Merge branch 'mptcp-multiple-subflows-path-management'

Mat Martineau says:

====================
Multipath TCP part 3: Multiple subflows and path management

v2 -> v3: Remove 'inline' in .c files, fix uapi bit macros, and rebase.

v1 -> v2: Rebase on current net-next, fix for netlink limit setting,
and update .gitignore for selftest.

This patch set allows more than one TCP subflow to be established and
used for a multipath TCP connection. Subflows are added to an existing
connection using the MP_JOIN option during the 3-way handshake. With
multiple TCP subflows available, sent data is now stored in the MPTCP
socket so it may be retransmitted on any TCP subflow if there is no
DATA_ACK before a timeout. If an MPTCP-level timeout occurs, data is
retransmitted using an available subflow. Storing this sent data
requires the addition of memory accounting at the MPTCP level, which was
previously delegated to the single subflow. Incoming DATA_ACKs now free
data from the MPTCP-level retransmit buffer.

IP addresses available for new subflow connections can now be advertised
and received with the ADD_ADDR option, and the corresponding REMOVE_ADDR
option likewise advertises that an address is no longer available.

The MPTCP path manager netlink interface has commands to set in-kernel
limits for the number of concurrent subflows and control the
advertisement of IP addresses between peers.

To track and debug MPTCP connections there are new MPTCP MIB counters,
and subflow context can be requested using inet_diag. The MPTCP
self-tests now validate multiple-subflow operation and the netlink path
manager interface.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

6 files changed, 1133 insertions, 6 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..f50976ee7d44 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 mptcp_join.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/mptcp_connect.c b/tools/testing/selftests/net/mptcp/mptcp_connect.c
index 702bab2c12da..cedee5b952ba 100644
--- a/tools/testing/selftests/net/mptcp/mptcp_connect.c
+++ b/tools/testing/selftests/net/mptcp/mptcp_connect.c
@@ -51,6 +51,7 @@ static bool tcpulp_audit;
 static int pf = AF_INET;
 static int cfg_sndbuf;
 static int cfg_rcvbuf;
+static bool cfg_join;
 
 static void die_usage(void)
 {
@@ -250,6 +251,7 @@ static int sock_connect_mptcp(const char * const remoteaddr,
 
 static size_t do_rnd_write(const int fd, char *buf, const size_t len)
 {
+	static bool first = true;
 	unsigned int do_w;
 	ssize_t bw;
 
@@ -257,10 +259,19 @@ static size_t do_rnd_write(const int fd, char *buf, const size_t len)
 	if (do_w == 0 || do_w > len)
 		do_w = len;
 
+	if (cfg_join && first && do_w > 100)
+		do_w = 100;
+
 	bw = write(fd, buf, do_w);
 	if (bw < 0)
 		perror("write");
 
+	/* let the join handshake complete, before going on */
+	if (cfg_join && first) {
+		usleep(200000);
+		first = false;
+	}
+
 	return bw;
 }
 
@@ -385,8 +396,11 @@ static int copyfd_io_poll(int infd, int peerfd, int outfd)
 					break;
 
 				/* ... but we still receive.
-				 * Close our write side.
+				 * Close our write side, ev. give some time
+				 * for address notification
 				 */
+				if (cfg_join)
+					usleep(400000);
 				shutdown(peerfd, SHUT_WR);
 			} else {
 				if (errno == EINTR)
@@ -403,6 +417,10 @@ static int copyfd_io_poll(int infd, int peerfd, int outfd)
 		}
 	}
 
+	/* leave some time for late join/announce */
+	if (cfg_join)
+		usleep(400000);
+
 	close(peerfd);
 	return 0;
 }
@@ -658,7 +676,7 @@ static void maybe_close(int fd)
 {
 	unsigned int r = rand();
 
-	if (r & 1)
+	if (!cfg_join && (r & 1))
 		close(fd);
 }
 
@@ -794,8 +812,12 @@ static void parse_opts(int argc, char **argv)
 {
 	int c;
 
