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. 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.
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.
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 <[email protected]>
> > Signed-off-by: Simon Horman <[email protected]>
> > ---
> > 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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