[ovs-dev] [PATCH] ofproto: Properly refresh rule modified time when nothing else changes.

Justin Pettit jpettit at nicira.com
Sat Jan 26 00:51:51 UTC 2013


Looks good.

--Justin


On Jan 25, 2013, at 3:00 PM, Ben Pfaff <blp at nicira.com> wrote:

> In Open vSwitch, a "modify" or "modify_strict" flow_mod is supposed to
> refresh the flow's last-modified time even if nothing else changes, because
> this interpretation makes the "learn" action more useful.  As commit
> 308881afb (ofproto: Reinterpret meaning of OpenFlow hard timeouts with
> OFPFC_MODIFY.) notes:
> 
>    I finally found a good use for hard timeouts in OpenFlow, but they
>    require a slight reinterpretation of the meaning of hard timeouts.
>    Until now, a hard timeout meant that a flow would be removed the
>    specified number of seconds after a flow was created.  Intervening
>    modifications with OFPFC_MODIFY(_STRICT) had no effect on the hard
>    timeout; the flow would still be deleted the specified number of
>    seconds after its original creation.
> 
>    This commit changes the effect of OFPFC_MODIFY(_STRICT).  Now,
>    modifying a flow resets its hard timeout counter.  A flow will time out
>    the specified number of seconds after creation or after the last time
>    it is modified, whichever comes later.
> 
> However, commit 080437614b (ofproto: Represent flow cookie changes as
> operations too.) broke this behavior because it incorrectly optimized out
> "modify" operations that didn't change the flow's actions or flow cookie.
> This commit fixes the problem, and adds a test to prevent future
> regression.
> 
> Thanks to Amar Padmanabhan <amar at nicira.com> for helping to track this
> down.
> 
> Bug #14538.
> Reported-by: Hiroshi Tanaka <htanaka at vmware.com>
> CC: Amar Padmanabhan <amar at nicira.com>
> Signed-off-by: Ben Pfaff <blp at nicira.com>
> ---
> ofproto/ofproto.c |   18 +++++++++---
> tests/learn.at    |   75 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 88 insertions(+), 5 deletions(-)
> 
> diff --git a/ofproto/ofproto.c b/ofproto/ofproto.c
> index bc27079..249f2d5 100644
> --- a/ofproto/ofproto.c
> +++ b/ofproto/ofproto.c
> @@ -3261,10 +3261,6 @@ modify_flows__(struct ofproto *ofproto, struct ofconn *ofconn,
>         new_cookie = (fm->new_cookie != htonll(UINT64_MAX)
>                       ? fm->new_cookie
>                       : rule->flow_cookie);
> -        if (!actions_changed && new_cookie == rule->flow_cookie) {
> -            /* No change at all. */
> -            continue;
> -        }
> 
>         op = ofoperation_create(group, rule, OFOPERATION_MODIFY, 0);
>         rule->flow_cookie = new_cookie;
> @@ -4247,7 +4243,19 @@ ofopgroup_complete(struct ofopgroup *group)
>     LIST_FOR_EACH_SAFE (op, next_op, group_node, &group->ops) {
>         struct rule *rule = op->rule;
> 
> -        if (!op->error && !ofproto_rule_is_hidden(rule)) {
> +        /* We generally want to report the change to active OpenFlow flow
> +           monitors (e.g. NXST_FLOW_MONITOR).  There are three exceptions:
> +
> +              - The operation failed.
> +
> +              - The affected rule is not visible to controllers.
> +
> +              - The operation's only effect was to update rule->modified. */
> +        if (!(op->error
> +              || ofproto_rule_is_hidden(rule)
> +              || (op->type == OFOPERATION_MODIFY
> +                  && op->ofpacts
> +                  && rule->flow_cookie == op->flow_cookie))) {
>             /* Check that we can just cast from ofoperation_type to
>              * nx_flow_update_event. */
>             BUILD_ASSERT_DECL((enum nx_flow_update_event) OFOPERATION_ADD
> diff --git a/tests/learn.at b/tests/learn.at
> index 47c1d32..800dc14 100644
