code: async function searchPrevRoutes(target) {
      const connNames = await listConnectionNames();
      const ret = [];
      for (const connName of connNames) {
          const cmd = [
              'nmcli', '-f', 'IP4.ROUTE', 'connection', 'show', connName,
          ];
          const output = await executeCommand(cmd);
          for (const line of output.split('\n')) {
              const exs = `dst\\s*=\\s*${target},\\snh\\s*=\\s*([\\d\.]+)`;
              const re = line.match(new RegExp(exs));
              if (!re) {
                  continue;
              }
              ret.push({
                  connName: connName,
                  target: target,
                  gatewayIP: re[1],
              });
          }
      }
      return ret;
  }
docs: Search previous route from NetworkManager
  @param {string} target : the destination network or host. e.g. 224.0.23.0/32
  @return {Array.<object>} Return list of previous route setting