+/* We previously built the data-struct for the existing ARC chain, if any, using a headers
+feed from the DKIM module. Use that to give the instance number for the ARC set we are
+about to build. */
+
+DEBUG(D_transport)
+ if (arc_sign_ctx.arcset_chain_last)
+ debug_printf("ARC: existing chain highest instance: %d\n",
+ arc_sign_ctx.arcset_chain_last->instance);
+ else
+ debug_printf("ARC: no existing chain\n");
+
+instance = arc_sign_ctx.arcset_chain_last ? arc_sign_ctx.arcset_chain_last->instance + 1 : 1;
+