Merge branch 'mptcp-C-flag-and-fixes'

Mat Martineau says:

====================
mptcp: Connection-time 'C' flag and two fixes

Here are six more patches from the MPTCP tree.

Most of them add support for the 'C' flag in the MPTCP connection-time
option headers. This flag affects how the initial address and port are
treated by each peer. Normally one peer may send MP_JOIN requests to the
remote address and port that were used when initiating the MPTCP
connection. The 'C' bit indicates that MP_JOINs should only be sent to
remote addresses that have been advertised with ADD_ADDR.

The other two patches are unrelated improvements.

Patches 1-4: Add the 'C' flag feature, a sysctl to optionally enable it,
and a selftest.

Patch 5: Adjust rp_filter settings in a selftest.

Patch 6: Improve rbuf cleanup for MPTCP sockets.
====================

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

Documentation/networking/mptcp-sysctl.rst

@@ -32,3 +32,16 @@ checksum_enabled - BOOLEAN
 	per-namespace sysctl.
 
 	Default: 0
+
+allow_join_initial_addr_port - BOOLEAN
+	Allow peers to send join requests to the IP address and port number used
+	by the initial subflow if the value is 1. This controls a flag that is
+	sent to the peer at connection time, and whether such join requests are
+	accepted or denied.
+
+	Joins to addresses advertised with ADD_ADDR are not affected by this
+	value.
+
+	This is a per-namespace sysctl.
+
+	Default: 1

include/net/mptcp.h

@@ -67,7 +67,8 @@ struct mptcp_out_options {
 	u8 backup;
 	u8 reset_reason:4,
 	   reset_transient:1,
-	   csum_reqd:1;
+	   csum_reqd:1,
+	   allow_join_id0:1;
 	u32 nonce;
 	u64 thmac;
 	u32 token;

net/mptcp/ctrl.c

@@ -24,6 +24,7 @@ struct mptcp_pernet {
 	u8 mptcp_enabled;
 	unsigned int add_addr_timeout;
 	u8 checksum_enabled;
+	u8 allow_join_initial_addr_port;
 };
 
 static struct mptcp_pernet *mptcp_get_pernet(struct net *net)
@@ -46,11 +47,17 @@ int mptcp_is_checksum_enabled(struct net *net)
 	return mptcp_get_pernet(net)->checksum_enabled;
 }
 
+int mptcp_allow_join_id0(struct net *net)
+{
+	return mptcp_get_pernet(net)->allow_join_initial_addr_port;
+}
+
 static void mptcp_pernet_set_defaults(struct mptcp_pernet *pernet)
 {
 	pernet->mptcp_enabled = 1;
 	pernet->add_addr_timeout = TCP_RTO_MAX;
 	pernet->checksum_enabled = 0;
+	pernet->allow_join_initial_addr_port = 1;
 }
 
 #ifdef CONFIG_SYSCTL
@@ -80,6 +87,14 @@ static struct ctl_table mptcp_sysctl_table[] = {
 		.extra1       = SYSCTL_ZERO,
 		.extra2       = SYSCTL_ONE
 	},
+	{
+		.procname = "allow_join_initial_addr_port",
+		.maxlen = sizeof(u8),
+		.mode = 0644,
+		.proc_handler = proc_dou8vec_minmax,
+		.extra1       = SYSCTL_ZERO,
+		.extra2       = SYSCTL_ONE
+	},
 	{}
 };
 
@@ -98,6 +113,7 @@ static int mptcp_pernet_new_table(struct net *net, struct mptcp_pernet *pernet)
 	table[0].data = &pernet->mptcp_enabled;
 	table[1].data = &pernet->add_addr_timeout;
 	table[2].data = &pernet->checksum_enabled;
+	table[3].data = &pernet->allow_join_initial_addr_port;
 
 	hdr = register_net_sysctl(net, MPTCP_SYSCTL_PATH, table);
 	if (!hdr)

net/mptcp/options.c

@@ -83,6 +83,9 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 		if (flags & MPTCP_CAP_CHECKSUM_REQD)
 			mp_opt->csum_reqd = 1;
 
