Hello everyone,
I am working for an embedded Linux firmware running on a CPE and I am
using an IP4 over IPv6 tunnel configured as following:
ip -f inet6 tunnel add tun1 mode ipip6 remote XX:XX:XX local XX:XX:XX
dev eth0
And it works fine until I don't try to test the fragment case: I send a
too big UDP packet and my expectation - and requirement (sob) - would
be a IPv6 packet fragmentation but what I get is a double
fragmentation (IPv4 and IPv6), then, summarizing:
IPv4 --> [IPv4-1-segment][IPv6] [IPv4-2-segment][IPv6]
Looking at the kernel code - which in I am not an expert - I observed
that the function ip_finish_output :
#if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
/* Policy lookup after SNAT yielded a new policy */
if (skb_dst(skb)->xfrm != NULL) {
IPCB(skb)->flags |= IPSKB_REROUTED;
return dst_output(skb);
}
#endif
#if defined(CONFIG_INET_IPSEC_OFFLOAD)
if ((skb->ipsec_offload == 0) &&
skb->len > ip_skb_dst_mtu(skb) && !skb_is_gso(skb))
#else
if (skb->len > ip_skb_dst_mtu(skb) && !skb_is_gso(skb))
#endif
return ip_fragment(skb, ip_finish_output2);
else
return ip_finish_output2(skb);
Does not care about it, it just fragments if the MTU does not match.
Is there any options to disable the fragmentation on IPV4 ? I am
misconfiguring something ? Why does the ipip6 has this wrong behavior ?
Thanks in advance,
Pietro.
Pietro Paolini
pulsarpietro@xxxxxxx
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