selftests: mptcp: Add a tool to get specific msk_info

This patch enables the retrieval of the mptcp_info structure corresponding
to a specified MPTCP socket (msk). When multiple MPTCP connections are
present, specific information can be obtained for a given connection
through the 'mptcp_diag_dump_one' by using the 'token' associated with
the msk.

Signed-off-by: Gang Yan <[email protected]>

Author: Dwyane-Yan

tools/testing/selftests/net/mptcp/Makefile

@@ -7,7 +7,7 @@ CFLAGS += -Wall -Wl,--no-as-needed -O2 -g -I$(top_srcdir)/usr/include $(KHDR_INC
 TEST_PROGS := mptcp_connect.sh pm_netlink.sh mptcp_join.sh diag.sh \
 	      simult_flows.sh mptcp_sockopt.sh userspace_pm.sh
 
-TEST_GEN_FILES = mptcp_connect pm_nl_ctl mptcp_sockopt mptcp_inq
+TEST_GEN_FILES = mptcp_connect pm_nl_ctl mptcp_sockopt mptcp_inq mptcp_diag
 
 TEST_FILES := mptcp_lib.sh settings
 

tools/testing/selftests/net/mptcp/mptcp_diag.c

@@ -0,0 +1,235 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025, Kylin Software*/
+
+#include <linux/sock_diag.h>
+#include <linux/rtnetlink.h>
+#include <linux/inet_diag.h>
+#include <linux/netlink.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <linux/tcp.h>
+
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <stdio.h>
+
+#ifndef IPPROTO_MPTCP
+#define IPPROTO_MPTCP 262
+#endif
+
+#ifndef MPTCP_INFO
+struct mptcp_info {
+	__u8    mptcpi_subflows;
+	__u8    mptcpi_add_addr_signal;
+	__u8    mptcpi_add_addr_accepted;
+	__u8    mptcpi_subflows_max;
+	__u8    mptcpi_add_addr_signal_max;
+	__u8    mptcpi_add_addr_accepted_max;
+	__u32   mptcpi_flags;
+	__u32   mptcpi_token;
+	__u64   mptcpi_write_seq;
+	__u64   mptcpi_snd_una;
+	__u64   mptcpi_rcv_nxt;
+	__u8    mptcpi_local_addr_used;
+	__u8    mptcpi_local_addr_max;
+	__u8    mptcpi_csum_enabled;
+	__u32   mptcpi_retransmits;
+	__u64   mptcpi_bytes_retrans;
+	__u64   mptcpi_bytes_sent;
+	__u64   mptcpi_bytes_received;
+	__u64   mptcpi_bytes_acked;
+};
+
+#define MPTCP_INFO              1
+#endif
+
+static void die_perror(const char *msg)
+{
+	perror(msg);
+	exit(1);
+}
+
+static void die_usage(int r)
+{
+	fprintf(stderr, "Usage: mptcp_diag -t\n");
+	exit(r);
+}
+
+static void send_query(int fd, __u32 token)
+{
+	struct sockaddr_nl nladdr = {
+		.nl_family = AF_NETLINK
+	};
+	struct {
+		struct nlmsghdr nlh;
+		struct inet_diag_req_v2 r;
+	} req = {
+		.nlh = {
+			.nlmsg_len = sizeof(req),
+			.nlmsg_type = SOCK_DIAG_BY_FAMILY,
+			.nlmsg_flags = NLM_F_REQUEST
+		},
+		.r = {
+			.sdiag_family = AF_INET,
+			.sdiag_protocol = IPPROTO_MPTCP,
+			.id.idiag_cookie[0] = token,
+		}
+	};
+	struct rtattr rta_proto;
+	struct iovec iov[6];
+	int iovlen = 1;
+	__u32 proto;
+
+	req.r.idiag_ext |= (1 << (INET_DIAG_INFO - 1));
+	proto = IPPROTO_MPTCP;
+	rta_proto.rta_type = INET_DIAG_REQ_PROTOCOL;
+	rta_proto.rta_len = RTA_LENGTH(sizeof(proto));
+
+	iov[0] = (struct iovec) {
+		.iov_base = &req,
+		.iov_len = sizeof(req)
+	};
+	iov[iovlen] = (struct iovec){ &rta_proto, sizeof(rta_proto)};
