Missing INET6_PROTO_FINAL in l2tp_ip6_protocol?

Missing INET6_PROTO_FINAL in l2tp_ip6_protocol?

[Shmulik Ladkani]

Hi,

inet6_protocol's INET6_PROTO_FINAL flag denotes handler is expected not
to request resubmission for local delivery.

For an INET6_PROTO_FINAL handler, the following actions gets executed
prior delivery, in ip6_input_finish:

			nf_reset(skb);

			skb_postpull_rcsum(skb, skb_network_header(skb),
					   skb_network_header_len(skb));

For some reason, l2tp_ip6_protocol handler is NOT marked as
INET6_PROTO_FINAL. Probably an oversight.

Since 'l2tp_ip6_recv' never results in a resubmission, the above actions
are not applied to skbs passed to l2tp_ip6.

Any reason why l2tp_ip6_protocol should NOT be marked INET6_PROTO_FINAL?

What's the consequences not executing the above actions for l2tp_ip6
packets?

Thanks,
Shmulik

Re: Missing INET6_PROTO_FINAL in l2tp_ip6_protocol?

[Hannes Frederic Sowa]

On 21.05.2016 14:50, Shmulik Ladkani wrote:
> Hi,
> 
> inet6_protocol's INET6_PROTO_FINAL flag denotes handler is expected not
> to request resubmission for local delivery.
> 
> For an INET6_PROTO_FINAL handler, the following actions gets executed
> prior delivery, in ip6_input_finish:
> 
> 			nf_reset(skb);
> 
> 			skb_postpull_rcsum(skb, skb_network_header(skb),
> 					   skb_network_header_len(skb));
> 
> For some reason, l2tp_ip6_protocol handler is NOT marked as
> INET6_PROTO_FINAL. Probably an oversight.
> 
> Since 'l2tp_ip6_recv' never results in a resubmission, the above actions
> are not applied to skbs passed to l2tp_ip6.
> 
> Any reason why l2tp_ip6_protocol should NOT be marked INET6_PROTO_FINAL?

I don't see any specific reason why it shouldn't be a INET6_PROTO_FINAL.
Anyway, receive path of L2TPv3 without UDP encapsulation doesn't deal
with checksums anyway, as far as I know.

> What's the consequences not executing the above actions for l2tp_ip6
> packets?

Probably not a whole lot in this case.

Bye,
Hannes

Re: Missing INET6_PROTO_FINAL in l2tp_ip6_protocol?

[Shmulik Ladkani]

On Sat, 21 May 2016 17:55:59 +0200 Hannes Frederic Sowa <hannes@stressinduktion.org> wrote:
> On 21.05.2016 14:50, Shmulik Ladkani wrote:
> > Hi,
> > 
> > inet6_protocol's INET6_PROTO_FINAL flag denotes handler is expected not
> > to request resubmission for local delivery.
> > 
> > For an INET6_PROTO_FINAL handler, the following actions gets executed
> > prior delivery, in ip6_input_finish:
> > 
> > 			nf_reset(skb);
> > 
> > 			skb_postpull_rcsum(skb, skb_network_header(skb),
> > 					   skb_network_header_len(skb));
> > 
> > For some reason, l2tp_ip6_protocol handler is NOT marked as
> > INET6_PROTO_FINAL. Probably an oversight.
> > 
> > Since 'l2tp_ip6_recv' never results in a resubmission, the above actions
> > are not applied to skbs passed to l2tp_ip6.
> > 
> > Any reason why l2tp_ip6_protocol should NOT be marked INET6_PROTO_FINAL?  
> 
> I don't see any specific reason why it shouldn't be a INET6_PROTO_FINAL.
> Anyway, receive path of L2TPv3 without UDP encapsulation doesn't deal
> with checksums anyway, as far as I know.
> 
> > What's the consequences not executing the above actions for l2tp_ip6
> > packets?  
> 
> Probably not a whole lot in this case.

OK, so the skb_postpull_rcsum is irrelevant for IPPROTO_L2TP over ipv6.

