On 1/28/25 12:46 AM, Jason Xing wrote:
Introduce the callback to correlate tcp_sendmsg timestamp with other
points, like SND/SW/ACK. We can let bpf trace the beginning of
tcp_sendmsg_locked() and fetch the socket addr, so that in
Instead of "fetch the socket addr...", should be "store the sendmsg timestamp at
the bpf_sk_storage ...".
tcp_tx_timestamp() we can correlate the tskey with the socket addr.
It is accurate since they are under the protect of socket lock.
More details can be found in the selftest.
The selftest uses the bpf_sk_storage to store the sendmsg timestamp at
fentry/tcp_sendmsg_locked and retrieves it back at tcp_tx_timestamp (i.e.
BPF_SOCK_OPS_TS_SND_CB added in this patch).
Signed-off-by: Jason Xing <kerneljasonxing@xxxxxxxxx>
---
include/uapi/linux/bpf.h | 7 +++++++
net/ipv4/tcp.c | 1 +
tools/include/uapi/linux/bpf.h | 7 +++++++
3 files changed, 15 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 800122a8abe5..accb3b314fff 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -7052,6 +7052,13 @@ enum {
* when SK_BPF_CB_TX_TIMESTAMPING
* feature is on.
*/
+ BPF_SOCK_OPS_TS_SND_CB, /* Called when every sendmsg syscall
+ * is triggered. For TCP, it stays
+ * in the last send process to
+ * correlate with tcp_sendmsg timestamp
+ * with other timestamping callbacks,
+ * like SND/SW/ACK.
Do you have a chance to look at how this will work at UDP?
