+/* IPv6 address according to http://www.ietf.org/rfc/rfc2373.txt
+ * This supports embedded IPv4 addresses as well but does not strictly check
+ * for the right prefix (::0:<v4> or ::FFFF:<v4>) because there are too many
+ * ways to correctly represent the zero bytes. It's up to the user to check
+ * for valid addresses. */
+HEX16 ([0-9A-Fa-f]{1,4})
+V6_PART ({HEX16}:{HEX16}|{IPV4_ADDR})
+IPV6_BASE ({HEX16}:){6}{V6_PART}|::({HEX16}:){5}{V6_PART}|({HEX16})?::({HEX16}:){4}{V6_PART}|(({HEX16}:){0,1}{HEX16})?::({HEX16}:){3}{V6_PART}|(({HEX16}:){0,2}{HEX16})?::({HEX16}:){2}{V6_PART}|(({HEX16}:){0,3}{HEX16})?::{HEX16}:{V6_PART}|(({HEX16}:){0,4}{HEX16})?::{V6_PART}|(({HEX16}:){0,5}{HEX16})?::{HEX16}|(({HEX16}:){0,6}{HEX16})?::
+IPV6_ADDR ({IPV6_BASE})|(\[{IPV6_BASE}\](:{PORT})?)
+