mctp: Implement extended addressing

This change allows an extended address struct - struct sockaddr_mctp_ext
- to be passed to sendmsg/recvmsg. This allows userspace to specify
output ifindex and physical address information (for sendmsg) or receive
the input ifindex/physaddr for incoming messages (for recvmsg). This is
typically used by userspace for MCTP address discovery and assignment
operations.

The extended addressing facility is conditional on a new sockopt:
MCTP_OPT_ADDR_EXT; userspace must explicitly enable addressing before
the kernel will consume/populate the extended address data.

Includes a fix for an uninitialised var:
Reported-by: kernel test robot <lkp@intel.com>

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

3 files changed, 21 insertions, 4 deletions

diff --git a/include/linux/socket.h b/include/linux/socket.h
index 7612d760b6a9..8ef26d89ef49 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -365,6 +365,7 @@ struct ucred {
 #define SOL_TLS		282
 #define SOL_XDP		283
 #define SOL_MPTCP	284
+#define SOL_MCTP	285
 
 /* IPX options */
 #define IPX_TYPE	1
diff --git a/include/net/mctp.h b/include/net/mctp.h
index 2a83443bdfac..23bec708f4c7 100644
--- a/include/net/mctp.h
+++ b/include/net/mctp.h
@@ -11,6 +11,7 @@
 
 #include <linux/bits.h>
 #include <linux/mctp.h>
+#include <linux/netdevice.h>
 #include <net/net_namespace.h>
 #include <net/sock.h>
 
@@ -58,6 +59,9 @@ struct mctp_sock {
 	mctp_eid_t	bind_addr;
 	__u8		bind_type;
 
+	/* sendmsg()/recvmsg() uses struct sockaddr_mctp_ext */
+	bool		addr_ext;
+
 	/* list of mctp_sk_key, for incoming tag lookup. updates protected
 	 * by sk->net->keys_lock
 	 */
@@ -153,7 +157,10 @@ struct mctp_sk_key {
 struct mctp_skb_cb {
 	unsigned int	magic;
 	unsigned int	net;
+	int		ifindex; /* extended/direct addressing if set */
 	mctp_eid_t	src;
+	unsigned char	halen;
+	unsigned char	haddr[MAX_ADDR_LEN];
 };
 
 /* skb control-block accessors with a little extra debugging for initial
@@ -177,6 +184,7 @@ static inline struct mctp_skb_cb *mctp_cb(struct sk_buff *skb)
 {
 	struct mctp_skb_cb *cb = (void *)skb->cb;
 
+	BUILD_BUG_ON(sizeof(struct mctp_skb_cb) > sizeof(skb->cb));
 	WARN_ON(cb->magic != 0x4d435450);
 	return (void *)(skb->cb);
 }
@@ -189,8 +197,7 @@ static inline struct mctp_skb_cb *mctp_cb(struct sk_buff *skb)
  *
  * 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.
+ * caller cannot block between mctp_route_lookup and mctp_route_release()
  */
 struct mctp_route {
 	mctp_eid_t		min, max;
@@ -210,8 +217,6 @@ struct mctp_route {
 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);
 
diff --git a/include/uapi/linux/mctp.h b/include/uapi/linux/mctp.h
index 6acd4ccafbf7..07b0318716fc 100644
--- a/include/uapi/linux/mctp.h
+++ b/include/uapi/linux/mctp.h
@@ -11,6 +11,7 @@
 
 #include <linux/types.h>
 #include <linux/socket.h>
+#include <linux/netdevice.h>
 
 typedef __u8			mctp_eid_t;
 
@@ -28,6 +29,14 @@ struct sockaddr_mctp {
 	__u8			__smctp_pad1;
 };
 
+struct sockaddr_mctp_ext {
+	struct sockaddr_mctp	smctp_base;
+	int			smctp_ifindex;
+	__u8			smctp_halen;
+	__u8			__smctp_pad0[3];
+	__u8			smctp_haddr[MAX_ADDR_LEN];
+};
+
 #define MCTP_NET_ANY		0x0
 
 #define MCTP_ADDR_NULL		0x00
@@ -36,4 +45,6 @@ struct sockaddr_mctp {
 #define MCTP_TAG_MASK		0x07
 #define MCTP_TAG_OWNER		0x08
 
+#define MCTP_OPT_ADDR_EXT	1
+
 #endif /* __UAPI_MCTP_H */