+		if (flags & MPTCP_CAP_DENY_JOIN_ID0)
+			mp_opt->deny_join_id0 = 1;
+
 		mp_opt->mp_capable = 1;
 		if (opsize >= TCPOLEN_MPTCP_MPC_SYNACK) {
 			mp_opt->sndr_key = get_unaligned_be64(ptr);
@@ -360,6 +363,7 @@ void mptcp_get_options(const struct sock *sk,
 	mp_opt->mp_prio = 0;
 	mp_opt->reset = 0;
 	mp_opt->csum_reqd = READ_ONCE(msk->csum_enabled);
+	mp_opt->deny_join_id0 = 0;
 
 	length = (th->doff * 4) - sizeof(struct tcphdr);
 	ptr = (const unsigned char *)(th + 1);
@@ -402,6 +406,7 @@ bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
 	if (subflow->request_mptcp) {
 		opts->suboptions = OPTION_MPTCP_MPC_SYN;
 		opts->csum_reqd = mptcp_is_checksum_enabled(sock_net(sk));
+		opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk));
 		*size = TCPOLEN_MPTCP_MPC_SYN;
 		return true;
 	} else if (subflow->request_join) {
@@ -490,6 +495,7 @@ static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
 		opts->sndr_key = subflow->local_key;
 		opts->rcvr_key = subflow->remote_key;
 		opts->csum_reqd = READ_ONCE(msk->csum_enabled);
+		opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk));
 
 		/* Section 3.1.
 		 * The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK
@@ -827,6 +833,7 @@ bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
 		opts->suboptions = OPTION_MPTCP_MPC_SYNACK;
 		opts->sndr_key = subflow_req->local_key;
 		opts->csum_reqd = subflow_req->csum_reqd;
+		opts->allow_join_id0 = subflow_req->allow_join_id0;
 		*size = TCPOLEN_MPTCP_MPC_SYNACK;
 		pr_debug("subflow_req=%p, local_key=%llu",
 			 subflow_req, subflow_req->local_key);
@@ -905,6 +912,9 @@ static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
 		return false;
 	}
 
+	if (mp_opt->deny_join_id0)
+		WRITE_ONCE(msk->pm.remote_deny_join_id0, true);
+
 	if (unlikely(!READ_ONCE(msk->pm.server_side)))
 		pr_warn_once("bogus mpc option on established client sk");
 	mptcp_subflow_fully_established(subflow, mp_opt);
@@ -1201,6 +1211,9 @@ void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
 		if (opts->csum_reqd)
 			flag |= MPTCP_CAP_CHECKSUM_REQD;
 
+		if (!opts->allow_join_id0)
+			flag |= MPTCP_CAP_DENY_JOIN_ID0;
+
 		*ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len,
 				      MPTCP_SUPPORTED_VERSION,
 				      flag);

net/mptcp/pm.c

@@ -320,6 +320,7 @@ void mptcp_pm_data_init(struct mptcp_sock *msk)
 	WRITE_ONCE(msk->pm.addr_signal, 0);
 	WRITE_ONCE(msk->pm.accept_addr, false);
 	WRITE_ONCE(msk->pm.accept_subflow, false);
+	WRITE_ONCE(msk->pm.remote_deny_join_id0, false);
 	msk->pm.status = 0;
 
 	spin_lock_init(&msk->pm.lock);

net/mptcp/pm_netlink.c

@@ -451,7 +451,8 @@ static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk)
 
 	/* check if should create a new subflow */
 	if (msk->pm.local_addr_used < local_addr_max &&
-	    msk->pm.subflows < subflows_max) {
+	    msk->pm.subflows < subflows_max &&
+	    !READ_ONCE(msk->pm.remote_deny_join_id0)) {
 		local = select_local_address(pernet, msk);
 		if (local) {
 			struct mptcp_addr_info remote = { 0 };

net/mptcp/protocol.c

@@ -442,49 +442,46 @@ static void mptcp_send_ack(struct mptcp_sock *msk)
 	}
 }
 
-static bool mptcp_subflow_cleanup_rbuf(struct sock *ssk)
+static void mptcp_subflow_cleanup_rbuf(struct sock *ssk)
 {
 	bool slow;
-	int ret;
 
