OpenBSD's PF packet filter 我加一点注释, 大伙看 …
Linux Socket Filtering aka Berkeley Packet Filter (BPF 2020-7-19 · The above example code attaches a socket filter for a PF_PACKET socket in order to let all IPv4/IPv6 packets with port 22 pass. The rest will be dropped for this socket. The setsockopt(2) call to SO_DETACH_FILTER doesn’t need any arguments and SO_LOCK_FILTER for preventing the filter to be detached, takes an integer value with 0 or 1. Packet Filter Rule Processing - Securing the Network in Packet Filter Rule Processing. PF processes the rules according to a "last match" policy, which means that the policy decision on a packet is determined by the last rule that matched the packet. This policy suggests that rules are best ordered from generally applicable rules first to more detailed match parameters later in the rule set.
One of Packet Filter's important abilities is "keeping state" or "stateful inspection". Stateful inspection refers to PF's ability to track the state, or progress, of a network connection. By storing information about each connection in a state table, PF is able to quickly determine if a packet passing through the firewall belongs to an already
linux 下的 包过滤器 BPF_xiahzp的专栏-CSDN博 … 2016-11-5 · 一， 导论 BPF（Berkeley Packet Filter）伯克利包过滤器。 是在linux 平台下的一个包过滤器。使用此过滤器可以在socket编程时非常方便的实现各种过滤规则。 要确保从socket中读取的是packet，也就是说是 MAC头+IP头+TCP/UDP头。 关于 关于socket(PF_PACKET, SOCK_RAW, … 2012-10-16
2020-6-5 · For PF_PACKET sockets, the filter is applied to layer 2 information, which includes either the whole link layer data frame for SOCK_RAW sockets or the whole IP packet; for TCP/UDP sockets, the filter is applied to layer 4 information (basically, port numbers and little other useful data). For this reason, layer 4 socket filtering is likely to
2004-1-31 · Introduction Packet filtering is the selective passing or blocking of data packets as they pass through a network interface. The criteria that pf(4) uses when inspecting packets is based on the Layer 3 (IPv4 and IPv6) and Layer 4 (TCP, UDP, ICMP, and ICMPv6) headers.The most often used criteria are source and destination address, source and destination port, and protocol. SOCK_RAW和PF_PACKET及其应用-随风去 … 2014-4-19 · SOCK_RAW给了用户更大的主动性，可以自己构造L4甚至L3的头，直接和内核进行交互，略过上层的协议栈，如ping命令： socket(PF_INET, SOCK_RAW, IPPROTO_ICMP) = 3