selftests: add PM netlink functional tests

This introduces basic self-tests for the PM netlink,
checking the basic APIs and possible exceptional
values.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 751 insertions, 3 deletions

diff --git a/tools/testing/selftests/net/mptcp/.gitignore b/tools/testing/selftests/net/mptcp/.gitignore
index d72f07642738..ea13b255a99d 100644
--- a/tools/testing/selftests/net/mptcp/.gitignore
+++ b/tools/testing/selftests/net/mptcp/.gitignore
@@ -1,2 +1,3 @@
 mptcp_connect
+pm_nl_ctl
 *.pcap
diff --git a/tools/testing/selftests/net/mptcp/Makefile b/tools/testing/selftests/net/mptcp/Makefile
index ba450e62dc5b..70c831fcaf70 100644
--- a/tools/testing/selftests/net/mptcp/Makefile
+++ b/tools/testing/selftests/net/mptcp/Makefile
@@ -1,12 +1,13 @@
 # SPDX-License-Identifier: GPL-2.0
 
 top_srcdir = ../../../../..
+KSFT_KHDR_INSTALL := 1
 
-CFLAGS =  -Wall -Wl,--no-as-needed -O2 -g
+CFLAGS =  -Wall -Wl,--no-as-needed -O2 -g  -I$(top_srcdir)/usr/include
 
-TEST_PROGS := mptcp_connect.sh
+TEST_PROGS := mptcp_connect.sh pm_netlink.sh
 
-TEST_GEN_FILES = mptcp_connect
+TEST_GEN_FILES = mptcp_connect pm_nl_ctl
 
 TEST_FILES := settings
 
diff --git a/tools/testing/selftests/net/mptcp/pm_netlink.sh b/tools/testing/selftests/net/mptcp/pm_netlink.sh
new file mode 100755
index 000000000000..8c7bd722476e
--- /dev/null
+++ b/tools/testing/selftests/net/mptcp/pm_netlink.sh
@@ -0,0 +1,130 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+ksft_skip=4
+ret=0
+
+usage() {
+	echo "Usage: $0 [ -h ]"
+}
+
+
+while getopts "$optstring" option;do
+	case "$option" in
+	"h")
+		usage $0
+		exit 0
+		;;
+	"?")
+		usage $0
+		exit 1
+		;;
+	esac
+done
+
+sec=$(date +%s)
+rndh=$(printf %x $sec)-$(mktemp -u XXXXXX)
+ns1="ns1-$rndh"
+err=$(mktemp)
+ret=0
+
+cleanup()
+{
+	rm -f $out
+	ip netns del $ns1
+}
+
+ip -Version > /dev/null 2>&1
+if [ $? -ne 0 ];then
+	echo "SKIP: Could not run test without ip tool"
+	exit $ksft_skip
+fi
+
+trap cleanup EXIT
+
+ip netns add $ns1 || exit $ksft_skip
+ip -net $ns1 link set lo up
+ip netns exec $ns1 sysctl -q net.mptcp.enabled=1
+
+check()
+{
+	local cmd="$1"
+	local expected="$2"
+	local msg="$3"
+	local out=`$cmd 2>$err`
+	local cmd_ret=$?
