Ethereal-users: Re: [Ethereal-users] Capturing IPv6 without IPv4 address assigned?
On Fri, Oct 27, 2000 at 10:47:04AM +0300, hannu.lammi@xxxxxxxxx wrote:
> is it possible to make Ethereal capture data on an interface which
> has only IPv6 address assigned?
Currently, no.
Tcpdump lets you do it, but warns you - and doesn't correctly handle
certain filtering options on IPv4 addresses (note that the lack of an
IPv4 address for the interface on which you're capturing doesn't *ipso
facto* mean there's no IPv4 traffic on your network).
Ethereal could either
1) let you do it and warn you *every time* with a message box,
which might get annoying;
2) let you do it and warn you the first time you do so on a
given interface within a given Ethereal session, which, it
turns out, is significantly harder to do than I'd thought
(given that, on an "Update list of packets in real time"
capture, the process that discovers that there's no IPv4
address isn't the process that would have to remember that in
order to remember it during an entire Ethereal session);
3) let you do it and not warn you.
2) isn't likely to happen any time in the near future, unless somebody
else comes up with a clever way of doing it and implements it, so your
choices are pretty much 1) and 3). Which of the two options in question
- 1) and 3) - do people prefer? (Preferences for 2) will be honored
only if accompanied by code to implement it correctly in such a fashion
that it works even with "Update list of packets in real time" captures.)
> In Linux (2.4.0-test9) the only interface listed in Capture Preferences
> is lo which has its 127.0.0.1 address in addition to IPv6 address.
That's probably an unrelated problem, as the code in Ethereal that
chooses whether to list an interface or not merely opens the interface
with "pcap_open_live()" - it does *not* attempt to get an IPv4 address
for the interface - so if an interface isn't listed you probably won't
even be able to capture on it if we *do* allow you to capture on
interfaces without IPv4 addresses.
