Allow underscores in DNS names

[Per Kristian Hove]

[Giorgos Keramidas, 2003-03-31]

|  If everyone else supports underscores (I've only tested Solaris and
|  Linux 2.4.20), then perhaps, just for the sake of interoperability
|  with other systems, we should too.

Just some data points (my opinion on this matter is irrelevant):

In addition to Linux 2.4, Windows XP and Solaris 8 (as reported by
DES), all of the following OSes allow (and, in some cases, have been
allowing for quite a while:-) underscores:



# HP-UX 10
$ uname -a
HP-UX xxxxxxxx B.10.10 A 9000/712 unknown
$ ping under_score.ofug.org -n 1
PING under_score.ofug.org: 64 byte packets
64 bytes from 127.0.0.1: icmp_seq=0. time=0. ms

----under_score.ofug.org PING Statistics----
1 packets transmitted, 1 packets received, 0% packet loss
round-trip (ms)  min/avg/max = 0/0/0



# Digtal Unix/OSF1 4 (Tru64/OSF1 5.1 behaves differently: "Unknown host")
$ uname -a
OSF1 xxxxxxxx V4.0 1229 alpha alpha
$ ping -c 1 under_score.ofug.org
PING under_score.ofug.org (127.0.0.1): 56 data bytes
64 bytes from 127.0.0.1: icmp_seq=0 ttl=64 time=1 ms


----under_score.ofug.org PING Statistics----
1 packets transmitted, 1 packets received, 0% packet loss
round-trip (ms)  min/avg/max = 1/1/1 ms



# Ultrix 4.3
$ uname -a
ULTRIX xxxxxxxx 4.3 0 VAX unknown
$ /usr/etc/ping under_score.ofug.org
under_score.ofug.org is alive



# IRIX 5
$ uname -a
IRIX xxxxxxxx 5.3 02091401 IP22 mips
$ /usr/etc/ping -c 1 under_score.ofug.org
PING under_score.ofug.org (127.0.0.1): 56 data bytes
64 bytes from 127.0.0.1: icmp_seq=0 ttl=255 time=0 ms


----under_score.ofug.org PING Statistics----
1 packets transmitted, 1 packets received, 0% packet loss
round-trip min/avg/max = 0/0/0 ms



# Solaris 2.6/SPARC
$ uname -a
SunOS xxxxxxxx 5.6 Generic_105181-29 sun4u sparc
$ ping under_score.ofug.org
under_score.ofug.org is alive



This probably only goes to show that the sanity checks were absent in
these releases, not that it was a deliberate decision to allow
underscores.


-- 
Per Kristian Hove
Dept. of Mathematical Sciences
Norwegian University of Science and Technology