Simon Burge <simonb@wasabisystems.com> writes:

> IPv6 appeared between 1.4 and 1.5.  Couldn't you add an autoconf
> test for the existance of, say, <netinet6/in6.h> ?

That's not a reliable test.

$ echo '#include <netinet6/in6.h>' | gcc -x c -E /dev/stdin > /dev/null 
In file included from /dev/stdin:1:
/usr/include/netinet6/in6.h:69: #error "do not include netinet6/in6.h directly, include netinet/in.h"

/Johan