-	while ((c = getopt(argc, argv, "6lp:s:hut:m:S:R:")) != -1) {
+	while ((c = getopt(argc, argv, "6jlp:s:hut:m:S:R:")) != -1) {
 		switch (c) {
+		case 'j':
+			cfg_join = true;
+			cfg_mode = CFG_MODE_POLL;
+			break;
 		case 'l':
 			listen_mode = true;
 			break;
diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
new file mode 100755
index 000000000000..dd42c2f692d0
--- /dev/null
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -0,0 +1,357 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+ret=0
+sin=""
+sout=""
+cin=""
+cout=""
+ksft_skip=4
+timeout=30
+capture=0
+
+TEST_COUNT=0
+
+init()
+{
+	capout=$(mktemp)
+
+	rndh=$(printf %x $sec)-$(mktemp -u XXXXXX)
+
+	ns1="ns1-$rndh"
+	ns2="ns2-$rndh"
+
+	for netns in "$ns1" "$ns2";do
+		ip netns add $netns || exit $ksft_skip
+		ip -net $netns link set lo up
+		ip netns exec $netns sysctl -q net.mptcp.enabled=1
+		ip netns exec $netns sysctl -q net.ipv4.conf.all.rp_filter=0
+		ip netns exec $netns sysctl -q net.ipv4.conf.default.rp_filter=0
+	done
+
+	#  ns1              ns2
+	# ns1eth1    ns2eth1
+	# ns1eth2    ns2eth2
+	# ns1eth3    ns2eth3
+	# ns1eth4    ns2eth4
+
+	for i in `seq 1 4`; do
+		ip link add ns1eth$i netns "$ns1" type veth peer name ns2eth$i netns "$ns2"
+		ip -net "$ns1" addr add 10.0.$i.1/24 dev ns1eth$i
+		ip -net "$ns1" addr add dead:beef:$i::1/64 dev ns1eth$i nodad
+		ip -net "$ns1" link set ns1eth$i up
+
+		ip -net "$ns2" addr add 10.0.$i.2/24 dev ns2eth$i
+		ip -net "$ns2" addr add dead:beef:$i::2/64 dev ns2eth$i nodad
+		ip -net "$ns2" link set ns2eth$i up
+
+		# let $ns2 reach any $ns1 address from any interface
+		ip -net "$ns2" route add default via 10.0.$i.1 dev ns2eth$i metric 10$i
+	done
+}
+
+cleanup_partial()
+{
+	rm -f "$capout"
+
+	for netns in "$ns1" "$ns2"; do
+		ip netns del $netns
+	done
+}
+
+cleanup()
+{
+	rm -f "$cin" "$cout"
+	rm -f "$sin" "$sout"
+	cleanup_partial
+}
+
+reset()
+{
+	cleanup_partial
+	init
+}
+
+for arg in "$@"; do
+	if [ "$arg" = "-c" ]; then
+		capture=1
+	fi
+done
+
+ip -Version > /dev/null 2>&1
+if [ $? -ne 0 ];then
+	echo "SKIP: Could not run test without ip tool"
+	exit $ksft_skip
+fi
+
+
+check_transfer()
+{
+	in=$1
+	out=$2
+	what=$3
+
+	cmp "$in" "$out" > /dev/null 2>&1
+	if [ $? -ne 0 ] ;then
+		echo "[ FAIL ] $what does not match (in, out):"
+		print_file_err "$in"
+		print_file_err "$out"
+
+		return 1
+	fi
+
+	return 0
+}
+
+do_ping()
+{
+	listener_ns="$1"
+	connector_ns="$2"
+	connect_addr="$3"
+
+	ip netns exec ${connector_ns} ping -q -c 1 $connect_addr >/dev/null
+	if [ $? -ne 0 ] ; then
+		echo "$listener_ns -> $connect_addr connectivity [ FAIL ]" 1>&2
+		ret=1
+	fi
+}
+
+do_transfer()
+{
+	listener_ns="$1"
+	connector_ns="$2"
+	cl_proto="$3"
+	srv_proto="$4"
+	connect_addr="$5"
+
+	port=$((10000+$TEST_COUNT))
+	TEST_COUNT=$((TEST_COUNT+1))
+
+	:> "$cout"
+	:> "$sout"
+	:> "$capout"
+
+	if [ $capture -eq 1 ]; then
+		if [ -z $SUDO_USER ] ; then
+			capuser=""
+		else
