[ovs-dev] [PATCH v1] ofproto-dpif-xlate: fix zone set from non frozen metadata field

Mark Gray mark.d.gray at redhat.com
Wed Feb 17 10:13:26 UTC 2021


I'm not too familiar with this code but I have some comments.

On 15/02/2021 09:50, Peng He wrote:
> CT zone could be set from a field that is not included in frozen
> metedata. Consider the belowing cases which is normally used in

Nits:

s/metedata/metadata
s/belowing cases which is/cases below which are

> OpenStack security group rules:
> 
> priority=100,in_port=1,tcp,ct_state=-trk,action=ct(zone=5,table=0)
> priority=100,in_port=1,tcp,ct_state=+trk,action=ct(commit,zone=NXM_NX_CT_ZONE[]),2
> 
> The zone is set from the first rule's ct action. These two rules will
> generate two megaflows: the first one uses zone=5 to query the CT module,
> the second one set zone from the first megaflow and commit to CT.
> 
> The current implementation will generate a megaflow which does not use
> ct_zone=5 as a match, but directly commit into the ct using zone=5, as zone is
> set by an Imm not a field.
> 
> Consider a situation that one changes the zone id (for example to 15)
> in the first rule however still keep the second rule unchanged. During
> this change, there is traffic hitting the two generated megaflows, the
> revaldiator would revalidate all megaflows, however, the revalidator will
> not change the second megaflow, because zone=5 is recorded in the
> megaflow, so the xlate will still translate the commit action into zone=5,
> and the new traffic will still commit to CT as zone=5, not zone=15,
> resulting in taffic drops and other issues.
> 
> Just like OVS set-field action, if the field X is set by Y, we should also
> mask Y as a match in the generated megaflow. An exception is that, if the zone
> is set by the field that is included in the frozen state and this upcall is
> a resume of a thawed xlate, the masking can be skipped, as if one changes
> the previous rule, the generated recirc_id will be changed, and all megaflows
> with the old recirc id will be invalid later, i.e. the revalidator will
> not reuse the old megaflows at all.
> 
> Fixes: 07659514c3 ("Add support for connection tracking.")
> Reported-by: Sai Su <susai.ss at bytedance.com>
> Signed-off-by: Peng He <hepeng.0320 at bytedance.com>
> ---
>  include/openvswitch/meta-flow.h |  1 +
>  lib/meta-flow.c                 | 13 +++++++++++
>  ofproto/ofproto-dpif-xlate.c    | 15 +++++++++++++
>  tests/system-traffic.at         | 39 +++++++++++++++++++++++++++++++++
>  4 files changed, 68 insertions(+)
> 
> diff --git a/include/openvswitch/meta-flow.h b/include/openvswitch/meta-flow.h
> index 95e52e358..045dce8f5 100644
> --- a/include/openvswitch/meta-flow.h
> +++ b/include/openvswitch/meta-flow.h
> @@ -2305,6 +2305,7 @@ void mf_set_flow_value_masked(const struct mf_field *,
>                                const union mf_value *mask,
>                                struct flow *);
>  bool mf_is_tun_metadata(const struct mf_field *);
> +bool mf_is_frozen_metadata(const struct mf_field *);
>  bool mf_is_pipeline_field(const struct mf_field *);
>  bool mf_is_set(const struct mf_field *, const struct flow *);
>  void mf_mask_field(const struct mf_field *, struct flow_wildcards *);
> diff --git a/lib/meta-flow.c b/lib/meta-flow.c
> index c808d205d..e03cd8d0c 100644
> --- a/lib/meta-flow.c
> +++ b/lib/meta-flow.c
> @@ -1788,6 +1788,19 @@ mf_is_tun_metadata(const struct mf_field *mf)
>             mf->id < MFF_TUN_METADATA0 + TUN_METADATA_NUM_OPTS;
>  }
>  
> +bool
> +mf_is_frozen_metadata(const struct mf_field *mf)
> +{
> +    if (mf->id >= MFF_TUN_ID && mf->id <= MFF_IN_PORT_OXM) {
> +        return true;
> +    }
> +
> +    if (mf->id >= MFF_REG0 && mf->id < MFF_ETH_SRC) {
> +        return true;
> +    }
> +    return false;
> +}
> +
>  bool
>  mf_is_pipeline_field(const struct mf_field *mf)
>  {
> diff --git a/ofproto/ofproto-dpif-xlate.c b/ofproto/ofproto-dpif-xlate.c
> index 7108c8a30..5d1f029fd 100644
> --- a/ofproto/ofproto-dpif-xlate.c
> +++ b/ofproto/ofproto-dpif-xlate.c
> @@ -6212,6 +6212,21 @@ compose_conntrack_action(struct xlate_ctx *ctx, struct ofpact_conntrack *ofc,
>                             &ctx->xin->flow, ctx->wc, zone);
>          }
>      }
> +
> +    if (ofc->zone_src.field) {
> +        if (ctx->xin->frozen_state) {
> +            /* If the upcall is a resume of a recirculation, we only need to
> +             * unwildcard the fields that are not in the frozen_metadata, as
> +             * when the rules update, OVS will generate a new recirc_id,
> +             * which will invalidate the megaflow with old the recirc_id.
> +             */
> +            if (!mf_is_frozen_metadata(ofc->zone_src.field)) {
> +                mf_mask_field(ofc->zone_src.field, ctx->wc);
Is this the only field we should check and un-wildcard here. This seems
like it would be applicable across other fields.
> +            }
> +        } else {
> +            mf_mask_field(ofc->zone_src.field, ctx->wc);
> +        }
> +    }

