Hi, friendly ping for this patch. Ilya Maximets <[email protected]> 于2021年5月22日周六 上午3:50写道： > > On 5/21/21 5:00 AM, 贺鹏 wrote: > > Hi, Ilya > > > > > > > > Ilya Maximets <[email protected]> 于2021年5月19日周三 下午8:50写道： > >> > >> On 2/27/21 10:34 AM, Peng He wrote: > >>> CT zone could be set from a field that is not included in frozen > >>> metadata. Consider the example rules which are typically seen in > >>> 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 sets the zone-id from the first megaflow and commit to CT. > >>> > >>> The current implementation will generate a megaflow that 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 convention, if a field X is set by Y > >>> (Y is a variable not an Imm), we should also mask Y as a match > >>> in the generated megaflow. An exception is that if the zone-id is > >>> set by the field that is included in the frozen state (i.e. regs) and this > >>> upcall is a resume of a thawed xlate, the un-wildcarding can be skipped, > >>> as the recirc_id is a hash of the values in these fields, and it will > >>> change > >>> following the changes of these fields. When the recirc_id changes, > >>> all megaflows with the old recirc id will be invalid later. > >>> > >>> Fixes: 07659514c3 ("Add support for connection tracking.") > >>> Reported-by: Sai Su <[email protected]> > >>> Signed-off-by: Peng He <[email protected]> > >>> --- > >>> include/openvswitch/meta-flow.h | 1 + > >>> lib/meta-flow.c | 13 ++++++++++ > >>> ofproto/ofproto-dpif-xlate.c | 12 +++++++++ > >>> tests/system-traffic.at | 45 +++++++++++++++++++++++++++++++++ > >>> 4 files changed, 71 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..14d00db1e 100644 > >>> --- a/ofproto/ofproto-dpif-xlate.c > >>> +++ b/ofproto/ofproto-dpif-xlate.c > >>> @@ -6195,6 +6195,18 @@ compose_conntrack_action(struct xlate_ctx *ctx, > >>> struct ofpact_conntrack *ofc, > >>> > >>> if (ofc->zone_src.field) { > >>> zone = mf_get_subfield(&ofc->zone_src, &ctx->xin->flow); > >>> + 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); > >>> + } > >>> + } else { > >>> + mf_mask_field(ofc->zone_src.field, ctx->wc); > >>> + } > >> > >> IIUC, in current code above block is equal to just a single line: > >> > >> mf_mask_field(ofc->zone_src.field, ctx->wc); > >> > >> That is because zone is not part of a frozen metadata, right? > > > > Yes, basically this is the reason. > > I think the original code only considers the case that the zone id is > > set by IMM, not > > by a reg. > > > >> > >> Can we just remove all this extra logic and unwildcard unconditionally? > >> I understand that this code might save us one match in case someday > >> zone will be part of a frozen metadata, but is that really important? > >> Is there any harm in unwildcarding this field unconditionally? > > > > I think the code can reduce the number of megaflows in case that the rule > > sets the zone-id using IMM. But I think unconditionally un-wildcarding is > > also > > OK. > > From what I managed to test, if value is taken from any register > populated by Imm, there are no extra matches in datapath flows. > Maybe I'm missing some cases, though. > > I tried to experiment a bit with this code and the test case. > First thing that I found is that we, probably, need to use > mf_write_subfield_flow() instead of mf_mask_field(), because > we should not unwildcard the whole field if only part of it > used. > > Second thing is that I tried to write following set of flows > that might not make much sense, but should probably work fine: > > priority=100,in_port=1,tcp,ct_state=-trk,action=ct(zone=5,table=0,commit,exec(load:0xffff0005->NXM_NX_CT_LABEL[[0..31]])) > priority=100,in_port=1,tcp,ct_state=+trk,action=ct(commit,zone=NXM_NX_CT_LABEL[[0..15]]),2 > > And what I see is that in resulted datapath flows there is no > match on ct_label. This happens because masks of ct_label and > ct_mark gets saved at the beginning of the function and restored > later, i.e. our un-wildcarding is lost. > > The third thing is that if I'm un-wildcarding before saving or > after restoring, I see a bit weird datapath flow after modification > of the first flow to: > > priority=100,in_port=1,tcp,ct_state=-trk,action=ct(zone=15,table=0,commit,exec(load:0xffff000f->NXM_NX_CT_LABEL[[0..31]])) > > There is a new datapath flow with a correct ct_label match, but > the old flow gets updated to have ct_label match on 0. This might > make some sense for this set of flows, but I'm not sure. > > Before flow-mod: > > recirc_id(0),in_port(ovs-p0),ct_state(-trk),eth(),eth_type(0x0800),ipv4(proto=6,frag=no), > actions:ct(commit,zone=5,label=0xffff0005/0xffffffff),recirc(0x1) > > recirc_id(0x1),in_port(ovs-p0),ct_state(+trk),ct_label(0x5/0xffff),eth(),eth_type(0x0800),ipv4(proto=6,frag=no), > actions:ct(commit,zone=5,label=0x5/0xffff),ovs-p1 > > After: > > recirc_id(0),in_port(ovs-p0),ct_state(-trk),eth(),eth_type(0x0800),ipv4(proto=6,frag=no), > actions:ct(commit,zone=15,label=0xffff000f/0xffffffff),recirc(0x1) > > recirc_id(0x1),in_port(ovs-p0),ct_state(+trk),ct_label(0/0xffff),eth(),eth_type(0x0800),ipv4(proto=6,frag=no), > actions:ct(commit,label=0/0xffff),ovs-p1 > > recirc_id(0x1),in_port(ovs-p0),ct_state(+trk),ct_label(0xf/0xffff),eth(),eth_type(0x0800),ipv4(proto=6,frag=no), > actions:ct(commit,zone=15,label=0xf/0xffff),ovs-p1 > > Best regards, Ilya Maximets.
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