Hi Pauli, On Sun, Mar 30, 2025 at 8:23 PM Pauli Virtanen <pav@xxxxxx> wrote: > > Add BPF_SOCK_OPS_TSTAMP_COMPLETION_CB and emit it on completion > timestamps. > > Enable that for Bluetooth. Thanks for working on this! It would be better if you can cc Martin in the next revision since he is one of co-authors of BPF timestamping. Using ./scripts/get_maintainer.pl will show you which group people you're supposed to cc. > > Tests: > https://lore.kernel.org/linux-bluetooth/a74e58b9cf12bc9c64a024d18e6e58999202f853.1743336056.git.pav@xxxxxx/ > > *** > > However, I don't quite see how to do the tskey management so > that BPF and socket timestamping do not interfere with each other. > > The tskey counter here increments only for sendmsg() that have > timestamping turned on. IIUC this works similarly as for UDP. I > understood the documentation so that stream sockets would do similarly, > but apparently TCP increments also for non-timestamped packets. TCP increments sequence number for every skb regardless of BPF timestamping feature. BPF timetamping uses the last byte of the last skb to generate the tskey in tcp_tx_timestamp(). So it means the tskey comes with the sequence number of each to-be-traced skb. It works for both socket and BPF timestamping features. > > If BPF needs tskey while socket timestamping is off, we can't increment > sk_tskey, as that interferes with counting by user applications doing > socket timestamps. That is the reason why in TCP we chose to implement the tskey of BPF timestamping in the socket timestamping area. Please take a look at tcp_tx_timestamp(). As for UDP implementation, it is a leftover that I will make work next month. > > Should the Bluetooth timestamping actually just increment the counters > for any packet, timestamped or not? It's supposed to be the same tskey shared with socket timestamping so that people don't need to separately take care of a new tskey management.That is to say, if the socket timestamping and BPF timestamping are turned on, sharing the same tskey will be consistent. Thanks, Jason > > Pauli Virtanen (3): > bpf: Add BPF_SOCK_OPS_TSTAMP_COMPLETION_CB callback > [RFC] bpf: allow non-TCP skbs for bpf_sock_ops_enable_tx_tstamp > [RFC] Bluetooth: enable bpf TX timestamping > > include/net/bluetooth/bluetooth.h | 1 + > include/uapi/linux/bpf.h | 5 +++++ > net/bluetooth/hci_conn.c | 21 +++++++++++++++++++-- > net/core/filter.c | 12 ++++++++++-- > net/core/skbuff.c | 3 +++ > 5 files changed, 38 insertions(+), 4 deletions(-) > > -- > 2.49.0 >
