On 04/13/2011 11:55 AM, Laine Stump wrote:
> The solution is to shorten the part of the original name used to
> generate the tap device name. However, simply truncating it is
> insufficient, because the last few characters of an interface name are
> often a number used to indicate one of a list of several similar
> devices (for example, "verylongname123", "verylongname124", etc) and
> simple truncation would lead to duplicate names. So instead we take
> the first 8 characters of $bridgename ("verylong" in the example), add
> on the final 3 bytes ("123"), then add "-nic" (so "verylong123-nic").
> Not pretty, but it is much more likely to generate a unique name, and
> is reproducible (unlike, say, a random number).
Should we also minimize the truncation by adding just "-n" instead of
"-nic", so that there are fewer user strings being butchered? Or would
that cause problems for existing users that already have bridge-nic and
would now also have bridge-n?
>
> - virAsprintf(&nicname, "%s-nic", brname);
> + if (strlen(brname) > (IFNAMSIZ - 5)) {
> + /* because the length of an ifname is limited to IFNAMSIZ-1
> + * (usually 15), and we're adding 4 more characters, we must
> + * truncate the original name to 11 to fit. In order to catch
> + * a possible numeric ending (eg virbr0, virbr1, etc), we grab
> + * the first 8 and last 3 characters of the string.
> + */
> + virAsprintf(&nicname, "%.*s%s-nic",
> + IFNAMSIZ - 8, /* space for last 3 chars + "-nic" + NULL */
> + brname, brname + strlen(brname) - 3);
> + } else {
> + virAsprintf(&nicname, "%s-nic", brname);
> + }
ACK.
--
Eric Blake eblake@xxxxxxxxxx +1-801-349-2682
Libvirt virtualization library http://libvirt.org
Attachment:
signature.asc
Description: OpenPGP digital signature
-- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list