Merge branch 'mptcp-part-two'

Christoph Paasch says:

====================
Multipath TCP part 2: Single subflow & RFC8684 support

v2 -> v3: Added RFC8684-style handshake (see below fore more details) and some minor fixes
v1 -> v2: Rebased on latest "Multipath TCP: Prerequisites" v3 series

This set adds MPTCP connection establishment, writing & reading MPTCP
options on data packets, a sysctl to allow MPTCP per-namespace, and self
tests. This is sufficient to establish and maintain a connection with a
MPTCP peer, but will not yet allow or initiate establishment of
additional MPTCP subflows.

We also add the necessary code for the RFC8684-style handshake.
RFC8684 obsoletes the experimental RFC6824 and makes MPTCP move-on to
version 1.

Originally our plan was to submit single-subflow and RFC8684 support in
two patchsets, but to simplify the merging-process and ensure that a coherent
MPTCP-version lands in Linux we decided to merge the two sets into a single
one.

The MPTCP patchset exclusively supports RFC 8684. Although all MPTCP
deployments are currently based on RFC 6824, future deployments will be
migrating to MPTCP version 1. 3GPP's 5G standardization also solely supports
RFC 8684. In addition, we believe that this initial submission of MPTCP will be
cleaner by solely supporting RFC 8684. If later on support for the old
MPTCP-version is required it can always be added in the future.

The major difference between RFC 8684 and RFC 6824 is that it has a better
support for servers using TCP SYN-cookies by reliably retransmitting the
MP_CAPABLE option.

Before ending this cover letter with some refs, it is worth mentioning
that we promise David Miller that merging this series will be rewarded by
Twitter dopamine hits :-D

Clone/fetch:
https://github.com/multipath-tcp/mptcp_net-next.git (tag: netdev-v3-part2)

Browse:
https://github.com/multipath-tcp/mptcp_net-next/tree/netdev-v3-part2

Thank you for your review. You can find us at mptcp@lists.01.org and
https://is.gd/mptcp_upstream
====================

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

1 files changed, 104 insertions, 1 deletions

diff --git a/include/net/mptcp.h b/include/net/mptcp.h
index 0573ae75c3db..27627e2d1bc2 100644
--- a/include/net/mptcp.h
+++ b/include/net/mptcp.h
@@ -9,6 +9,7 @@
 #define __NET_MPTCP_H
 
 #include <linux/skbuff.h>
+#include <linux/tcp.h>
 #include <linux/types.h>
 
 /* MPTCP sk_buff extension data */
@@ -22,12 +23,49 @@ struct mptcp_ext {
 			data_fin:1,
 			use_ack:1,
 			ack64:1,
-			__unused:3;
+			mpc_map:1,
+			__unused:2;
 	/* one byte hole */
 };
 
+struct mptcp_out_options {
+#if IS_ENABLED(CONFIG_MPTCP)
+	u16 suboptions;
+	u64 sndr_key;
+	u64 rcvr_key;
+	struct mptcp_ext ext_copy;
+#endif
+};
+
 #ifdef CONFIG_MPTCP
 
+void mptcp_init(void);
+
+static inline bool sk_is_mptcp(const struct sock *sk)
+{
+	return tcp_sk(sk)->is_mptcp;
+}
+
+static inline bool rsk_is_mptcp(const struct request_sock *req)
+{
+	return tcp_rsk(req)->is_mptcp;
+}
+
+void mptcp_parse_option(const struct sk_buff *skb, const unsigned char *ptr,
+			int opsize, struct tcp_options_received *opt_rx);
+bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
+		       unsigned int *size, struct mptcp_out_options *opts);
+void mptcp_rcv_synsent(struct sock *sk);
+bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
+			  struct mptcp_out_options *opts);
+bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
+			       unsigned int *size, unsigned int remaining,
+			       struct mptcp_out_options *opts);
+void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb,
+			    struct tcp_options_received *opt_rx);
+
+void mptcp_write_options(__be32 *ptr, struct mptcp_out_options *opts);
+
 /* move the skb extension owership, with the assumption that 'to' is
  * newly allocated
  */
@@ -70,6 +108,59 @@ static inline bool mptcp_skb_can_collapse(const struct sk_buff *to,
 
 #else
 
+static inline void mptcp_init(void)
+{
+}
+
+static inline bool sk_is_mptcp(const struct sock *sk)
+{
+	return false;
+}
+
+static inline bool rsk_is_mptcp(const struct request_sock *req)
+{
+	return false;
+}
+
+static inline void mptcp_parse_option(const struct sk_buff *skb,
+				      const unsigned char *ptr, int opsize,
+				      struct tcp_options_received *opt_rx)
+{
+}
+
+static inline bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
+				     unsigned int *size,
+				     struct mptcp_out_options *opts)
+{
+	return false;
+}
+
+static inline void mptcp_rcv_synsent(struct sock *sk)
+{
+}
+
+static inline bool mptcp_synack_options(const struct request_sock *req,
+					unsigned int *size,
+					struct mptcp_out_options *opts)
+{
+	return false;
+}
+
+static inline bool mptcp_established_options(struct sock *sk,
+					     struct sk_buff *skb,
+					     unsigned int *size,
+					     unsigned int remaining,
+					     struct mptcp_out_options *opts)
+{
+	return false;
+}
+
+static inline void mptcp_incoming_options(struct sock *sk,
+					  struct sk_buff *skb,
+					  struct tcp_options_received *opt_rx)
+{
+}
+
 static inline void mptcp_skb_ext_move(struct sk_buff *to,
 				      const struct sk_buff *from)
 {
@@ -82,4 +173,16 @@ static inline bool mptcp_skb_can_collapse(const struct sk_buff *to,
 }
 
 #endif /* CONFIG_MPTCP */
+
+void mptcp_handle_ipv6_mapped(struct sock *sk, bool mapped);
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+int mptcpv6_init(void);
+#elif IS_ENABLED(CONFIG_IPV6)
+static inline int mptcpv6_init(void)
+{
+	return 0;
+}
+#endif
+
 #endif /* __NET_MPTCP_H */