Merge branch 'mptcp-add-mp_prio-support-and-rework-local-address-ids'

Mat Martineau says:

====================
MPTCP: Add MP_PRIO support and rework local address IDs

Patches 1 and 2 rework the assignment of local address IDs to allow them
to be assigned by a userspace path manager, and add corresponding self
tests.

Patches 2-8 add the ability to change subflow priority after a subflow
has been established. Each subflow in a MPTCP connection has a priority
level: "regular" or "backup". Data should only be sent on backup
subflows if no regular subflows are available. The priority level can be
set when the subflow connection is established (as was already
implemented), or during the life of the connection by sending MP_PRIO in
the TCP options (as added here). Self tests are included.
====================

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

include/uapi/linux/mptcp.h

···
 	MPTCP_PM_CMD_FLUSH_ADDRS,
 	MPTCP_PM_CMD_SET_LIMITS,
 	MPTCP_PM_CMD_GET_LIMITS,
+	MPTCP_PM_CMD_SET_FLAGS,
 
 	__MPTCP_PM_CMD_AFTER_LAST
 };

net/mptcp/mib.c

···
 	SNMP_MIB_ITEM("EchoAdd", MPTCP_MIB_ECHOADD),
 	SNMP_MIB_ITEM("RmAddr", MPTCP_MIB_RMADDR),
 	SNMP_MIB_ITEM("RmSubflow", MPTCP_MIB_RMSUBFLOW),
+	SNMP_MIB_ITEM("MPPrioTx", MPTCP_MIB_MPPRIOTX),
+	SNMP_MIB_ITEM("MPPrioRx", MPTCP_MIB_MPPRIORX),
 	SNMP_MIB_SENTINEL
 };
 

net/mptcp/mib.h

···
 	MPTCP_MIB_ECHOADD,		/* Received ADD_ADDR with echo-flag=1 */
 	MPTCP_MIB_RMADDR,		/* Received RM_ADDR */
 	MPTCP_MIB_RMSUBFLOW,		/* Remove a subflow */
+	MPTCP_MIB_MPPRIOTX,		/* Transmit a MP_PRIO */
+	MPTCP_MIB_MPPRIORX,		/* Received a MP_PRIO */
 	__MPTCP_MIB_MAX
 };
 

net/mptcp/options.c

···
 		pr_debug("RM_ADDR: id=%d", mp_opt->rm_id);
 		break;
 
+	case MPTCPOPT_MP_PRIO:
+		if (opsize != TCPOLEN_MPTCP_PRIO)
+			break;
+
+		mp_opt->mp_prio = 1;
+		mp_opt->backup = *ptr++ & MPTCP_PRIO_BKUP;
+		pr_debug("MP_PRIO: prio=%d", mp_opt->backup);
+		break;
+
 	case MPTCPOPT_MP_FASTCLOSE:
 		if (opsize != TCPOLEN_MPTCP_FASTCLOSE)
 			break;
···
 	mp_opt->port = 0;
 	mp_opt->rm_addr = 0;
 	mp_opt->dss = 0;
+	mp_opt->mp_prio = 0;
 
 	length = (th->doff * 4) - sizeof(struct tcphdr);
 	ptr = (const unsigned char *)(th + 1);
···
 	return true;
 }
 
+static bool mptcp_established_options_mp_prio(struct sock *sk,
+					      unsigned int *size,
+					      unsigned int remaining,
+					      struct mptcp_out_options *opts)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+
+	if (!subflow->send_mp_prio)
+		return false;
+
+	if (remaining < TCPOLEN_MPTCP_PRIO)
+		return false;
+
+	*size = TCPOLEN_MPTCP_PRIO;
+	opts->suboptions |= OPTION_MPTCP_PRIO;
+	opts->backup = subflow->request_bkup;
+
+	pr_debug("prio=%d", opts->backup);
+
+	return true;
+}
+
 bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 			       unsigned int *size, unsigned int remaining,
 			       struct mptcp_out_options *opts)
···
 		remaining -= opt_size;
 		ret = true;
 	} else if (mptcp_established_options_rm_addr(sk, &opt_size, remaining, opts)) {
+		*size += opt_size;
+		remaining -= opt_size;
+		ret = true;
+	}
+
+	if (mptcp_established_options_mp_prio(sk, &opt_size, remaining, opts)) {
 		*size += opt_size;
 		remaining -= opt_size;
 		ret = true;
···
 		mp_opt.rm_addr = 0;
 	}
 
