Re: [PATCH] selftests: mptcp: add comment for getaddrinfo

[Geliang Tang <geliang@kernel.org>]

Hi zhenwei,

On Mon, 2025-04-07 at 16:51 +0800, zhenwei pi wrote:
> mptcp_connect.c is a startup tutorial of MPTCP programming, however
> there is a lack of ai_protocol(IPPROTO_MPTCP) usage. Add comment for
> getaddrinfo MPTCP support.
> 
> Signed-off-by: zhenwei pi <zhenwei.pi@linux.dev>
> Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
> ---
>  tools/testing/selftests/net/mptcp/mptcp_connect.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect.c
> b/tools/testing/selftests/net/mptcp/mptcp_connect.c
> index c83a8b47bbdf..6b9031273964 100644
> --- a/tools/testing/selftests/net/mptcp/mptcp_connect.c
> +++ b/tools/testing/selftests/net/mptcp/mptcp_connect.c
> @@ -179,6 +179,18 @@ static void xgetnameinfo(const struct sockaddr
> *addr, socklen_t addrlen,
>  	}
>  }
>  
> +/* There is a lack of MPTCP support from glibc, these code leads
> error:
> + *	struct addrinfo hints = {
> + *		.ai_protocol = IPPROTO_MPTCP,
> + *		...
> + *	};
> + *	err = getaddrinfo(node, service, &hints, res);
> + *	...
> + * So using IPPROTO_TCP to resolve, and use TCP/MPTCP to create
> socket.
> + *
> + * glibc starts to support MPTCP since v2.42.
> + * Link:
> https://sourceware.org/git/?p=glibc.git;a=commit;h=a8e9022e0f82

Thanks for adding getaddrinfo mptcp support to glibc. I think we should
not only add a comment for getaddrinfo mptcp here, but also add an
example of using it in mptcp_connect.c. I will work with you to
implement this example in v2.

Thanks,
-Geliang

> + */
>  static void xgetaddrinfo(const char *node, const char *service,
>  			 const struct addrinfo *hints,
>  			 struct addrinfo **res)