bin/108743: [who] IPv6 addresses truncated to maximum IPv4 address length

[Jonathan Liu]

>Number:         108743
>Category:       bin
>Synopsis:       [who] IPv6 addresses truncated to maximum IPv4 address length
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sun Feb 04 06:20:20 GMT 2007
>Closed-Date:
>Last-Modified:
>Originator:     Jonathan Liu
>Release:        6.2-RELEASE
>Organization:
>Environment:
FreeBSD freebsd 6.2-RELEASE FreeBSD 6.2-RELEASE #0: Fri Jan 12 10:40:27 UTC 2007     root at dessler.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  i386
>Description:
When a remote user logs into a FreeBSD machine using IPv6 with either ssh or telnet, typing the "who" command shows the remote user's IPv6 address truncated to the maximum IPv4 address length (16 characters).

This makes it very difficult to track down the user's IPv6 address if the address is longer than 16 characters in IPv6 shorthand form.

For example, the IPv6 address fd00:0:100::5:123 would be truncated to fd00:0:100::5:12.

Example output:
testuser           ttyp1     4 Feb 16:39 (fd00:0:100::5:12)
>How-To-Repeat:
On FreeBSD machine:
ifconfig lnc0 inet6 fd00:0:100::5:1
echo 'sshd_enable="YES"'>>/etc/rc.conf
/etc/rc.d/sshd start

On remote machine (FreeBSD):
ifconfig lnc0 inet6 fd00:0:100::5:123
ssh myusername at fd00:0:100::5:1

Then, back on FreeBSD machine:
who
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: