[ovs-dev] [PATCH 2/3] Combine conjunctions with identical matches into one flow.

Mark Michelson mmichels at redhat.com
Mon Oct 28 15:58:58 UTC 2019


On 10/28/19 11:33 AM, Numan Siddique wrote:
> On Sat, Oct 26, 2019 at 2:37 AM Mark Michelson <mmichels at redhat.com> wrote:
>>
>> As stated in previous commits, conjunctive matches have an issue where
>> it is possible to install multiple flows that have identical matches.
>> This results in ambiguity, and can lead to features (such as ACLs) not
>> functioning properly.
>>
>> This change fixes the problem by combining conjunctions with identical
>> matches into a single flow. As an example, in the past we may have had
>> something like:
>>
>> nw_dst=10.0.0.1 actions=conjunction(2,1/2)
>> nw_dst=10.0.0.1 actions=conjunction(3,1/2)
>>
>> This commit changes this into
>>
>> nw_dst=10.0.0.1 actions=conjunction(2,1/2),conjunction(3,1/2)
>>
>> This way, there is only a single flow with the proscribed match, and
>> there is no ambiguity.
>>
>> Signed-off-by: Mark Michelson <mmichels at redhat.com>
>> ---
>>   controller/lflow.c  |  5 ++--
>>   controller/ofctrl.c | 73 +++++++++++++++++++++++++++++++++++++++++++++--------
>>   controller/ofctrl.h |  6 +++++
>>   tests/ovn.at        | 17 +++++--------
>>   4 files changed, 79 insertions(+), 22 deletions(-)
>>
>> diff --git a/controller/lflow.c b/controller/lflow.c
>> index e3ed20cd4..34b7c36a6 100644
>> --- a/controller/lflow.c
>> +++ b/controller/lflow.c
>> @@ -736,8 +736,9 @@ consider_logical_flow(
>>                   dst->clause = src->clause;
>>                   dst->n_clauses = src->n_clauses;
>>               }
>> -            ofctrl_add_flow(flow_table, ptable, lflow->priority, 0, &m->match,
>> -                            &conj, &lflow->header_.uuid);
>> +
>> +            ofctrl_add_or_append_flow(flow_table, ptable, lflow->priority, 0,
>> +                                      &m->match, &conj, &lflow->header_.uuid);
>>               ofpbuf_uninit(&conj);
>>           }
>>       }
>> diff --git a/controller/ofctrl.c b/controller/ofctrl.c
>> index 3131baff0..afb0036f1 100644
>> --- a/controller/ofctrl.c
>> +++ b/controller/ofctrl.c
>> @@ -69,6 +69,11 @@ struct ovn_flow {
>>       uint64_t cookie;
>>   };
>>
>> +static struct ovn_flow *ovn_flow_alloc(uint8_t table_id, uint16_t priority,
>> +                                       uint64_t cookie,
>> +                                       const struct match *match,
>> +                                       const struct ofpbuf *actions,
>> +                                       const struct uuid *sb_uuid);
>>   static uint32_t ovn_flow_match_hash(const struct ovn_flow *);
>>   static struct ovn_flow *ovn_flow_lookup(struct hmap *flow_table,
>>                                           const struct ovn_flow *target,
>> @@ -657,16 +662,8 @@ ofctrl_check_and_add_flow(struct ovn_desired_flow_table *flow_table,
>>                             const struct uuid *sb_uuid,
>>                             bool log_duplicate_flow)
>>   {
>> -    struct ovn_flow *f = xmalloc(sizeof *f);
>> -    f->table_id = table_id;
>> -    f->priority = priority;
>> -    minimatch_init(&f->match, match);
>> -    f->ofpacts = xmemdup(actions->data, actions->size);
>> -    f->ofpacts_len = actions->size;
>> -    f->sb_uuid = *sb_uuid;
>> -    f->match_hmap_node.hash = ovn_flow_match_hash(f);
>> -    f->uuid_hindex_node.hash = uuid_hash(&f->sb_uuid);
>> -    f->cookie = cookie;
>> +    struct ovn_flow *f = ovn_flow_alloc(table_id, priority, cookie, match,
>> +                                        actions, sb_uuid);
>>
>>       ovn_flow_log(f, "ofctrl_add_flow");
>>
>> @@ -721,9 +718,65 @@ ofctrl_add_flow(struct ovn_desired_flow_table *desired_flows,
>>       ofctrl_check_and_add_flow(desired_flows, table_id, priority, cookie,
>>                                 match, actions, sb_uuid, true);
>>   }
>> +
>> +void
>> +ofctrl_add_or_append_flow(struct ovn_desired_flow_table *desired_flows,
>> +                          uint8_t table_id, uint16_t priority, uint64_t cookie,
>> +                          const struct match *match,
>> +                          const struct ofpbuf *actions,
>> +                          const struct uuid *sb_uuid)
>> +{
>> +    struct ovn_flow *f = ovn_flow_alloc(table_id, priority, cookie, match,
>> +                                        actions, sb_uuid);
>> +
>> +    ovn_flow_log(f, "ofctrl_add_or_append_flow");
>> +
>> +    struct ovn_flow *existing;
>> +    existing = ovn_flow_lookup(&desired_flows->match_flow_table, f, false);
>> +    if (existing) {
>> +        /* There's already a flow with this particular match. Append the
>> +         * action to that flow rather than adding a new flow
>> +         */
>> +        uint64_t compound_stub[64 / 8];
>> +        struct ofpbuf compound;
>> +        ofpbuf_use_stub(&compound, compound_stub, sizeof(compound_stub));
>> +        ofpbuf_put(&compound, existing->ofpacts, existing->ofpacts_len);
>> +        ofpbuf_put(&compound, f->ofpacts, f->ofpacts_len);
> 
> Instead of making use of a stub and copying the existing and new
> actions, can't we just
> copy the new actions to "existing->ofpacts" using ofpbuf_put() ?