+	if (mp_opt.mp_prio) {
+		mptcp_pm_mp_prio_received(sk, mp_opt.backup);
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPPRIORX);
+		mp_opt.mp_prio = 0;
+	}
+
 	if (!mp_opt.dss)
 		return;
 
···
 		*ptr++ = mptcp_option(MPTCPOPT_RM_ADDR,
 				      TCPOLEN_MPTCP_RM_ADDR_BASE,
 				      0, opts->rm_id);
+	}
+
+	if (OPTION_MPTCP_PRIO & opts->suboptions) {
+		const struct sock *ssk = (const struct sock *)tp;
+		struct mptcp_subflow_context *subflow;
+
+		subflow = mptcp_subflow_ctx(ssk);
+		subflow->send_mp_prio = 0;
+
+		*ptr++ = mptcp_option(MPTCPOPT_MP_PRIO,
+				      TCPOLEN_MPTCP_PRIO,
+				      opts->backup, TCPOPT_NOP);
 	}
 
 	if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {

net/mptcp/pm.c

···
 	spin_unlock_bh(&pm->lock);
 }
 
+void mptcp_pm_mp_prio_received(struct sock *sk, u8 bkup)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+
+	pr_debug("subflow->backup=%d, bkup=%d\n", subflow->backup, bkup);
+	subflow->backup = bkup;
+}
+
 /* path manager helpers */
 
 bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, unsigned int remaining,

net/mptcp/pm_netlink.c

···
 	u8			retrans_times;
 };
 
+#define MAX_ADDR_ID		255
+#define BITMAP_SZ DIV_ROUND_UP(MAX_ADDR_ID + 1, BITS_PER_LONG)
+
 struct pm_nl_pernet {
 	/* protects pernet updates */
 	spinlock_t		lock;
···
 	unsigned int		local_addr_max;
 	unsigned int		subflows_max;
 	unsigned int		next_id;
+	unsigned long		id_bitmap[BITMAP_SZ];
 };
 
 #define MPTCP_PM_ADDR_MAX	8
···
 	}
 }
 
+int mptcp_pm_nl_mp_prio_send_ack(struct mptcp_sock *msk,
+				 struct mptcp_addr_info *addr,
+				 u8 bkup)
+{
+	struct mptcp_subflow_context *subflow;
+
+	pr_debug("bkup=%d", bkup);
+
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+		struct sock *sk = (struct sock *)msk;
+		struct mptcp_addr_info local;
+
+		local_address((struct sock_common *)ssk, &local);
+		if (!addresses_equal(&local, addr, addr->port))
+			continue;
+
+		subflow->backup = bkup;
+		subflow->send_mp_prio = 1;
+		subflow->request_bkup = bkup;
+		__MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPPRIOTX);
+
+		spin_unlock_bh(&msk->pm.lock);
+		pr_debug("send ack for mp_prio");
+		lock_sock(ssk);
+		tcp_send_ack(ssk);
+		release_sock(ssk);
+		spin_lock_bh(&msk->pm.lock);
+
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
 void mptcp_pm_nl_rm_addr_received(struct mptcp_sock *msk)
 {
 	struct mptcp_subflow_context *subflow, *tmp;
···
 	/* to keep the code simple, don't do IDR-like allocation for address ID,
 	 * just bail when we exceed limits
 	 */
-	if (pernet->next_id > 255)
-		goto out;
+	if (pernet->next_id == MAX_ADDR_ID)
+		pernet->next_id = 1;
 	if (pernet->addrs >= MPTCP_PM_ADDR_MAX)
+		goto out;
+	if (test_bit(entry->addr.id, pernet->id_bitmap))
 		goto out;
 
 	/* do not insert duplicate address, differentiate on port only
···
 			goto out;
 	}
 