+
+	printf "%-50s %s" "$msg"
+	if [ $cmd_ret -ne 0 ]; then
+		echo "[FAIL] command execution '$cmd' stderr "
+		cat $err
+		ret=1
+	elif [ "$out" = "$expected" ]; then
+		echo "[ OK ]"
+	else
+		echo -n "[FAIL] "
+		echo "expected '$expected' got '$out'"
+		ret=1
+	fi
+}
+
+check "ip netns exec $ns1 ./pm_nl_ctl dump" "" "defaults addr list"
+check "ip netns exec $ns1 ./pm_nl_ctl limits" "accept 0
+subflows 0" "defaults limits"
+
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.1.1
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.1.2 flags subflow dev lo
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.1.3 flags signal,backup
+check "ip netns exec $ns1 ./pm_nl_ctl get 1" "id 1 flags  10.0.1.1 " "simple add/get addr"
+
+check "ip netns exec $ns1 ./pm_nl_ctl dump" \
+"id 1 flags  10.0.1.1
+id 2 flags subflow dev lo 10.0.1.2
+id 3 flags signal,backup 10.0.1.3 " "dump addrs"
+
+ip netns exec $ns1 ./pm_nl_ctl del 2
+check "ip netns exec $ns1 ./pm_nl_ctl get 2" "" "simple del addr"
+check "ip netns exec $ns1 ./pm_nl_ctl dump" \
+"id 1 flags  10.0.1.1
+id 3 flags signal,backup 10.0.1.3 " "dump addrs after del"
+
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.1.3
+check "ip netns exec $ns1 ./pm_nl_ctl get 4" "" "duplicate addr"
+
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.1.4 id 10 flags signal
+check "ip netns exec $ns1 ./pm_nl_ctl get 4" "id 4 flags signal 10.0.1.4 " "id addr increment"
+
+for i in `seq 5 9`; do
+	ip netns exec $ns1 ./pm_nl_ctl add 10.0.1.$i flags signal >/dev/null 2>&1
+done
+check "ip netns exec $ns1 ./pm_nl_ctl get 9" "id 9 flags signal 10.0.1.9 " "hard addr limit"
+check "ip netns exec $ns1 ./pm_nl_ctl get 10" "" "above hard addr limit"
+
+for i in `seq 9 256`; do
+	ip netns exec $ns1 ./pm_nl_ctl del $i
+	ip netns exec $ns1 ./pm_nl_ctl add 10.0.0.9
+done
+check "ip netns exec $ns1 ./pm_nl_ctl dump" "id 1 flags  10.0.1.1
+id 3 flags signal,backup 10.0.1.3
+id 4 flags signal 10.0.1.4
+id 5 flags signal 10.0.1.5
+id 6 flags signal 10.0.1.6
+id 7 flags signal 10.0.1.7
+id 8 flags signal 10.0.1.8 " "id limit"
+
+ip netns exec $ns1 ./pm_nl_ctl flush
+check "ip netns exec $ns1 ./pm_nl_ctl dump" "" "flush addrs"
+
+ip netns exec $ns1 ./pm_nl_ctl limits 9 1
+check "ip netns exec $ns1 ./pm_nl_ctl limits" "accept 0
+subflows 0" "rcv addrs above hard limit"
+
+ip netns exec $ns1 ./pm_nl_ctl limits 1 9
+check "ip netns exec $ns1 ./pm_nl_ctl limits" "accept 0
+subflows 0" "subflows above hard limit"
+
+ip netns exec $ns1 ./pm_nl_ctl limits 8 8
+check "ip netns exec $ns1 ./pm_nl_ctl limits" "accept 8
+subflows 8" "set limits"
+
+exit $ret
diff --git a/tools/testing/selftests/net/mptcp/pm_nl_ctl.c b/tools/testing/selftests/net/mptcp/pm_nl_ctl.c
new file mode 100644
index 000000000000..de9209305026
--- /dev/null
