# Re: \[Patch net-next 02/13\] ipv4: introduce tracepoint trace\_ip\_queue\_xmit()

- From: Martin KaFai Lau \<hidden\>
- Date: 2021-08-11 23:08:37 
- List: netdev
- Page: https://ratatoskr.run/netdev/2021/08/7776457
- Thread: https://ratatoskr.run/netdev/2021/08/11208686/t.md

```text
On Wed, Aug 11, 2021 at 03:48:36PM -0700, Cong Wang wrote:
> On Wed, Aug 11, 2021 at 2:23 PM Martin KaFai Lau [ref] wrote:
> > Instead of adding tracepoints, the bpf fexit prog can be used here and
> > the bpf prog will have the sk, skb, and ret available (example in fexit_test.c).
> > Some tracepoints in this set can also be done with bpf fentry/fexit.
> > Does bpf fentry/fexit work for your use case?
> 
> Well, kprobe works too in this perspective. The problem with kprobe
> or fexit is that there is no guarantee the function still exists in kernel
> during iteration. Kernel is free to delete or rename it. With tracepoint,
> even if ip_queue_xmit() were renamed, the same tracepoint must
> remain in the kernel.
Some of the function names are hardly changed.  Considering it is
not always cost free based on another thread, this is not a strong
enough reason to add so many tracepoints while other options
are available.
```