1 files changed, 264 insertions, 198 deletions

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index 7adcbc1f7d49..c41273cefc51 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -81,12 +81,11 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 		 * is if both hosts in their SYNs set A=0."
 		 */
 		if (flags & MPTCP_CAP_CHECKSUM_REQD)
-			mp_opt->csum_reqd = 1;
+			mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
 
-		if (flags & MPTCP_CAP_DENY_JOIN_ID0)
-			mp_opt->deny_join_id0 = 1;
+		mp_opt->deny_join_id0 = !!(flags & MPTCP_CAP_DENY_JOIN_ID0);
 
-		mp_opt->mp_capable = 1;
+		mp_opt->suboptions |= OPTIONS_MPTCP_MPC;
 		if (opsize >= TCPOLEN_MPTCP_MPC_SYNACK) {
 			mp_opt->sndr_key = get_unaligned_be64(ptr);
 			ptr += 8;
@@ -101,7 +100,7 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 			 * equivalent to those in a DSS option and can be used
 			 * interchangeably."
 			 */
-			mp_opt->dss = 1;
+			mp_opt->suboptions |= OPTION_MPTCP_DSS;
 			mp_opt->use_map = 1;
 			mp_opt->mpc_map = 1;
 			mp_opt->data_len = get_unaligned_be16(ptr);
@@ -109,7 +108,7 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 		}
 		if (opsize == TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM) {
 			mp_opt->csum = (__force __sum16)get_unaligned_be16(ptr);
-			mp_opt->csum_reqd = 1;
+			mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
 			ptr += 2;
 		}
 		pr_debug("MP_CAPABLE version=%x, flags=%x, optlen=%d sndr=%llu, rcvr=%llu len=%d csum=%u",
@@ -118,7 +117,7 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 		break;
 
 	case MPTCPOPT_MP_JOIN:
-		mp_opt->mp_join = 1;
+		mp_opt->suboptions |= OPTIONS_MPTCP_MPJ;
 		if (opsize == TCPOLEN_MPTCP_MPJ_SYN) {
 			mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
 			mp_opt->join_id = *ptr++;
@@ -144,7 +143,7 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 			memcpy(mp_opt->hmac, ptr, MPTCPOPT_HMAC_LEN);
 			pr_debug("MP_JOIN hmac");
 		} else {
-			mp_opt->mp_join = 0;
+			mp_opt->suboptions &= ~OPTIONS_MPTCP_MPJ;
 		}
 		break;
 
@@ -192,8 +191,7 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 		    opsize != expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM)
 			break;
 
-		mp_opt->dss = 1;
-
+		mp_opt->suboptions |= OPTION_MPTCP_DSS;
 		if (mp_opt->use_ack) {
 			if (mp_opt->ack64) {
 				mp_opt->data_ack = get_unaligned_be64(ptr);
@@ -222,14 +220,15 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 			ptr += 2;
 
 			if (opsize == expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM) {
-				mp_opt->csum_reqd = 1;
+				mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
 				mp_opt->csum = (__force __sum16)get_unaligned_be16(ptr);
 				ptr += 2;
 			}
 
 			pr_debug("data_seq=%llu subflow_seq=%u data_len=%u csum=%d:%u",
 				 mp_opt->data_seq, mp_opt->subflow_seq,
-				 mp_opt->data_len, mp_opt->csum_reqd, mp_opt->csum);
+				 mp_opt->data_len, !!(mp_opt->suboptions & OPTION_MPTCP_CSUMREQD),
+				 mp_opt->csum);
 		}
 
 		break;
@@ -260,8 +259,10 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 				break;
 		}
 
-		mp_opt->add_addr = 1;
+		mp_opt->suboptions |= OPTION_MPTCP_ADD_ADDR;
 		mp_opt->addr.id = *ptr++;
+		mp_opt->addr.port = 0;
+		mp_opt->ahmac = 0;
 		if (mp_opt->addr.family == AF_INET) {
 			memcpy((u8 *)&mp_opt->addr.addr.s_addr, (u8 *)ptr, 4);
 			ptr += 4;
@@ -298,7 +299,7 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 
 		ptr++;
 
