diff mbox series

[mptcp-next,v3,1/2] selftests: mptcp: Add a tool to get specific msk_info

Message ID 3cd22d64f08ef8564e934a0de0331fc89fd6095b.1740115494.git.yangang@kylinos.cn (mailing list archive)
State Superseded, archived
Delegated to: Matthieu Baerts
Headers show
Series selftests: mptcp: add tests for increasing | expand

Checks

Context Check Description
matttbe/build success Build and static analysis OK
matttbe/checkpatch warning total: 0 errors, 1 warnings, 0 checks, 266 lines checked
matttbe/shellcheck success MPTCP selftests files have not been modified
matttbe/KVM_Validation__normal warning Unstable: 1 failed test(s): selftest_mptcp_connect
matttbe/KVM_Validation__debug success Success! ✅
matttbe/KVM_Validation__btf-normal__only_bpftest_all_ success Success! ✅
matttbe/KVM_Validation__btf-debug__only_bpftest_all_ warning Unstable: 1 failed test(s): bpftest_test_progs_mptcp

Commit Message

Gang Yan Feb. 21, 2025, 5:34 a.m. UTC 
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 <yangang@kylinos.cn>
---
 tools/testing/selftests/net/mptcp/Makefile    |   2 +-
 .../testing/selftests/net/mptcp/mptcp_diag.c  | 258 ++++++++++++++++++
 2 files changed, 259 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/net/mptcp/mptcp_diag.c

Comments

Matthieu Baerts Feb. 21, 2025, 11:55 a.m. UTC | #1 
Hi Gang Yan,

On 21/02/2025 06:34, Gang Yan wrote:
> 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 <yangang@kylinos.cn>

Please add a changelog here next time:

  ---
  Notes:
  - v4:
    - (...)

> ---
>  tools/testing/selftests/net/mptcp/Makefile    |   2 +-
>  .../testing/selftests/net/mptcp/mptcp_diag.c  | 258 ++++++++++++++++++
>  2 files changed, 259 insertions(+), 1 deletion(-)
>  create mode 100644 tools/testing/selftests/net/mptcp/mptcp_diag.c
> 
> diff --git a/tools/testing/selftests/net/mptcp/Makefile b/tools/testing/selftests/net/mptcp/Makefile
> index c76525fe2b84..340e1a777e16 100644
> --- a/tools/testing/selftests/net/mptcp/Makefile
> +++ b/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
>  
> diff --git a/tools/testing/selftests/net/mptcp/mptcp_diag.c b/tools/testing/selftests/net/mptcp/mptcp_diag.c
> new file mode 100644
> index 000000000000..aec3d99cb948
> --- /dev/null
> +++ b/tools/testing/selftests/net/mptcp/mptcp_diag.c
> @@ -0,0 +1,258 @@
> +// 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

I don't think you need this ifdef, because you didn't add:

  #include <linux/mptcp.h>

I think it is easier not to add it to easily deal with the different
kernel versions.

> +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;
A few items are missing, see

  https://www.mptcp.dev/mptcp-info.html#mptcp-socket-level

or:


https://github.com/multipath-tcp/mptcp_net-next/blob/export/include/uapi/linux/mptcp.h

Please add them here, and print them below.

> +};
> +
> +#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 void print_info_msg(struct mptcp_info *info)
> +{
> +	printf("Token & Flags\n");
> +	printf("token:	       %x\n", info->mptcpi_token);
> +	printf("flags:	       %x\n", info->mptcpi_flags);
> +	printf("csum_enabled:  %u\n", info->mptcpi_csum_enabled);
> +
> +	printf("\nBasic Info\n");
> +	printf("subflows:            %-5u subflows_max:          %u\n",
> +	       info->mptcpi_subflows,
> +	       info->mptcpi_subflows_max);
> +	printf("local_addr_used:     %-5u local_addr_max:        %u\n",
> +	       info->mptcpi_local_addr_used,
> +	       info->mptcpi_local_addr_max);
> +	printf("add_addr_signal:     %-5u add_addr_accepted:     %u\n",
> +	       info->mptcpi_add_addr_signal,
> +	       info->mptcpi_add_addr_accepted);
> +	printf("add_addr_signal_max: %-5u add_addr_accepted_max: %u\n",
> +	       info->mptcpi_add_addr_signal_max,
> +	       info->mptcpi_add_addr_accepted_max);

It is a good idea to take less space, but it makes the parsing slightly
more complex. Maybe easier to simply print one item per line?

> +
> +	printf("\nTransmission Info\n");
> +	printf("write_seq:	  %llx\n", info->mptcpi_write_seq);
> +	printf("snd_una:	  %llx\n", info->mptcpi_snd_una);
> +	printf("rcv_nxt:	  %llx\n", info->mptcpi_rcv_nxt);
> +	printf("retransmits:	  %u\n", info->mptcpi_retransmits);
> +	printf("retransmit bytes: %llu\n", info->mptcpi_bytes_retrans);
> +	printf("bytes_sent:	  %llu\n", info->mptcpi_bytes_sent);
> +	printf("bytes_received:   %llu\n", info->mptcpi_bytes_received);
> +	printf("bytes_acked:	  %llu\n", info->mptcpi_bytes_acked);
> +}
> +
> +static void 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]);

Mmh, I don't think that's safe to use that directly: the mptcp_info
structure has not been frozen in time, new items have been added along
versions. The selftests can be used with any kernel versions, which
means that the "struct mptcp_info" seen at build time by the userspace
might be bigger or smaller than the one used by the kernel being tested.

