mptcp: add the incoming MP_PRIO support

This patch added the incoming MP_PRIO logic:

Added a flag named mp_prio in struct mptcp_options_received, to mark the
MP_PRIO is received, and save the priority value to struct
mptcp_options_received's backup member. Then invoke
mptcp_pm_mp_prio_received with the receiving subsocket and the backup
value.

In mptcp_pm_mp_prio_received, get the subflow context according the input
subsocket, and change the subflow's backup as the incoming priority value.
Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/mptcp/options.c

@@ -282,6 +282,15 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 		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;
@@ -313,6 +322,7 @@ void mptcp_get_options(const struct sk_buff *skb,
 	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);
@@ -1022,6 +1032,11 @@ void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
 		mp_opt.rm_addr = 0;
 	}
 
+	if (mp_opt.mp_prio) {
+		mptcp_pm_mp_prio_received(sk, mp_opt.backup);
+		mp_opt.mp_prio = 0;
+	}
+
 	if (!mp_opt.dss)
 		return;
 

net/mptcp/pm.c

@@ -207,6 +207,14 @@ void mptcp_pm_rm_addr_received(struct mptcp_sock *msk, u8 rm_id)
 	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/protocol.h

@@ -88,6 +88,9 @@
 #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
 #define MPTCP_NOSPACE		1
@@ -118,6 +121,7 @@ struct mptcp_options_received {
 		dss : 1,
 		add_addr : 1,
 		rm_addr : 1,
+		mp_prio : 1,
 		family : 4,
 		echo : 1,
 		backup : 1;
@@ -553,6 +557,7 @@ void mptcp_pm_add_addr_received(struct mptcp_sock *msk,
 				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);