Jay,
You can do an identifier search of "ipv6_rcv" on lxr.linux.no, and
then you will find the a ipv6_packet_type has the structure:
60 static struct packet_type ipv6_packet_type = {
61 .type = __constant_htons(ETH_P_IPV6),
62 .func = ipv6_rcv,
63 };
Then search for ipv6_packet_type:
You will see that it is added by the device in:
696 void __init ipv6_packet_init(void)
697 {
698 dev_add_pack(&ipv6_packet_type);
699 }
Now search for dev_add_pack; you will see that list_add_rcu is invoked:
272 void dev_add_pack(struct packet_type *pt)
273 {
274 int hash;
275
276 spin_lock_bh(&ptype_lock);
277 if (pt->type == htons(ETH_P_ALL)) {
278 netdev_nit++;
279 list_add_rcu(&pt->list, &ptype_all);
280 } else {
281 hash = ntohs(pt->type) & 15;
282 list_add_rcu(&pt->list, &ptype_base[hash]);
283 }
284 spin_unlock_bh(&ptype_lock);
285 }
Now search for netif_receive_skb; (invoked when an skb is queued):
This effectively calls deliver_skb (which pushes the packet up the stack)
Now look for deliver_skb; you will find that it will call:
1559 return pt_prev->func(skb, skb->dev, pt_prev);
So now ipv6_rcv would be called if it is an IPv6 packet.
Ok now the packet can finally take the flow for a regular IPv6 packet! :-)
Thanks,
Avinash.
On 7/25/06, Jay Cliburn <jacliburn@xxxxxxxxxxxxx> wrote:
I'm trying to trace a received IPv6 packet through the kernel, but I'm
having a hard time. I can't find the point at which a packet IP header
is examined by the kernel which then says, "You're IPv4; you go this
way," or "You're IPv6; you go that way."
I can follow the packet through the device driver until it's handed up
to netif_rx() in net/core/dev.c, at which time it gets enqueued and an
interrupt is raised, but I can't find the entry point for the packet on
the other side of the interrupt. It looks like the packet eventually
ends up at ipv6_rcv() in /net/ipv6/ip6_input.c, but I can't find how it
gets there, nor what happened after it was enqueued that identified it
as an IPv6 packet.
Can someone point me in the right direction?
Thanks,
Jay
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