1·It means that for attackers there exists a way of constructing network datagrams that contain wrong data.
它指的是攻击者有办法构造包含错误数据的网络数据报。
2·Specify the network interface for outgoing multicast datagrams sent on this socket.
指定向此套接字上发送多播数据报的网络接口。
3·Before a host computer can send IP datagrams beyond its directly attached subnet, it must discover the address of at least one router on that subnet.
在主机可以向其直接连接的子网外发送IP数据报之前，主机必须至少在该子网上发现一个路由器的地址。