MEDIUM: protocol: use a family array to index the protocol handlers

Instead of walking over a list, we now have a direct mapping between
protocol families and their respective handlers. This will allow fast
lookups.
diff --git a/include/proto/protocol.h b/include/proto/protocol.h
index 1842faf..13a3c0a 100644
--- a/include/proto/protocol.h
+++ b/include/proto/protocol.h
@@ -22,8 +22,11 @@
 #ifndef _PROTO_PROTOCOL_H
 #define _PROTO_PROTOCOL_H
 
+#include <sys/socket.h>
 #include <types/protocol.h>
 
+extern struct protocol *__protocol_by_family[AF_MAX];
+
 /* Registers the protocol <proto> */
 void protocol_register(struct protocol *proto);
 
@@ -51,7 +54,12 @@
 int protocol_enable_all(void);
 
 /* returns the protocol associated to family <family> or NULL if not found */
-struct protocol *protocol_by_family(int family);
+static inline struct protocol *protocol_by_family(int family)
+{
+	if (family >= 0 && family < AF_MAX)
+		return __protocol_by_family[family];
+	return NULL;
+}
 
 #endif /* _PROTO_PROTOCOL_H */
 
diff --git a/src/protocol.c b/src/protocol.c
index 84d23da..3caccb6 100644
--- a/src/protocol.c
+++ b/src/protocol.c
@@ -10,6 +10,8 @@
  *
  */
 
+#include <sys/socket.h>
+
 #include <common/config.h>
 #include <common/errors.h>
 #include <common/mini-clist.h>
@@ -19,11 +21,14 @@
 
 /* List head of all registered protocols */
 static struct list protocols = LIST_HEAD_INIT(protocols);
+struct protocol *__protocol_by_family[AF_MAX] = { };
 
 /* Registers the protocol <proto> */
 void protocol_register(struct protocol *proto)
 {
 	LIST_ADDQ(&protocols, &proto->list);
+	if (proto->sock_domain >= 0 && proto->sock_domain < AF_MAX)
+		__protocol_by_family[proto->sock_domain] = proto;
 }
 
 /* Unregisters the protocol <proto>. Note that all listeners must have
@@ -109,18 +114,6 @@
 	return err;
 }
 
-/* Returns the protocol handler for socket family <family> or NULL if not found */
-struct protocol *protocol_by_family(int family)
-{
-	struct protocol *proto;
-
-	list_for_each_entry(proto, &protocols, list) {
-		if (proto->sock_domain == family)
-			return proto;
-	}
-	return NULL;
-}
-
 /*
  * Local variables:
  *  c-indent-level: 8