tipc: add framework for node capabilities exchange

The TIPC protocol spec has defined a 13 bit capability bitmap in
the neighbor discovery header, as a means to maintain compatibility
between different code and protocol generations. Until now this field
has been unused.

We now introduce the basic framework for exchanging capabilities
between nodes at first contact. After exchange, a peer node's
capabilities are stored as a 16 bit bitmap in struct tipc_node.
Reviewed-by: Erik Hugne <erik.hugne@ericsson.com>
Reviewed-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/discover.c

@@ -89,6 +89,7 @@ static void tipc_disc_init_msg(struct net *net, struct sk_buff *buf, u32 type,
 		      MAX_H_SIZE, dest_domain);
 	msg_set_non_seq(msg, 1);
 	msg_set_node_sig(msg, tn->random);
+	msg_set_node_capabilities(msg, 0);
 	msg_set_dest_domain(msg, dest_domain);
 	msg_set_bc_netid(msg, tn->net_id);
 	b_ptr->media->addr2msg(msg_media_addr(msg), &b_ptr->addr);
@@ -133,6 +134,7 @@ void tipc_disc_rcv(struct net *net, struct sk_buff *buf,
 	u32 net_id = msg_bc_netid(msg);
 	u32 mtyp = msg_type(msg);
 	u32 signature = msg_node_sig(msg);
+	u16 caps = msg_node_capabilities(msg);
 	bool addr_match = false;
 	bool sign_match = false;
 	bool link_up = false;
@@ -167,6 +169,7 @@ void tipc_disc_rcv(struct net *net, struct sk_buff *buf,
 	if (!node)
 		return;
 	tipc_node_lock(node);
+	node->capabilities = caps;
 	link = node->links[bearer->identity];
 
 	/* Prepare to validate requesting node's signature and media address */

net/tipc/msg.h

@@ -510,7 +510,6 @@ static inline struct tipc_msg *msg_get_wrapped(struct tipc_msg *m)
 #define DSC_REQ_MSG		0
 #define DSC_RESP_MSG		1
 
-
 /*
  * Word 1
  */
@@ -534,6 +533,16 @@ static inline void msg_set_node_sig(struct tipc_msg *m, u32 n)
 	msg_set_bits(m, 1, 0, 0xffff, n);
 }
 
+static inline u32 msg_node_capabilities(struct tipc_msg *m)
+{
+	return msg_bits(m, 1, 15, 0x1fff);
+}
+
+static inline void msg_set_node_capabilities(struct tipc_msg *m, u32 n)
+{
+	msg_set_bits(m, 1, 15, 0x1fff, n);
+}
+
 
 /*
  * Word 2

net/tipc/node.h

@@ -106,6 +106,7 @@ struct tipc_node_bclink {
  * @list: links to adjacent nodes in sorted list of cluster's nodes
  * @working_links: number of working links to node (both active and standby)
  * @link_cnt: number of links to node
+ * @capabilities: bitmap, indicating peer node's functional capabilities
  * @signature: node instance identifier
  * @link_id: local and remote bearer ids of changing link, if any
  * @publ_list: list of publications
@@ -125,7 +126,8 @@ struct tipc_node {
 	struct tipc_node_bclink bclink;
 	struct list_head list;
 	int link_cnt;
-	int working_links;
+	u16 working_links;
+	u16 capabilities;
 	u32 signature;
 	u32 link_id;
 	struct list_head publ_list;