-		mp_opt->rm_addr = 1;
+		mp_opt->suboptions |= OPTION_MPTCP_RM_ADDR;
 		mp_opt->rm_list.nr = opsize - TCPOLEN_MPTCP_RM_ADDR_BASE;
 		for (i = 0; i < mp_opt->rm_list.nr; i++)
 			mp_opt->rm_list.ids[i] = *ptr++;
@@ -309,7 +310,7 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 		if (opsize != TCPOLEN_MPTCP_PRIO)
 			break;
 
-		mp_opt->mp_prio = 1;
+		mp_opt->suboptions |= OPTION_MPTCP_PRIO;
 		mp_opt->backup = *ptr++ & MPTCP_PRIO_BKUP;
 		pr_debug("MP_PRIO: prio=%d", mp_opt->backup);
 		break;
@@ -321,7 +322,7 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 		ptr += 2;
 		mp_opt->rcvr_key = get_unaligned_be64(ptr);
 		ptr += 8;
-		mp_opt->fastclose = 1;
+		mp_opt->suboptions |= OPTION_MPTCP_FASTCLOSE;
 		break;
 
 	case MPTCPOPT_RST:
@@ -330,12 +331,23 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 
 		if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST))
 			break;
-		mp_opt->reset = 1;
+
+		mp_opt->suboptions |= OPTION_MPTCP_RST;
 		flags = *ptr++;
 		mp_opt->reset_transient = flags & MPTCP_RST_TRANSIENT;
 		mp_opt->reset_reason = *ptr;
 		break;
 
+	case MPTCPOPT_MP_FAIL:
+		if (opsize != TCPOLEN_MPTCP_FAIL)
+			break;
+
+		ptr += 2;
+		mp_opt->suboptions |= OPTION_MPTCP_FAIL;
+		mp_opt->fail_seq = get_unaligned_be64(ptr);
+		pr_debug("MP_FAIL: data_seq=%llu", mp_opt->fail_seq);
+		break;
+
 	default:
 		break;
 	}
@@ -345,25 +357,12 @@ void mptcp_get_options(const struct sock *sk,
 		       const struct sk_buff *skb,
 		       struct mptcp_options_received *mp_opt)
 {
-	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
-	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 	const struct tcphdr *th = tcp_hdr(skb);
 	const unsigned char *ptr;
 	int length;
 
 	/* initialize option status */
-	mp_opt->mp_capable = 0;
-	mp_opt->mp_join = 0;
-	mp_opt->add_addr = 0;
-	mp_opt->ahmac = 0;
-	mp_opt->fastclose = 0;
-	mp_opt->addr.port = 0;
-	mp_opt->rm_addr = 0;
-	mp_opt->dss = 0;
-	mp_opt->mp_prio = 0;
-	mp_opt->reset = 0;
-	mp_opt->csum_reqd = READ_ONCE(msk->csum_enabled);
-	mp_opt->deny_join_id0 = 0;
+	mp_opt->suboptions = 0;
 
 	length = (th->doff * 4) - sizeof(struct tcphdr);
 	ptr = (const unsigned char *)(th + 1);
@@ -592,6 +591,7 @@ static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
 		dss_size = map_size;
 		if (skb && snd_data_fin_enable)
 			mptcp_write_data_fin(subflow, skb, &opts->ext_copy);
+		opts->suboptions = OPTION_MPTCP_DSS;
 		ret = true;
 	}
 
@@ -615,6 +615,7 @@ static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
 		opts->ext_copy.ack64 = 0;
 	}
 	opts->ext_copy.use_ack = 1;
+	opts->suboptions = OPTION_MPTCP_DSS;
 	WRITE_ONCE(msk->old_wspace, __mptcp_space((struct sock *)msk));
 
 	/* Add kind/length/subtype/flag overhead if mapping is not populated */
@@ -667,29 +668,34 @@ static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff *
 	bool port;
 	int len;
 