You can't use ofpbuf_put() directly since existing->ofpacts is of type 
ofpact, not ofpbuf. And I don't think you can cast existing->ofpacts to 
an ofpbuf since existing->ofpacts was created from the 'data' member of 
an ofpbuf; we don't have the metadata, such as the method by which the 
data was allocated.

So maybe it's possible to create a new ofpbuf but have it use the 
existing->ofpacts buffer? I was looking and here are the issues:

1) ofpbuf_clone_data() creates a copy of the data passed in rather than 
using it directly. So it still requires freeing existing->ofpacts and 
reassigning it.
2) ofpbuf_use_stub() would result in overwriting the data passed into it 
unless we adjust the ofpbuf's size so that it points past the end of the 
data we passed in. I can't find any example of this being done in OVS.

If you have a good idea on how to re-use existing->ofpacts, then I'll 
happily do it.

> 
> ofpbuf_put() will take care of reallocating the memory if required.
> 
> Other than that, this and the 1st patch of this series, looks good to me.
> 
> Thanks
> Numan
> 
>> +
>> +        free(existing->ofpacts);
>> +        existing->ofpacts = xmemdup(compound.data, compound.size);
>> +        existing->ofpacts_len = compound.size;
>> +
>> +        ovn_flow_destroy(f);
>> +    } else {
>> +        hmap_insert(&desired_flows->match_flow_table, &f->match_hmap_node,
>> +                    f->match_hmap_node.hash);
>> +        hindex_insert(&desired_flows->uuid_flow_table, &f->uuid_hindex_node,
>> +                      f->uuid_hindex_node.hash);
>> +    }
>> +}
>>
>>   /* ovn_flow. */
>>
>> +static struct ovn_flow *
>> +ovn_flow_alloc(uint8_t table_id, uint16_t priority, uint64_t cookie,
>> +               const struct match *match, const struct ofpbuf *actions,
>> +               const struct uuid *sb_uuid)
>> +{
>> +    struct ovn_flow *f = xmalloc(sizeof *f);
>> +    f->table_id = table_id;
>> +    f->priority = priority;
>> +    minimatch_init(&f->match, match);
>> +    f->ofpacts = xmemdup(actions->data, actions->size);
>> +    f->ofpacts_len = actions->size;
>> +    f->sb_uuid = *sb_uuid;
>> +    f->match_hmap_node.hash = ovn_flow_match_hash(f);
>> +    f->uuid_hindex_node.hash = uuid_hash(&f->sb_uuid);
>> +    f->cookie = cookie;
>> +
>> +    return f;
>> +}
>> +
>>   /* Returns a hash of the match key in 'f'. */
>>   static uint32_t
>>   ovn_flow_match_hash(const struct ovn_flow *f)
>> diff --git a/controller/ofctrl.h b/controller/ofctrl.h
>> index 1e9ac16b9..21d2ce648 100644
>> --- a/controller/ofctrl.h
>> +++ b/controller/ofctrl.h
>> @@ -70,6 +70,12 @@ void ofctrl_add_flow(struct ovn_desired_flow_table *, uint8_t table_id,
>>                        const struct match *, const struct ofpbuf *ofpacts,
>>                        const struct uuid *);
>>
>> +void ofctrl_add_or_append_flow(struct ovn_desired_flow_table *desired_flows,
>> +                               uint8_t table_id, uint16_t priority,
