On 1/15/25 4:41 PM, Jason Xing wrote:
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index a0aff1b4eb61..87420c0f2235 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -7037,6 +7037,9 @@ enum {
* feature is on. It indicates the
* recorded timestamp.
*/
+ BPF_SOCK_OPS_TS_TCP_SND_CB, /* Called when every tcp_sendmsg
+ * syscall is triggered
+ */
UDP will need this also?
Yep.
Then the TCP naming will need to be adjusted.
While on UDP, how the UDP bpf callback will look like during sendmsg?
@@ -1067,10 +1068,15 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
int flags, err, copied = 0;
int mss_now = 0, size_goal, copied_syn = 0;
int process_backlog = 0;
+ u32 first_write_seq = 0;
int zc = 0;
long timeo;
flags = msg->msg_flags;
+ if (SK_BPF_CB_FLAG_TEST(sk, SK_BPF_CB_TX_TIMESTAMPING)) {
+ first_write_seq = tp->write_seq;
+ bpf_skops_tx_timestamping(sk, NULL, BPF_SOCK_OPS_TS_TCP_SND_CB);
My preference is to skip this bpf callout for now and depends on a bpf trace
program if it is really needed.
I have no idea if the bpf program wants to record the timestamp here
without the above three lines? Please enlighten me more. Thanks in
advance.
I guess there is one way which I don't know yet to monitor at the
beginning of tcp_sendmsg_locked().
The tracing bpf program (fentry in particular here). Give the one-liner bpftrace
script a try.
Take a look at trace_tcp_connect in test_sk_storage_tracing.c. It uses fentry
and also bpf_sk_storage_get.
If tcp_sendmsg_locked is inline-d, it can go up to the tcp_sendmsg(). It would
be nice to have a stable bpf callback if it is really useful but I suspect this
can be revisited later with the UDP support.
[ I will followup other replies later. ]
