Mit sk_buff zum hinzufügen eines Ethernet-frame-header

Habe ich ein kernel-Modul, das fängt ausgehenden Internet-Verkehr(Netfilter hook: LOCAL_OUT)
An diesem Haken, gibt es noch keine Ethernet-header.

Baute ich den Ethernet-header und es ist bereit zu verwenden, aber wie kann ich hängen Sie es an die skb, so dass ich senden kann, die ganze skb struct zu dev_queue_xmit() ?

Gibt es eine Anleitung, wie man manipulieren sk_buff Daten, die Sie mir geben können für weitere Informationen?

Als eine Probe, die ich versuche zu tun, was ich tun möchte auf alle ECHO-ICMP-Verkehr; dies ist der code, den ich habe.
Aber bei der überprüfung mit Wireshark auf dem anderen Rechner bekomme ich eine funktionierende Ethernet-header, sondern ein LEERES IP-Paket...wie kommt das?

static unsigned int post_icmp_check(unsigned int hooknum,
                 struct sk_buff *skb,
                 const struct net_device *in,
                 const struct net_device *out,
                 int (*okfn)(struct sk_buff *))
{
  struct iphdr *iph;
  struct icmphdr *icmph;
  struct sk_buff *sb;
  struct ethhdr *ethh;
  unsigned char *frame = NULL; //Used just to copy the skb->data and replace it, that's all
  unsigned char *ptr;

  /* Allocations and initial assignations  */
  sb = skb_copy(skb, GFP_ATOMIC); /* Making a private copy because we cannot modify all fields in the public one */
  iph = ip_hdr(sb);

  if(iph->protocol == IPPROTO_ICMP){
      printk(KERN_ALERT"POST ICMP traffic!\n");

      icmph = icmp_hdr(sb);
      if(icmph->type == ICMP_ECHO){
          frame = (unsigned char *)kmalloc(ntohs(iph->tot_len) + (ETH_HLEN*8), GFP_KERNEL);
          ptr = (frame +  (ETH_HLEN * 8));

          ethh = (struct ethhdr*) frame;      //00:1a:80:7e:96:ba
          ethh->h_source[0] = 0x00;   
          ethh->h_source[1] = 0x1a;           
          ethh->h_source[2] = 0x80;
          ethh->h_source[3] = 0x7e;
          ethh->h_source[4] = 0x96;
          ethh->h_source[5] = 0xba;
          ethh->h_dest[0] = 0xff;
          ethh->h_dest[1] = 0xff;
          ethh->h_dest[2] = 0xff;
          ethh->h_dest[3] = 0xff;
          ethh->h_dest[4] = 0xff;
          ethh->h_dest[5] = 0xff;
          ethh->h_proto = htons(ETH_P_IP);
          memcpy(ptr, skb->data, ntohs(iph->tot_len)); /* Copying the rest of the data from the skb to sb */
          sb->data = frame;

          //icmph = icmp_hdr(sb);

          //icmph->un.echo.sequence = htons(i++);         
          //icmph->checksum = 0;
          //icmph->checksum =  in_cksum((unsigned short *)icmph, ntohs(iph->tot_len) - sizeof(struct iphdr));
          sb->dev = out;
          printk(KERN_ALERT"%s\n",sb->dev->name);
          if(sb->dev == NULL)
              printk(KERN_ALERT"dev is NULL!");           
          dev_queue_xmit(sb);
          return NF_STOLEN;
}

EDIT : Und ja, ich bin hardcoding meine eigene MAC und die übertragung der Rahmen, der Einfachheit halber nur.

EDIT2:
So gebe ich dieser Funktion das original sk_buff gefangen von net_filter und die entsprechenden net_device
Ich habe versucht zu Folgen, was Sie sagte, und Lesen Sie eine kleine Anleitung über die Funktionen für die sK_buff.
Dennoch, wenn ich dev_queue_xmit() die zurückgegebenen sk_buff von dieser Funktion, ich bekomme eine komplette kernel-crash.

static struct sk_buff* set_skb(struct sk_buff *org_skb, struct net_device *dev)
{
    int header_size;
    unsigned char *data;
    struct icmphdr *icmph;
    struct iphdr *iph;      
    struct icmphdr *temp_icmph;
    struct iphdr *temp_iph;         
    unsigned char myaddr[] = {0x00,0x1a,0x80,0x7e,0x96,0xba};
    unsigned char addr [] = {0xff,0xff,0xff,0xff,0xff,0xff};    
    struct sk_buff *skb;

    temp_iph = ip_hdr(org_skb); 
    temp_icmph = icmp_hdr(org_skb);

    skb = alloc_skb(ntohs((temp_iph->tot_len) + (ETH_HLEN*8)), GFP_KERNEL); /* Allocating enough space for everything */

    /* icmp_hlen which is always 8, ip_hlen */
    header_size = 8 + ntohs(temp_iph->ihl*4);


    /* reserve headroom This actually allocates the IP and ICMP headers memory */
    skb_reserve(skb, header_size);

    /* payload */
    data = skb_put(skb, org_skb->data_len);/* This function allocates room for the data */
    memcpy(data, org_skb->data, org_skb->data_len);

    icmph = (struct icmphdr*)skb_push(skb, 8); 
    /* set up icmp header here */
    memcpy(icmph, temp_icmph, 8);   

    iph = (struct iphdr*)skb_push(skb, temp_iph->ihl*4);
    /* set up ip header here */
    memcpy(iph, temp_iph, temp_iph->ihl*4); 

    /*
     * This function sets up the ethernet header,
     * destination address addr, source address myaddr
     */
    dev_hard_header(skb, dev, ETH_P_IP, addr, myaddr, dev->addr_len);
    return skb;
}

