Comments on: Printing sk_buff data

By: Ethelene Xiong

Ethelene Xiong — Mon, 26 Sep 2022 02:54:20 +0000

why the len is not the “len = skb->tail – skb->mac_header;”?

By: Netfilter Kernel module doesn't get the ftp packets' data – MVR

Netfilter Kernel module doesn't get the ftp packets' data – MVR — Sun, 27 Mar 2022 06:13:45 +0000

[…] Here is my code. And I wirte a pkt_hex_dump functioin to dump all my packets’s bytes above the Internet layer(Include Internet layer) accroding to this Printing sk_buff data: […]

By: tomkcook

tomkcook — Wed, 21 Apr 2021 09:02:33 +0000

In reply to tomkcook. Though of course printk("%06x\t%02x ", ii, data[ii++]) is undefined - you need to move the increment to a separate statement.

By: Joseph Cheng

Joseph Cheng — Wed, 21 Apr 2021 00:29:26 +0000

Is it possible to print unfragmented ping message , ” ping -l 8972 -f 192.168.0.108 –t” , sent from another computer ?

Thanks.

By: tomkcook

tomkcook — Tue, 20 Apr 2021 20:27:47 +0000

Might I humbly suggest the following which is somewhat simpler and has much the same effect:

void dump_skb(struct sk_buff *skb) { size_t len; printk("Packet hex dump:\n"); uint8_t *data = (uint8_t *) skb_mac_header(skb);


        if (skb_is_nonlinear(skb)) {

                len = skb->data_len;

        } else {

                len = skb->len;

        }
        for (size_t ii = 0; ii < len; ++ii) {

                printk("%06x\t%02x ", ii, data[ii++]);

for (; ii < len && (ii % 16 != 0); ++ii) { printk(KERN_CONT "%02x ", (uint32_t)(data[ii])); } printk(KERN_CONT "\n"); } }

In particular, using %06d as a format specifier and then adding 10 to li every time you print a row of 16 bytes is pretty horrible…

By: gregoireg

gregoireg — Wed, 12 Aug 2020 16:12:40 +0000

Very very useful page. Thank you for writing this.

By: anuj

anuj — Mon, 15 Jun 2020 11:01:20 +0000

This was very helpful, thanks 😀