+	if (!entry->addr.id) {
+find_next:
+		entry->addr.id = find_next_zero_bit(pernet->id_bitmap,
+						    MAX_ADDR_ID + 1,
+						    pernet->next_id);
+		if ((!entry->addr.id || entry->addr.id > MAX_ADDR_ID) &&
+		    pernet->next_id != 1) {
+			pernet->next_id = 1;
+			goto find_next;
+		}
+	}
+
+	if (!entry->addr.id || entry->addr.id > MAX_ADDR_ID)
+		goto out;
+
+	__set_bit(entry->addr.id, pernet->id_bitmap);
+	if (entry->addr.id > pernet->next_id)
+		pernet->next_id = entry->addr.id;
+
 	if (entry->addr.flags & MPTCP_PM_ADDR_FLAG_SIGNAL)
 		pernet->add_addr_signal_max++;
 	if (entry->addr.flags & MPTCP_PM_ADDR_FLAG_SUBFLOW)
 		pernet->local_addr_max++;
 
-	entry->addr.id = pernet->next_id++;
 	pernet->addrs++;
 	list_add_tail_rcu(&entry->list, &pernet->local_addr_list);
 	ret = entry->addr.id;
···
 	entry->addr = skc_local;
 	entry->addr.ifindex = 0;
 	entry->addr.flags = 0;
+	entry->addr.id = 0;
 	ret = mptcp_pm_nl_append_new_local_addr(pernet, entry);
 	if (ret < 0)
 		kfree(entry);
···
 
 	pernet->addrs--;
 	list_del_rcu(&entry->list);
+	__clear_bit(entry->addr.id, pernet->id_bitmap);
 	spin_unlock_bh(&pernet->lock);
 
 	mptcp_nl_remove_subflow_and_signal_addr(sock_net(skb->sk), &entry->addr);
···
 	spin_lock_bh(&pernet->lock);
 	list_splice_init(&pernet->local_addr_list, &free_list);
 	__reset_counters(pernet);
+	pernet->next_id = 1;
+	bitmap_zero(pernet->id_bitmap, MAX_ADDR_ID + 1);
 	spin_unlock_bh(&pernet->lock);
 	__flush_addrs(sock_net(skb->sk), &free_list);
 	return 0;
···
 	struct pm_nl_pernet *pernet;
 	int id = cb->args[0];
 	void *hdr;
+	int i;
 
 	pernet = net_generic(net, pm_nl_pernet_id);
 
 	spin_lock_bh(&pernet->lock);
-	list_for_each_entry(entry, &pernet->local_addr_list, list) {
-		if (entry->addr.id <= id)
-			continue;
+	for (i = id; i < MAX_ADDR_ID + 1; i++) {
+		if (test_bit(i, pernet->id_bitmap)) {
+			entry = __lookup_addr_by_id(pernet, i);
+			if (!entry)
+				break;
 
-		hdr = genlmsg_put(msg, NETLINK_CB(cb->skb).portid,
-				  cb->nlh->nlmsg_seq, &mptcp_genl_family,
-				  NLM_F_MULTI, MPTCP_PM_CMD_GET_ADDR);
-		if (!hdr)
-			break;
+			if (entry->addr.id <= id)
+				continue;
 
-		if (mptcp_nl_fill_addr(msg, entry) < 0) {
-			genlmsg_cancel(msg, hdr);
-			break;
+			hdr = genlmsg_put(msg, NETLINK_CB(cb->skb).portid,
+					  cb->nlh->nlmsg_seq, &mptcp_genl_family,
+					  NLM_F_MULTI, MPTCP_PM_CMD_GET_ADDR);
+			if (!hdr)
+				break;
+
+			if (mptcp_nl_fill_addr(msg, entry) < 0) {
+				genlmsg_cancel(msg, hdr);
+				break;
+			}
+
+			id = entry->addr.id;
+			genlmsg_end(msg, hdr);
 		}
-
-		id = entry->addr.id;
-		genlmsg_end(msg, hdr);
 	}
 	spin_unlock_bh(&pernet->lock);
 
