Add generic mechanism for background protocols (e.g. ARP, IGMP)

src/core/background.c

@@ -0,0 +1,47 @@
+#include "background.h"
+
+static struct background backgrounds[0] __table_start ( background );
+static struct background backgrounds_end[0] __table_end ( background );
+
+/** @file */
+
+/**
+ * Call send method of all background protocols
+ *
+ * @v timestamp		Current time
+ * @ret None		-
+ * @err None		-
+ *
+ * This calls each background protocol's background::send() method.
+ */
+void background_send ( unsigned long timestamp ) {
+	struct background *background;
+
+	for ( background = backgrounds ; background < backgrounds_end ;
+	      background++ ) {
+		if ( background->send )
+			background->send ( timestamp );
+	}
+}
+
+/**
+ * Call process method of all background protocols
+ *
+ * @v timestamp		Current time
+ * @v ptype		Packet type
+ * @v ip		IP header, if present
+ * @ret None		-
+ * @err None		-
+ *
+ * This calls each background protocol's background::process() method.
+ */
+void background_process ( unsigned long timestamp, unsigned short ptype,
+			  struct iphdr *ip ) {
+	struct background *background;
+
+	for ( background = backgrounds ; background < backgrounds_end ;
+	      background++ ) {
+		if ( background->process )
+			background->process ( timestamp, ptype, ip );
+	}
+}

src/include/background.h

@@ -0,0 +1,52 @@
+#ifndef BACKGROUND_H
+#define BACKGROUND_H
+
+/** @file
+ *
+ * Background protocols
+ *
+ * Some protocols (e.g. ARP, IGMP) operate in the background; the
+ * upper layers are not aware of their operation.  When an ARP query
+ * for the local station's IP address arrives, Etherboot must reply to
+ * it regardless of what other operations are currently in progress.
+ *
+ * Background protocols are called in two circumstances: when
+ * Etherboot is about to poll for a packet, and when Etherboot has
+ * received a packet that the upper layer (whatever that may currently
+ * be) isn't interested in.
+ *
+ */
+
+#include "tables.h"
+#include "ip.h"
+
+/** A background protocol */
+struct background {
+	/** Send method
+	 *
+	 * This method will be called whenever Etherboot is about to
+	 * poll for a packet.  The background protocol should use this
+	 * method to send out any periodic transmissions that it may
+	 * require.
+	 */
+	void ( *send ) ( unsigned long timestamp );
+	/** Process method
+	 *
+	 * This method will be called whenever Etherboot has received
+	 * a packet and doesn't know what to do with it.
+	 */
+	void ( *process ) ( unsigned long timestamp, unsigned short ptype,
+			    struct iphdr *ip );
+};
+
+/** A member of the background protocols table */
+#define __background __table ( background, 01 )
+
+/* Functions in background.c */
+
+extern void background_send ( unsigned long timestamp );
+
+extern void background_process ( unsigned long timestamp, unsigned short ptype,
+				 struct iphdr *ip );
+
+#endif /* BACKGROUND_H */