On Mon, Mar 27, 2017 at 07:42:58PM +0530, nusid...@redhat.com wrote:
> From: Numan Siddique <nusid...@redhat.com>
>
> This patch adds a new OVN action 'dns_lookup' to support native DNS.
> ovn-controller parses this action and adds a NXT_PACKET_IN2
> OF flow with 'pause' flag set.
>
> A new table 'DNS' is added in the SB DB to look up and resolve
> the DNS queries. When a valid DNS packet is received by
> ovn-controller, it looks up the DNS name in the 'DNS' table
> and if successful, it frames a DNS reply, resumes the packet
> and stores 1 in the 1-bit subfield. If the packet is invalid
> or cannot be resolved, it resumes the packet without any
> modifications and stores 0 in the 1-bit subfield.
>
> reg0[4] = dns_lookup(); next;
>
> An upcoming patch will use this action and adds logical flows.
>
> Signed-off-by: Numan Siddique <nusid...@redhat.com>
I didn't do a thorough review, but here's a suggested incremental for
the documentation. (I started by noticing that a DNS request should
have udp.dst 53, not udp.src 53, and then got carried away a little.)
diff --git a/ovn/ovn-sb.xml b/ovn/ovn-sb.xml
index e0e4f67b3bb6..692925aa9856 100644
--- a/ovn/ovn-sb.xml
+++ b/ovn/ovn-sb.xml
@@ -1482,21 +1482,21 @@
</p>
<p>
- When this action is applied to a valid DNS (UDP packet with
- udp.src 53) request packet, it changes the packet into a DNS reply
- if it is able to resolve the query and stores 1 in <var>R</var>.
- It leaves the packet unchanged if it is not able to resolve and
- stores 0 in <var>R</var>.
+ When this action is applied to a valid DNS request (a UDP packet
+ typically directed to port 53), it attempts to resolve the query
+ using the contents of the <ref table="DNS"/> table. If it is
+ successful, it changes the packet into a DNS reply and stores 1 in
+ <var>R</var>. If the action is applied to a non-DNS packet, an
+ invalid DNS request packet, or a valid DNS request for which the
+ <ref table="DNS"/> table does not supply an answer, it leaves the
+ packet unchanged and stores 0 in <var>R</var>.
</p>
<p>
- When this action is applied to a non-DNS or an invalid
- DNS request packet , it leaves the packet unchanged and stores
- 0 in <var>R</var>.
- </p>
-
- <p>
- The contents of the <ref table="DNS"/> table control the DNS
lookup.
+ Regardless of success, the action does not make any of the changes
+ to the flow that are necessary to direct the packet back to the
+ requester. The logical pipeline can implement this behavior with
+ matches and actions in later tables.
</p>
<p>
@@ -1505,6 +1505,10 @@
reg0[3] = dns_lookup();
</code>
</p>
+
+ <p>
+ <b>Prerequisite:</b> <code>udp</code>
+ </p>
</dd>
</dl>
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