Re: [PATCH net-next v2 04/12] net-timestamp: add static key to control the whole bpf extension

Jason Xing wrote:

From: Jason Xing <kernelxing@tencent.com>

Willem suggested that we use a static key to control. The advantage
is that we will not affect the existing applications at all if we
don't load BPF program.

In this patch, except the static key, I also add one logic that is
used to test if the socket has enabled its tsflags in order to
support bpf logic to allow both cases to happen at the same time.

These two features are unrelated, should probably be separate patches.

Or else, the skb carring related timestamp flag doesn't know which
way of printing is desirable.

One thing important is this patch allows print from both applications
and bpf program at the same time. Now we have three kinds of print:
1) only BPF program prints
2) only application program prints
3) both can print without side effect

Signed-off-by: Jason Xing <kernelxing@tencent.com>