net: ipv6: Handle delivery_time in ipv6 defrag

A latter patch will postpone the delivery_time clearing until the stack
knows the skb is being delivered locally (i.e. calling
skb_clear_delivery_time() at ip_local_deliver_finish() for IPv4
and at ip6_input_finish() for IPv6). That will allow other kernel
forwarding path (e.g. ip[6]_forward) to keep the delivery_time also.

A very similar IPv6 defrag codes have been duplicated in
multiple places: regular IPv6, nf_conntrack, and 6lowpan.

Unlike the IPv4 defrag which is done before ip_local_deliver_finish(),
the regular IPv6 defrag is done after ip6_input_finish().
Thus, no change should be needed in the regular IPv6 defrag
logic because skb_clear_delivery_time() should have been called.

6lowpan also does not need special handling on delivery_time
because it is a non-inet packet_type.

However, cf_conntrack has a case in NF_INET_PRE_ROUTING that needs
to do the IPv6 defrag earlier. Thus, it needs to save the
mono_delivery_time bit in the inet_frag_queue which is similar
to how it is handled in the previous patch for the IPv4 defrag.

This patch chooses to do it consistently and stores the mono_delivery_time
in the inet_frag_queue for all cases such that it will be easier
for the future refactoring effort on the IPv6 reasm code.

Signed-off-by: Martin KaFai Lau <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/ieee802154/6lowpan/reassembly.c

···
 		goto err;
 
 	fq->q.stamp = skb->tstamp;
+	fq->q.mono_delivery_time = skb->mono_delivery_time;
 	if (frag_type == LOWPAN_DISPATCH_FRAG1)
 		fq->q.flags |= INET_FRAG_FIRST_IN;
 

net/ipv6/netfilter/nf_conntrack_reasm.c

···
 		fq->iif = dev->ifindex;
 
 	fq->q.stamp = skb->tstamp;
+	fq->q.mono_delivery_time = skb->mono_delivery_time;
 	fq->q.meat += skb->len;
 	fq->ecn |= ecn;
 	if (payload_len > fq->q.max_size)

net/ipv6/reassembly.c

···
 		fq->iif = dev->ifindex;
 
 	fq->q.stamp = skb->tstamp;
+	fq->q.mono_delivery_time = skb->mono_delivery_time;
 	fq->q.meat += skb->len;
 	fq->ecn |= ecn;
 	add_frag_mem_limit(fq->q.fqdir, skb->truesize);