>This argues for adding a comment, perhaps
>
>  /* XXX Set at boot time based on available memory. */
>

Sure, which is why the second patch I posted has:

+int bpf_maxbufsize = (256 * 1024)      /* XXX should be set dynamically */


I use grep a lot, so I was trying to fit the comment on the same line
as the variable.  256K is where I crossed over the point of
diminishing returns on a 133MHz Pentium (Intel Endeavour motherboard).

After sleeping on it, it should really be 1Mbyte or so for modern
machines with gigabit ethernet.