1 files changed, 231 insertions, 0 deletions
diff --git a/include/net/mctp.h b/include/net/mctp.h
new file mode 100644
index 000000000000..54bbe042c973
--- /dev/null
+++ b/include/net/mctp.h
@@ -0,0 +1,231 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Management Component Transport Protocol (MCTP)
+ *
+ * Copyright (c) 2021 Code Construct
+ * Copyright (c) 2021 Google
+ */
+
+#ifndef __NET_MCTP_H
+#define __NET_MCTP_H
+
+#include <linux/bits.h>
+#include <linux/mctp.h>
+#include <net/net_namespace.h>
+#include <net/sock.h>
+
+/* MCTP packet definitions */
+struct mctp_hdr {
+	u8	ver;
+	u8	dest;
+	u8	src;
+	u8	flags_seq_tag;
+};
+
+#define MCTP_VER_MIN	1
+#define MCTP_VER_MAX	1
+
+/* Definitions for flags_seq_tag field */
+#define MCTP_HDR_FLAG_SOM	BIT(7)
+#define MCTP_HDR_FLAG_EOM	BIT(6)
+#define MCTP_HDR_FLAG_TO	BIT(3)
+#define MCTP_HDR_FLAGS		GENMASK(5, 3)
+#define MCTP_HDR_SEQ_SHIFT	4
+#define MCTP_HDR_SEQ_MASK	GENMASK(1, 0)
+#define MCTP_HDR_TAG_SHIFT	0
+#define MCTP_HDR_TAG_MASK	GENMASK(2, 0)
+
+#define MCTP_HEADER_MAXLEN	4
+
+#define MCTP_INITIAL_DEFAULT_NET	1
+
+static inline bool mctp_address_ok(mctp_eid_t eid)
+{
+	return eid >= 8 && eid < 255;
+}
+
+static inline struct mctp_hdr *mctp_hdr(struct sk_buff *skb)
+{
+	return (struct mctp_hdr *)skb_network_header(skb);
+}
+
+/* socket implementation */
+struct mctp_sock {
+	struct sock	sk;
+
+	/* bind() params */
+	int		bind_net;
+	mctp_eid_t	bind_addr;
+	__u8		bind_type;
+
+	/* list of mctp_sk_key, for incoming tag lookup. updates protected
+	 * by sk->net->keys_lock
+	 */
+	struct hlist_head keys;
+};
+
+/* Key for matching incoming packets to sockets or reassembly contexts.
+ * Packets are matched on (src,dest,tag).
+ *
+ * Lifetime requirements:
+ *
+ *  - keys are free()ed via RCU
+ *
+ *  - a mctp_sk_key contains a reference to a struct sock; this is valid
+ *    for the life of the key. On sock destruction (through unhash), the key is
+ *    removed from lists (see below), and will not be observable after a RCU
+ *    grace period.
+ *
+ *    any RX occurring within that grace period may still queue to the socket,
+ *    but will hit the SOCK_DEAD case before the socket is freed.
+ *
+ * - these mctp_sk_keys appear on two lists:
+ *     1) the struct mctp_sock->keys list
+ *     2) the struct netns_mctp->keys list
+ *
+ *        updates to either list are performed under the netns_mctp->keys
+ *        lock.
+ *
+ * - a key may have a sk_buff attached as part of an in-progress message
+ *   reassembly (->reasm_head). The reassembly context is protected by
+ *   reasm_lock, which may be acquired with the keys lock (above) held, if
+ *   necessary. Consequently, keys lock *cannot* be acquired with the
+ *   reasm_lock held.
+ *
+ * - there are two destruction paths for a mctp_sk_key:
+ *
+ *    - through socket unhash (see mctp_sk_unhash). This performs the list
+ *      removal under keys_lock.
+ *
+ *    - where a key is established to receive a reply message: after receiving
+ *      the (complete) reply, or during reassembly errors. Here, we clean up
+ *      the reassembly context (marking reasm_dead, to prevent another from
+ *      starting), and remove the socket from the netns & socket lists.
