On 12/01/11 04:26, Roc Bai wrote:
> 2011/1/11 Jan Engelhardt<jengelh@xxxxxxxxxx>:
>>
>> On Tuesday 2011-01-11 04:22, Roc Bai wrote:
>>>>> Dear all:
>>>>> in my service, there are four net card. eth0, eth1, eth2,
eth3. I
>>>>> want to forward the data in from eth0 to eth1, eth2, eth3 with
>>>>> different application protocol. Does some body send me some ideas on
>>>>> it?
>>>>
>>>> If you want to re-route packages, that has to happen in pre-routing.
>>>> If you want to use DNAT for examples, just add a rule to the
>>>> PREROUTING chain in the nat table.
>>>
>>> I think the DNAT should change the package data, including the IP or
>>> higher level protocol header, isn't it?
>>
>> That is the point of NAT. NAT is _not_ routing/forwarding (dammit).
>> And it's "packet", not "package".
>>
>>> I think the best idea which can redirect the package is to add/change
>>> the route rule to do it. I have write some source codes which doesn't
>>> work.
>>
>> That's redundant (and as you can see, error prone). Just use
>> the iproute utilities to define extra rules and routes, which
>> are known to work.
>>
>>> ncf_get_entry() can generate a dst_entry whose dev point to the eth2
>>> net_device structure. But when i use tcpdum -i eth2. I cannot get the
>>> package from eth0. So it doesn't work.
>>
>> I don't expect it to. You are using a global variable, which is not
>> SMP-safe without a lock.
>> You might find Paul McKenny's Parallel Programming Book helping.
> Jan, thanks your comments.
> I want to make the packet ( I think it's right now:) ) redirected to
> an anticipant port, so I haven't consider the concurrent problem now.
>
> In the requirement, redirect the packet with protocal is the first
> step, and in the second step, the system should redirect the packet
> with application packet content, such as GET in HTTP.
>
> eth0 ---------- if (GET in SKB), redirect to ----------> eth2
>
> So i think i have to write my module to redirect the packet now, and
> then i can change little in the future. That's the key why i thouldn't
> to use the exist nat/diverter tool.
>
> Maybe i want to know how to set the SKB in the
> ip_route_input_common() routine. Then the SKB can be send out from
> eth2 port. So
> whether my plan is right, to create a dst-entry and add it to
> skb->_skb_refdst? and Whether the dst_entry optiosn values are
> corrent?
>
This discussion is showing signs of being an XYZ problem.
http://www.perlmonks.org/index.pl?node_id=542341
Roc Bai, are you attempting to do this redirection for *any* protocol?
or just for some specific ones related to a not mentioned task?
AYJ
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