Re: [mptcp-next v2 5/7] selftests: mptcp: add a helper to get subflow_info

[Matthieu Baerts <matttbe@kernel.org>]

Hello,

On 16/04/2025 10:59, Gang Yan wrote:
> This patch adds 'get_subflow_info' in 'mptcp_diag', which can check whether
> a TCP connection is an MPTCP subflow based on the "INET_ULP_INFO_MPTCP"
> with tcp_diag method.
> 
> Co-developed-by: Geliang Tang <geliang@kernel.org>
> Signed-off-by: Geliang Tang <geliang@kernel.org>
> Signed-off-by: Gang Yan <yangang@kylinos.cn>
> ---
>  .../testing/selftests/net/mptcp/mptcp_diag.c  | 86 ++++++++++++++++++-
>  1 file changed, 84 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/net/mptcp/mptcp_diag.c b/tools/testing/selftests/net/mptcp/mptcp_diag.c
> index 2116b40bc927..28b1704d0c78 100644
> --- a/tools/testing/selftests/net/mptcp/mptcp_diag.c
> +++ b/tools/testing/selftests/net/mptcp/mptcp_diag.c
> @@ -8,6 +8,7 @@
>  #include <sys/socket.h>
>  #include <netinet/in.h>
>  #include <linux/tcp.h>
> +#include <arpa/inet.h>
>  
>  #include <unistd.h>
>  #include <stdlib.h>
> @@ -19,8 +20,13 @@
>  #define IPPROTO_MPTCP 262
>  #endif
>  
> +#define parse_rtattr_nested(tb, max, rta) \
> +	(parse_rtattr_flags((tb), (max), RTA_DATA(rta), RTA_PAYLOAD(rta), \
> +			    NLA_F_NESTED))
> +
>  struct params {
>  	__u32 target_token;
> +	char subflow_addr[1024];

detail: maybe add a 's': subflow_addrs.

>  };
>  
>  struct mptcp_info {

(...)

> @@ -244,6 +285,41 @@ static void get_mptcpinfo(__u32 token)
>  	close(fd);
>  }
>  
> +static void get_subflow_info(char *subflow_addr)
> +{
> +	struct inet_diag_req_v2 r = {
> +		.sdiag_family           = AF_INET,
> +		.sdiag_protocol         = IPPROTO_TCP,
> +	};
> +	int sport, dport;
> +	char saddr[64];	// Take ipv6 into consideration

Detail: the comments are usually with the "/* ... */" style. You can
also remove the comment and declare both [sd]addr on the same line I think.

> +	char daddr[64];
> +	int ret;
> +	int fd;
> +
> +	ret = sscanf(subflow_addr, "%s %d %s %d", saddr, &sport, daddr, &dport);
> +	if (ret != 4)
> +		die_perror("IP PORT Pairs has style problems!");
> +
> +	printf("%s:%d -> %s:%d\n", saddr, sport, daddr, dport);
> +
> +	fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_SOCK_DIAG);
> +	if (fd < 0)
> +		die_perror("Netlink socket");
> +
> +	r.id.idiag_cookie[0] = INET_DIAG_NOCOOKIE;
> +	r.id.idiag_cookie[1] = INET_DIAG_NOCOOKIE;

Can you not set it above, when declaring 'r'? Same for 'idiag_ext'.

> +	r.id.idiag_sport = htons(sport);
> +	r.id.idiag_dport = htons(dport);
> +	r.id.idiag_if = 0;

Do you need to explicitly set it to 0? Is it not 0 by default?

> +
> +	inet_pton(AF_INET, saddr, &r.id.idiag_src);
> +	inet_pton(AF_INET, daddr, &r.id.idiag_dst);
> +	r.idiag_ext |= (1 << (INET_DIAG_INFO - 1));
> +	send_query(fd, &r, IPPROTO_TCP);
> +	recv_nlmsg(fd, IPPROTO_TCP);
> +}
> +
>  static void parse_opts(int argc, char **argv, struct params *p)
>  {
>  	int c;

(...)

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.