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SubjectRe: Bind to protocol with AF_PACKET doesn't work for outgoing packets

> Just to have an symmetric API. Everything else is too ugly to explain
> in manpages ;)

Explaining is easy. Blah-blah-blah... Sockets bound to ETH_P_ALL
are able to get copy of output packets which is useful f.e.
for packet sniffers (ref to [libpacp],[tcpdump]). In later kernels
this can be disabled with option PACKET_NOOUTPUT. When this option
is not supported user of packet socket bound to ETH_P_ALL has to filter
output packets at user level checking for pkt_type == PACKET_OUTPUT
or using an equivalent BPF applet.

> That would require changing/breaking PF_PACKET, no?

No. Ideally the option could be PACKET_GRAB_OUTPUT and be disabled
by default (for symmetry :-)). But as soon as it was forgotten,
it has to be enabled by default.

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