+++ b/tools/testing/selftests/net/mptcp/pm_nl_ctl.c
@@ -0,0 +1,616 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <errno.h>
+#include <error.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <sys/socket.h>
+#include <sys/types.h>
+
+#include <arpa/inet.h>
+#include <net/if.h>
+
+#include <linux/rtnetlink.h>
+#include <linux/genetlink.h>
+
+#include "linux/mptcp.h"
+
+#ifndef MPTCP_PM_NAME
+#define MPTCP_PM_NAME		"mptcp_pm"
+#endif
+
+static void syntax(char *argv[])
+{
+	fprintf(stderr, "%s add|get|del|flush|dump|accept [<args>]\n", argv[0]);
+	fprintf(stderr, "\tadd [flags signal|subflow|backup] [id <nr>] [dev <name>] <ip>\n");
+	fprintf(stderr, "\tdel <id>\n");
+	fprintf(stderr, "\tget <id>\n");
+	fprintf(stderr, "\tflush\n");
+	fprintf(stderr, "\tdump\n");
+	fprintf(stderr, "\tlimits [<rcv addr max> <subflow max>]\n");
+	exit(0);
+}
+
+static int init_genl_req(char *data, int family, int cmd, int version)
+{
+	struct nlmsghdr *nh = (void *)data;
+	struct genlmsghdr *gh;
+	int off = 0;
+
+	nh->nlmsg_type = family;
+	nh->nlmsg_flags = NLM_F_REQUEST;
+	nh->nlmsg_len = NLMSG_LENGTH(GENL_HDRLEN);
+	off += NLMSG_ALIGN(sizeof(*nh));
+
+	gh = (void *)(data + off);
+	gh->cmd = cmd;
+	gh->version = version;
+	off += NLMSG_ALIGN(sizeof(*gh));
+	return off;
+}
+
+static void nl_error(struct nlmsghdr *nh)
+{
+	struct nlmsgerr *err = (struct nlmsgerr *)NLMSG_DATA(nh);
+	int len = nh->nlmsg_len - sizeof(*nh);
+	uint32_t off;
+
+	if (len < sizeof(struct nlmsgerr))
+		error(1, 0, "netlink error message truncated %d min %ld", len,
+		      sizeof(struct nlmsgerr));
+
+	if (!err->error) {
+		/* check messages from kernel */
+		struct rtattr *attrs = (struct rtattr *)NLMSG_DATA(nh);
+
+		while (RTA_OK(attrs, len)) {
+			if (attrs->rta_type == NLMSGERR_ATTR_MSG)
+				fprintf(stderr, "netlink ext ack msg: %s\n",
+					(char *)RTA_DATA(attrs));
+			if (attrs->rta_type == NLMSGERR_ATTR_OFFS) {
+				memcpy(&off, RTA_DATA(attrs), 4);
+				fprintf(stderr, "netlink err off %d\n",
+					(int)off);
+			}
+			attrs = RTA_NEXT(attrs, len);
+		}
+	} else {
+		fprintf(stderr, "netlink error %d", err->error);
+	}
+}
+
+/* do a netlink command and, if max > 0, fetch the reply  */
+static int do_nl_req(int fd, struct nlmsghdr *nh, int len, int max)
+{
+	struct sockaddr_nl nladdr = { .nl_family = AF_NETLINK };
+	socklen_t addr_len;
+	void *data = nh;
+	int rem, ret;
+	int err = 0;
+
+	nh->nlmsg_len = len;
+	ret = sendto(fd, data, len, 0, (void *)&nladdr, sizeof(nladdr));
+	if (ret != len)
+		error(1, errno, "send netlink: %uB != %uB\n", ret, len);
+	if (max == 0)
+		return 0;
+
+	addr_len = sizeof(nladdr);
+	rem = ret = recvfrom(fd, data, max, 0, (void *)&nladdr, &addr_len);
+	if (ret < 0)
+		error(1, errno, "recv netlink: %uB\n", ret);
+