+	iov[iovlen + 1] = (struct iovec){ &proto, sizeof(proto)};
+	req.nlh.nlmsg_len += RTA_LENGTH(sizeof(proto));
+	iovlen += 2;
+	struct msghdr msg = {
+		.msg_name = &nladdr,
+		.msg_namelen = sizeof(nladdr),
+		.msg_iov = iov,
+		.msg_iovlen = iovlen
+	};
+
+	for (;;) {
+		if (sendmsg(fd, &msg, 0) < 0) {
+			if (errno == EINTR)
+				continue;
+			die_perror("sendmsg");
+		}
+		break;
+	}
+}
+
+static void parse_rtattr_flags(struct rtattr *tb[], int max, struct rtattr *rta,
+		       int len, unsigned short flags)
+{
+	unsigned short type;
+
+	memset(tb, 0, sizeof(struct rtattr *) * (max + 1));
+	while (RTA_OK(rta, len)) {
+		type = rta->rta_type & ~flags;
+		if ((type <= max) && (!tb[type]))
+			tb[type] = rta;
+		rta = RTA_NEXT(rta, len);
+	}
+}
+
+static struct mptcp_info *parse_nlmsg(struct nlmsghdr *nlh)
+{
+	struct inet_diag_msg *r = NLMSG_DATA(nlh);
+	struct rtattr *tb[INET_DIAG_MAX+1];
+	struct mptcp_info *info;
+
+	parse_rtattr_flags(tb, INET_DIAG_MAX, (struct rtattr *)(r+1),
+			   nlh->nlmsg_len - NLMSG_LENGTH(sizeof(*r)),
+			   NLA_F_NESTED);
+
+	if (tb[INET_DIAG_INFO]) {
+		info = RTA_DATA(tb[INET_DIAG_INFO]);
+		return info;
+	}
+
+	die_perror("Has no INET_DIAG_INFO");
+	return info;
+}
+
+static struct mptcp_info *recv_nlmsg(int fd, struct nlmsghdr *nlh)
+{
+	char rcv_buff[8192];
+	struct sockaddr_nl rcv_nladdr = {
+		.nl_family = AF_NETLINK
+	};
+	struct iovec rcv_iov = {
+		.iov_base = rcv_buff,
+		.iov_len = sizeof(rcv_buff)
+	};
+	struct msghdr rcv_msg = {
+		.msg_name = &rcv_nladdr,
+		.msg_namelen = sizeof(rcv_nladdr),
+		.msg_iov = &rcv_iov,
+		.msg_iovlen = 1
+	};
+	struct mptcp_info *info = NULL;
+	int len;
+
+	len = recvmsg(fd, &rcv_msg, 0);
+	nlh = (struct nlmsghdr *)rcv_buff;
+
+	while (NLMSG_OK(nlh, len)) {
+		if (nlh->nlmsg_type == NLMSG_DONE) {
+			printf("NLMSG_DONE\n");
+			break;
+		} else if (nlh->nlmsg_type == NLMSG_ERROR) {
+			struct nlmsgerr *err;
+
+			err = (struct nlmsgerr *)NLMSG_DATA(nlh);
+			printf("Error %d:%s\n", -(err->error), strerror(-(err->error)));
+			break;
+		}
+		info = parse_nlmsg(nlh);
+		nlh = NLMSG_NEXT(nlh, len);
+	}
+	close(fd);
+	return info;
+}
+
+static struct mptcp_info *get_mptcpinfo(__u32 token)
+{
+	struct nlmsghdr *nlh = NULL;
+	int fd;
+
+	fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_SOCK_DIAG);
+	if (fd < 0)
+		die_perror("Netlink socket");
+
+	send_query(fd, token);
+	return recv_nlmsg(fd, nlh);
+}
+
+static void parse_opts(int argc, char **argv, __u32 *target_token)
+{
+	int c;
+
+	while ((c = getopt(argc, argv, "ht:")) != -1) {
+		switch (c) {
+		case 'h':
+			die_usage(1);
+			break;
+		case 't':
+			sscanf(optarg, "%x", target_token);
+			break;
+		default:
+			die_usage(1);
+			break;
+		}
+	}
+}
+
+int main(int argc, char *argv[])
+{
+	struct mptcp_info *info = NULL;
+	__u32 target_token;
+
+	parse_opts(argc, argv, &target_token);
+	info = get_mptcpinfo(target_token);
+
+	if (info)
+		printf("token:%x\n", info->mptcpi_token);
+	else
+		perror("No Such msk using this token!\n");
+
+	return 0;
+}
+