 	slow = lock_sock_fast(ssk);
-	ret = tcp_can_send_ack(ssk);
-	if (ret)
+	if (tcp_can_send_ack(ssk))
 		tcp_cleanup_rbuf(ssk, 1);
 	unlock_sock_fast(ssk, slow);
-	return ret;
+}
+
+static bool mptcp_subflow_could_cleanup(const struct sock *ssk, bool rx_empty)
+{
+	const struct inet_connection_sock *icsk = inet_csk(ssk);
+	bool ack_pending = READ_ONCE(icsk->icsk_ack.pending);
+	const struct tcp_sock *tp = tcp_sk(ssk);
+
+	return (ack_pending & ICSK_ACK_SCHED) &&
+		((READ_ONCE(tp->rcv_nxt) - READ_ONCE(tp->rcv_wup) >
+		  READ_ONCE(icsk->icsk_ack.rcv_mss)) ||
+		 (rx_empty && ack_pending &
+			      (ICSK_ACK_PUSHED2 | ICSK_ACK_PUSHED)));
 }
 
 static void mptcp_cleanup_rbuf(struct mptcp_sock *msk)
 {
-	struct sock *ack_hint = READ_ONCE(msk->ack_hint);
 	int old_space = READ_ONCE(msk->old_wspace);
 	struct mptcp_subflow_context *subflow;
 	struct sock *sk = (struct sock *)msk;
-	bool cleanup;
+	int space =  __mptcp_space(sk);
+	bool cleanup, rx_empty;
 
-	/* this is a simple superset of what tcp_cleanup_rbuf() implements
-	 * so that we don't have to acquire the ssk socket lock most of the time
-	 * to do actually nothing
-	 */
-	cleanup = __mptcp_space(sk) - old_space >= max(0, old_space);
-	if (!cleanup)
-		return;
+	cleanup = (space > 0) && (space >= (old_space << 1));
+	rx_empty = !atomic_read(&sk->sk_rmem_alloc);
 
-	/* if the hinted ssk is still active, try to use it */
-	if (likely(ack_hint)) {
-		mptcp_for_each_subflow(msk, subflow) {
-			struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
 
-			if (ack_hint == ssk && mptcp_subflow_cleanup_rbuf(ssk))
-				return;
-		}
+		if (cleanup || mptcp_subflow_could_cleanup(ssk, rx_empty))
+			mptcp_subflow_cleanup_rbuf(ssk);
 	}
-
-	/* otherwise pick the first active subflow */
-	mptcp_for_each_subflow(msk, subflow)
-		if (mptcp_subflow_cleanup_rbuf(mptcp_subflow_tcp_sock(subflow)))
-			return;
 }
 
 static bool mptcp_check_data_fin(struct sock *sk)
@@ -629,7 +626,6 @@ static bool __mptcp_move_skbs_from_subflow(struct mptcp_sock *msk,
 			break;
 		}
 	} while (more_data_avail);
-	WRITE_ONCE(msk->ack_hint, ssk);
 
 	*bytes += moved;
 	return done;
@@ -1910,7 +1906,6 @@ static bool __mptcp_move_skbs(struct mptcp_sock *msk)
 		__mptcp_update_rmem(sk);
 		done = __mptcp_move_skbs_from_subflow(msk, ssk, &moved);
 		mptcp_data_unlock(sk);
-		tcp_cleanup_rbuf(ssk, moved);
 
 		if (unlikely(ssk->sk_err))
 			__mptcp_error_report(sk);
@@ -1926,7 +1921,6 @@ static bool __mptcp_move_skbs(struct mptcp_sock *msk)
 		ret |= __mptcp_ofo_queue(msk);
 		__mptcp_splice_receive_queue(sk);
 		mptcp_data_unlock(sk);
-		mptcp_cleanup_rbuf(msk);
 	}
 	if (ret)
 		mptcp_check_data_fin((struct sock *)msk);
@@ -2175,9 +2169,6 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
 	if (ssk == msk->last_snd)
 		msk->last_snd = NULL;
 