However, one more thing WRT to INET6_PROTO_FINAL not being set - we're
also missing the multicast filtering of 'ip6_input_finish':

			if (ipv6_addr_is_multicast(&hdr->daddr) &&
			    !ipv6_chk_mcast_addr(skb->dev, &hdr->daddr,
			    &hdr->saddr) &&
			    !ipv6_is_mld(skb, nexthdr, skb_network_header_len(skb)))
				goto discard;

I assume no reason to allow multicast daddr which aren't in the mc_list
(or saddr excluded) to pass up into 'l2tp_ip6_recv'?

Re: Missing INET6_PROTO_FINAL in l2tp_ip6_protocol?

[Hannes Frederic Sowa]

On 21.05.2016 22:02, Shmulik Ladkani wrote:
> On Sat, 21 May 2016 17:55:59 +0200 Hannes Frederic Sowa <hannes@stressinduktion.org> wrote:
>> On 21.05.2016 14:50, Shmulik Ladkani wrote:
>>> Hi,
>>>
>>> inet6_protocol's INET6_PROTO_FINAL flag denotes handler is expected not
>>> to request resubmission for local delivery.
>>>
>>> For an INET6_PROTO_FINAL handler, the following actions gets executed
>>> prior delivery, in ip6_input_finish:
>>>
>>> 			nf_reset(skb);
>>>
>>> 			skb_postpull_rcsum(skb, skb_network_header(skb),
>>> 					   skb_network_header_len(skb));
>>>
>>> For some reason, l2tp_ip6_protocol handler is NOT marked as
>>> INET6_PROTO_FINAL. Probably an oversight.
>>>
>>> Since 'l2tp_ip6_recv' never results in a resubmission, the above actions
>>> are not applied to skbs passed to l2tp_ip6.
>>>
>>> Any reason why l2tp_ip6_protocol should NOT be marked INET6_PROTO_FINAL?  
>>
>> I don't see any specific reason why it shouldn't be a INET6_PROTO_FINAL.
>> Anyway, receive path of L2TPv3 without UDP encapsulation doesn't deal
>> with checksums anyway, as far as I know.
>>
>>> What's the consequences not executing the above actions for l2tp_ip6
>>> packets?  
>>
>> Probably not a whole lot in this case.
> 
> OK, so the skb_postpull_rcsum is irrelevant for IPPROTO_L2TP over ipv6.
> 
> However, one more thing WRT to INET6_PROTO_FINAL not being set - we're
> also missing the multicast filtering of 'ip6_input_finish':
> 
> 			if (ipv6_addr_is_multicast(&hdr->daddr) &&
> 			    !ipv6_chk_mcast_addr(skb->dev, &hdr->daddr,
> 			    &hdr->saddr) &&
> 			    !ipv6_is_mld(skb, nexthdr, skb_network_header_len(skb)))
> 				goto discard;
> 
> I assume no reason to allow multicast daddr which aren't in the mc_list
> (or saddr excluded) to pass up into 'l2tp_ip6_recv'?
> 

Good point, seems we would benefit of the addition of the PROTO_FINAL
flag. Could you test and send a patch?

Thanks,
Hannes

Re: Missing INET6_PROTO_FINAL in l2tp_ip6_protocol?

[Shmulik Ladkani]

Hi,

On Mon, 23 May 2016 13:05:50 +0200, hannes@stressinduktion.org wrote:
> > However, one more thing WRT to INET6_PROTO_FINAL not being set - we're
> > also missing the multicast filtering of 'ip6_input_finish':
> > 
> > 			if (ipv6_addr_is_multicast(&hdr->daddr) &&
> > 			    !ipv6_chk_mcast_addr(skb->dev, &hdr->daddr,
> > 			    &hdr->saddr) &&
> > 			    !ipv6_is_mld(skb, nexthdr, skb_network_header_len(skb)))
> > 				goto discard;
> > 
> > I assume no reason to allow multicast daddr which aren't in the mc_list
> > (or saddr excluded) to pass up into 'l2tp_ip6_recv'?
> > 
> 
> Good point, seems we would benefit of the addition of the PROTO_FINAL
> flag. Could you test and send a patch?

Will do.

Regards,
Shmulik