On Thu, Aug 03, 2023 at 03:30:39PM +0800, Geliang Tang wrote:
> Add a hook named update_socket_protocol in __sys_socket(), for bpf
> progs to attach to and update socket protocol. One user case is to
> force legacy TCP apps to create and use MPTCP sockets instead of
> TCP ones.
>
> Define a mod_ret set named bpf_mptcp_fmodret_ids, add the hook
> update_socket_protocol into this set, and register it in
> bpf_mptcp_kfunc_init().
>
> Signed-off-by: Geliang Tang <geliang.tang@xxxxxxxx>
...
> diff --git a/net/socket.c b/net/socket.c
> index 2b0e54b2405c..586a437d7a5e 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -1644,11 +1644,36 @@ struct file *__sys_socket_file(int family, int type, int protocol)
> return sock_alloc_file(sock, flags, NULL);
> }
>
> +/**
Hi Geliang Tang,
nit: The format of the text below is not in kernel doc format,
so it is probably better if the comment begins with '/*'
rather than '/**'.
> + * A hook for bpf progs to attach to and update socket protocol.
> + *
> + * A static noinline declaration here could cause the compiler to
> + * optimize away the function. A global noinline declaration will
> + * keep the definition, but may optimize away the callsite.
> + * Therefore, __weak is needed to ensure that the call is still
> + * emitted, by telling the compiler that we don't know what the
> + * function might eventually be.
> + *
> + * __diag_* below are needed to dismiss the missing prototype warning.
> + */
...
