Hi,
If you check the return value, you might find that netif_rx returns
SUCCESS, the function always succeeds, the packet might be getting dropped
in ip_rcv() in all probability. One thing you can do to isolate the
problem, is set skb->nfmark when your PRE_ROUTING hook catches the packet
and you have to forward it by encapsulating the ip header, then in you
NF_IP_FORWARD hook or POST_ROUTING hook, you can check if you get the
packet.
Also, before you call netif_rx, it is important to set skb->mac.raw field
to the position where the packets ethernet header begins. You can try using
the function eth_type_trans. Try these things, and let us know how it goes.
Amit
Ravi Kumar <ravivsn@rocsys.com>@nl.linux.org on 07/05/2004 09:52:42 AM
Sent by: kernelnewbies-bounce@nl.linux.org
To: venum <venum@intoto.com>
cc: kernelnewbies@nl.linux.org
Subject: Re: netif_rx dropping the packet
Hi Venu Maya,
There are numerous ways to take in packet. Apart from netfilter hooks,
dev_add_pack and ether hooks , packets can also taken by creating dummy
ethernet device.
As I understand, the problem is in encapsulation module. You would like
to see ipip.c/ip_gre.c as a proof of concept. After you attach the IP
header+ UDP Header + Your payload, and based on route look up , you get
device onto which the packet has to be sent to. use ip_send to send
packets to stack. (Refer to ipip.h, you can use IPTUNNEL_XMIT )
/* remember this to set in sk_buff */
skb->dst = &rt->u.dst;
Let me know how it goes,
-Ravi
ROCSYS Technologies Ltd
http://www.rocsys.com
bhaskar wrote:
> Hi,
> How did you capture the packet. I mean netfilter hooks, or using
> dev_add_pack or ....
>
> Regards
> bhaskar
>
>
> venum wrote:
>
>> Hi
>>
>> I am facing a problem with the part of kernel code that I am
>> developing for
>> a linux router. The objective is to encapsulate the received IP
>> packet with
>> a UDP header and an extra IP header and forward it to a different
>> destination.
>> I am encapsulating the original packet and passing it to the stack using
>> 'netif_rx'. I want the stack to forward the packet to changed
>> destination.
>> At the destination the packet will be decapsulated.
>> But once the packet is given to the 'netif_rx', stack is dropping the
>> packet
>> silently.
>> I don't know which part of the stack code is dropping the packet.
>>
>> I need help in debugging this problem.I am giving the following details
>> about the encapsulation:
>>
>> Dump of the ICMP ping packet received:
>> 0 0 24 c0 2d 63 0 80 48 18 9e 5a 8 0 45 0
>> 0 3c 1 cb 0 0 80 1 dc 18 ac 10 2 5c ac 10
>> 2 61 8 0 4a 5c 2 0 1 0 61 62 63 64 65 66
>> 67 68 69 6a 6b 6c 6d 6e 6f 70 71 72 73 74 75 76
>> 77 61 62 63 64 65 66 67 68 69
>>
>> Packet Dump after Encapsulation: This packet is given to stack using
>> 'netif_rx'
>> 45 0 0 74 56 34 0 0 f0 11 ba 8b ac 10 16 1
>> ac 10 16 3 d4 31 d4 31 0 8 0 0 1 1 1 11
>> 22 33 44 55 66 0 0 0 0 0 0 0 24 c0 2d 63
>> 0 80 48 18 9e 5a 8 0 45 0 0 3c 1 cb 0 0
>> 80 1 dc 18 ac 10 2 5c ac 10 2 61 8 0 4a 5c
>> 2 0 1 0 61 62 63 64 65 66 67 68 69 6a 6b 6c
>> 6d 6e 6f 70 71 72 73 74 75 76 77 61 62 63 64 65
>> 66 67 68 69
>> I want this packet to be routed to IP address 172.16.22.3. The required
>> route is configured.
>> Is any thing wrong in the above encapsulated packet ?
>> I am modifiying the follwing skb params:
>>
>> pSkb->ip_summed = CHECKSUM_UNNECESSARY;
>> /* I have tried others like NONE,HW with no improvements
>> */
>>
>> pSkb->protocol = htons(ETH_P_IP);
>> /* Since it is always an IP packet */
>>
>> Can anyone help me find out the problem. I will provide any other
>> details if
>> required.
>>
>> TIA,
>> venu maya
>>
>>
>>
>> --
>> Kernelnewbies: Help each other learn about the Linux kernel.
>> Archive: http://mail.nl.linux.org/kernelnewbies/
>> FAQ: http://kernelnewbies.org/faq/
>>
>>
>>
>
>
> --
> Kernelnewbies: Help each other learn about the Linux kernel.
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> FAQ: http://kernelnewbies.org/faq/
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