+			capuser="-Z $SUDO_USER"
+		fi
+
+		capfile="mp_join-${listener_ns}.pcap"
+
+		echo "Capturing traffic for test $TEST_COUNT into $capfile"
+		ip netns exec ${listener_ns} tcpdump -i any -s 65535 -B 32768 $capuser -w $capfile > "$capout" 2>&1 &
+		cappid=$!
+
+		sleep 1
+	fi
+
+	ip netns exec ${listener_ns} ./mptcp_connect -j -t $timeout -l -p $port -s ${srv_proto} 0.0.0.0 < "$sin" > "$sout" &
+	spid=$!
+
+	sleep 1
+
+	ip netns exec ${connector_ns} ./mptcp_connect -j -t $timeout -p $port -s ${cl_proto} $connect_addr < "$cin" > "$cout" &
+	cpid=$!
+
+	wait $cpid
+	retc=$?
+	wait $spid
+	rets=$?
+
+	if [ $capture -eq 1 ]; then
+	    sleep 1
+	    kill $cappid
+	fi
+
+	if [ ${rets} -ne 0 ] || [ ${retc} -ne 0 ]; then
+		echo " client exit code $retc, server $rets" 1>&2
+		echo "\nnetns ${listener_ns} socket stat for $port:" 1>&2
+		ip netns exec ${listener_ns} ss -nita 1>&2 -o "sport = :$port"
+		echo "\nnetns ${connector_ns} socket stat for $port:" 1>&2
+		ip netns exec ${connector_ns} ss -nita 1>&2 -o "dport = :$port"
+
+		cat "$capout"
+		return 1
+	fi
+
+	check_transfer $sin $cout "file received by client"
+	retc=$?
+	check_transfer $cin $sout "file received by server"
+	rets=$?
+
+	if [ $retc -eq 0 ] && [ $rets -eq 0 ];then
+		cat "$capout"
+		return 0
+	fi
+
+	cat "$capout"
+	return 1
+}
+
+make_file()
+{
+	name=$1
+	who=$2
+
+	SIZE=1
+
+	dd if=/dev/urandom of="$name" bs=1024 count=$SIZE 2> /dev/null
+	echo -e "\nMPTCP_TEST_FILE_END_MARKER" >> "$name"
+
+	echo "Created $name (size $SIZE KB) containing data sent by $who"
+}
+
+run_tests()
+{
+	listener_ns="$1"
+	connector_ns="$2"
+	connect_addr="$3"
+	lret=0
+
+	do_transfer ${listener_ns} ${connector_ns} MPTCP MPTCP ${connect_addr}
+	lret=$?
+	if [ $lret -ne 0 ]; then
+		ret=$lret
+		return
+	fi
+}
+
+chk_join_nr()
+{
+	local msg="$1"
+	local syn_nr=$2
+	local syn_ack_nr=$3
+	local ack_nr=$4
+	local count
+	local dump_stats
+
+	printf "%-36s %s" "$msg" "syn"
+	count=`ip netns exec $ns1 nstat -as | grep MPTcpExtMPJoinSynRx | awk '{print $2}'`
+	[ -z "$count" ] && count=0
+	if [ "$count" != "$syn_nr" ]; then
+		echo "[fail] got $count JOIN[s] syn expected $syn_nr"
+		ret=1
+		dump_stats=1
+	else
+		echo -n "[ ok ]"
+	fi
+
+	echo -n " - synack"
+	count=`ip netns exec $ns2 nstat -as | grep MPTcpExtMPJoinSynAckRx | awk '{print $2}'`
+	[ -z "$count" ] && count=0
+	if [ "$count" != "$syn_ack_nr" ]; then
+		echo "[fail] got $count JOIN[s] synack expected $syn_ack_nr"
+		ret=1
+		dump_stats=1
+	else
+		echo -n "[ ok ]"
+	fi
+
+	echo -n " - ack"
+	count=`ip netns exec $ns1 nstat -as | grep MPTcpExtMPJoinAckRx | awk '{print $2}'`
+	[ -z "$count" ] && count=0
+	if [ "$count" != "$ack_nr" ]; then
+		echo "[fail] got $count JOIN[s] ack expected $ack_nr"
+		ret=1
+		dump_stats=1
+	else
+		echo "[ ok ]"
+	fi
+	if [ "${dump_stats}" = 1 ]; then
+		echo Server ns stats
+		ip netns exec $ns1 nstat -as | grep MPTcp
+		echo Client ns stats
+		ip netns exec $ns2 nstat -as | grep MPTcp
