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Allow the BPF to be select for EVFILT_WRITE with kqueue.
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Authored by harti on Sep 15 2021, 8:35 AM.
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Summary

Allow the BPF to be select for EVFILT_WRITE with kqueue. This is required for Boost asio to be able to use a BPF file descriptor even if it is used only for reading. Asio insists on installing a write filter.

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harti requested review of this revision.Sep 15 2021, 8:35 AM
sys/net/bpf.c
2193

I'd prefer a bit less code duplication:

struct filterops *ops;

...

switch (kn->kn_filter) {
case EVFILT_READ:
   ops = &bpfread_filtops;
   break;
case EVFILT_WRITE:
   ops = &bpwrite_filtops;
   break;
default:
   return (EINVAL);
}

...

Also it seems you need to modify kqueue(2).

Reduce code duplication.
Update kqueue.2.

This revision is now accepted and ready to land.Oct 1 2021, 8:03 AM