Merge branch 'mptcp-MP_FAIL-timeout'

Mat Martineau says:

====================
mptcp: Timeout for MP_FAIL response

When one peer sends an infinite mapping to coordinate fallback from
MPTCP to regular TCP, the other peer is expected to send a packet with
the MPTCP MP_FAIL option to acknowledge the infinite mapping. Rather
than leave the connection in some half-fallback state, this series adds
a timeout after which the infinite mapping sender will reset the
connection.

Patch 1 adds a fallback self test.

Patches 2-5 make use of the MPTCP socket's retransmit timer to reset the
MPTCP connection if no MP_FAIL was received.

Patches 6 and 7 extends the self test to check MP_FAIL-related MIBs.
====================

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

net/mptcp/pm.c

@@ -287,11 +287,27 @@ void mptcp_pm_mp_fail_received(struct sock *sk, u64 fail_seq)
 {
 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
+	struct sock *s = (struct sock *)msk;
 
 	pr_debug("fail_seq=%llu", fail_seq);
 
-	if (!mptcp_has_another_subflow(sk) && READ_ONCE(msk->allow_infinite_fallback))
+	if (mptcp_has_another_subflow(sk) || !READ_ONCE(msk->allow_infinite_fallback))
+		return;
+
+	if (!READ_ONCE(subflow->mp_fail_response_expect)) {
+		pr_debug("send MP_FAIL response and infinite map");
+
+		subflow->send_mp_fail = 1;
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFAILTX);
 		subflow->send_infinite_map = 1;
+	} else if (s && inet_sk_state_load(s) != TCP_CLOSE) {
+		pr_debug("MP_FAIL response received");
+
+		mptcp_data_lock(s);
+		if (inet_sk_state_load(s) != TCP_CLOSE)
+			sk_stop_timer(s, &s->sk_timer);
+		mptcp_data_unlock(s);
+	}
 }
 
 /* path manager helpers */

net/mptcp/protocol.c

@@ -1605,8 +1605,10 @@ void __mptcp_push_pending(struct sock *sk, unsigned int flags)
 
 out:
 	/* ensure the rtx timer is running */
+	mptcp_data_lock(sk);
 	if (!mptcp_timer_pending(sk))
 		mptcp_reset_timer(sk);
+	mptcp_data_unlock(sk);
 	if (copied)
 		__mptcp_check_send_data_fin(sk);
 }
@@ -2167,10 +2169,38 @@ static void mptcp_retransmit_timer(struct timer_list *t)
 	sock_put(sk);
 }
 
+static struct mptcp_subflow_context *
+mp_fail_response_expect_subflow(struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_context *subflow, *ret = NULL;
+
+	mptcp_for_each_subflow(msk, subflow) {
+		if (READ_ONCE(subflow->mp_fail_response_expect)) {
+			ret = subflow;
+			break;
+		}
+	}
+
+	return ret;
+}
+
+static void mptcp_check_mp_fail_response(struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+
+	bh_lock_sock(sk);
+	subflow = mp_fail_response_expect_subflow(msk);
+	if (subflow)
+		__set_bit(MPTCP_FAIL_NO_RESPONSE, &msk->flags);
+	bh_unlock_sock(sk);
+}
+
 static void mptcp_timeout_timer(struct timer_list *t)
 {
 	struct sock *sk = from_timer(sk, t, sk_timer);
 
+	mptcp_check_mp_fail_response(mptcp_sk(sk));
 	mptcp_schedule_work(sk);
 	sock_put(sk);
 }
@@ -2491,8 +2521,27 @@ static void __mptcp_retrans(struct sock *sk)
 reset_timer:
 	mptcp_check_and_set_pending(sk);
 
+	mptcp_data_lock(sk);
 	if (!mptcp_timer_pending(sk))
 		mptcp_reset_timer(sk);
+	mptcp_data_unlock(sk);
+}
+
+static void mptcp_mp_fail_no_response(struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_context *subflow;
+	struct sock *ssk;
+	bool slow;
+
+	subflow = mp_fail_response_expect_subflow(msk);
+	if (subflow) {
+		pr_debug("MP_FAIL doesn't respond, reset the subflow");
+
+		ssk = mptcp_subflow_tcp_sock(subflow);
+		slow = lock_sock_fast(ssk);
+		mptcp_subflow_reset(ssk);
+		unlock_sock_fast(ssk, slow);
+	}
 }
 
 static void mptcp_worker(struct work_struct *work)
@@ -2535,6 +2584,9 @@ static void mptcp_worker(struct work_struct *work)
 	if (test_and_clear_bit(MPTCP_WORK_RTX, &msk->flags))
 		__mptcp_retrans(sk);
 