···
 	return -EMSGSIZE;
 }
 
+static int mptcp_nl_addr_backup(struct net *net,
+				struct mptcp_addr_info *addr,
+				u8 bkup)
+{
+	long s_slot = 0, s_num = 0;
+	struct mptcp_sock *msk;
+	int ret = -EINVAL;
+
+	while ((msk = mptcp_token_iter_next(net, &s_slot, &s_num)) != NULL) {
+		struct sock *sk = (struct sock *)msk;
+
+		if (list_empty(&msk->conn_list))
+			goto next;
+
+		lock_sock(sk);
+		spin_lock_bh(&msk->pm.lock);
+		ret = mptcp_pm_nl_mp_prio_send_ack(msk, addr, bkup);
+		spin_unlock_bh(&msk->pm.lock);
+		release_sock(sk);
+
+next:
+		sock_put(sk);
+		cond_resched();
+	}
+
+	return ret;
+}
+
+static int mptcp_nl_cmd_set_flags(struct sk_buff *skb, struct genl_info *info)
+{
+	struct nlattr *attr = info->attrs[MPTCP_PM_ATTR_ADDR];
+	struct pm_nl_pernet *pernet = genl_info_pm_nl(info);
+	struct mptcp_pm_addr_entry addr, *entry;
+	struct net *net = sock_net(skb->sk);
+	u8 bkup = 0;
+	int ret;
+
+	ret = mptcp_pm_parse_addr(attr, info, true, &addr);
+	if (ret < 0)
+		return ret;
+
+	if (addr.addr.flags & MPTCP_PM_ADDR_FLAG_BACKUP)
+		bkup = 1;
+
+	list_for_each_entry(entry, &pernet->local_addr_list, list) {
+		if (addresses_equal(&entry->addr, &addr.addr, true)) {
+			ret = mptcp_nl_addr_backup(net, &entry->addr, bkup);
+			if (ret)
+				return ret;
+
+			if (bkup)
+				entry->addr.flags |= MPTCP_PM_ADDR_FLAG_BACKUP;
+			else
+				entry->addr.flags &= ~MPTCP_PM_ADDR_FLAG_BACKUP;
+		}
+	}
+
+	return 0;
+}
+
 static const struct genl_small_ops mptcp_pm_ops[] = {
 	{
 		.cmd    = MPTCP_PM_CMD_ADD_ADDR,
···
 		.cmd    = MPTCP_PM_CMD_GET_LIMITS,
 		.doit   = mptcp_nl_cmd_get_limits,
 	},
+	{
+		.cmd    = MPTCP_PM_CMD_SET_FLAGS,
+		.doit   = mptcp_nl_cmd_set_flags,
+		.flags  = GENL_ADMIN_PERM,
+	},
 };
 
 static struct genl_family mptcp_genl_family __ro_after_init = {
···
 	INIT_LIST_HEAD_RCU(&pernet->local_addr_list);
 	__reset_counters(pernet);
 	pernet->next_id = 1;
+	bitmap_zero(pernet->id_bitmap, MAX_ADDR_ID + 1);
 	spin_lock_init(&pernet->lock);
 	return 0;
 }

net/mptcp/protocol.h

···
 #define OPTION_MPTCP_ADD_ADDR6	BIT(7)
 #define OPTION_MPTCP_RM_ADDR	BIT(8)
 #define OPTION_MPTCP_FASTCLOSE	BIT(9)
+#define OPTION_MPTCP_PRIO	BIT(10)
 
 /* MPTCP option subtypes */
 #define MPTCPOPT_MP_CAPABLE	0
···
 #define TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT	24
 #define TCPOLEN_MPTCP_PORT_LEN		4
 #define TCPOLEN_MPTCP_RM_ADDR_BASE	4
+#define TCPOLEN_MPTCP_PRIO		4
 #define TCPOLEN_MPTCP_FASTCLOSE		12
 
 /* MPTCP MP_JOIN flags */
···
 #define MPTCP_ADDR_ECHO		BIT(0)
 #define MPTCP_ADDR_IPVERSION_4	4
 #define MPTCP_ADDR_IPVERSION_6	6
+
+/* MPTCP MP_PRIO flags */
+#define MPTCP_PRIO_BKUP		BIT(0)
 
