We do try using SIOCGIFWHADDR; but it's not being defined apparently
given the header files we're including.
If you could take a look at gen_uuid.c (attached) and tell me what I'm doing wrong for the Hurd.
AF_LINK is defined unconditionally in glibc, along with all other address/protocol families (libc/sysdeps/generic/bits/socket.h is used). If generic defines all possible address families, I conclude that defined AF_LINK doesn't mean that it's implemented.
So it's best if you have configure check whether struct sockaddr_dl is defined, instead of checking for AF_LINK. Perhaps AC_CHECK_TYPE?
Regards, ogi