Recent tty changes and snp

Poul-Henning Kamp phk at
Sat Jun 12 07:15:10 GMT 2004

In message <20040611194808.GA55868 at>, Dan Nelson writes:
>I think the snp device got left out of the recent struct tty changes; I
>get the following panic when running "watch -W /dev/sometty" and typing
>a character.  Read-only watching a tty also causes a panic when I start
>typing on the real tty.

This is not intentional breakage, but it may be unavoidable breakage :-(

Snoop(4) is great functionality and I would have killed to have it
several times along my career, unfortunately its implementation is
a POS.

I'm currently pondering using bpf(4) for the task instead, but the
uneven layering of the tty layer has not offered me a clearcut place
to stick the code yet.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

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