Re: [PATCH bpf-next v2 1/2] net/smc: Introduce BPF injection capability for SMC

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Hi Martin,

Sorry to have been responding so late,  I've been working on the link_update you mentioned in last week, I have completed the support and testing of the related functions of it. and it is expected to be released in the
next few days.

As you mentioned, I do have much experience in kernel network development, so I plan to resend the PATCH in the form of RFC.
I really hope to receive your suggestions in next serials. Thank you.😉

Best wishes.
D. Wythe


On 3/25/23 7:27 AM, Martin KaFai Lau wrote:
On 3/23/23 9:08 PM, D. Wythe wrote:

The latest design is that users can register a negotiator implementation indexed by name, smc_sock can use bpf_setsockopt to specify whether a specific negotiation implementation is required via name. If there are no settings, there will be no negotiators.

What do you think?

tbh, bpf_setsockopt is many steps away. It needs to begin with a syscall setsockopt first. There is little reason it can only be done with a bpf prog. and how does the user know which negotiator a smc sock is using? Currently, ss can learn the tcp-cc of a sk.

~~~~~~~~

If this effort is serious, the code quality has to be much improved. The obvious bug and unused variables make this set at most a RFC.

From the bpf perspective, it is ok-ish to start with a global negotiator first and skip the setsockopt details for now. However, it needs to be have a name. The new link_update (https://lore.kernel.org/bpf/20230323032405.3735486-1-kuifeng@xxxxxxxx/) has to work also. The struct_ops is rcu reader safe, so leverage it whenever it can instead of the read/write lock. It is how struct_ops work for tcp, so try to stay consistent as much as possible in the networking stack.


In addition, I am very sorry that I have not issued my implementation for such a long time, and I have encountered some problems with the implementation because the SMC needs to be built as kernel module, I have struggled with the bpf_setsockopt implementation, and there are some new self-testes that need to be written.


Regarding compiling as module,

+ifneq ($(CONFIG_SMC),)
+ifeq ($(CONFIG_BPF_SYSCALL),y)
+obj-y                += smc/bpf_smc_struct_ops.o
+endif

struct_ops does not support module now. It is on the todo list. The bpf_smc_struct_ops.o above can only be used when CONFIG_SMC=y. Otherwise, the bpf_smc_struct_ops is always built in while most users will never load the smc module.




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