May be you know that there are differenet types of NF_HOOKS. If a firewall wants to hook for packets, generally they do at Pre-routing and post routing. In the virtual tunnel, you create, the packets will be of SELF to OUTGOING type. The in and outgoing self packets will defnitely hit the above hooks. So, you need not bother about Netfilter hooks. You can use IPTUNNEL_XMIT macro ,defined in ipip.h
#define IPTUNNEL_XMIT() do { \
int err; \
int pkt_len = skb->len; \
\
skb->ip_summed = CHECKSUM_NONE; \
iph->tot_len = htons(skb->len); \
printk("<1>Total Length:%d\n",skb->len); \
ip_select_ident(iph, &rt->u.dst, NULL); \
ip_send_check(iph); \
err = NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, skb, NULL, rt->u.dst.dev, do_ip_send); \
} while (0)
static inline int do_ip_send(struct sk_buff *skb)
{
return ip_send(skb);
}Cheers, -Ravi ROCSYS Technologies Ltd., http://www.rocsys.com
venum wrote:
Hi Ravi Kumar,
Thanks for the response. I am encapsulating the packet in the dummy ethernet device.From the Send function of this dummy device,I am passing the packet to thestack using 'netif_rx' so that it will go through all the 'net filter' hooks. I do not know if I can use 'ip_send' for the same purpose.
--- venu maya
----- Original Message ----- From: "Ravi Kumar" <ravivsn@rocsys.com> To: "venum" <venum@intoto.com> Cc: <kernelnewbies@nl.linux.org> Sent: Monday, July 05, 2004 9:52 AM Subject: Re: netif_rx dropping the packet
usingHi 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
'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
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--
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. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
-- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
