mctp: Add MCTP base

Add basic Kconfig, an initial (empty) af_mctp source object, and
{AF,PF}_MCTP definitions, and the required definitions for a new
protocol type.
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -11032,6 +11032,13 @@ F:	drivers/mailbox/arm_mhuv2.c
 F:	include/linux/mailbox/arm_mhuv2_message.h
 F:	Documentation/devicetree/bindings/mailbox/arm,mhuv2.yaml
 
+MANAGEMENT COMPONENT TRANSPORT PROTOCOL (MCTP)
+M:	Jeremy Kerr <jk@codeconstruct.com.au>
+M:	Matt Johnston <matt@codeconstruct.com.au>
+L:	netdev@vger.kernel.org
+S:	Maintained
+F:	net/mctp/
+
 MAN-PAGES: MANUAL PAGES FOR LINUX -- Sections 2, 3, 4, 5, and 7
 M:	Michael Kerrisk <mtk.manpages@gmail.com>
 L:	linux-man@vger.kernel.org

include/linux/socket.h

@@ -223,8 +223,11 @@ struct ucred {
 				 * reuses AF_INET address family
 				 */
 #define AF_XDP		44	/* XDP sockets			*/
+#define AF_MCTP		45	/* Management component
+				 * transport protocol
+				 */
 
-#define AF_MAX		45	/* For now.. */
+#define AF_MAX		46	/* For now.. */
 
 /* Protocol families, same as address families. */
 #define PF_UNSPEC	AF_UNSPEC
@@ -274,6 +277,7 @@ struct ucred {
 #define PF_QIPCRTR	AF_QIPCRTR
 #define PF_SMC		AF_SMC
 #define PF_XDP		AF_XDP
+#define PF_MCTP		AF_MCTP
 #define PF_MAX		AF_MAX
 
 /* Maximum queue length specifiable by listen.  */

include/uapi/linux/mctp.h

+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * Management Component Transport Protocol (MCTP)
+ *
+ * Copyright (c) 2021 Code Construct
+ * Copyright (c) 2021 Google
+ */
+
+#ifndef __UAPI_MCTP_H
+#define __UAPI_MCTP_H
+
+struct sockaddr_mctp {
+};
+
+#endif /* __UAPI_MCTP_H */

net/Kconfig

@@ -363,6 +363,7 @@ source "net/bluetooth/Kconfig"
 source "net/rxrpc/Kconfig"
 source "net/kcm/Kconfig"
 source "net/strparser/Kconfig"
+source "net/mctp/Kconfig"
 
 config FIB_RULES
 	bool

net/Makefile

@@ -78,3 +78,4 @@ obj-$(CONFIG_QRTR)		+= qrtr/
 obj-$(CONFIG_NET_NCSI)		+= ncsi/
 obj-$(CONFIG_XDP_SOCKETS)	+= xdp/
 obj-$(CONFIG_MPTCP)		+= mptcp/
+obj-$(CONFIG_MCTP)		+= mctp/

net/core/sock.c

@@ -226,6 +226,7 @@ static struct lock_class_key af_family_kern_slock_keys[AF_MAX];
   x "AF_IEEE802154",	x "AF_CAIF"	,	x "AF_ALG"      , \
   x "AF_NFC"   ,	x "AF_VSOCK"    ,	x "AF_KCM"      , \
   x "AF_QIPCRTR",	x "AF_SMC"	,	x "AF_XDP"	, \
+  x "AF_MCTP"  , \
   x "AF_MAX"
 
 static const char *const af_family_key_strings[AF_MAX+1] = {

net/mctp/Kconfig

+
+menuconfig MCTP
+	depends on NET
+	tristate "MCTP core protocol support"
+	help
+	  Management Component Transport Protocol (MCTP) is an in-system
+	  protocol for communicating between management controllers and
+	  their managed devices (peripherals, host processors, etc.). The
+	  protocol is defined by DMTF specification DSP0236.
+
+	  This option enables core MCTP support. For communicating with other
+	  devices, you'll want to enable a driver for a specific hardware
+	  channel.

net/mctp/Makefile

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

net/mctp/af_mctp.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Management Component Transport Protocol (MCTP)
+ *
+ * Copyright (c) 2021 Code Construct
+ * Copyright (c) 2021 Google
+ */
+
+#include <linux/module.h>
+
+MODULE_DESCRIPTION("MCTP core");
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Jeremy Kerr <jk@codeconstruct.com.au>");

net/socket.c

@@ -212,6 +212,7 @@ static const char * const pf_family_names[] = {
 	[PF_QIPCRTR]	= "PF_QIPCRTR",
 	[PF_SMC]	= "PF_SMC",
 	[PF_XDP]	= "PF_XDP",
+	[PF_MCTP]	= "PF_MCTP",
 };
 
 /*

security/selinux/hooks.c

@@ -1330,7 +1330,9 @@ static inline u16 socket_type_to_security_class(int family, int type, int protoc
 			return SECCLASS_SMC_SOCKET;
 		case PF_XDP:
 			return SECCLASS_XDP_SOCKET;
-#if PF_MAX > 45
+		case PF_MCTP:
+			return SECCLASS_MCTP_SOCKET;
+#if PF_MAX > 46
 #error New address family defined, please update this function.
 #endif
 		}

security/selinux/include/classmap.h

@@ -246,6 +246,8 @@ struct security_class_mapping secclass_map[] = {
 	    NULL } },
 	{ "xdp_socket",
 	  { COMMON_SOCK_PERMS, NULL } },
+	{ "mctp_socket",
+	  { COMMON_SOCK_PERMS, NULL } },
 	{ "perf_event",
 	  { "open", "cpu", "kernel", "tracepoint", "read", "write", NULL } },
 	{ "lockdown",
@@ -255,6 +257,6 @@ struct security_class_mapping secclass_map[] = {
 	{ NULL }
   };
 
-#if PF_MAX > 45
+#if PF_MAX > 46
 #error New address family defined, please update secclass_map.
 #endif