-	if ((mptcp_pm_should_add_signal_ipv6(msk) ||
-	     mptcp_pm_should_add_signal_port(msk) ||
-	     mptcp_pm_should_add_signal_echo(msk)) &&
-	    skb && skb_is_tcp_pure_ack(skb)) {
-		pr_debug("drop other suboptions");
-		opts->suboptions = 0;
-		opts->ext_copy.use_ack = 0;
-		opts->ext_copy.use_map = 0;
-		remaining += opt_size;
-		drop_other_suboptions = true;
-	}
-
+	/* add addr will strip the existing options, be sure to avoid breaking
+	 * MPC/MPJ handshakes
+	 */
 	if (!mptcp_pm_should_add_signal(msk) ||
-	    !(mptcp_pm_add_addr_signal(msk, remaining, &opts->addr, &echo, &port)))
+	    (opts->suboptions & (OPTION_MPTCP_MPJ_ACK | OPTION_MPTCP_MPC_ACK)) ||
+	    !mptcp_pm_add_addr_signal(msk, skb, opt_size, remaining, &opts->addr,
+		    &echo, &port, &drop_other_suboptions))
 		return false;
 
+	if (drop_other_suboptions)
+		remaining += opt_size;
 	len = mptcp_add_addr_len(opts->addr.family, echo, port);
 	if (remaining < len)
 		return false;
 
 	*size = len;
-	if (drop_other_suboptions)
+	if (drop_other_suboptions) {
+		pr_debug("drop other suboptions");
+		opts->suboptions = 0;
+
+		/* note that e.g. DSS could have written into the memory
+		 * aliased by ahmac, we must reset the field here
+		 * to avoid appending the hmac even for ADD_ADDR echo
+		 * options
+		 */
+		opts->ahmac = 0;
 		*size -= opt_size;
+	}
 	opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
 	if (!echo) {
 		opts->ahmac = add_addr_generate_hmac(msk->local_key,
@@ -739,7 +745,12 @@ static bool mptcp_established_options_mp_prio(struct sock *sk,
 {
 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 
-	if (!subflow->send_mp_prio)
+	/* can't send MP_PRIO with MPC, as they share the same option space:
+	 * 'backup'. Also it makes no sense at all
+	 */
+	if (!subflow->send_mp_prio ||
+	    ((OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_SYNACK |
+	      OPTION_MPTCP_MPC_ACK) & opts->suboptions))
 		return false;
 
 	/* account for the trailing 'nop' option */
@@ -755,7 +766,7 @@ static bool mptcp_established_options_mp_prio(struct sock *sk,
 	return true;
 }
 
-static noinline void mptcp_established_options_rst(struct sock *sk, struct sk_buff *skb,
+static noinline bool mptcp_established_options_rst(struct sock *sk, struct sk_buff *skb,
 						   unsigned int *size,
 						   unsigned int remaining,
 						   struct mptcp_out_options *opts)
@@ -763,12 +774,36 @@ static noinline void mptcp_established_options_rst(struct sock *sk, struct sk_bu
 	const struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 
 	if (remaining < TCPOLEN_MPTCP_RST)
-		return;
+		return false;
 
 	*size = TCPOLEN_MPTCP_RST;
 	opts->suboptions |= OPTION_MPTCP_RST;
 	opts->reset_transient = subflow->reset_transient;
 	opts->reset_reason = subflow->reset_reason;
+
+	return true;
+}
+
+static bool mptcp_established_options_mp_fail(struct sock *sk,
+					      unsigned int *size,
+					      unsigned int remaining,
+					      struct mptcp_out_options *opts)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+
+	if (likely(!subflow->send_mp_fail))
+		return false;
+
+	if (remaining < TCPOLEN_MPTCP_FAIL)
+		return false;
+
+	*size = TCPOLEN_MPTCP_FAIL;
+	opts->suboptions |= OPTION_MPTCP_FAIL;
+	opts->fail_seq = subflow->map_seq;
+
+	pr_debug("MP_FAIL fail_seq=%llu", opts->fail_seq);
+
+	return true;
 }
 
 bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
@@ -787,15 +822,28 @@ bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 		return false;
 
 	if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST)) {
-		mptcp_established_options_rst(sk, skb, size, remaining, opts);
+		if (mptcp_established_options_mp_fail(sk, &opt_size, remaining, opts)) {
+			*size += opt_size;
+			remaining -= opt_size;
+		}
+		if (mptcp_established_options_rst(sk, skb, &opt_size, remaining, opts)) {
+			*size += opt_size;
+			remaining -= opt_size;
+		}
 		return true;
 	}
 
 	snd_data_fin = mptcp_data_fin_enabled(msk);
 	if (mptcp_established_options_mp(sk, skb, snd_data_fin, &opt_size, remaining, opts))
 		ret = true;
-	else if (mptcp_established_options_dss(sk, skb, snd_data_fin, &opt_size, remaining, opts))
+	else if (mptcp_established_options_dss(sk, skb, snd_data_fin, &opt_size, remaining, opts)) {
 		ret = true;
+		if (mptcp_established_options_mp_fail(sk, &opt_size, remaining, opts)) {
+			*size += opt_size;
+			remaining -= opt_size;
+			return true;
+		}
+	}
 
 	/* we reserved enough space for the above options, and exceeding the
 	 * TCP option space would be fatal
@@ -868,7 +916,7 @@ static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
 		 */
 		if (TCP_SKB_CB(skb)->seq == subflow->ssn_offset + 1 &&
 		    TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq &&
-		    subflow->mp_join && mp_opt->mp_join &&
+		    subflow->mp_join && (mp_opt->suboptions & OPTIONS_MPTCP_MPJ) &&
 		    READ_ONCE(msk->pm.server_side))
 			tcp_send_ack(ssk);
 		goto fully_established;
@@ -885,8 +933,8 @@ static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
 		return subflow->mp_capable;
 	}
 
-	if ((mp_opt->dss && mp_opt->use_ack) ||
-	    (mp_opt->add_addr && !mp_opt->echo)) {
+	if (((mp_opt->suboptions & OPTION_MPTCP_DSS) && mp_opt->use_ack) ||
+	    ((mp_opt->suboptions & OPTION_MPTCP_ADD_ADDR) && !mp_opt->echo)) {
 		/* subflows are fully established as soon as we get any
 		 * additional ack, including ADD_ADDR.
 		 */
@@ -899,7 +947,7 @@ static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
 	 * then fallback to TCP. Fallback scenarios requires a reset for
 	 * MP_JOIN subflows.
 	 */
-	if (!mp_opt->mp_capable) {
+	if (!(mp_opt->suboptions & OPTIONS_MPTCP_MPC)) {
 		if (subflow->mp_join)
 			goto reset;
 		subflow->mp_capable = 0;
@@ -971,9 +1019,11 @@ static void ack_update_msk(struct mptcp_sock *msk,
 	old_snd_una = msk->snd_una;
 	new_snd_una = mptcp_expand_seq(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
 
-	/* ACK for data not even sent yet? Ignore. */
-	if (after64(new_snd_una, snd_nxt))
-		new_snd_una = old_snd_una;
+	/* ACK for data not even sent yet and even above recovery bound? Ignore.*/
+	if (unlikely(after64(new_snd_una, snd_nxt))) {
+		if (!msk->recovery || after64(new_snd_una, msk->recovery_snd_nxt))
+			new_snd_una = old_snd_una;
+	}
 
 	new_wnd_end = new_snd_una + tcp_sk(ssk)->snd_wnd;
 
@@ -1061,48 +1111,51 @@ bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
 	if (!check_fully_established(msk, sk, subflow, skb, &mp_opt))
 		return sk->sk_state != TCP_CLOSE;
 