+ */
+struct mctp_sk_key {
+	mctp_eid_t	peer_addr;
+	mctp_eid_t	local_addr;
+	__u8		tag; /* incoming tag match; invert TO for local */
+
+	/* we hold a ref to sk when set */
+	struct sock	*sk;
+
+	/* routing lookup list */
+	struct hlist_node hlist;
+
+	/* per-socket list */
+	struct hlist_node sklist;
+
+	/* incoming fragment reassembly context */
+	spinlock_t	reasm_lock;
+	struct sk_buff	*reasm_head;
+	struct sk_buff	**reasm_tailp;
+	bool		reasm_dead;
+	u8		last_seq;
+
+	struct rcu_head	rcu;
+};
+
+struct mctp_skb_cb {
+	unsigned int	magic;
+	unsigned int	net;
+	mctp_eid_t	src;
+};
+
+/* skb control-block accessors with a little extra debugging for initial
+ * development.
+ *
+ * TODO: remove checks & mctp_skb_cb->magic; replace callers of __mctp_cb
+ * with mctp_cb().
+ *
+ * __mctp_cb() is only for the initial ingress code; we should see ->magic set
+ * at all times after this.
+ */
+static inline struct mctp_skb_cb *__mctp_cb(struct sk_buff *skb)
+{
+	struct mctp_skb_cb *cb = (void *)skb->cb;
+
+	cb->magic = 0x4d435450;
+	return cb;
+}
+
+static inline struct mctp_skb_cb *mctp_cb(struct sk_buff *skb)
+{
+	struct mctp_skb_cb *cb = (void *)skb->cb;
+
+	WARN_ON(cb->magic != 0x4d435450);
+	return (void *)(skb->cb);
+}
+
+/* Route definition.
+ *
+ * These are held in the pernet->mctp.routes list, with RCU protection for
+ * removed routes. We hold a reference to the netdev; routes need to be
+ * dropped on NETDEV_UNREGISTER events.
+ *
+ * Updates to the route table are performed under rtnl; all reads under RCU,
+ * so routes cannot be referenced over a RCU grace period. Specifically: A
+ * caller cannot block between mctp_route_lookup and passing the route to
+ * mctp_do_route.
+ */
+struct mctp_route {
+	mctp_eid_t		min, max;
+
+	struct mctp_dev		*dev;
+	unsigned int		mtu;
+	int			(*output)(struct mctp_route *route,
+					  struct sk_buff *skb);
+
+	struct list_head	list;
+	refcount_t		refs;
+	struct rcu_head		rcu;
+};
+
+/* route interfaces */
+struct mctp_route *mctp_route_lookup(struct net *net, unsigned int dnet,
+				     mctp_eid_t daddr);
+
+int mctp_do_route(struct mctp_route *rt, struct sk_buff *skb);
+
+int mctp_local_output(struct sock *sk, struct mctp_route *rt,
+		      struct sk_buff *skb, mctp_eid_t daddr, u8 req_tag);
+
+/* routing <--> device interface */
+unsigned int mctp_default_net(struct net *net);
+int mctp_default_net_set(struct net *net, unsigned int index);
+int mctp_route_add_local(struct mctp_dev *mdev, mctp_eid_t addr);
+int mctp_route_remove_local(struct mctp_dev *mdev, mctp_eid_t addr);
+void mctp_route_remove_dev(struct mctp_dev *mdev);
+
+/* neighbour definitions */
+enum mctp_neigh_source {
+	MCTP_NEIGH_STATIC,
+	MCTP_NEIGH_DISCOVER,
+};
+
+struct mctp_neigh {
+	struct mctp_dev		*dev;
+	mctp_eid_t		eid;
+	enum mctp_neigh_source	source;
+
+	unsigned char		ha[MAX_ADDR_LEN];
+
+	struct list_head	list;
+	struct rcu_head		rcu;
+};
+
+int mctp_neigh_init(void);
+void mctp_neigh_exit(void);
+
+// ret_hwaddr may be NULL, otherwise must have space for MAX_ADDR_LEN
+int mctp_neigh_lookup(struct mctp_dev *dev, mctp_eid_t eid,
+		      void *ret_hwaddr);
+void mctp_neigh_remove_dev(struct mctp_dev *mdev);
+
+int mctp_routes_init(void);
+void mctp_routes_exit(void);
+
+void mctp_device_init(void);
+void mctp_device_exit(void);
+
+#endif /* __NET_MCTP_H */