>> +                               uint64_t cookie, const struct match *match,
>> +                               const struct ofpbuf *actions,
>> +                               const struct uuid *sb_uuid);
>> +
>>   void ofctrl_remove_flows(struct ovn_desired_flow_table *, const struct uuid *);
>>
>>   void ovn_desired_flow_table_init(struct ovn_desired_flow_table *);
>> diff --git a/tests/ovn.at b/tests/ovn.at
>> index 641a646fc..50d8efeec 100644
>> --- a/tests/ovn.at
>> +++ b/tests/ovn.at
>> @@ -12247,7 +12247,7 @@ ovn-nbctl create Address_Set name=set1 \
>>   addresses=\"10.0.0.4\",\"10.0.0.5\",\"10.0.0.6\"
>>   ovn-nbctl create Address_Set name=set2 \
>>   addresses=\"10.0.0.7\",\"10.0.0.8\",\"10.0.0.9\"
>> -ovn-nbctl acl-add ls1 to-lport 1002 \
>> +ovn-nbctl acl-add ls1 to-lport 1001 \
>>   'ip4 && ip4.src == $set1 && ip4.dst == $set1' allow
>>   ovn-nbctl acl-add ls1 to-lport 1001 \
>>   'ip4 && ip4.src == $set1 && ip4.dst == $set2' drop
>> @@ -12296,7 +12296,7 @@ cat 2.expected > expout
>>   $PYTHON "$ovs_srcdir/utilities/ovs-pcap.in" hv1/vif2-tx.pcap > 2.packets
>>   AT_CHECK([cat 2.packets], [0], [expout])
>>
>> -# There should be total of 12 flows present with conjunction action and 2 flows
>> +# There should be total of 9 flows present with conjunction action and 2 flows
>>   # with conj match. Eg.
>>   # table=44, priority=2002,conj_id=2,metadata=0x1 actions=resubmit(,45)
>>   # table=44, priority=2001,conj_id=3,metadata=0x1 actions=drop
>> @@ -12306,14 +12306,11 @@ AT_CHECK([cat 2.packets], [0], [expout])
>>   # priority=2001,ip,metadata=0x1,nw_dst=10.0.0.7 actions=conjunction(3,2/2)
>>   # priority=2001,ip,metadata=0x1,nw_dst=10.0.0.9 actions=conjunction(3,2/2)
>>   # priority=2001,ip,metadata=0x1,nw_dst=10.0.0.8 actions=conjunction(3,2/2)
>> -# priority=2002,ip,metadata=0x1,nw_src=10.0.0.6 actions=conjunction(2,1/2)
>> -# priority=2002,ip,metadata=0x1,nw_src=10.0.0.4 actions=conjunction(2,1/2)
>> -# priority=2002,ip,metadata=0x1,nw_src=10.0.0.5 actions=conjunction(2,1/2)
>> -# priority=2001,ip,metadata=0x1,nw_src=10.0.0.6 actions=conjunction(3,1/2)
>> -# priority=2001,ip,metadata=0x1,nw_src=10.0.0.4 actions=conjunction(3,1/2)
>> -# priority=2001,ip,metadata=0x1,nw_src=10.0.0.5 actions=conjunction(3,1/2)
>> -
>> -OVS_WAIT_UNTIL([test 12 = `as hv1 ovs-ofctl dump-flows br-int | \
>> +# priority=2002,ip,metadata=0x1,nw_src=10.0.0.6 actions=conjunction(2,1/2),conjunction(3,1/2)
>> +# priority=2002,ip,metadata=0x1,nw_src=10.0.0.4 actions=conjunction(2,1/2),conjunction(3,1/2)
>> +# priority=2002,ip,metadata=0x1,nw_src=10.0.0.5 actions=conjunction(2,1/2),conjunction(3,1/2)
>> +
>> +OVS_WAIT_UNTIL([test 9 = `as hv1 ovs-ofctl dump-flows br-int | \
>>   grep conjunction | wc -l`])
>>   OVS_WAIT_UNTIL([test 2 = `as hv1 ovs-ofctl dump-flows br-int | \
>>   grep conj_id | wc -l`])
>> --
>> 2.14.5
>>
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