lkml.org 
[lkml]   [2004]   [Feb]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectSending built-by-hand packet and kernel panic.

Hi!

Can any experienced network programmer give a quick look at the
following? I try to send a TCP packet built by hand. It works, but it
also leads to a kernel panic if a second packet is to be sent. As I'm
not an experienced kernel programmer, I guess I'm doing some stupid
thing that can be easily solved.

Basically, my code just fills a sk_buff structure and sends it with NF_HOOK.

Thanks for any help,
Emmanuel



/* skb is allocated 56 bytes = TCP message with no data
(detailed hereafter)
* + 2 extra bytes before the ethernet header (see hereafter)
*/
skb = alloc_skb(56, GFP_ATOMIC);
skb_reserve(skb, 2); /* for 16-bit alignment*/
/* ethernet header is 14 byte long */
eth = (__u8 *) skb_put(skb, 14);
/* ip header is 20 byte long */
iph = (struct iphdr *)skb_put(skb, sizeof(struct iphdr));
/* tcp header (no options) is 20 byte long */
tcph = (struct tcphdr *)skb_put(skb, sizeof(struct tcphdr));

/* skb->dst AND skb->dev (the latter is set by the former) */
if (ip_route_output(&rt, ip_dst, 0, 0, 0) != 0)
{
printk("ip_route_output failed.\n");
return -1;
}
skb->dst = (struct rt_entry *) rt; /* A trick from ip_route_input.c */
skb->dev = skb->dst->dev;

/* Socket allocation. */
if (sock_create(PF_INET, SOCK_RAW, IPPROTO_RAW, &sending_socket) < 0)
{
printk("Error socket creation.\n");
sock_release(sending_socket);
return -1;
}
sk = kmalloc(sizeof(struct sock), GFP_KERNEL);
memcpy(&(sending_socket->sk), sk, sizeof(struct sock));
sock_release(sending_socket);
if (sk == NULL)
{
printk("Error: sk == NULL\n");
return -1;
}
/* Now, set the sock field. */
skb->sk = sk;

/* TRANSPORT HEADER: TCP */
/* here, TCP header data is filled in tcph. */
skb->h.th = tcph;
/* NETWORK HEADER: IP */
/* here, IP header data is filled in iph*/
skb->nh.iph = iph;
/* LINK HEADER: ETHERNET */
/* here, ethernet header data is filled in iph*/
skb->mac.ethernet = ((u8 *)iph) - 14;

/* Fix me:
* Scheduling priority put at max, choose more correct value.
*/
skb->priority = 15;
/* To choose right pkt_type when receiving a packet.
* We're not receivng anything, but I set the value like the guys
* in pktgen.c did, there should be a reason for that.
*/
skb->protocol = __constant_htons(ETH_P_IP);

/* TIMESTAMP */
/* last, so it's closest to sending time. */
do_gettimeofday(&skb->stamp);

printk("Going to send initialized skb! ...\n");
// if (NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, skb, NULL, skb->dev,
output_maybe_reroute) < 0)
NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, skb, NULL, skb->dev,
ip_finish_output) < 0

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 14:00    [W:1.613 / U:0.012 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site