 /* MPTCP socket flags */
 #define MPTCP_DATA_READY	0
···
 		dss : 1,
 		add_addr : 1,
 		rm_addr : 1,
+		mp_prio : 1,
 		family : 4,
 		echo : 1,
 		backup : 1;
···
 		map_valid : 1,
 		mpc_map : 1,
 		backup : 1,
+		send_mp_prio : 1,
 		rx_eof : 1,
 		can_ack : 1,        /* only after processing the remote a key */
 		disposable : 1;	    /* ctx can be free at ulp release time */
···
 				const struct mptcp_addr_info *addr);
 void mptcp_pm_add_addr_send_ack(struct mptcp_sock *msk);
 void mptcp_pm_rm_addr_received(struct mptcp_sock *msk, u8 rm_id);
+void mptcp_pm_mp_prio_received(struct sock *sk, u8 bkup);
+int mptcp_pm_nl_mp_prio_send_ack(struct mptcp_sock *msk,
+				 struct mptcp_addr_info *addr,
+				 u8 bkup);
 void mptcp_pm_free_anno_list(struct mptcp_sock *msk);
 struct mptcp_pm_add_entry *
 mptcp_pm_del_add_timer(struct mptcp_sock *msk,

tools/testing/selftests/net/mptcp/mptcp_join.sh

···
 	rm_nr_ns1="$7"
 	rm_nr_ns2="$8"
 	speed="$9"
+	bkup="${10}"
 
 	port=$((10000+$TEST_COUNT))
 	TEST_COUNT=$((TEST_COUNT+1))
···
 		fi
 	fi
 
+	if [ ! -z $bkup ]; then
+		sleep 1
+		for netns in "$ns1" "$ns2"; do
+			dump=(`ip netns exec $netns ./pm_nl_ctl dump`)
+			if [ ${#dump[@]} -gt 0 ]; then
+				addr=${dump[${#dump[@]} - 1]}
+				backup="ip netns exec $netns ./pm_nl_ctl set $addr flags $bkup"
+				$backup
+			fi
+		done
+	fi
+
 	wait $cpid
 	retc=$?
 	wait $spid
···
 	rm_nr_ns1="${5:-0}"
 	rm_nr_ns2="${6:-0}"
 	speed="${7:-fast}"
+	bkup="${8:-""}"
 	lret=0
 	oldin=""
 
···
 	fi
 
 	do_transfer ${listener_ns} ${connector_ns} MPTCP MPTCP ${connect_addr} \
-		${test_linkfail} ${rm_nr_ns1} ${rm_nr_ns2} ${speed}
+		${test_linkfail} ${rm_nr_ns1} ${rm_nr_ns2} ${speed} ${bkup}
 	lret=$?
 
 	if [ "$test_linkfail" -eq 1 ];then
···
 	[ -z "$count" ] && count=0
 	if [ "$count" != "$rm_subflow_nr" ]; then
 		echo "[fail] got $count RM_SUBFLOW[s] expected $rm_subflow_nr"
+		ret=1
+		dump_stats=1
+	else
+		echo "[ ok ]"
+	fi
+
+	if [ "${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
+}
+
+chk_prio_nr()
+{
+	local mp_prio_nr_tx=$1
+	local mp_prio_nr_rx=$2
+	local count
+	local dump_stats
+
+	printf "%-39s %s" " " "ptx"
+	count=`ip netns exec $ns1 nstat -as | grep MPTcpExtMPPrioTx | awk '{print $2}'`
+	[ -z "$count" ] && count=0
+	if [ "$count" != "$mp_prio_nr_tx" ]; then
+		echo "[fail] got $count MP_PRIO[s] TX expected $mp_prio_nr_tx"
+		ret=1
+		dump_stats=1
+	else
+		echo -n "[ ok ]"
+	fi
+
+	echo -n " - prx   "
+	count=`ip netns exec $ns1 nstat -as | grep MPTcpExtMPPrioRx | awk '{print $2}'`
+	[ -z "$count" ] && count=0
+	if [ "$count" != "$mp_prio_nr_rx" ]; then
+		echo "[fail] got $count MP_PRIO[s] RX expected $mp_prio_nr_rx"
 		ret=1
 		dump_stats=1
 	else
···
 chk_join_nr "remove subflow and signal IPv6" 2 2 2
 chk_add_nr 1 1
 chk_rm_nr 1 1
+
+# single subflow, backup
+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,backup
+run_tests $ns1 $ns2 10.0.1.1 0 0 0 slow nobackup
+chk_join_nr "single subflow, backup" 1 1 1
+chk_prio_nr 0 1
+
+# single address, backup
+reset
+ip netns exec $ns1 ./pm_nl_ctl limits 0 1
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.2.1 flags signal
+ip netns exec $ns2 ./pm_nl_ctl limits 1 1
+run_tests $ns1 $ns2 10.0.1.1 0 0 0 slow backup
+chk_join_nr "single address, backup" 1 1 1
+chk_add_nr 1 1
+chk_prio_nr 1 0
 
