Allow write access to bpf in pcap_open()

[Joerg Sonnenberger]

On Sun, Oct 17, 2004 at 09:52:24PM +0200, Frank Denis wrote:
>   Hello.
>   
>   libpcap as shipped in DragonFly 1.1-current opens the descriptor with
> O_RDONLY.
> 
>   This is not consistent with most other operating systems. Linux doesn't
> use bpf but it's possible to inject packets through the descriptor. Same
> thing on Solaris. NetBSD and OpenBSD made local changes to pcap_open() a
> long time ago to allow this.

I don't exactly like this change until we also have the support for
priviledge separation in BPF. I put the later on my TODO list, but it
will take a while until it moves to top.

> 
>   It would be nice if the same change was introduced in DragonFly as well.
> It would unbreak things like ucarp.

What's ucarp?

Joerg