[http] Support HTTP redirection

src/net/tcp/http.c

 static int http_response_to_rc ( unsigned int response ) {
 	switch ( response ) {
 	case 200:
+	case 301:
+	case 302:
 		return 0;
 	case 404:
 		return -ENOENT;
 	return 0;
 }
 
+/**
+ * Handle HTTP Location header
+ *
+ * @v http		HTTP request
+ * @v value		HTTP header value
+ * @ret rc		Return status code
+ */
+static int http_rx_location ( struct http_request *http, const char *value ) {
+	int rc;
+
+	/* Redirect to new location */
+	DBGC ( http, "HTTP %p redirecting to %s\n", http, value );
+	if ( ( rc = xfer_redirect ( &http->xfer, LOCATION_URI_STRING,
+				    value ) ) != 0 ) {
+		DBGC ( http, "HTTP %p could not redirect: %s\n",
+		       http, strerror ( rc ) );
+		return rc;
+	}
+
+	return 0;
+}
+
 /**
  * Handle HTTP Content-Length header
  *
 
 /** List of HTTP header handlers */
 static struct http_header_handler http_header_handlers[] = {
+	{
+		.header = "Location",
+		.rx = http_rx_location,
+	},
 	{
 		.header = "Content-Length",
 		.rx = http_rx_content_length,