EDIT3:

Apr 20 23:44:09 DHS-1022CYB kernel: [ 1139.520104] Loading Test module...
Apr 20 23:44:09 DHS-1022CYB kernel: [ 1139.520168] *********************HERE WE GO**********************
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.760448] PGD 114952067 PUD 12d932067 PMD 0 
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.760762] CPU 0 
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.760809] Modules linked in: myModule(P) binfmt_misc rfcomm ppdev sco bridge stp bnep l2cap joydev fbcon tileblit font bitblit softcursor vga16fb vgastate snd_hda_codec_realtek pcmcia arc4 snd_hda_intel snd_hda_codec snd_hwdep snd_pcm_oss snd_mixer_oss snd_pcm snd_seq_dummy snd_seq_oss snd_seq_midi snd_rawmidi snd_seq_midi_event iwlagn snd_seq iwlcore snd_timer radeon ttm drm_kms_helper snd_seq_device mac80211 tifm_7xx1 led_class usbhid yenta_socket hid rsrc_nonstatic btusb bluetooth uvcvideo videodev v4l1_compat v4l2_compat_ioctl32 snd drm tifm_core i2c_algo_bit psmouse sony_laptop pcmcia_core serio_raw cfg80211 soundcore snd_page_alloc video output intel_agp lp parport ohci1394 ieee1394 r8169 mii
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.762642] Pid: 3423, comm: ping Tainted: P           2.6.32-33-generic #70-Ubuntu VGN-CR31Z_R
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.762753] RIP: 0010:[<ffffffffa042c081>]  [<ffffffffa042c081>] post_icmp_check+0x81/0x1e0 [myModule]
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.762891] RSP: 0018:ffff88011494f948  EFLAGS: 00010246
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.762965] RAX: 0000000000000000 RBX: ffff88013bb62000 RCX: 00000000000000d0
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.763059] RDX: 0000000000000000 RSI: ffff88013bb62000 RDI: 0000000000000000
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.763153] RBP: ffff88011494f988 R08: 00000000ffffffff R09: 0000000000000001
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.763248] R10: ffffffff81591000 R11: ffff880137c9c9ef R12: ffff880130ba8100
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.763346] R13: ffffffff81831070 R14: ffff880130ba8100 R15: 0000000000000003
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.763441] FS:  00007f3377ef6700(0000) GS:ffff880028200000(0000) knlGS:0000000000000000
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.763546] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.763626] CR2: 0000000000000000 CR3: 0000000114863000 CR4: 00000000000006f0
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.763721] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.763815] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.763910] Process ping (pid: 3423, threadinfo ffff88011494e000, task ffff880139b6c4d0)
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.764052]  ffff88011494fde8 0000000000000040 0000000000609420 0000000000000000
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.764195] <0> ffff88011494fa10 0000000080000000 ffffffff81831070 ffff880130ba8100
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.768380] <0> ffff88011494f9d8 ffffffff81486f1c ffff88013bb62000 0000000000000000
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.770015]  [<ffffffff81486f1c>] nf_iterate+0x6c/0xb0
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.770015]  [<ffffffff81491b20>] ? dst_output+0x0/0x20
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.770015]  [<ffffffff81486fd4>] nf_hook_slow+0x74/0x100
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.770015]  [<ffffffff81491b20>] ? dst_output+0x0/0x20
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.770015]  [<ffffffff81493c3f>] __ip_local_out+0x9f/0xb0
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.770015]  [<ffffffff81493c66>] ip_local_out+0x16/0x30
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.770015]  [<ffffffff81493f0a>] ip_push_pending_frames+0x28a/0x410
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.770015]  [<ffffffff8148cd02>] ? ip_route_output_flow+0x82/0xb0
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.770015]  [<ffffffff814b40b5>] raw_sendmsg+0x3a5/0x5c0
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.770015]  [<ffffffff814be5b9>] inet_sendmsg+0x29/0x60
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.770015]  [<ffffffff81285389>] ? apparmor_socket_sendmsg+0x19/0x20
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.770015]  [<ffffffff8145004b>] sock_sendmsg+0x10b/0x140
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.770015]  [<ffffffff81084cc0>] ? autoremove_wake_function+0x0/0x40
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.770015]  [<ffffffff8144f5b4>] ? move_addr_to_kernel+0x64/0x70
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.770015]  [<ffffffff8145a706>] ? verify_iovec+0x66/0xd0
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.770015]  [<ffffffff814504c3>] sys_sendmsg+0x233/0x3a0
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.770015]  [<ffffffff811131c9>] ? __do_fault+0x439/0x500
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.770015]  [<ffffffff81541845>] ? _spin_lock_irq+0x15/0x20
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.770015]  [<ffffffff810787ae>] ? do_sigaction+0x13e/0x1e0
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.770015]  [<ffffffff815444a8>] ? do_page_fault+0x158/0x3b0
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.770015]  [<ffffffff810121b2>] system_call_fastpath+0x16/0x1b
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.770015]  RSP <ffff88011494f948>
Apr 20 23:44:12 DHS-1022CYB kernel: [ 1142.887370] ---[ end trace 404e94883c3bf110 ]---

Und das war das kernel-log-Ergebnis nach dem crash.

EDIT4:
Um die Dinge klarer, dies ist der Teil des Codes, der ruft tatsächlich mein set_skb()

if(icmph->type == ICMP_ECHO){
            memcpy(dev, out, sizeof(*out)); 
            sb = set_skb(skb, dev);
            printk(KERN_ALERT"%s\n",sb->dev->name);           
            dev_queue_xmit(sb);
            return NF_STOLEN;
        }

InformationsquelleAutor Fingolfin | 2012-04-20

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