+	/* Beware: the NLMSG_NEXT macro updates the 'rem' argument */
+	for (; NLMSG_OK(nh, rem); nh = NLMSG_NEXT(nh, rem)) {
+		if (nh->nlmsg_type == NLMSG_ERROR) {
+			nl_error(nh);
+			err = 1;
+		}
+	}
+	if (err)
+		error(1, 0, "bailing out due to netlink error[s]");
+	return ret;
+}
+
+static int genl_parse_getfamily(struct nlmsghdr *nlh)
+{
+	struct genlmsghdr *ghdr = NLMSG_DATA(nlh);
+	int len = nlh->nlmsg_len;
+	struct rtattr *attrs;
+
+	if (nlh->nlmsg_type != GENL_ID_CTRL)
+		error(1, errno, "Not a controller message, len=%d type=0x%x\n",
+		      nlh->nlmsg_len, nlh->nlmsg_type);
+
+	len -= NLMSG_LENGTH(GENL_HDRLEN);
+
+	if (len < 0)
+		error(1, errno, "wrong controller message len %d\n", len);
+
+	if (ghdr->cmd != CTRL_CMD_NEWFAMILY)
+		error(1, errno, "Unknown controller command %d\n", ghdr->cmd);
+
+	attrs = (struct rtattr *) ((char *) ghdr + GENL_HDRLEN);
+	while (RTA_OK(attrs, len)) {
+		if (attrs->rta_type == CTRL_ATTR_FAMILY_ID)
+			return *(__u16 *)RTA_DATA(attrs);
+		attrs = RTA_NEXT(attrs, len);
+	}
+
+	error(1, errno, "can't find CTRL_ATTR_FAMILY_ID attr");
+	return -1;
+}
+
+static int resolve_mptcp_pm_netlink(int fd)
+{
+	char data[NLMSG_ALIGN(sizeof(struct nlmsghdr)) +
+		  NLMSG_ALIGN(sizeof(struct genlmsghdr)) +
+		  1024];
+	struct nlmsghdr *nh;
+	struct rtattr *rta;
+	int namelen;
+	int off = 0;
+
+	memset(data, 0, sizeof(data));
+	nh = (void *)data;
+	off = init_genl_req(data, GENL_ID_CTRL, CTRL_CMD_GETFAMILY, 0);
+
+	rta = (void *)(data + off);
+	namelen = strlen(MPTCP_PM_NAME) + 1;
+	rta->rta_type = CTRL_ATTR_FAMILY_NAME;
+	rta->rta_len = RTA_LENGTH(namelen);
+	memcpy(RTA_DATA(rta), MPTCP_PM_NAME, namelen);
+	off += NLMSG_ALIGN(rta->rta_len);
+
+	do_nl_req(fd, nh, off, sizeof(data));
+	return genl_parse_getfamily((void *)data);
+}
+
+int add_addr(int fd, int pm_family, int argc, char *argv[])
+{
+	char data[NLMSG_ALIGN(sizeof(struct nlmsghdr)) +
+		  NLMSG_ALIGN(sizeof(struct genlmsghdr)) +
+		  1024];
+	struct rtattr *rta, *nest;
+	struct nlmsghdr *nh;
+	u_int16_t family;
+	u_int32_t flags;
+	int nest_start;
+	u_int8_t id;
+	int off = 0;
+	int arg;
+
+	memset(data, 0, sizeof(data));
+	nh = (void *)data;
+	off = init_genl_req(data, pm_family, MPTCP_PM_CMD_ADD_ADDR,
+			    MPTCP_PM_VER);
+
+	if (argc < 3)
+		syntax(argv);
+
+	nest_start = off;
+	nest = (void *)(data + off);
+	nest->rta_type = NLA_F_NESTED | MPTCP_PM_ATTR_ADDR;
+	nest->rta_len = RTA_LENGTH(0);
+	off += NLMSG_ALIGN(nest->rta_len);
+
+	/* addr data */
+	rta = (void *)(data + off);
+	if (inet_pton(AF_INET, argv[2], RTA_DATA(rta))) {
+		family = AF_INET;
+		rta->rta_type = MPTCP_PM_ADDR_ATTR_ADDR4;
+		rta->rta_len = RTA_LENGTH(4);
+	} else if (inet_pton(AF_INET6, argv[2], RTA_DATA(rta))) {
+		family = AF_INET6;
+		rta->rta_type = MPTCP_PM_ADDR_ATTR_ADDR6;
+		rta->rta_len = RTA_LENGTH(16);
