mctp: Add device handling and netlink interface

This change adds the infrastructure for managing MCTP netdevices; we add
a pointer to the AF_MCTP-specific data to struct netdevice, and hook up
the rtnetlink operations for adding and removing addresses.

Includes changes from Matt Johnston <matt@codeconstruct.com.au>.

Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -11039,6 +11039,7 @@ L:	netdev@vger.kernel.org
 S:	Maintained
 F:	drivers/net/mctp/
 F:	include/net/mctp.h
+F:	include/net/mctpdevice.h
 F:	net/mctp/
 
 MAN-PAGES: MANUAL PAGES FOR LINUX -- Sections 2, 3, 4, 5, and 7

include/linux/netdevice.h

@@ -1823,6 +1823,7 @@ enum netdev_ml_priv_type {
  *	@ieee802154_ptr: IEEE 802.15.4 low-rate Wireless Personal Area Network
  *			 device struct
  *	@mpls_ptr:	mpls_dev struct pointer
+ *	@mctp_ptr:	MCTP specific data
  *
  *	@dev_addr:	Hw address (before bcast,
  *			because most packets are unicast)
@@ -2110,6 +2111,9 @@ struct net_device {
 #if IS_ENABLED(CONFIG_MPLS_ROUTING)
 	struct mpls_dev __rcu	*mpls_ptr;
 #endif
+#if IS_ENABLED(CONFIG_MCTP)
+	struct mctp_dev __rcu	*mctp_ptr;
+#endif
 
 /*
  * Cache lines mostly used on receive path (including eth_type_trans())

include/net/mctp.h

@@ -10,6 +10,7 @@
 #define __NET_MCTP_H
 
 #include <linux/bits.h>
+#include <linux/mctp.h>
 
 /* MCTP packet definitions */
 struct mctp_hdr {
@@ -32,4 +33,17 @@ struct mctp_hdr {
 #define MCTP_HDR_TAG_SHIFT	0
 #define MCTP_HDR_TAG_MASK	GENMASK(2, 0)
 
+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);
+}
+
+void mctp_device_init(void);
+void mctp_device_exit(void);
+
 #endif /* __NET_MCTP_H */

include/net/mctpdevice.h

@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Management Component Transport Protocol (MCTP) - device
+ * definitions.
+ *
+ * Copyright (c) 2021 Code Construct
+ * Copyright (c) 2021 Google
+ */
+
+#ifndef __NET_MCTPDEVICE_H
+#define __NET_MCTPDEVICE_H
+
+#include <linux/list.h>
+#include <linux/types.h>
+#include <linux/refcount.h>
+
+struct mctp_dev {
+	struct net_device	*dev;
+
+	unsigned int		net;
+
+	/* Only modified under RTNL. Reads have addrs_lock held */
+	u8			*addrs;
+	size_t			num_addrs;
+	spinlock_t		addrs_lock;
+
+	struct rcu_head		rcu;
+};
+
+#define MCTP_INITIAL_DEFAULT_NET	1
+
+struct mctp_dev *mctp_dev_get_rtnl(const struct net_device *dev);
+struct mctp_dev *__mctp_dev_get(const struct net_device *dev);
+
+#endif /* __NET_MCTPDEVICE_H */

include/uapi/linux/if_ether.h

@@ -151,6 +151,9 @@
 #define ETH_P_MAP	0x00F9		/* Qualcomm multiplexing and
 					 * aggregation protocol
 					 */
+#define ETH_P_MCTP	0x00FA		/* Management component transport
+					 * protocol packets
+					 */
 
 /*
  *	This is an Ethernet frame header.

include/uapi/linux/if_link.h

@@ -1260,4 +1260,14 @@ struct ifla_rmnet_flags {
 	__u32	mask;
 };
 
+/* MCTP section */
+
+enum {
+	IFLA_MCTP_UNSPEC,
+	IFLA_MCTP_NET,
+	__IFLA_MCTP_MAX,
+};
+
+#define IFLA_MCTP_MAX (__IFLA_MCTP_MAX - 1)
+
 #endif /* _UAPI_LINUX_IF_LINK_H */

include/uapi/linux/mctp.h

@@ -26,6 +26,7 @@ struct sockaddr_mctp {
 };
 
 #define MCTP_NET_ANY		0x0
+#define MCTP_NET_DEFAULT	0x0
 
 #define MCTP_ADDR_NULL		0x00
 #define MCTP_ADDR_ANY		0xff

net/mctp/Makefile

@@ -1,3 +1,3 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_MCTP) += mctp.o
-mctp-objs := af_mctp.o
+mctp-objs := af_mctp.o device.o

net/mctp/af_mctp.c

@@ -6,13 +6,18 @@
  * Copyright (c) 2021 Google
  */
 
+#include <linux/if_arp.h>
 #include <linux/net.h>
 #include <linux/mctp.h>
 #include <linux/module.h>
 #include <linux/socket.h>
 
+#include <net/mctp.h>
+#include <net/mctpdevice.h>
 #include <net/sock.h>
 
+/* socket implementation */
+
 struct mctp_sock {
 	struct sock	sk;
 };
@@ -152,6 +157,8 @@ static __init int mctp_init(void)
 	if (rc)
 		goto err_unreg_sock;
 
+	mctp_device_init();
+
 	return 0;
 
 err_unreg_sock:
@@ -162,6 +169,7 @@ static __init int mctp_init(void)
 
 static __exit void mctp_exit(void)
 {
+	mctp_device_exit();
 	proto_unregister(&mctp_proto);
 	sock_unregister(PF_MCTP);
 }