+	if (test_and_clear_bit(MPTCP_FAIL_NO_RESPONSE, &msk->flags))
+		mptcp_mp_fail_no_response(msk);
+
 unlock:
 	release_sock(sk);
 	sock_put(sk);
@@ -2651,8 +2703,10 @@ void mptcp_subflow_shutdown(struct sock *sk, struct sock *ssk, int how)
 		} else {
 			pr_debug("Sending DATA_FIN on subflow %p", ssk);
 			tcp_send_ack(ssk);
+			mptcp_data_lock(sk);
 			if (!mptcp_timer_pending(sk))
 				mptcp_reset_timer(sk);
+			mptcp_data_unlock(sk);
 		}
 		break;
 	}
@@ -2753,8 +2807,10 @@ static void __mptcp_destroy_sock(struct sock *sk)
 	/* join list will be eventually flushed (with rst) at sock lock release time*/
 	list_splice_init(&msk->conn_list, &conn_list);
 
-	sk_stop_timer(sk, &msk->sk.icsk_retransmit_timer);
+	mptcp_data_lock(sk);
+	mptcp_stop_timer(sk);
 	sk_stop_timer(sk, &sk->sk_timer);
+	mptcp_data_unlock(sk);
 	msk->pm.status = 0;
 
 	/* clears msk->subflow, allowing the following loop to close
@@ -2816,7 +2872,9 @@ cleanup:
 		__mptcp_destroy_sock(sk);
 		do_cancel_work = true;
 	} else {
+		mptcp_data_lock(sk);
 		sk_reset_timer(sk, &sk->sk_timer, jiffies + TCP_TIMEWAIT_LEN);
+		mptcp_data_unlock(sk);
 	}
 	release_sock(sk);
 	if (do_cancel_work)
@@ -2861,8 +2919,10 @@ static int mptcp_disconnect(struct sock *sk, int flags)
 		__mptcp_close_ssk(sk, ssk, subflow, MPTCP_CF_FASTCLOSE);
 	}
 
-	sk_stop_timer(sk, &msk->sk.icsk_retransmit_timer);
+	mptcp_data_lock(sk);
+	mptcp_stop_timer(sk);
 	sk_stop_timer(sk, &sk->sk_timer);
+	mptcp_data_unlock(sk);
 
 	if (mptcp_sk(sk)->token)
 		mptcp_event(MPTCP_EVENT_CLOSED, mptcp_sk(sk), NULL, GFP_KERNEL);

net/mptcp/protocol.h

@@ -116,6 +116,7 @@
 #define MPTCP_WORK_EOF		3
 #define MPTCP_FALLBACK_DONE	4
 #define MPTCP_WORK_CLOSE_SUBFLOW 5
+#define MPTCP_FAIL_NO_RESPONSE	6
 
 /* MPTCP socket release cb flags */
 #define MPTCP_PUSH_PENDING	1
@@ -448,6 +449,7 @@ struct mptcp_subflow_context {
 		stale : 1,	    /* unable to snd/rcv data, do not use for xmit */
 		local_id_valid : 1; /* local_id is correctly initialized */
 	enum mptcp_data_avail data_avail;
+	bool	mp_fail_response_expect;
 	u32	remote_nonce;
 	u64	thmac;
 	u32	local_nonce;

net/mptcp/subflow.c

@@ -968,6 +968,7 @@ static enum mapping_status get_mapping_status(struct sock *ssk,
 {
 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
 	bool csum_reqd = READ_ONCE(msk->csum_enabled);
+	struct sock *sk = (struct sock *)msk;
 	struct mptcp_ext *mpext;
 	struct sk_buff *skb;
 	u16 data_len;
@@ -1009,6 +1010,12 @@ static enum mapping_status get_mapping_status(struct sock *ssk,
 		pr_debug("infinite mapping received");
 		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_INFINITEMAPRX);
 		subflow->map_data_len = 0;
+		if (sk && inet_sk_state_load(sk) != TCP_CLOSE) {
+			mptcp_data_lock(sk);
+			if (inet_sk_state_load(sk) != TCP_CLOSE)
+				sk_stop_timer(sk, &sk->sk_timer);
+			mptcp_data_unlock(sk);
+		}
 		return MAPPING_INVALID;
 	}
 