-	if (ssk == msk->ack_hint)
-		msk->ack_hint = NULL;
-
 	if (ssk == msk->first)
 		msk->first = NULL;
 
@@ -2392,7 +2383,6 @@ static int __mptcp_init_sock(struct sock *sk)
 	msk->rmem_released = 0;
 	msk->tx_pending_data = 0;
 
-	msk->ack_hint = NULL;
 	msk->first = NULL;
 	inet_csk(sk)->icsk_sync_mss = mptcp_sync_mss;
 	WRITE_ONCE(msk->csum_enabled, mptcp_is_checksum_enabled(sock_net(sk)));

net/mptcp/protocol.h

@@ -79,8 +79,9 @@
 #define MPTCP_VERSION_MASK	(0x0F)
 #define MPTCP_CAP_CHECKSUM_REQD	BIT(7)
 #define MPTCP_CAP_EXTENSIBILITY	BIT(6)
+#define MPTCP_CAP_DENY_JOIN_ID0	BIT(5)
 #define MPTCP_CAP_HMAC_SHA256	BIT(0)
-#define MPTCP_CAP_FLAG_MASK	(0x3F)
+#define MPTCP_CAP_FLAG_MASK	(0x1F)
 
 /* MPTCP DSS flags */
 #define MPTCP_DSS_DATA_FIN	BIT(4)
@@ -137,7 +138,8 @@ struct mptcp_options_received {
 		mp_prio : 1,
 		echo : 1,
 		csum_reqd : 1,
-		backup : 1;
+		backup : 1,
+		deny_join_id0 : 1;
 	u32	token;
 	u32	nonce;
 	u64	thmac;
@@ -192,6 +194,7 @@ struct mptcp_pm_data {
 	bool		work_pending;
 	bool		accept_addr;
 	bool		accept_subflow;
+	bool		remote_deny_join_id0;
 	u8		add_addr_signaled;
 	u8		add_addr_accepted;
 	u8		local_addr_used;
@@ -240,7 +243,6 @@ struct mptcp_sock {
 	bool		use_64bit_ack; /* Set when we received a 64-bit DSN */
 	bool		csum_enabled;
 	spinlock_t	join_list_lock;
-	struct sock	*ack_hint;
 	struct work_struct work;
 	struct sk_buff  *ooo_last_skb;
 	struct rb_root  out_of_order_queue;
@@ -350,7 +352,8 @@ struct mptcp_subflow_request_sock {
 	u16	mp_capable : 1,
 		mp_join : 1,
 		backup : 1,
-		csum_reqd : 1;
+		csum_reqd : 1,
+		allow_join_id0 : 1;
 	u8	local_id;
 	u8	remote_id;
 	u64	local_key;
@@ -540,6 +543,7 @@ static inline void mptcp_subflow_delegated_done(struct mptcp_subflow_context *su
 int mptcp_is_enabled(struct net *net);
 unsigned int mptcp_get_add_addr_timeout(struct net *net);
 int mptcp_is_checksum_enabled(struct net *net);
+int mptcp_allow_join_id0(struct net *net);
 void mptcp_subflow_fully_established(struct mptcp_subflow_context *subflow,
 				     struct mptcp_options_received *mp_opt);
 bool mptcp_subflow_data_available(struct sock *sk);

net/mptcp/subflow.c

@@ -109,6 +109,7 @@ static void subflow_init_req(struct request_sock *req, const struct sock *sk_lis
 	subflow_req->mp_capable = 0;
 	subflow_req->mp_join = 0;
 	subflow_req->csum_reqd = mptcp_is_checksum_enabled(sock_net(sk_listener));
+	subflow_req->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk_listener));
 	subflow_req->msk = NULL;
 	mptcp_token_init_request(req);
 }
@@ -407,6 +408,8 @@ static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
 
 		if (mp_opt.csum_reqd)
 			WRITE_ONCE(mptcp_sk(parent)->csum_enabled, true);
+		if (mp_opt.deny_join_id0)
+			WRITE_ONCE(mptcp_sk(parent)->pm.remote_deny_join_id0, true);
 		subflow->mp_capable = 1;
 		subflow->can_ack = 1;
 		subflow->remote_key = mp_opt.sndr_key;