+	} else
+		error(1, errno, "can't parse ip %s", argv[2]);
+	off += NLMSG_ALIGN(rta->rta_len);
+
+	/* family */
+	rta = (void *)(data + off);
+	rta->rta_type = MPTCP_PM_ADDR_ATTR_FAMILY;
+	rta->rta_len = RTA_LENGTH(2);
+	memcpy(RTA_DATA(rta), &family, 2);
+	off += NLMSG_ALIGN(rta->rta_len);
+
+	for (arg = 3; arg < argc; arg++) {
+		if (!strcmp(argv[arg], "flags")) {
+			char *tok, *str;
+
+			/* flags */
+			flags = 0;
+			if (++arg >= argc)
+				error(1, 0, " missing flags value");
+
+			/* do not support flag list yet */
+			for (str = argv[arg]; (tok = strtok(str, ","));
+			     str = NULL) {
+				if (!strcmp(tok, "subflow"))
+					flags |= MPTCP_PM_ADDR_FLAG_SUBFLOW;
+				else if (!strcmp(tok, "signal"))
+					flags |= MPTCP_PM_ADDR_FLAG_SIGNAL;
+				else if (!strcmp(tok, "backup"))
+					flags |= MPTCP_PM_ADDR_FLAG_BACKUP;
+				else
+					error(1, errno,
+					      "unknown flag %s", argv[arg]);
+			}
+
+			rta = (void *)(data + off);
+			rta->rta_type = MPTCP_PM_ADDR_ATTR_FLAGS;
+			rta->rta_len = RTA_LENGTH(4);
+			memcpy(RTA_DATA(rta), &flags, 4);
+			off += NLMSG_ALIGN(rta->rta_len);
+		} else if (!strcmp(argv[arg], "id")) {
+			if (++arg >= argc)
+				error(1, 0, " missing id value");
+
+			id = atoi(argv[arg]);
+			rta = (void *)(data + off);
+			rta->rta_type = MPTCP_PM_ADDR_ATTR_ID;
+			rta->rta_len = RTA_LENGTH(1);
+			memcpy(RTA_DATA(rta), &id, 1);
+			off += NLMSG_ALIGN(rta->rta_len);
+		} else if (!strcmp(argv[arg], "dev")) {
+			int32_t ifindex;
+
+			if (++arg >= argc)
+				error(1, 0, " missing dev name");
+
+			ifindex = if_nametoindex(argv[arg]);
+			if (!ifindex)
+				error(1, errno, "unknown device %s", argv[arg]);
+
+			rta = (void *)(data + off);
+			rta->rta_type = MPTCP_PM_ADDR_ATTR_IF_IDX;
+			rta->rta_len = RTA_LENGTH(4);
+			memcpy(RTA_DATA(rta), &ifindex, 4);
+			off += NLMSG_ALIGN(rta->rta_len);
+		} else
+			error(1, 0, "unknown keyword %s", argv[arg]);
+	}
+	nest->rta_len = off - nest_start;
+
+	do_nl_req(fd, nh, off, 0);
+	return 0;
+}
+
+int del_addr(int fd, int pm_family, int argc, char *argv[])
+{
+	char data[NLMSG_ALIGN(sizeof(struct nlmsghdr)) +
+		  NLMSG_ALIGN(sizeof(struct genlmsghdr)) +
+		  1024];
+	struct rtattr *rta, *nest;
+	struct nlmsghdr *nh;
+	int nest_start;
+	u_int8_t id;
+	int off = 0;
+
+	memset(data, 0, sizeof(data));
+	nh = (void *)data;
+	off = init_genl_req(data, pm_family, MPTCP_PM_CMD_DEL_ADDR,
+			    MPTCP_PM_VER);
+
+	/* the only argument is the address id */
+	if (argc != 3)
+		syntax(argv);
+
+	id = atoi(argv[2]);
+
+	nest_start = off;
+	nest = (void *)(data + off);
+	nest->rta_type = NLA_F_NESTED | MPTCP_PM_ATTR_ADDR;
+	nest->rta_len =  RTA_LENGTH(0);
+	off += NLMSG_ALIGN(nest->rta_len);
+
+	/* build a dummy addr with only the ID set */
+	rta = (void *)(data + off);
