On 06/10/10 04:44, Jung-uk Kim wrote:
bpf(4) can only timestamp packets with microtime(9). I want to expand
it to be able to use different format and resolution. The patch is
here:
http://people.freebsd.org/~jkim/bpf_tstamp.diff
With this patch, we can select different format and resolution of the
timestamps. It is done via ioctl(2) with BIOCSTSTAMP command.
Similarly, you can get the current format and resolution with
BIOCGTSTAMP command. Currently, the following functions are
available:
BPF_T_MICROTIME microtime(9)
BPF_T_NANOTIME nanotime(9)
BPF_T_BINTIME bintime(9)
BPF_T_MICROTIME_FAST getmicrotime(9)
BPF_T_NANOTIME_FAST getnanotime(9)
BPF_T_BINTIME_FAST getbintime(9)
BPF_T_NONE ignore time stamps
This sounds great, assuming it is extensible such that it's easy to add
new methods in the future.
(Note: Additionally, there is an experimental machanism to tag packets
with timestamps in struct bintime format via mbuf_tags(9) from lower
layer, e.g., device driver. However, I didn't test it because I
wasn't sure whether this is the right thing to do.)
This is also an important feature for newer NICs, but I'm also not sure
if tags are the right way to do it. It certainly wouldn't be a bad way
to start though.
While I was here, I moved the bogus SIZEOF_BPF_HDR macro into bpf.c
and tried to make it little bit more correct. For example, the
32-bit shim should be able to handle alignment more properly for
non-Ethernet DLTs. I tried my best not to break ABI/API (especially
for 32-bit platforms) and relevant places are all marked with
BURN_BRIDGES.
What do you think? Is it worth committing?
I won't comment on the actual patch, but the ideas described above get
the thumbs up from me.
Cheers,
Lawrence
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