[ovs-dev] [PATCH 2/4] connmgr: Remove unnecessary reason fixup logic
YAMAMOTO Takashi
yamamoto at valinux.co.jp
Wed Mar 12 08:00:09 UTC 2014
> On Wed, Mar 12, 2014 at 12:00:12PM +0900, YAMAMOTO Takashi wrote:
>> > A packet_in message may be sent for one of two reasons.
>> >
>> > 1. As the result of an controller action supplied in a rule.
>> > This is executed if a packet matches the match for the rule.
>> > The packet_in reason is explicitly part of the action and
>> > is thus correct.
>>
>> for OFPACT_CONTROLLER (NX thing) it's correct.
>> for OFPACT_OUTPUT (OF standard way), it isn't.
>>
>> for the latter, reason=OFPR_ACTION is hardcoded in xlate_output_action.
>> OF1.3 (1.3.3 5.4.) states reason=table-miss for table-miss flow entry
>> and thus needs the fixup logic in question.
>
> Thanks, I think understand now.
>
> But I wonder if there are some problems that cause the fixup never to be
> invoked.
i'm sure it worked correctly, at least when the patch was merged.
>
> i. For the reasons described in patch 3 of this series
> rule_dpif_is_table_miss() always returns false and thus
> pin->generated_by_table_miss is always false.
>
> This means that the if condition in wire_reason() is never true.
table-miss flows (in the sense of OF1.3) are not OVS internal flows.
they are ordinary flows with priority=0 and empty match.
a controller can freely install and remove them.
>
> ii. It seems to me that the fixup should be invoked if
> pin->generated_by_table_miss is false as what you describe
> immediately above is that the fixup logic is needed
> explicit output actions rather than for table misses.
i guess you are confused by ofproto->miss_rule and OF1.3 table-miss flows.
they are different things. generated_by_table_miss is true if the pin
is caused by OF1.3 table-miss flow. it isn't for ofproto->miss_rule.
YAMAMOTO Takashi
>
> And I believe there are further problems which we reach (like a bonus level
> of an arcade game) once the above issues are addressed:
>
> Bonus i. The reason is forced to no_match even for
> OFPACT_CONTROLLER with reason set to action.
>
> I wonder if this could be resolved by adding a from_output_action
> field to struct ofproto_packet_in and setting it using a parameter
> passed to execute_controller_action().
>
> Bonus ii. parse_controller() emits an output action rather than a
> controller action if the reason is action and the controller_id
> is 0. This seems to assume that an output action always
> has action as its reason. But as we know this is not
> the case for OpenFlow 1.3+
>
> I propose simplifying parse_controller() to always emit
> a controller action.
>
> My proposal is as follows:
>
> * Drop this patch
> * Address the issues described above
> * Add a test to exercise the fixup (I have one locally)
> * Rebase patch 4 of this series
>
>
> Does that sound reasonable to you or am I still confused about
> how this is fixup?
>
>>
>> YAMAMOTO Takashi
>>
>> >
>> > 2. As the result of the failure to match a packet against any rule.
>> > In this case a rule present in TBL_INTERNAL is used. This rule
>> > has the packet_in reason set to OFPR_NO_MATCH.
>> >
>> > This is the behaviour described in OpenFlow 1.1 and 1.2 when
>> > a miss occurs. And to date it is the behaviour provided
>> > by Open vSwtich for all OpenFlow versions.
>> >
>> > When this behaviour is in effect OFPR_NO_MATCH is the desired
>> > packet_in reason and by virtue of the TBL_INTERNAL rule described
>> > above is always that value.
>> >
>> > So for both cases the packet_in reason is always correct.
>> > And following this reasoning there seems to be no need to fix it up.
>> >
>> > What there is a need for, which this patch does not address, is for packets
>> > to be dropped rather than forwarded to OpenFlow1.3 controllers when a miss
>> > occurs and an alternate behaviour has not been selected using Table Mod. I
>> > plan to address this in subsequent patches.
>> >
>> > As well as not been necessary, I believe that the logic that this patch
>> > removes has not been executed because pin->generated_by_table_miss is never
>> > true without a separate patch that I have proposed, "ofproto-dpip: Set
>> > generated_by_table_miss for miss rule". So I do not expect there to be any
>> > run-time affect of this change.
>> >
>> > This patch does not remove pin->generated_by_table_miss, although it
>> > is now set but never used, as I plan to use when implementing the
>> > OpenFlow1.3 drop-on-miss behaviour described above.