+	rta->rta_type = MPTCP_PM_ADDR_ATTR_ID;
+	rta->rta_len = RTA_LENGTH(1);
+	memcpy(RTA_DATA(rta), &id, 1);
+	off += NLMSG_ALIGN(rta->rta_len);
+	nest->rta_len = off - nest_start;
+
+	do_nl_req(fd, nh, off, 0);
+	return 0;
+}
+
+static void print_addr(struct rtattr *attrs, int len)
+{
+	uint16_t family = 0;
+	char str[1024];
+	uint32_t flags;
+	uint8_t id;
+
+	while (RTA_OK(attrs, len)) {
+		if (attrs->rta_type == MPTCP_PM_ADDR_ATTR_FAMILY)
+			memcpy(&family, RTA_DATA(attrs), 2);
+		if (attrs->rta_type == MPTCP_PM_ADDR_ATTR_ADDR4) {
+			if (family != AF_INET)
+				error(1, errno, "wrong IP (v4) for family %d",
+				      family);
+			inet_ntop(AF_INET, RTA_DATA(attrs), str, sizeof(str));
+			printf("%s ", str);
+		}
+		if (attrs->rta_type == MPTCP_PM_ADDR_ATTR_ADDR6) {
+			if (family != AF_INET6)
+				error(1, errno, "wrong IP (v6) for family %d",
+				      family);
+			inet_ntop(AF_INET6, RTA_DATA(attrs), str, sizeof(str));
+			printf("%s ", str);
+		}
+		if (attrs->rta_type == MPTCP_PM_ADDR_ATTR_ID) {
+			memcpy(&id, RTA_DATA(attrs), 1);
+			printf("id %d ", id);
+		}
+		if (attrs->rta_type == MPTCP_PM_ADDR_ATTR_FLAGS) {
+			memcpy(&flags, RTA_DATA(attrs), 4);
+
+			printf("flags ");
+			if (flags & MPTCP_PM_ADDR_FLAG_SIGNAL) {
+				printf("signal");
+				flags &= ~MPTCP_PM_ADDR_FLAG_SIGNAL;
+				if (flags)
+					printf(",");
+			}
+
+			if (flags & MPTCP_PM_ADDR_FLAG_SUBFLOW) {
+				printf("subflow");
+				flags &= ~MPTCP_PM_ADDR_FLAG_SUBFLOW;
+				if (flags)
+					printf(",");
+			}
+
+			if (flags & MPTCP_PM_ADDR_FLAG_BACKUP) {
+				printf("backup");
+				flags &= ~MPTCP_PM_ADDR_FLAG_BACKUP;
+				if (flags)
+					printf(",");
+			}
+
+			/* bump unknown flags, if any */
+			if (flags)
+				printf("0x%x", flags);
+			printf(" ");
+		}
+		if (attrs->rta_type == MPTCP_PM_ADDR_ATTR_IF_IDX) {
+			char name[IF_NAMESIZE], *ret;
+			int32_t ifindex;
+
+			memcpy(&ifindex, RTA_DATA(attrs), 4);
+			ret = if_indextoname(ifindex, name);
+			if (ret)
+				printf("dev %s ", ret);
+			else
+				printf("dev unknown/%d", ifindex);
+		}
+
+		attrs = RTA_NEXT(attrs, len);
+	}
+	printf("\n");
+}
+
+static void print_addrs(struct nlmsghdr *nh, int pm_family, int total_len)
+{
+	struct rtattr *attrs;
+
+	for (; NLMSG_OK(nh, total_len); nh = NLMSG_NEXT(nh, total_len)) {
+		int len = nh->nlmsg_len;
+
+		if (nh->nlmsg_type == NLMSG_DONE)
+			break;
+		if (nh->nlmsg_type == NLMSG_ERROR)
+			nl_error(nh);
+		if (nh->nlmsg_type != pm_family)
+			continue;
+
+		len -= NLMSG_LENGTH(GENL_HDRLEN);
+		attrs = (struct rtattr *) ((char *) NLMSG_DATA(nh) +
+					   GENL_HDRLEN);
+		while (RTA_OK(attrs, len)) {
+			if (attrs->rta_type ==
+			    (MPTCP_PM_ATTR_ADDR | NLA_F_NESTED))
+				print_addr((void *)RTA_DATA(attrs),
+					   attrs->rta_len);
+			attrs = RTA_NEXT(attrs, len);
