrinfo(3) refuses to resolve IPv6 addresses if hint flag AI_ADDRCONFIG is specified and when there are no IPv6 addresses other than link-local are configured. Unfortunately that happens even with AI_NUMERICHOST. This makes it impossible to use nc6 with IPv6 loopback or link-local addresses on such systems, e.g.

$ nc6 -n fe80::a00:27ff:fefd:3b2a%eth0 12345
nc6: forward host lookup failed for remote endpoint fe80::a00:27ff:fefd:3b2a%eth0: Address family for hostname not supported

The code to resolve addresses in network.c does

#ifdef HAVE_GETADDRINFO_AI_ADDRCONFIG
        hints.ai_flags |= AI_ADDRCONFIG;
#endif
        if (ca_is_flag_set(attrs, CA_NUMERIC_MODE))
                hints.ai_flags |= AI_NUMERICHOST;

this should be perhaps changed to the (untested):

        if (ca_is_flag_set(attrs, CA_NUMERIC_MODE))
                hints.ai_flags |= AI_NUMERICHOST;
#ifdef HAVE_GETADDRINFO_AI_ADDRCONFIG
        else
                hints.ai_flags |= AI_ADDRCONFIG;
#endif

so that AI_ADDRCONFIG is not specified when numeric host address is used.