[peerdist] Allow for the use of a hosted cache server

Allow a PeerDist hosted cache server to be specified via the
${peerhost} setting, e.g.:

  # Use 192.168.0.1 as hosted cache server
  set peerhost 192.168.0.1

Note that this simply treats the hosted cache server as a permanently
discovered peer for all segments.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/net/peerdisc.c

 #include <ipxe/netdevice.h>
 #include <ipxe/timer.h>
 #include <ipxe/fault.h>
+#include <ipxe/settings.h>
 #include <ipxe/pccrd.h>
 #include <ipxe/peerdisc.h>
 
  */
 unsigned int peerdisc_timeout_secs = PEERDISC_DEFAULT_TIMEOUT_SECS;
 
+/** Hosted cache server */
+static char *peerhost;
+
 static struct peerdisc_segment * peerdisc_find ( const char *id );
 static int peerdisc_discovered ( struct peerdisc_segment *segment,
 				 const char *location );
 	char *uuid_copy;
 	char *id_copy;
 	unsigned int i;
+	int rc;
 
 	/* Generate a random message UUID.  This does not require high
 	 * quality randomness.
 	/* Allocate and initialise structure */
 	segment = zalloc ( sizeof ( *segment ) + id_len + uuid_len );
 	if ( ! segment )
-		return NULL;
+		goto err_alloc;
 	id_copy = ( ( ( void * ) segment ) + sizeof ( *segment ) );
 	memcpy ( id_copy, id, id_len );
 	uuid_copy = ( ( ( void * ) id_copy ) + id_len );
 	INIT_LIST_HEAD ( &segment->peers );
 	INIT_LIST_HEAD ( &segment->clients );
 	timer_init ( &segment->timer, peerdisc_expired, &segment->refcnt );
-	DBGC2 ( segment, "PEERDISC %p discovering %s\n", segment, segment->id );
 
-	/* Start discovery timer */
-	start_timer_nodelay ( &segment->timer );
+	/* Add hosted cache server or initiate discovery */
+	if ( peerhost ) {
+
+		/* Add hosted cache server to list of peers */
+		if ( ( rc = peerdisc_discovered ( segment, peerhost ) ) != 0 )
+			goto err_peerhost;
+
+	} else {
+
+		/* Start discovery timer */
+		start_timer_nodelay ( &segment->timer );
+		DBGC2 ( segment, "PEERDISC %p discovering %s\n",
+			segment, segment->id );
+	}
 
 	/* Add to list of segments, transfer reference to list, and return */
 	list_add_tail ( &segment->list, &peerdisc_segments );
 	return segment;
+
+ err_peerhost:
+	ref_put ( &segment->refcnt );
+ err_alloc:
+	return NULL;
 }
 
 /**
 	if ( list_empty ( &peerdisc_segments ) )
 		peerdisc_socket_close ( 0 );
 }
+
+/******************************************************************************
+ *
+ * Settings
+ *
+ ******************************************************************************
+ */
+
+/** PeerDist hosted cache server setting */
+const struct setting peerhost_setting __setting ( SETTING_MISC, peerhost ) = {
+	.name = "peerhost",
+	.description = "PeerDist hosted cache",
+	.type = &setting_type_string,
+};
+
+/**
+ * Apply PeerDist discovery settings
+ *
+ * @ret rc		Return status code
+ */
+static int apply_peerdisc_settings ( void ) {
+
+	/* Free any existing hosted cache server */
+	free ( peerhost );
+	peerhost = NULL;
+
+	/* Fetch hosted cache server */
+	fetch_string_setting_copy ( NULL, &peerhost_setting, &peerhost );
+	if ( peerhost ) {
+		DBGC ( &peerhost, "PEERDISC using hosted cache %s\n",
+		       peerhost );
+	}
+
+	return 0;
+}
+
+/** PeerDist discovery settings applicator */
+struct settings_applicator peerdisc_applicator __settings_applicator = {
+	.apply = apply_peerdisc_settings,
+};