+	fi
+}
+
+sin=$(mktemp)
+sout=$(mktemp)
+cin=$(mktemp)
+cout=$(mktemp)
+init
+make_file "$cin" "client"
+make_file "$sin" "server"
+trap cleanup EXIT
+
+run_tests $ns1 $ns2 10.0.1.1
+chk_join_nr "no JOIN" "0" "0" "0"
+
+# subflow limted by client
+reset
+ip netns exec $ns2 ./pm_nl_ctl add 10.0.3.2 flags subflow
+run_tests $ns1 $ns2 10.0.1.1
+chk_join_nr "single subflow, limited by client" 0 0 0
+
+# subflow limted by server
+reset
+ip netns exec $ns2 ./pm_nl_ctl limits 0 1
+ip netns exec $ns2 ./pm_nl_ctl add 10.0.3.2 flags subflow
+run_tests $ns1 $ns2 10.0.1.1
+chk_join_nr "single subflow, limited by server" 1 1 0
+
+# subflow
+reset
+ip netns exec $ns1 ./pm_nl_ctl limits 0 1
+ip netns exec $ns2 ./pm_nl_ctl limits 0 1
+ip netns exec $ns2 ./pm_nl_ctl add 10.0.3.2 flags subflow
+run_tests $ns1 $ns2 10.0.1.1
+chk_join_nr "single subflow" 1 1 1
+
+# multiple subflows
+reset
+ip netns exec $ns1 ./pm_nl_ctl limits 0 2
+ip netns exec $ns2 ./pm_nl_ctl limits 0 2
+ip netns exec $ns2 ./pm_nl_ctl add 10.0.3.2 flags subflow
+ip netns exec $ns2 ./pm_nl_ctl add 10.0.2.2 flags subflow
+run_tests $ns1 $ns2 10.0.1.1
+chk_join_nr "multiple subflows" 2 2 2
+
+# multiple subflows limited by serverf
+reset
+ip netns exec $ns1 ./pm_nl_ctl limits 0 1
+ip netns exec $ns2 ./pm_nl_ctl limits 0 2
+ip netns exec $ns2 ./pm_nl_ctl add 10.0.3.2 flags subflow
+ip netns exec $ns2 ./pm_nl_ctl add 10.0.2.2 flags subflow
+run_tests $ns1 $ns2 10.0.1.1
+chk_join_nr "multiple subflows, limited by server" 2 2 1
+
+# add_address, unused
+reset
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.2.1 flags signal
+run_tests $ns1 $ns2 10.0.1.1
+chk_join_nr "unused signal address" 0 0 0
+
+# accept and use add_addr
+reset
+ip netns exec $ns1 ./pm_nl_ctl limits 0 1
+ip netns exec $ns2 ./pm_nl_ctl limits 1 1
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.2.1 flags signal
+run_tests $ns1 $ns2 10.0.1.1
+chk_join_nr "signal address" 1 1 1
+
+# accept and use add_addr with an additional subflow
+# note: signal address in server ns and local addresses in client ns must
+# belong to different subnets or one of the listed local address could be
+# used for 'add_addr' subflow
+reset
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.2.1 flags signal
+ip netns exec $ns1 ./pm_nl_ctl limits 0 2
+ip netns exec $ns2 ./pm_nl_ctl limits 1 2
+ip netns exec $ns2 ./pm_nl_ctl add 10.0.3.2 flags subflow
+run_tests $ns1 $ns2 10.0.1.1
+chk_join_nr "subflow and signal" 2 2 2
+
+# accept and use add_addr with additional subflows
+reset
+ip netns exec $ns1 ./pm_nl_ctl limits 0 3
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.2.1 flags signal
+ip netns exec $ns2 ./pm_nl_ctl limits 1 3
+ip netns exec $ns2 ./pm_nl_ctl add 10.0.3.2 flags subflow
+ip netns exec $ns2 ./pm_nl_ctl add 10.0.4.2 flags subflow
+run_tests $ns1 $ns2 10.0.1.1
+chk_join_nr "multiple subflows and signal" 3 3 3
+
+exit $ret
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;
+}