Re: [PATCH net-next 3/4] net/smc: Introduce smc_bpf_ops

Martin KaFai Lau
2024-10-25T18:30:25Z

On 10/25/24 4:05 AM, D. Wythe wrote:
> Our main concern is to avoid introducing kfuncs as much as possible. For our
> subsystem, we might need to maintain it in a way that maintains a uapi, as we
> certainly have user applications depending on it.

The smc_bpf_ops can read/write the tp and ireq. In patch 4, there is
'tp->syn_smc = 1'. I assume the real bpf prog will read something from the tp to
make the decision also. Note that tp/ireq is also not in the uapi but the CO-RE
can help in case the tp->syn_smc bool is moved around.

From looking at the selftest in patch 4 again, I think all it needs is for the
bpf prog (i.e. the ops) to return a bool instead of allowing the bpf prog to
write or call a kfunc to change the tp/ireq.