+		}
+	}
+}
+
+int get_addr(int fd, int pm_family, int argc, char *argv[])
+{
+	char data[NLMSG_ALIGN(sizeof(struct nlmsghdr)) +
+		  NLMSG_ALIGN(sizeof(struct genlmsghdr)) +
+		  1024];
+	struct rtattr *rta, *nest;
+	struct nlmsghdr *nh;
+	int nest_start;
+	u_int8_t id;
+	int off = 0;
+
+	memset(data, 0, sizeof(data));
+	nh = (void *)data;
+	off = init_genl_req(data, pm_family, MPTCP_PM_CMD_GET_ADDR,
+			    MPTCP_PM_VER);
+
+	/* the only argument is the address id */
+	if (argc != 3)
+		syntax(argv);
+
+	id = atoi(argv[2]);
+
+	nest_start = off;
+	nest = (void *)(data + off);
+	nest->rta_type = NLA_F_NESTED | MPTCP_PM_ATTR_ADDR;
+	nest->rta_len =  RTA_LENGTH(0);
+	off += NLMSG_ALIGN(nest->rta_len);
+
+	/* build a dummy addr with only the ID set */
+	rta = (void *)(data + off);
+	rta->rta_type = MPTCP_PM_ADDR_ATTR_ID;
+	rta->rta_len = RTA_LENGTH(1);
+	memcpy(RTA_DATA(rta), &id, 1);
+	off += NLMSG_ALIGN(rta->rta_len);
+	nest->rta_len = off - nest_start;
+
+	print_addrs(nh, pm_family, do_nl_req(fd, nh, off, sizeof(data)));
+	return 0;
+}
+
+int dump_addrs(int fd, int pm_family, int argc, char *argv[])
+{
+	char data[NLMSG_ALIGN(sizeof(struct nlmsghdr)) +
+		  NLMSG_ALIGN(sizeof(struct genlmsghdr)) +
+		  1024];
+	pid_t pid = getpid();
+	struct nlmsghdr *nh;
+	int off = 0;
+
+	memset(data, 0, sizeof(data));
+	nh = (void *)data;
+	off = init_genl_req(data, pm_family, MPTCP_PM_CMD_GET_ADDR,
+			    MPTCP_PM_VER);
+	nh->nlmsg_flags |= NLM_F_DUMP;
+	nh->nlmsg_seq = 1;
+	nh->nlmsg_pid = pid;
+	nh->nlmsg_len = off;
+
+	print_addrs(nh, pm_family, do_nl_req(fd, nh, off, sizeof(data)));
+	return 0;
+}
+
+int flush_addrs(int fd, int pm_family, int argc, char *argv[])
+{
+	char data[NLMSG_ALIGN(sizeof(struct nlmsghdr)) +
+		  NLMSG_ALIGN(sizeof(struct genlmsghdr)) +
+		  1024];
+	struct nlmsghdr *nh;
+	int off = 0;
+
+	memset(data, 0, sizeof(data));
+	nh = (void *)data;
+	off = init_genl_req(data, pm_family, MPTCP_PM_CMD_FLUSH_ADDRS,
+			    MPTCP_PM_VER);
+
+	do_nl_req(fd, nh, off, 0);
+	return 0;
+}
+
+static void print_limits(struct nlmsghdr *nh, int pm_family, int total_len)
+{
+	struct rtattr *attrs;
+	uint32_t max;
+
+	for (; NLMSG_OK(nh, total_len); nh = NLMSG_NEXT(nh, total_len)) {
+		int len = nh->nlmsg_len;
+
+		if (nh->nlmsg_type == NLMSG_DONE)
+			break;
+		if (nh->nlmsg_type == NLMSG_ERROR)
+			nl_error(nh);
+		if (nh->nlmsg_type != pm_family)
+			continue;
+
+		len -= NLMSG_LENGTH(GENL_HDRLEN);
+		attrs = (struct rtattr *) ((char *) NLMSG_DATA(nh) +
+					   GENL_HDRLEN);
+		while (RTA_OK(attrs, len)) {
+			int type = attrs->rta_type;
+
+			if (type != MPTCP_PM_ATTR_RCV_ADD_ADDRS &&
+			    type != MPTCP_PM_ATTR_SUBFLOWS)
+				goto next;
+
+			memcpy(&max, RTA_DATA(attrs), 4);
+			printf("%s %u\n", type == MPTCP_PM_ATTR_SUBFLOWS ?
