somehow got lost between NetBSD and Linux. Output side mbuf-walking
code now correctly bytestuffs mbuf chains, as well as single mbufs
and clusters.
* Update radio error-parsing code to Stuart's latest stable code.
We now parse error messages the older code didn't.
* Note where radio-crash watchdogs should be added (the linux code
is there, #ifdef'ed out). This still just doesn't work.
The radio reset doesn't always work even when slattatch is first started,
but I have a radio with old firmware, which may be a contributing factor.
* Correct the checks for the tty output queue being overfull; estimate
the stuffed pkt size as (original * 65/64) + STRIP_HDRLEN + 2,
instead of SLIP's (2*SLMTU). Re-enable the disabled check now the
size estimate isn't excessively large.
* Fix BPF tapping of strip interfaces, STRIP packets are wrapped
in a SLIP bpf header. This implies no BPF support for arp or atalk,
even though Linux boxes are sending arp requests and gratuitous arps.
There may be no good fix short of adding explicit STRIP encapsulation
support to bpf/tcpdump.
* Still need a solid walkthrough, and rewrite to eliminate redundant
receive-side mbuf copying.