> --- a/tests/learn.at
> +++ b/tests/learn.at
> @@ -122,6 +122,81 @@ NXST_FLOW reply:
> OVS_VSWITCHD_STOP
> AT_CLEANUP
> 
> +dnl This test checks that repeated uses of a "learn" action cause the
> +dnl modified time of the learned flow to advance.  Otherwise, the
> +dnl learned flow will expire after its hard timeout even though it's
> +dnl supposed to be refreshed.  (The expiration can be hard to see since
> +dnl it gets re-learned again the next time a packet appears, but
> +dnl sometimes the expiration can cause temporary flooding etc.)
> +AT_SETUP([learning action - learn refreshes hard_age])
> +OVS_VSWITCHD_START(
> +  [add-port br0 p1 -- set Interface p1 type=dummy ofport_request=1 -- \
> +   add-port br0 p2 -- set Interface p2 type=dummy ofport_request=2 -- \
> +   add-port br0 p3 -- set Interface p3 type=dummy ofport_request=3])
> +
> +ovs-appctl time/stop
> +
> +# Set up flow table for MAC learning.
> +AT_DATA([flows.txt], [[
> +table=0 actions=learn(table=1, hard_timeout=10, NXM_OF_ETH_DST[]=NXM_OF_ETH_SRC[], output:NXM_OF_IN_PORT[]), resubmit(,1)
> +table=1 priority=0 actions=flood
> +]])
> +AT_CHECK([ovs-ofctl add-flows br0 flows.txt])
> +
> +# Trace an ICMP packet arriving on port 3, to create a MAC learning entry.
> +flow="in_port(3),eth(src=50:54:00:00:00:07,dst=50:54:00:00:00:05),eth_type(0x0800),ipv4(src=192.168.0.2,dst=192.168.0.1,proto=1,tos=0,ttl=64,frag=no),icmp(type=0,code=0)"
> +AT_CHECK([ovs-appctl ofproto/trace br0 "$flow" -generate], [0], [stdout])
> +actual=`tail -1 stdout | sed 's/Datapath actions: //'`
> +
> +expected="1,2,100"
> +AT_CHECK([ovs-dpctl normalize-actions "$flow" "$expected"], [0], [stdout])
> +mv stdout expout
> +AT_CHECK([ovs-dpctl normalize-actions "$flow" "$actual"], [0], [expout])
> +
> +# Check that the MAC learning entry appeared.
> +AT_CHECK([ovs-ofctl dump-flows br0 table=1 | ofctl_strip | sort], [0], [dnl
> + table=1, hard_timeout=10, dl_dst=50:54:00:00:00:07 actions=output:3
> + table=1, priority=0 actions=FLOOD
> +NXST_FLOW reply:
> +])
> +
> +# For 25 seconds, make sure that the MAC learning entry doesn't
> +# disappear as long as we refresh it every second.
> +for i in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25; do
> +    ovs-appctl time/warp 1000
> +    AT_CHECK([ovs-appctl ofproto/trace br0 "$flow" -generate], [0], [stdout])
> +
> +    # Check that the entry is there.
> +    AT_CHECK([ovs-ofctl dump-flows br0 table=1], [0], [stdout])
> +    AT_CHECK([ofctl_strip < stdout | sort], [0], [dnl
> + table=1, hard_timeout=10, dl_dst=50:54:00:00:00:07 actions=output:3
> + table=1, priority=0 actions=FLOOD
> +NXST_FLOW reply:
> +])
> +
> +    if test $i != 1; then
> +        # Check that hard_age has appeared.  We need to do this separately
> +        # from the above check because ofctl_strip removes it.  dump-flows
> +        # only prints hard_age when it is different from the flow's duration
> +        # (that is, the number of seconds from the time it was created),
> +        # so we only check for it after we've refreshed the flow once.
> +        AT_CHECK([grep dl_dst=50:54:00:00:00:07 stdout | grep -c hard_age],
> +                 [0], [1
> +])
> +    fi
> +done
> +
> +# Make sure that 15 seconds without refreshing makes the flow time out.
> +ovs-appctl time/warp 5000
> +ovs-appctl time/warp 5000
> +ovs-appctl time/warp 5000
> +    AT_CHECK([ovs-ofctl dump-flows br0 table=1 | ofctl_strip | sort], [0], [dnl
> + table=1, priority=0 actions=FLOOD
> +NXST_FLOW reply:
> +])
> +OVS_VSWITCHD_STOP
> +AT_CLEANUP
> +
> AT_SETUP([learning action - TCPv4 port learning])
> OVS_VSWITCHD_START(
>   [add-port br0 p1 -- set Interface p1 type=dummy -- \
> -- 
> 1.7.2.5
> 
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