-	if (mp_opt.fastclose &&
-	    msk->local_key == mp_opt.rcvr_key) {
-		WRITE_ONCE(msk->rcv_fastclose, true);
-		mptcp_schedule_work((struct sock *)msk);
-	}
+	if (unlikely(mp_opt.suboptions != OPTION_MPTCP_DSS)) {
+		if ((mp_opt.suboptions & OPTION_MPTCP_FASTCLOSE) &&
+		    msk->local_key == mp_opt.rcvr_key) {
+			WRITE_ONCE(msk->rcv_fastclose, true);
+			mptcp_schedule_work((struct sock *)msk);
+		}
 
-	if (mp_opt.add_addr && add_addr_hmac_valid(msk, &mp_opt)) {
-		if (!mp_opt.echo) {
-			mptcp_pm_add_addr_received(msk, &mp_opt.addr);
-			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDR);
-		} else {
-			mptcp_pm_add_addr_echoed(msk, &mp_opt.addr);
-			mptcp_pm_del_add_timer(msk, &mp_opt.addr, true);
-			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADD);
+		if ((mp_opt.suboptions & OPTION_MPTCP_ADD_ADDR) &&
+		    add_addr_hmac_valid(msk, &mp_opt)) {
+			if (!mp_opt.echo) {
+				mptcp_pm_add_addr_received(msk, &mp_opt.addr);
+				MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDR);
+			} else {
+				mptcp_pm_add_addr_echoed(msk, &mp_opt.addr);
+				mptcp_pm_del_add_timer(msk, &mp_opt.addr, true);
+				MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADD);
+			}
+
+			if (mp_opt.addr.port)
+				MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_PORTADD);
 		}
 
-		if (mp_opt.addr.port)
-			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_PORTADD);
+		if (mp_opt.suboptions & OPTION_MPTCP_RM_ADDR)
+			mptcp_pm_rm_addr_received(msk, &mp_opt.rm_list);
 
-		mp_opt.add_addr = 0;
-	}
+		if (mp_opt.suboptions & OPTION_MPTCP_PRIO) {
+			mptcp_pm_mp_prio_received(sk, mp_opt.backup);
+			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPPRIORX);
+		}
 
-	if (mp_opt.rm_addr) {
-		mptcp_pm_rm_addr_received(msk, &mp_opt.rm_list);
-		mp_opt.rm_addr = 0;
-	}
+		if (mp_opt.suboptions & OPTION_MPTCP_FAIL) {
+			mptcp_pm_mp_fail_received(sk, mp_opt.fail_seq);
+			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFAILRX);
+		}
 
-	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.suboptions & OPTION_MPTCP_RST) {
+			subflow->reset_seen = 1;
+			subflow->reset_reason = mp_opt.reset_reason;
+			subflow->reset_transient = mp_opt.reset_transient;
+		}
 
-	if (mp_opt.reset) {
-		subflow->reset_seen = 1;
-		subflow->reset_reason = mp_opt.reset_reason;
-		subflow->reset_transient = mp_opt.reset_transient;
+		if (!(mp_opt.suboptions & OPTION_MPTCP_DSS))
+			return true;
 	}
 
-	if (!mp_opt.dss)
-		return true;
-
 	/* we can't wait for recvmsg() to update the ack_seq, otherwise
 	 * monodirectional flows will stuck
 	 */
@@ -1129,7 +1182,7 @@ bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
 
 	memset(mpext, 0, sizeof(*mpext));
 
-	if (mp_opt.use_map) {
+	if (likely(mp_opt.use_map)) {
 		if (mp_opt.mpc_map) {
 			/* this is an MP_CAPABLE carrying MPTCP data
 			 * we know this map the first chunk of data
@@ -1149,7 +1202,7 @@ bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
 		}
 		mpext->data_len = mp_opt.data_len;
 		mpext->use_map = 1;
-		mpext->csum_reqd = mp_opt.csum_reqd;
+		mpext->csum_reqd = !!(mp_opt.suboptions & OPTION_MPTCP_CSUMREQD);
 
