ethernet: Remove FCS bit

[zlei]

Summary

The last consumer ng_atmllc has been removed in 105a4f7b3cb6 .

[zlei]

This is a breaking change. 3rd party drivers should take care of it.

[emaste]

This is a breaking change. 3rd party drivers should take care of it.

It's fairly straightforward for 3rd party drivers to chase this tough, I don't think it's a big concern.

[zlei]

In D42391#1030031, @emaste wrote:

This is a breaking change. 3rd party drivers should take care of it.

It's fairly straightforward for 3rd party drivers to chase this tough, I don't think it's a big concern.

I spent lots of time to check the 3rd party consumers ( mostly done by searching on github ) of M_HASFCS . There's only little consumers so I think it is time to commit this :)

[zlei]

While Linux does support tap traffic without good CRC (FCS) via tcpdump / bpf. I think that is most useful for developing drivers / hardwares or diagnosing noisy wireless environment, but I think that (enable capturing bad CRC via bpf) should be turned on per interface and still those packets with bad CRC should not enter net stack. So I'm convinced this is the right approach.

[adrian]

I'm sure I've seen FCSes in 802.11 bpf traces? Maybe that's happening at the 802.11 radiotap level?

[zlei]

In D42391#1031131, @adrian wrote:

I'm sure I've seen FCSes in 802.11 bpf traces? Maybe that's happening at the 802.11 radiotap level?

I'm not familiar with 802.11, But the manpage https://man.freebsd.org/cgi/man.cgi?query=ieee80211_radiotap says radiotap level would get FCS.

IEEE80211_RADIOTAP_F_FCS

Frame contents includes the FCS.

CC @bz , he is working on 802.11 .