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

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:

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Fri, Mar 10, 2017 at 03:19:13PM CET, simon.horman@netronome.com wrote:

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On Tue, Feb 21, 2017 at 04:28:10PM +0100, Jiri Pirko wrote:

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Thu, Feb 02, 2017 at 11:37:34AM CET, simon.horman@netronome.com wrote:

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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 <redacted>
---

[...]

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@@ -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.

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+		    (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.