Re: [PATCH/RFC net-next 1/2] flow dissector: ND support

[Jiri Pirko <jiri@resnulli.us>]

Mon, Mar 13, 2017 at 02:50:08PM CET, simon.horman@netronome.com wrote:
>On Fri, Mar 10, 2017 at 03:27:32PM +0100, Jiri Pirko wrote:
>> Fri, Mar 10, 2017 at 03:19:13PM CET, simon.horman@netronome.com wrote:
>> >On Tue, Feb 21, 2017 at 04:28:10PM +0100, Jiri Pirko wrote:
>> >> Thu, Feb 02, 2017 at 11:37:34AM CET, simon.horman@netronome.com wrote:
>> >> >Allow dissection of Neighbour Discovery target IP, and source and
>> >> >destination link-layer addresses for neighbour solicitation and
>> >> >advertisement messages.
>> >> >
>> >> >Signed-off-by: Simon Horman <simon.horman@netronome.com>
>> >> >---
>> >> 
>> >> [...]
>> >> 
>> >> >@@ -633,6 +702,18 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
>> >> > 						     FLOW_DISSECTOR_KEY_ICMP,
>> >> > 						     target_container);
>> >> > 		key_icmp->icmp = skb_flow_get_be16(skb, nhoff, data, hlen);
>> >> >+
>> >> >+		if (dissector_uses_key(flow_dissector, FLOW_DISSECTOR_KEY_ND) &&
>> >> >+		    ip_proto == IPPROTO_IPV6 && key_icmp->code == 0 &&
>> >> 
>> >> IPPROTO_IPV6 say "IPv6-in-IPv4 tunnelling". Please use "NEXTHDR_IPV6"
>> >> instead.
>> >
>> >Thanks, will do.
>> >
>> >> >+		    (key_icmp->type == NDISC_NEIGHBOUR_SOLICITATION ||
>> >> >+		     key_icmp->type == NDISC_NEIGHBOUR_ADVERTISEMENT)) {
>> >> >+			key_nd = skb_flow_dissector_target(flow_dissector,
>> >> >+							   FLOW_DISSECTOR_KEY_ND,
>> >> >+							   target_container);
>> >> >+			if (!(skb_flow_dissect_nd(skb, key_nd, data, nhoff,
>> >> >+						  hlen, ipv6_payload_len)))
>> >> >+				goto out_bad;
>> >> >+		}
>> >> 
>> >> You should put this under "switch (ip_proto) {"
>> >
>> >I see that makes sense in terms of the check against ip_proto.
>> >But I added it here to allow checking against key_icmp->code
>> >and key_icmp->type as well.
>> 
>> Sure. Just add under "switch (ip_proto) {" and call a wrapper nd
>> function from there. In that function, you check dissector_uses_key and
>> other needed things.
>
>Hi Jiri,
>
>I'm sorry but I'm having a bit of trouble understanding how best to
>structure the extraction of ICMP and ND.
>
>The way I see things is this:
>
>* ICMP extraction may occur for IPv4 or IPv6 although currently neither
>  IPv4 nor IPv6 is a condition of ICMP extraction.
>* ND extraction may only occur for IPv6
>* ND extraction may only occur for certain ICMP code/type values;
>  thus ICMP extraction should occur before ND extraction.
>
>I wonder if a good alternative to the approach I took above in my patch
>would  be to provide:
>* ICMP extraction conditional on IPv4 and;
>* ICMP extraction conditional on IPv6 followed by
>  ND extraction conditional on ICMP type and code

Makes sense to me.