[LARTC] packet in the kernel

[LARTC] packet in the kernel

[Simone84bo]

Hi all,
Can someone say me the theoretic way of packet in the kernel.
When the packet will be send to a IMQ device?
When the packet arrives to post routing time?
When operation of NAT occur? befor or later that the packet will send to net
device?

Thanks
Bye
Simone 
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Re: [LARTC] packet in the kernel

[Rodolfo Brasnarof]

[-- Attachment #1: Type: text/plain, Size: 949 bytes --]

On Wed, 7 Mar 2007 10:53:12 +0100
Simone84bo <simone84bo@email.it> wrote:

> Hi all,
> Can someone say me the theoretic way of packet in the kernel.

Perhaps this diagram can help you:

	http://l7-filter.sourceforge.net/PacketFlow.png

I'll attach another one in asciiart I picked from somewhere (maybe
this list itself).


> When the packet will be send to a IMQ device?
> When the packet arrives to post routing time?
> When operation of NAT occur? befor or later that the packet will send
> to net device?

When loading imq module, my kernel says:

	IMQ starting with 2 devices...
	IMQ driver loaded successfully.
	        Hooking IMQ before NAT on PREROUTING.
	        Hooking IMQ after NAT on POSTROUTING.


This is the default option, but you can choose from all 4 options at
compile time:

	CONFIG_IMQ=m
	# CONFIG_IMQ_BEHAVIOR_AA is not set
	# CONFIG_IMQ_BEHAVIOR_AB is not set
	CONFIG_IMQ_BEHAVIOR_BA=y
	# CONFIG_IMQ_BEHAVIOR_BB is not set


[-- Attachment #2: packetflow.txt --]
[-- Type: text/plain, Size: 4945 bytes --]


    Kernel Packet Traveling Diagram

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

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