@@ -1217,6 +1224,12 @@ fallback:
 				tcp_send_active_reset(ssk, GFP_ATOMIC);
 				while ((skb = skb_peek(&ssk->sk_receive_queue)))
 					sk_eat_skb(ssk, skb);
+			} else {
+				WRITE_ONCE(subflow->mp_fail_response_expect, true);
+				/* The data lock is acquired in __mptcp_move_skbs() */
+				sk_reset_timer((struct sock *)msk,
+					       &((struct sock *)msk)->sk_timer,
+					       jiffies + TCP_RTO_MAX);
 			}
 			WRITE_ONCE(subflow->data_avail, MPTCP_SUBFLOW_NODATA);
 			return true;

tools/testing/selftests/net/mptcp/config

@@ -12,6 +12,9 @@ CONFIG_NF_TABLES=m
 CONFIG_NFT_COMPAT=m
 CONFIG_NETFILTER_XTABLES=m
 CONFIG_NETFILTER_XT_MATCH_BPF=m
+CONFIG_NETFILTER_XT_MATCH_LENGTH=m
+CONFIG_NETFILTER_XT_MATCH_STATISTIC=m
+CONFIG_NETFILTER_XT_TARGET_MARK=m
 CONFIG_NF_TABLES_INET=y
 CONFIG_NFT_TPROXY=m
 CONFIG_NFT_SOCKET=m
@@ -19,3 +22,8 @@ CONFIG_IP_ADVANCED_ROUTER=y
 CONFIG_IP_MULTIPLE_TABLES=y
 CONFIG_IP_NF_TARGET_REJECT=m
 CONFIG_IPV6_MULTIPLE_TABLES=y
+CONFIG_NET_ACT_CSUM=m
+CONFIG_NET_ACT_PEDIT=m
+CONFIG_NET_CLS_ACT=y
+CONFIG_NET_CLS_FW=m
+CONFIG_NET_SCH_INGRESS=m

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

@@ -266,6 +266,58 @@ reset_with_allow_join_id0()
 	ip netns exec $ns2 sysctl -q net.mptcp.allow_join_initial_addr_port=$ns2_enable
 }
 
+# Modify TCP payload without corrupting the TCP packet
+#
+# This rule inverts a 8-bit word at byte offset 148 for the 2nd TCP ACK packets
+# carrying enough data.
+# Once it is done, the TCP Checksum field is updated so the packet is still
+# considered as valid at the TCP level.
+# Because the MPTCP checksum, covering the TCP options and data, has not been
+# updated, the modification will be detected and an MP_FAIL will be emitted:
+# what we want to validate here without corrupting "random" MPTCP options.
+#
+# To avoid having tc producing this pr_info() message for each TCP ACK packets
+# not carrying enough data:
+#
+#     tc action pedit offset 162 out of bounds
+#
+# Netfilter is used to mark packets with enough data.
+reset_with_fail()
+{
+	reset "${1}" || return 1
+
+	ip netns exec $ns1 sysctl -q net.mptcp.checksum_enabled=1
+	ip netns exec $ns2 sysctl -q net.mptcp.checksum_enabled=1
+
+	check_invert=1
+	validate_checksum=1
+	local i="$2"
+	local ip="${3:-4}"
+	local tables
+
+	tables="iptables"
+	if [ $ip -eq 6 ]; then
+		tables="ip6tables"
+	fi
+
+	ip netns exec $ns2 $tables \
+		-t mangle \
+		-A OUTPUT \
+		-o ns2eth$i \
+		-p tcp \
+		-m length --length 150:9999 \
+		-m statistic --mode nth --packet 1 --every 99999 \
+		-j MARK --set-mark 42 || exit 1
+
+	tc -n $ns2 qdisc add dev ns2eth$i clsact || exit 1
+	tc -n $ns2 filter add dev ns2eth$i egress \
+		protocol ip prio 1000 \
+		handle 42 fw \
+		action pedit munge offset 148 u8 invert \
+		pipe csum tcp \
+		index 100 || exit 1
+}
+
 fail_test()
 {
 	ret=1
@@ -961,6 +1013,7 @@ chk_csum_nr()
 	local csum_ns2=${2:-0}
 	local count
 	local dump_stats
+	local extra_msg=""
 	local allow_multi_errors_ns1=0
 	local allow_multi_errors_ns2=0
 
@@ -976,6 +1029,9 @@ chk_csum_nr()
 	printf "%-${nr_blank}s %s" " " "sum"
 	count=$(ip netns exec $ns1 nstat -as | grep MPTcpExtDataCsumErr | awk '{print $2}')
 	[ -z "$count" ] && count=0
+	if [ "$count" != "$csum_ns1" ]; then
+		extra_msg="$extra_msg ns1=$count"
+	fi
 	if { [ "$count" != $csum_ns1 ] && [ $allow_multi_errors_ns1 -eq 0 ]; } ||
 	   { [ "$count" -lt $csum_ns1 ] && [ $allow_multi_errors_ns1 -eq 1 ]; }; then
 		echo "[fail] got $count data checksum error[s] expected $csum_ns1"
@@ -987,28 +1043,58 @@ chk_csum_nr()
 	echo -n " - csum  "
 	count=$(ip netns exec $ns2 nstat -as | grep MPTcpExtDataCsumErr | awk '{print $2}')
 	[ -z "$count" ] && count=0
+	if [ "$count" != "$csum_ns2" ]; then
+		extra_msg="$extra_msg ns2=$count"
+	fi
 	if { [ "$count" != $csum_ns2 ] && [ $allow_multi_errors_ns2 -eq 0 ]; } ||
 	   { [ "$count" -lt $csum_ns2 ] && [ $allow_multi_errors_ns2 -eq 1 ]; }; then
 		echo "[fail] got $count data checksum error[s] expected $csum_ns2"
 		fail_test
 		dump_stats=1
 	else
-		echo "[ ok ]"
+		echo -n "[ ok ]"
 	fi
 	[ "${dump_stats}" = 1 ] && dump_stats
+
+	echo "$extra_msg"
 }
 
