iptables整体模块结构图

转自 http://www.yuanma.org/data/2009/0401/article_3597.htm

 

                         Network
                    -----------+-----------
                               |
                     +---------+---------+
                     |     PREROUTING    |
                     | +-------+-------+ |
                     | |   conntrack   | |
                     | +-------+-------+ |
                     | |    mangle     | | <- MARK WRITE 
                     | +-------+-------+ |
                     | |      IMQ      | |
                     | +-------+-------+ |
                     | |      nat      | | <- DEST REWRITE
                     | +-------+-------+ |     DNAT or REDIRECT
                     +---------+---------+
                               |
                       +-------+-------+
                       |    ipchains   |
                       |     input     |
                       +-------+-------+
                               |
                       +-------+-------+
                       |      QOS      |
                       |    INGRESS    |
                       +-------+-------+
                               |
         packet is for +-------+-------+ packet is for
          this machine |     INPUT     | another address
        +--------------+    ROUTING    +--------------+
        |              |    + PDBB     |              |
        |              +---------------+              |
+-------+-------+                                     |
|     INPUT     |                                     |
| +-----+-----+ |                                     |
| |   filter  | |                                     |
| +-----+-----+ |                                     |
+-------+-------+                                     |
        |                                             |
+-------+-------+                                     |
|     Local     |                             +-------+-------+
|    Process    |                             |    FORWARD    |
+-------+-------+                             | +-----+-----+ |
        |                                     | |  mangle   | | <- MARK WRITE
+-------+-------+                             | +-----+-----+ |
|    OUTPUT     |                             | |  filter   | |
|    ROUTING    |                             | +-----+-----+ |
+-------+-------+                             +-------+-------+
        |                                             |
+-------+-------+                                     |
|     OUTPUT    |                             +-------+-------+
| +-----------+ |                             |    ipchains   |
| | conntrack | |                             |    forward    |
| +-----+-----+ |                             +-------+-------+
| |   mangle  | | <- MARK WRITE                       |
| +-----+-----+ |                                     |
| |    nat    | | <-DEST REWRITE                      |
| +-----+-----+ |     DNAT or REDIRECT                |
| |   filter  | |                                     |
| +-----+-----+ |                                     |
+-------+-------+                                     |
        |                                             |
        +------------------+       +------------------+
                           |       |
                        +--+-------+--+
                        |   ipchains  |
                        |    output   |
                        +------+------+
                               |
                     +---------+---------+
                     |    POSTROUTING    |
                     | +-------+-------+ |
                     | |    mangle     | | <- MARK WRITE
                     | +-------+-------+ |
                     | |      nat      | | <-SOURCE REWRITE
                     | +-------+-------+ |     SNAT or MASQUERADE
                     | |   conntrack   | |
                     | +-------+-------+ |
                     | |      IMQ      | |
                     | +-------+-------+ |
                     +---------+---------+
                               |
                        +------+------+
                        |     QOS     |
                        |    EGRESS   |
                        +------+------+
                               |
                    -----------+-----------
                            Network