 		if (mpext->csum_reqd)
 			mpext->csum = mp_opt.csum;
@@ -1196,8 +1249,88 @@ static u16 mptcp_make_csum(const struct mptcp_ext *mpext)
 void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
 			 struct mptcp_out_options *opts)
 {
-	if ((OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_SYNACK |
-	     OPTION_MPTCP_MPC_ACK) & opts->suboptions) {
+	if (unlikely(OPTION_MPTCP_FAIL & opts->suboptions)) {
+		const struct sock *ssk = (const struct sock *)tp;
+		struct mptcp_subflow_context *subflow;
+
+		subflow = mptcp_subflow_ctx(ssk);
+		subflow->send_mp_fail = 0;
+
+		*ptr++ = mptcp_option(MPTCPOPT_MP_FAIL,
+				      TCPOLEN_MPTCP_FAIL,
+				      0, 0);
+		put_unaligned_be64(opts->fail_seq, ptr);
+		ptr += 2;
+	}
+
+	/* RST is mutually exclusive with everything else */
+	if (unlikely(OPTION_MPTCP_RST & opts->suboptions)) {
+		*ptr++ = mptcp_option(MPTCPOPT_RST,
+				      TCPOLEN_MPTCP_RST,
+				      opts->reset_transient,
+				      opts->reset_reason);
+		return;
+	}
+
+	/* DSS, MPC, MPJ and ADD_ADDR are mutually exclusive, see
+	 * mptcp_established_options*()
+	 */
+	if (likely(OPTION_MPTCP_DSS & opts->suboptions)) {
+		struct mptcp_ext *mpext = &opts->ext_copy;
+		u8 len = TCPOLEN_MPTCP_DSS_BASE;
+		u8 flags = 0;
+
+		if (mpext->use_ack) {
+			flags = MPTCP_DSS_HAS_ACK;
+			if (mpext->ack64) {
+				len += TCPOLEN_MPTCP_DSS_ACK64;
+				flags |= MPTCP_DSS_ACK64;
+			} else {
+				len += TCPOLEN_MPTCP_DSS_ACK32;
+			}
+		}
+
+		if (mpext->use_map) {
+			len += TCPOLEN_MPTCP_DSS_MAP64;
+
+			/* Use only 64-bit mapping flags for now, add
+			 * support for optional 32-bit mappings later.
+			 */
+			flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
+			if (mpext->data_fin)
+				flags |= MPTCP_DSS_DATA_FIN;
+
+			if (opts->csum_reqd)
+				len += TCPOLEN_MPTCP_DSS_CHECKSUM;
+		}
+
+		*ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags);
+
+		if (mpext->use_ack) {
+			if (mpext->ack64) {
+				put_unaligned_be64(mpext->data_ack, ptr);
+				ptr += 2;
+			} else {
+				put_unaligned_be32(mpext->data_ack32, ptr);
+				ptr += 1;
+			}
+		}
+
+		if (mpext->use_map) {
+			put_unaligned_be64(mpext->data_seq, ptr);
+			ptr += 2;
+			put_unaligned_be32(mpext->subflow_seq, ptr);
+			ptr += 1;
+			if (opts->csum_reqd) {
+				put_unaligned_be32(mpext->data_len << 16 |
+						   mptcp_make_csum(mpext), ptr);
+			} else {
+				put_unaligned_be32(mpext->data_len << 16 |
+						   TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
+			}
+		}
+	} else if ((OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_SYNACK |
+		    OPTION_MPTCP_MPC_ACK) & opts->suboptions) {
 		u8 len, flag = MPTCP_CAP_HMAC_SHA256;
 
 		if (OPTION_MPTCP_MPC_SYN & opts->suboptions) {
@@ -1244,10 +1377,31 @@ void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
 					   TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
 		}
 		ptr += 1;
-	}
 
