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unixzen/iptables-cheatsheet.md

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Created June 26, 2023 09:06
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iptables-cheatsheet.md

https://www.digitalocean.com/community/tutorials/a-deep-dive-into-iptables-and-netfilter-architecture https://www.netfilter.org/documentation/HOWTO/netfilter-hacking-HOWTO-3.html

The netfilter hooks in the kernel and where they hook in the packet flow


      Netfilter Hooks                                        +----------->      local process    ---------+
                                                             |                                            |
                                                             |                                            |
                                                             |                                            |
                                                             |                                            v
                                                             |
                                               +-------------+--------+                         +----------------------+
                                               |                      |                         |                      |
                                               |        input         |                         |     output           |
                                               |                      |                         |                      |
                                               +------+---------------+                         +----------+-----------+
                                                      ^                                                    |
                                                      |                                                    |
     +------------------------+                       |                                                    |
     |                        |                       |                  +---------------------+           +------------->  +-------------------------+
+--> |     pre routing        |                                          |                     |                            |                         |
     |                        +------------------  route     ----------> |      forward        +--------------------------> |     post routing        |
     |                        |                    lookup                |                     |                            |                         |
     +------------------------+                                          +---------------------+                            +-------------------------+
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