s = format (s, "SPAN: mirrored %U -> %U",
format_vnet_sw_if_index_name, vnm, t->src_sw_if_index,
format_vnet_sw_if_index_name, vnm, t->mirror_sw_if_index);
s = format (s, "SPAN: mirrored %U -> %U",
format_vnet_sw_if_index_name, vnm, t->src_sw_if_index,
format_vnet_sw_if_index_name, vnm, t->mirror_sw_if_index);