>> >
>> > Cc: YAMAMOTO Takashi <yamamoto at valinux.co.jp>
>> > Signed-off-by: Simon Horman <horms at verge.net.au>
>> > ---
>> > ofproto/connmgr.c | 32 ++++----------------------------
>> > 1 file changed, 4 insertions(+), 28 deletions(-)
>> >
>> > diff --git a/ofproto/connmgr.c b/ofproto/connmgr.c
>> > index 033ab7d..954a0f9 100644
>> > --- a/ofproto/connmgr.c
>> > +++ b/ofproto/connmgr.c
>> > @@ -1452,8 +1452,7 @@ ofconn_send(const struct ofconn *ofconn, struct ofpbuf *msg,
>> > ^L
>> > /* Sending asynchronous messages. */
>> >
>> > -static void schedule_packet_in(struct ofconn *, struct ofproto_packet_in,
>> > - enum ofp_packet_in_reason wire_reason);
>> > +static void schedule_packet_in(struct ofconn *, struct ofproto_packet_in);
>> >
>> > /* Sends an OFPT_PORT_STATUS message with 'opp' and 'reason' to appropriate
>> > * controllers managed by 'mgr'. For messages caused by a controller
>> > @@ -1526,25 +1525,6 @@ connmgr_send_flow_removed(struct connmgr *mgr,
>> > }
>> > }
>> >
>> > -/* Normally a send-to-controller action uses reason OFPR_ACTION. However, in
>> > - * OpenFlow 1.3 and later, packet_ins generated by a send-to-controller action
>> > - * in a "table-miss" flow (one with priority 0 and completely wildcarded) are
>> > - * sent as OFPR_NO_MATCH. This function returns the reason that should
>> > - * actually be sent on 'ofconn' for 'pin'. */
>> > -static enum ofp_packet_in_reason
>> > -wire_reason(struct ofconn *ofconn, const struct ofproto_packet_in *pin)
>> > -{
>> > - if (pin->generated_by_table_miss && pin->up.reason == OFPR_ACTION) {
>> > - enum ofputil_protocol protocol = ofconn_get_protocol(ofconn);
>> > -
>> > - if (protocol != OFPUTIL_P_NONE
>> > - && ofputil_protocol_to_ofp_version(protocol) >= OFP13_VERSION) {
>> > - return OFPR_NO_MATCH;
>> > - }
>> > - }
>> > - return pin->up.reason;
>> > -}
>> > -
>> > /* Given 'pin', sends an OFPT_PACKET_IN message to each OpenFlow controller as
>> > * necessary according to their individual configurations.
>> > *
>> > @@ -1556,11 +1536,9 @@ connmgr_send_packet_in(struct connmgr *mgr,
>> > struct ofconn *ofconn;
>> >
>> > LIST_FOR_EACH (ofconn, node, &mgr->all_conns) {
>> > - enum ofp_packet_in_reason reason = wire_reason(ofconn, pin);
>> > -
>> > - if (ofconn_receives_async_msg(ofconn, OAM_PACKET_IN, reason)
>> > + if (ofconn_receives_async_msg(ofconn, OAM_PACKET_IN, pin->up.reason)
>> > && ofconn->controller_id == pin->controller_id) {
>> > - schedule_packet_in(ofconn, *pin, reason);
>> > + schedule_packet_in(ofconn, *pin);
>> > }
>> > }
>> > }
>> > @@ -1586,8 +1564,7 @@ do_send_packet_ins(struct ofconn *ofconn, struct list *txq)
>> > /* Takes 'pin', composes an OpenFlow packet-in message from it, and passes it
>> > * to 'ofconn''s packet scheduler for sending. */
>> > static void
>> > -schedule_packet_in(struct ofconn *ofconn, struct ofproto_packet_in pin,
>> > - enum ofp_packet_in_reason wire_reason)
>> > +schedule_packet_in(struct ofconn *ofconn, struct ofproto_packet_in pin)
>> > {
>> > struct connmgr *mgr = ofconn->connmgr;
>> > uint16_t controller_max_len;
>> > @@ -1595,7 +1572,6 @@ schedule_packet_in(struct ofconn *ofconn, struct ofproto_packet_in pin,
>> >
>> > pin.up.total_len = pin.up.packet_len;
>> >
>> > - pin.up.reason = wire_reason;
>> > if (pin.up.reason == OFPR_ACTION) {
>> > controller_max_len = pin.send_len; /* max_len */
>> > } else {
>> > --
>> > 1.8.5.2
>>
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