+ sz = asprintf(&buf, M_TEMP, "%s-%s-%s", uuid, if_name(ifp),
+ jailname);
+ if (sz < 0) {
+ /* Fall back to a random mac address. */
I was wondering if it would be valuable to give this fall back something
like:
printf("%s: unable to create fixed mac address; using random
mac address", if_name(ifp));
This will only be printed in rare circumstances. But in that case will
provide valuable information.
That would potentially be valuable, yes. On the other hand, we traditionally
don???t sprinkle a lot of printf()s around in the kernel. This is extremely
unlikely to happen, and if it does odds are attaching the interface will
fail at an earlier or later point, you may struggle to pass packets and run
into any number of other issues.
It???s also possible to diagnose absent the printf(), because the MAC
address will be locally administered rather than within the FreeBSD OUI.
So, in short: not a bad idea. You can argue it both ways, and I find myself
(weakly) on the opposite side.
Would displaying the message only when verbose boot mode is enabled be
a suitable compromise?
We could completely avoid the problems of dynamic allocation by calling
SHA1Update three times, feeding each piece of data separately.
For bonus points, use a single char[] to save stack space, too. Maybe
use a union, for legibility, and to ensure the proper size without ugly
assertions.
Eric
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