-mp_capable_done:
-	if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
+		/* MPC is additionally mutually exclusive with MP_PRIO */
+		goto mp_capable_done;
+	} else if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
+		*ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
+				      TCPOLEN_MPTCP_MPJ_SYN,
+				      opts->backup, opts->join_id);
+		put_unaligned_be32(opts->token, ptr);
+		ptr += 1;
+		put_unaligned_be32(opts->nonce, ptr);
+		ptr += 1;
+	} else if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
+		*ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
+				      TCPOLEN_MPTCP_MPJ_SYNACK,
+				      opts->backup, opts->join_id);
+		put_unaligned_be64(opts->thmac, ptr);
+		ptr += 2;
+		put_unaligned_be32(opts->nonce, ptr);
+		ptr += 1;
+	} else if (OPTION_MPTCP_MPJ_ACK & opts->suboptions) {
+		*ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
+				      TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
+		memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
+		ptr += 5;
+	} else if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
 		u8 len = TCPOLEN_MPTCP_ADD_ADDR_BASE;
 		u8 echo = MPTCP_ADDR_ECHO;
 
@@ -1305,6 +1459,19 @@ mp_capable_done:
 		}
 	}
 
+	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);
+	}
+
+mp_capable_done:
 	if (OPTION_MPTCP_RM_ADDR & opts->suboptions) {
 		u8 i = 1;
 
@@ -1325,107 +1492,6 @@ mp_capable_done:
 		}
 	}
 
-	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) {
-		*ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
-				      TCPOLEN_MPTCP_MPJ_SYN,
-				      opts->backup, opts->join_id);
-		put_unaligned_be32(opts->token, ptr);
-		ptr += 1;
-		put_unaligned_be32(opts->nonce, ptr);
-		ptr += 1;
-	}
-
-	if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
-		*ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
-				      TCPOLEN_MPTCP_MPJ_SYNACK,
-				      opts->backup, opts->join_id);
-		put_unaligned_be64(opts->thmac, ptr);
-		ptr += 2;
-		put_unaligned_be32(opts->nonce, ptr);
-		ptr += 1;
-	}
-
-	if (OPTION_MPTCP_MPJ_ACK & opts->suboptions) {
-		*ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
-				      TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
-		memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
-		ptr += 5;
-	}
-
-	if (OPTION_MPTCP_RST & opts->suboptions)
-		*ptr++ = mptcp_option(MPTCPOPT_RST,
-				      TCPOLEN_MPTCP_RST,
-				      opts->reset_transient,
-				      opts->reset_reason);
-
-	if (opts->ext_copy.use_ack || opts->ext_copy.use_map) {
-		struct mptcp_ext *mpext = &opts->ext_copy;
-		u8 len = TCPOLEN_MPTCP_DSS_BASE;
-		u8 flags = 0;
-
-		if (mpext->use_ack) {
-			flags = MPTCP_DSS_HAS_ACK;
-			if (mpext->ack64) {
-				len += TCPOLEN_MPTCP_DSS_ACK64;
-				flags |= MPTCP_DSS_ACK64;
-			} else {
-				len += TCPOLEN_MPTCP_DSS_ACK32;
-			}
-		}
-
-		if (mpext->use_map) {
-			len += TCPOLEN_MPTCP_DSS_MAP64;
-
-			/* Use only 64-bit mapping flags for now, add
-			 * support for optional 32-bit mappings later.
-			 */
-			flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
-			if (mpext->data_fin)
-				flags |= MPTCP_DSS_DATA_FIN;
-
-			if (opts->csum_reqd)
-				len += TCPOLEN_MPTCP_DSS_CHECKSUM;
-		}
-
-		*ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags);
-
-		if (mpext->use_ack) {
-			if (mpext->ack64) {
-				put_unaligned_be64(mpext->data_ack, ptr);
-				ptr += 2;
-			} else {
-				put_unaligned_be32(mpext->data_ack32, ptr);
-				ptr += 1;
-			}
-		}
-
-		if (mpext->use_map) {
-			put_unaligned_be64(mpext->data_seq, ptr);
-			ptr += 2;
-			put_unaligned_be32(mpext->subflow_seq, ptr);
-			ptr += 1;
-			if (opts->csum_reqd) {
-				put_unaligned_be32(mpext->data_len << 16 |
-						   mptcp_make_csum(mpext), ptr);
-			} else {
-				put_unaligned_be32(mpext->data_len << 16 |
-						   TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
-			}
-		}
-	}
-
 	if (tp)
 		mptcp_set_rwin(tp);
 }