C :: Compare IPv6 Source And Destination Address From Pcap?

I want to examine every packet of a pcap trace file and if packet n+1 source address == packet n destination address && packet n+1 destination address == packet n source address i want to get the time between those 2 packages.

Problem: I can't compare the ipv6 adresses of src and destination.

comparing src and src is no problem. dst with dst as well

Code: ....

handle = pcap_open_offline(argv[fnum], errbuf);
while (packet = pcap_next(handle,&header))
{
...
struct ip6_hdr *ip_hdr = (struct ip6_hdr *)packet;
if (memcmp(&(ip_hdr->ip6_dst),ipv6_src,sizeof(ip_hdr->ip6_dst)))
{
.....

[code]....

if i try to compare these adresses i will never get a match. But i use a trace file with much matches. Do i need a offset in pkt_ptr? I saw some examples which deals with it.

Code:

uint32_t* test = (uint32_t*)ipv6_dst;
for (uint32_t j=0;j<sizeof(ip_hdr->ip6_dst);j++)
{
printf ("%x", *(test+j));
}
printf ("

[Code] ......

with given addresses:

Source: 2001:6f8:1c2c:2000:54c2:b056:f097:2830
Destination: 2a01:238:43f5:d900:2bf:784a:e3f8:9cd7