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This patch introduces a new callback in tcp_tx_timestamp() to correlate tcp_sendmsg timestamp with timestamps from other tx timestamping callbacks (e.g., SND/SW/ACK). Without this patch, BPF program wouldn't know which timestamps belong to which flow because of no socket lock protection. This new callback is inserted in tcp_tx_timestamp() to address this issue because tcp_tx_timestamp() still owns the same socket lock with tcp_sendmsg_locked() in the meanwhile tcp_tx_timestamp() initializes the timestamping related fields for the skb, especially tskey. The tskey is the bridge to do the correlation. For TCP, BPF program hooks the beginning of tcp_sendmsg_locked() and then stores the sendmsg timestamp at the bpf_sk_storage, correlating this timestamp with its tskey that are later used in other sending timestamping callbacks. Signed-off-by: Jason Xing <kerneljasonxing@gmail.com> Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org> Reviewed-by: Willem de Bruijn <willemb@google.com> Link: https://patch.msgid.link/20250220072940.99994-11-kerneljasonxing@gmail.com
Linux kernel
============
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