If it is smaller, it means there will be garbage at the end, and we
should not display that. In this case, it would be better to copy data
from tb[INET_DIAG_INFO] to a local structure. See how it is handled on
IPRoute2 side with ss with the different "info" structures:

https://git.kernel.org/pub/scm/network/iproute2/iproute2.git/tree/misc/ss.c#n3324

  if (tb[INET_DIAG_INFO]) {
      struct mptcp_info *info;
      int len = RTA_PAYLOAD(tb[INET_DIAG_INFO]);

      /* workaround for older kernels with less fields */
      if (len < sizeof(*info)) {
          info = alloca(sizeof(*info));
          memcpy(info, RTA_DATA(tb[INET_DIAG_INFO]), len);
          memset((char *)info + len, 0, sizeof(*info) - len);
      } else
          info = RTA_DATA(tb[INET_DIAG_INFO]);

      print_info_msg(info);
  }


> +		print_info_msg(info);
> +	}
> +}
> +
> +static void 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
> +	};
> +	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;
> +		}
> +		parse_nlmsg(nlh);
> +		nlh = NLMSG_NEXT(nlh, len);
> +	}
> +}
> +
> +static void 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);
> +	recv_nlmsg(fd, nlh);
> +
> +	close(fd);
> +}
> +
> +static void parse_opts(int argc, char **argv, __u32 *target_token)
> +{
> +	int c;
Please add:

  if (argc < 2)
      die_usage(1)

To make use at least '-t' is passed.

> +
> +	while ((c = getopt(argc, argv, "ht:")) != -1) {
> +		switch (c) {
> +		case 'h':
> +			die_usage(0);
> +			break;
> +		case 't':
> +			sscanf(optarg, "%x", target_token);
> +			break;
> +		default:
> +			die_usage(1);
> +			break;
> +		}
> +	}
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +	__u32 target_token;
> +
> +	parse_opts(argc, argv, &target_token);
> +	get_mptcpinfo(target_token);
> +
> +	return 0;
> +}
> +

Cheers,
Matt
diff mbox series

Patch

diff --git a/tools/testing/selftests/net/mptcp/Makefile b/tools/testing/selftests/net/mptcp/Makefile
index c76525fe2b84..340e1a777e16 100644
--- a/tools/testing/selftests/net/mptcp/Makefile
+++ b/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
 
diff --git a/tools/testing/selftests/net/mptcp/mptcp_diag.c b/tools/testing/selftests/net/mptcp/mptcp_diag.c
new file mode 100644
index 000000000000..aec3d99cb948
--- /dev/null
+++ b/tools/testing/selftests/net/mptcp/mptcp_diag.c
@@ -0,0 +1,258 @@ 
+// 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 void print_info_msg(struct mptcp_info *info)
+{
+	printf("Token & Flags\n");
+	printf("token:	       %x\n", info->mptcpi_token);
+	printf("flags:	       %x\n", info->mptcpi_flags);
+	printf("csum_enabled:  %u\n", info->mptcpi_csum_enabled);
+
+	printf("\nBasic Info\n");
+	printf("subflows:            %-5u subflows_max:          %u\n",
+	       info->mptcpi_subflows,
+	       info->mptcpi_subflows_max);
+	printf("local_addr_used:     %-5u local_addr_max:        %u\n",
+	       info->mptcpi_local_addr_used,
+	       info->mptcpi_local_addr_max);
+	printf("add_addr_signal:     %-5u add_addr_accepted:     %u\n",
+	       info->mptcpi_add_addr_signal,
+	       info->mptcpi_add_addr_accepted);
+	printf("add_addr_signal_max: %-5u add_addr_accepted_max: %u\n",
+	       info->mptcpi_add_addr_signal_max,
+	       info->mptcpi_add_addr_accepted_max);
+
+	printf("\nTransmission Info\n");
+	printf("write_seq:	  %llx\n", info->mptcpi_write_seq);
+	printf("snd_una:	  %llx\n", info->mptcpi_snd_una);
+	printf("rcv_nxt:	  %llx\n", info->mptcpi_rcv_nxt);
+	printf("retransmits:	  %u\n", info->mptcpi_retransmits);
+	printf("retransmit bytes: %llu\n", info->mptcpi_bytes_retrans);
+	printf("bytes_sent:	  %llu\n", info->mptcpi_bytes_sent);
+	printf("bytes_received:   %llu\n", info->mptcpi_bytes_received);
+	printf("bytes_acked:	  %llu\n", info->mptcpi_bytes_acked);
+}
+
+static void 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]);
+		print_info_msg(info);
+	}
+}
+
+static void 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
+	};
+	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;
+		}
+		parse_nlmsg(nlh);
+		nlh = NLMSG_NEXT(nlh, len);
+	}
+}
+
+static void 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);
+	recv_nlmsg(fd, nlh);
+
+	close(fd);
+}
+
+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(0);
+			break;
+		case 't':
+			sscanf(optarg, "%x", target_token);
+			break;
+		default:
+			die_usage(1);
+			break;
+		}
+	}
+}
+
+int main(int argc, char *argv[])
+{
+	__u32 target_token;
+
+	parse_opts(argc, argv, &target_token);
+	get_mptcpinfo(target_token);
+
+	return 0;
+}
+