On 07/06, Xin Liu wrote:
> Since commit 2585cd62f098 ("bpf: Only reply field should be writeable"),
> sockops is not allowd to modify the replylong field except replylong[0].
> The reason is that the replylong[1] to replylong[3] field is not used
> at that time.
>
> But in actual use, we can call `BPF_CGROUP_RUN_PROG_SOCK_OPS` in the
> kernel modules and expect sockops to return some useful data.
>
> The design comment about bpf_sock_ops::replylong in
> include/uapi/linux/bpf.h is described as follows:
>
> ```
> struct bpf_sock_ops {
> __u32 op;
> union {
> __u32 args[4]; /* Optionally passed to bpf program */
> __u32 reply; /* Returned by bpf program */
> __u32 replylong[4]; /* Optioznally returned by bpf prog */
> };
> ...
> ```
>
> It seems to contradict the purpose for which the field was originally
> designed. Let's remove this restriction.
>
> Fixes: 2585cd62f098 ("bpf: Only reply field should be writeable")
The commit you reference explicitly says that there is no reason to allow
replylong[1..3] because there is no use for them. Has something changed
since it was added? Any reason to expose those fields?
