Libnet11 build IPv6 packet manually

Question

I am trying to use Libnet11 function:

int libnet_write_raw_ipv6 (libnet_t *l, u_int8_t *packet, u_int32_t size)

to inject IPv6 packet on network layer. I had created IPv6 packet and captured it with Wireshark. Wireshark reported: malformed packet(wireshark says that next header value in IPv6 is wrong and payload size is too big in my opinion)

I hope, someone could help me with minimal code example, showing how to manually build IPv6 packet (with ICMPv6 extension header) with libnet11 (libnet_write_raw_ipv6()).

I assume that the minimal code might look like this:

packet_len = 40 + 16; // 40B ~ IPv6 packet, 16B ~ ICMPv6 header
u_char *buf = NULL;

struct ip6_hdr *ip6 = NULL;
struct icmp6_hdr *icmp6 = NULL;

l = libnet_init();
if ( (buf = malloc(packet_len)) == NULL ) {
    // error
}

// create IPv6 header
ip6 = (struct ip6_hdr *) buf;
ip6->ip6_flow   = 0;
ip6->ip6_vfc    = 6 << 4;
ip6->ip6_plen   = 16;              // ICMPv6 packet size
ip6->ip6_nxt    = IPPROTO_ICMPV6;  // 0x3a
ip6->ip6_hlim   = 64;
memcpy(&(ip6->ip6_src), &src_addr, sizeof(struct in6_addr));
memcpy(&(ip6->ip6_dst), &dst_addr, sizeof(struct in6_addr));

// create ICMPv6 header
icmp6 = (struct icmp6_hdr *) (buf + 40); // 40B ~ IPv6 packet size
icmp6->icmp6_type = ICMP6_ECHO_REQUEST;
icmp6->icmp6_code = 0;
icmp6->icmp6_cksum= 0;
icmp6->icmp6_data32[0] = 0;

libnet_do_checksum(l, (u_int8_t *)buf, IPPROTO_ICMPV6, packet_len);

written = libnet_write_raw_ipv6(l, buf, packet_len);
if ( written != packet_len )
    perror("Failed to send packet");

libnet_destroy(l);
free(buf);

I tried to find code examples but with no success. Thank you in advance.

Martin

What does wireshark show for the next header? You might need to call htnos() to flip the byte order if it's coming up as 0x3A00 instead of 0x003A. — PherricOxide, Nov 14 '12 at 19:59
The payload length in your ip header needs to be converted to big-endian order. That's why you are getting a 'payload size too big' warning. — Lucas Aschenbach, Jul 03 '22 at 16:36

mfontanini · Answer 1 · 2013-11-24T17:50:40.667

If you're using C++, then I'd recommend you libtins, a packet crafting a sniffing library. This short snippet does exactly what you want:

#include <tins/tins.h>

using namespace Tins;

void test(const IPv6Address &dst, const IPv6Address &src) {
    PacketSender sender;
    IPv6 ipv6 = IPv6(dst, src) / ICMPv6();
    ipv6.hop_limit(64);
    sender.send(ipv6);
}

int main() {
    // now use it
    test("f0ef:1234::1", "f000::1");
}

score 0 · Answer 2 · answered Mar 17 '14 at 16:48

0

You can create it with raw sockets though. I also had to do something similar but couldn't find anything as a reference.

To do it with raw sockets, this link gives you a nice explanation

answered Mar 17 '14 at 16:48

Akshay

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Libnet11 build IPv6 packet manually

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