+					  "subflows" : "accept", max);
+
+next:
+			attrs = RTA_NEXT(attrs, len);
+		}
+	}
+}
+
+int get_set_limits(int fd, int pm_family, int argc, char *argv[])
+{
+	char data[NLMSG_ALIGN(sizeof(struct nlmsghdr)) +
+		  NLMSG_ALIGN(sizeof(struct genlmsghdr)) +
+		  1024];
+	uint32_t rcv_addr = 0, subflows = 0;
+	int cmd, len = sizeof(data);
+	struct nlmsghdr *nh;
+	int off = 0;
+
+	/* limit */
+	if (argc == 4) {
+		rcv_addr = atoi(argv[2]);
+		subflows = atoi(argv[3]);
+		cmd = MPTCP_PM_CMD_SET_LIMITS;
+	} else {
+		cmd = MPTCP_PM_CMD_GET_LIMITS;
+	}
+
+	memset(data, 0, sizeof(data));
+	nh = (void *)data;
+	off = init_genl_req(data, pm_family, cmd, MPTCP_PM_VER);
+
+	/* limit */
+	if (cmd == MPTCP_PM_CMD_SET_LIMITS) {
+		struct rtattr *rta = (void *)(data + off);
+
+		rta->rta_type = MPTCP_PM_ATTR_RCV_ADD_ADDRS;
+		rta->rta_len = RTA_LENGTH(4);
+		memcpy(RTA_DATA(rta), &rcv_addr, 4);
+		off += NLMSG_ALIGN(rta->rta_len);
+
+		rta = (void *)(data + off);
+		rta->rta_type = MPTCP_PM_ATTR_SUBFLOWS;
+		rta->rta_len = RTA_LENGTH(4);
+		memcpy(RTA_DATA(rta), &subflows, 4);
+		off += NLMSG_ALIGN(rta->rta_len);
+
+		/* do not expect a reply */
+		len = 0;
+	}
+
+	len = do_nl_req(fd, nh, off, len);
+	if (cmd == MPTCP_PM_CMD_GET_LIMITS)
+		print_limits(nh, pm_family, len);
+	return 0;
+}
+
+int main(int argc, char *argv[])
+{
+	int fd, pm_family;
+
+	if (argc < 2)
+		syntax(argv);
+
+	fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_GENERIC);
+	if (fd == -1)
+		error(1, errno, "socket netlink");
+
+	pm_family = resolve_mptcp_pm_netlink(fd);
+
+	if (!strcmp(argv[1], "add"))
+		return add_addr(fd, pm_family, argc, argv);
+	else if (!strcmp(argv[1], "del"))
+		return del_addr(fd, pm_family, argc, argv);
+	else if (!strcmp(argv[1], "flush"))
+		return flush_addrs(fd, pm_family, argc, argv);
+	else if (!strcmp(argv[1], "get"))
+		return get_addr(fd, pm_family, argc, argv);
+	else if (!strcmp(argv[1], "dump"))
+		return dump_addrs(fd, pm_family, argc, argv);
+	else if (!strcmp(argv[1], "limits"))
+		return get_set_limits(fd, pm_family, argc, argv);
+
+	fprintf(stderr, "unknown sub-command: %s", argv[1]);
+	syntax(argv);
+	return 0;
+}