 # single subflow, syncookies
 reset_with_cookies

tools/testing/selftests/net/mptcp/pm_netlink.sh

···
 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
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.1.4 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
···
 
 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
+	ip netns exec $ns1 ./pm_nl_ctl add 10.0.0.9 id $((i+1))
 done
 check "ip netns exec $ns1 ./pm_nl_ctl dump" "id 1 flags  10.0.1.1
+id 2 flags  10.0.0.9
 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
···
 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"
+
+ip netns exec $ns1 ./pm_nl_ctl flush
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.1.1
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.1.2
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.1.3 id 100
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.1.4
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.1.5 id 254
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.1.6
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.1.7
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.1.8
+check "ip netns exec $ns1 ./pm_nl_ctl dump" "id 1 flags  10.0.1.1
+id 2 flags  10.0.1.2
+id 3 flags  10.0.1.7
+id 4 flags  10.0.1.8
+id 100 flags  10.0.1.3
+id 101 flags  10.0.1.4
+id 254 flags  10.0.1.5
+id 255 flags  10.0.1.6" "set ids"
+
+ip netns exec $ns1 ./pm_nl_ctl flush
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.0.1
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.0.2 id 254
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.0.3
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.0.4
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.0.5 id 253
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.0.6
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.0.7
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.0.8
+check "ip netns exec $ns1 ./pm_nl_ctl dump" "id 1 flags  10.0.0.1
+id 2 flags  10.0.0.4
+id 3 flags  10.0.0.6
+id 4 flags  10.0.0.7
+id 5 flags  10.0.0.8
+id 253 flags  10.0.0.5
+id 254 flags  10.0.0.2
+id 255 flags  10.0.0.3" "wrap-around ids"
 
 exit $ret

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

···
 
 static void syntax(char *argv[])
 {
-	fprintf(stderr, "%s add|get|del|flush|dump|accept [<args>]\n", argv[0]);
+	fprintf(stderr, "%s add|get|set|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, "\tset <ip> [flags backup|nobackup]\n");
 	fprintf(stderr, "\tflush\n");
 	fprintf(stderr, "\tdump\n");
 	fprintf(stderr, "\tlimits [<rcv addr max> <subflow max>]\n");
···
 	return 0;
 }
 
+int set_flags(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_int32_t flags = 0;
+	u_int16_t family;
+	int nest_start;
+	int off = 0;
+	int arg;
+
+	memset(data, 0, sizeof(data));
+	nh = (void *)data;
+	off = init_genl_req(data, pm_family, MPTCP_PM_CMD_SET_FLAGS,
+			    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 */
+			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, "backup"))
+					flags |= MPTCP_PM_ADDR_FLAG_BACKUP;
+				else if (strcmp(tok, "nobackup"))
+					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 {
+			error(1, 0, "unknown keyword %s", argv[arg]);
+		}
+	}
+	nest->rta_len = off - nest_start;
+
+	do_nl_req(fd, nh, off, 0);
+	return 0;
+}
+
 int main(int argc, char *argv[])
 {
 	int fd, pm_family;
···
 		return dump_addrs(fd, pm_family, argc, argv);
 	else if (!strcmp(argv[1], "limits"))
 		return get_set_limits(fd, pm_family, argc, argv);
+	else if (!strcmp(argv[1], "set"))
+		return set_flags(fd, pm_family, argc, argv);
 
 	fprintf(stderr, "unknown sub-command: %s", argv[1]);
 	syntax(argv);