Add a new line after the bracket

>      nl_msg_put_u16(ctx->odp_actions, OVS_CT_ATTR_ZONE, zone);
>      put_ct_mark(&ctx->xin->flow, ctx->odp_actions, ctx->wc);
>      put_ct_label(&ctx->xin->flow, ctx->odp_actions, ctx->wc);
> diff --git a/tests/system-traffic.at b/tests/system-traffic.at
> index fb5b9a36d..bee50e530 100644
> --- a/tests/system-traffic.at
> +++ b/tests/system-traffic.at
> @@ -1927,6 +1927,45 @@ tcp,orig=(src=10.1.1.3,dst=10.1.1.4,sport=<cleared>,dport=<cleared>),reply=(src=
>  OVS_TRAFFIC_VSWITCHD_STOP
>  AT_CLEANUP
>  
> +AT_SETUP([conntrack - zones from other field])
> +CHECK_CONNTRACK()
> +OVS_TRAFFIC_VSWITCHD_START()
> +
> +ADD_NAMESPACES(at_ns0, at_ns1)
> +
> +ADD_VETH(p0, at_ns0, br0, "10.1.1.1/24")
> +ADD_VETH(p1, at_ns1, br0, "10.1.1.2/24")
> +
> +dnl Allow any traffic from ns0->ns1. Only allow nd, return traffic from ns1->ns0.
> +AT_DATA([flows.txt], [dnl
> +priority=1,action=drop
> +priority=10,arp,action=normal
> +priority=10,icmp,action=normal
> +priority=100,in_port=1,tcp,ct_state=-trk,action=ct(zone=5,table=0)
> +priority=100,in_port=1,tcp,ct_state=+trk,action=ct(commit,zone=NXM_NX_CT_ZONE[]),2
> +priority=100,in_port=2,ct_state=-trk,tcp,action=ct(table=0,zone=5)
> +priority=100,in_port=2,ct_state=+trk,ct_zone=5,tcp,action=1
> +])
> +
> +AT_CHECK([ovs-ofctl --bundle add-flows br0 flows.txt])
> +
> +OVS_START_L7([at_ns1], [http])
> +
> +dnl HTTP requests from p0->p1 should work fine.
> +NS_CHECK_EXEC([at_ns0], [wget 10.1.1.2 -t 3 -T 1 --retry-connrefused -v -o wget0.log])
> +
> +AT_CHECK([ovs-appctl dpctl/dump-conntrack | FORMAT_CT(10.1.1.2)], [0], [dnl
> +tcp,orig=(src=10.1.1.1,dst=10.1.1.2,sport=<cleared>,dport=<cleared>),reply=(src=10.1.1.2,dst=10.1.1.1,sport=<cleared>,dport=<cleared>),zone=5,protoinfo=(state=<cleared>)
> +])
> +
> +AT_CHECK([ovs-appctl dpctl/dump-flows --names filter=in_port=ovs-p0 | strip_used | grep "+trk" ], [0], [dnl
> +ct_state(+trk),ct_zone(0x5),recirc_id(0x2),in_port(ovs-p0),packet_type(ns=0,id=0),eth_type(0x0800),ipv4(proto=6,frag=no), packets:5, bytes:465, used:0.0s, flags:FP., actions:ct(commit,zone=5),ovs-p1
> +])

This test fails for me. It looks like the order of the output from
dpctl/dump-flows is different and the recirc_id is different. Could
easily be an issue on my side but I am not sure what it is.

+++ /home/magray/ovs/tests/system-kmod-testsuite.dir/at-groups/41/stdout
       2021-02-17 04:57:36.171766685 -0500
@@ -1,2 +1,2 @@
-ct_state(+trk),ct_zone(0x5),recirc_id(0x2),in_port(ovs-p0),packet_type(ns=0,id=0),eth_type(0x0800),ipv4(proto=6,frag=no),
packets:5, bytes:465, used:0.0s, flags:FP., actions:ct(commit,zone=5),ovs-p1
+recirc_id(0x1),in_port(ovs-p0),ct_state(+trk),ct_zone(0x5),eth(),eth_type(0x0800),ipv4(proto=6,frag=no),
packets:5, bytes:465, used:0.0s, flags:FP., actions:ct(commit,zone=5),ovs-p1

It seems this test does not test the situation that you mention in the
commit message: "Consider a situation .. "? Can you add a check for that?

> +
> +OVS_TRAFFIC_VSWITCHD_STOP
> +AT_CLEANUP
> +
> +
>  AT_SETUP([conntrack - multiple bridges])
>  CHECK_CONNTRACK()
>  OVS_TRAFFIC_VSWITCHD_START(
> 



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