 chk_fail_nr()
 {
 	local fail_tx=$1
 	local fail_rx=$2
+	local ns_invert=${3:-""}
 	local count
 	local dump_stats
+	local ns_tx=$ns1
+	local ns_rx=$ns2
+	local extra_msg=""
+	local allow_tx_lost=0
+	local allow_rx_lost=0
+
+	if [[ $ns_invert = "invert" ]]; then
+		ns_tx=$ns2
+		ns_rx=$ns1
+		extra_msg=" invert"
+	fi
+
+	if [[ "${fail_tx}" = "-"* ]]; then
+		allow_tx_lost=1
+		fail_tx=${fail_tx:1}
+	fi
+	if [[ "${fail_rx}" = "-"* ]]; then
+		allow_rx_lost=1
+		fail_rx=${fail_rx:1}
+	fi
 
 	printf "%-${nr_blank}s %s" " " "ftx"
-	count=$(ip netns exec $ns1 nstat -as | grep MPTcpExtMPFailTx | awk '{print $2}')
+	count=$(ip netns exec $ns_tx nstat -as | grep MPTcpExtMPFailTx | awk '{print $2}')
 	[ -z "$count" ] && count=0
 	if [ "$count" != "$fail_tx" ]; then
+		extra_msg="$extra_msg,tx=$count"
+	fi
+	if { [ "$count" != "$fail_tx" ] && [ $allow_tx_lost -eq 0 ]; } ||
+	   { [ "$count" -gt "$fail_tx" ] && [ $allow_tx_lost -eq 1 ]; }; then
 		echo "[fail] got $count MP_FAIL[s] TX expected $fail_tx"
 		fail_test
 		dump_stats=1
@@ -1017,17 +1103,23 @@ chk_fail_nr()
 	fi
 
 	echo -n " - failrx"
-	count=$(ip netns exec $ns2 nstat -as | grep MPTcpExtMPFailRx | awk '{print $2}')
+	count=$(ip netns exec $ns_rx nstat -as | grep MPTcpExtMPFailRx | awk '{print $2}')
 	[ -z "$count" ] && count=0
 	if [ "$count" != "$fail_rx" ]; then
+		extra_msg="$extra_msg,rx=$count"
+	fi
+	if { [ "$count" != "$fail_rx" ] && [ $allow_rx_lost -eq 0 ]; } ||
+	   { [ "$count" -gt "$fail_rx" ] && [ $allow_rx_lost -eq 1 ]; }; then
 		echo "[fail] got $count MP_FAIL[s] RX expected $fail_rx"
 		fail_test
 		dump_stats=1
 	else
-		echo "[ ok ]"
+		echo -n "[ ok ]"
 	fi
 
 	[ "${dump_stats}" = 1 ] && dump_stats
+
+	echo "$extra_msg"
 }
 
 chk_fclose_nr()
@@ -1199,7 +1291,7 @@ chk_join_nr()
 		echo "[ ok ]"
 	fi
 	[ "${dump_stats}" = 1 ] && dump_stats
-	if [ $checksum -eq 1 ]; then
+	if [ $validate_checksum -eq 1 ]; then
 		chk_csum_nr $csum_ns1 $csum_ns2
 		chk_fail_nr $fail_nr $fail_nr
 		chk_rst_nr $rst_nr $rst_nr
@@ -2590,6 +2682,22 @@ fastclose_tests()
 	fi
 }
 
+pedit_action_pkts()
+{
+	tc -n $ns2 -j -s action show action pedit index 100 | \
+		sed 's/.*"packets":\([0-9]\+\),.*/\1/'
+}
+
+fail_tests()
+{
+	# single subflow
+	if reset_with_fail "Infinite map" 1; then
+		run_tests $ns1 $ns2 10.0.1.1 128
+		chk_join_nr 0 0 0 +1 +0 1 0 1 "$(pedit_action_pkts)"
+		chk_fail_nr 1 -1 invert
+	fi
+}
+
 implicit_tests()
 {
 	# userspace pm type prevents add_addr
@@ -2658,6 +2766,7 @@ all_tests_sorted=(
 	d@deny_join_id0_tests
 	m@fullmesh_tests
 	z@fastclose_tests
+	F@fail_tests
 	I@implicit_tests
 )