[ovs-dev,v7,7/9] features: Add detection for sample with registers.

diff --git a/controller/chassis.c b/controller/chassis.c
index 4942ba281d..42a2894dce 100644
--- a/controller/chassis.c
+++ b/controller/chassis.c
@@ -67,6 +67,8 @@  struct ovs_chassis_cfg {
     struct ds iface_types;
     /* Is this chassis an interconnection gateway. */
     bool is_interconn;
+    /* Does OVS support sampling with ids taken from registers? */
+    bool sample_with_regs;
 };
 
 static void
@@ -338,6 +340,8 @@  chassis_parse_ovs_config(const struct ovsrec_open_vswitch_table *ovs_table,
                                   &ovs_cfg->iface_types);
 
     ovs_cfg->is_interconn = get_is_interconn(&cfg->external_ids, chassis_id);
+    ovs_cfg->sample_with_regs =
+        ovs_feature_is_supported(OVS_SAMPLE_REG_SUPPORT);
 
     return true;
 }
@@ -372,6 +376,8 @@  chassis_build_other_config(const struct ovs_chassis_cfg *ovs_cfg,
     smap_replace(config, OVN_FEATURE_LS_DPG_COLUMN, "true");
     smap_replace(config, OVN_FEATURE_CT_COMMIT_NAT_V2, "true");
     smap_replace(config, OVN_FEATURE_CT_COMMIT_TO_ZONE, "true");
+    smap_replace(config, OVN_FEATURE_SAMPLE_WITH_REGISTERS,
+                 ovs_cfg->sample_with_regs ? "true" : "false");
 }
 
 /*
@@ -523,6 +529,14 @@  chassis_other_config_changed(const struct ovs_chassis_cfg *ovs_cfg,
         return true;
     }
 
+    bool chassis_sample_with_regs =
+        smap_get_bool(&chassis_rec->other_config,
+                      OVN_FEATURE_SAMPLE_WITH_REGISTERS,
+                      false);
+    if (chassis_sample_with_regs != ovs_cfg->sample_with_regs) {
+        return true;
+    }
+
     return false;
 }
 
@@ -656,6 +670,7 @@  update_supported_sset(struct sset *supported)
     sset_add(supported, OVN_FEATURE_LS_DPG_COLUMN);
     sset_add(supported, OVN_FEATURE_CT_COMMIT_NAT_V2);
     sset_add(supported, OVN_FEATURE_CT_COMMIT_TO_ZONE);
+    sset_add(supported, OVN_FEATURE_SAMPLE_WITH_REGISTERS);
 }
 
 static void
diff --git a/include/ovn/features.h b/include/ovn/features.h
index 97669410af..4275f75269 100644
--- a/include/ovn/features.h
+++ b/include/ovn/features.h
@@ -29,6 +29,7 @@ 
 #define OVN_FEATURE_LS_DPG_COLUMN "ls-dpg-column"
 #define OVN_FEATURE_CT_COMMIT_NAT_V2 "ct-commit-nat-v2"
 #define OVN_FEATURE_CT_COMMIT_TO_ZONE "ct-commit-to-zone"
+#define OVN_FEATURE_SAMPLE_WITH_REGISTERS "ovn-sample-with-registers"
 
 /* OVS datapath supported features.  Based on availability OVN might generate
  * different types of openflows.
@@ -39,6 +40,7 @@  enum ovs_feature_support_bits {
     OVS_CT_TUPLE_FLUSH_BIT,
     OVS_DP_HASH_L4_SYM_BIT,
     OVS_OF_GROUP_SUPPORT_BIT,
+    OVS_SAMPLE_REG_SUPPORT_BIT,
 };
 
 enum ovs_feature_value {
@@ -47,6 +49,7 @@  enum ovs_feature_value {
     OVS_CT_TUPLE_FLUSH_SUPPORT = (1 << OVS_CT_TUPLE_FLUSH_BIT),
     OVS_DP_HASH_L4_SYM_SUPPORT = (1 << OVS_DP_HASH_L4_SYM_BIT),
     OVS_OF_GROUP_SUPPORT = (1 << OVS_OF_GROUP_SUPPORT_BIT),
+    OVS_SAMPLE_REG_SUPPORT = (1 << OVS_SAMPLE_REG_SUPPORT_BIT),
 };
 
 void ovs_feature_support_destroy(void);
diff --git a/lib/features.c b/lib/features.c
index d3591d6410..ab0327d516 100644
--- a/lib/features.c
+++ b/lib/features.c
@@ -25,6 +25,8 @@ 
 #include "openvswitch/vlog.h"
 #include "openvswitch/ofpbuf.h"
 #include "openvswitch/rconn.h"
+#include "openvswitch/ofp-actions.h"
+#include "openvswitch/ofp-bundle.h"
 #include "openvswitch/ofp-msgs.h"
 #include "openvswitch/ofp-meter.h"
 #include "openvswitch/ofp-group.h"
@@ -185,6 +187,87 @@  group_features_handle_response(struct ovs_openflow_feature *feature,
     return supported_ovs_features & feature->value;
 }
 
+static void
+sample_with_reg_send_request(struct ovs_openflow_feature *feature)
+{
+    struct ofputil_bundle_ctrl_msg ctrl = {
+        .bundle_id = 0,
+        .flags     = OFPBF_ORDERED | OFPBF_ATOMIC,
+        .type      = OFPBCT_OPEN_REQUEST,
+    };
+    rconn_send(swconn,
+               ofputil_encode_bundle_ctrl_request(OFP15_VERSION, &ctrl), NULL);
+
+    uint8_t actions_stub[64];
+    struct ofpbuf actions;
+    ofpbuf_use_stub(&actions, actions_stub, sizeof(actions_stub));
+
+    struct mf_subfield subfield = {
+        .field = mf_from_id(MFF_REG0),
+        .n_bits = 32,
+        .ofs = 0
+    };
+
+    struct ofpact_sample *sample = ofpact_put_SAMPLE(&actions);
+    sample->probability = UINT16_MAX;
+    sample->collector_set_id = 0;
+    sample->obs_domain_src = subfield;
+    sample->obs_point_src = subfield;
+    sample->sampling_port = OFPP_NONE;
+
+    struct ofputil_flow_mod fm = {
+        .priority = 0,
+        .table_id = 0,
+        .ofpacts = actions.data,
+        .ofpacts_len = actions.size,
+        .command = OFPFC_ADD,
+        .new_cookie = htonll(0),
+        .buffer_id = UINT32_MAX,
+        .out_port = OFPP_ANY,
+        .out_group = OFPG_ANY,
+    };
+
+    struct match match;
+    match_init_catchall(&match);
+    minimatch_init(&fm.match, &match);
+
+    struct ofpbuf *fm_msg = ofputil_encode_flow_mod(&fm, OFPUTIL_P_OF15_OXM);
+
+    struct ofputil_bundle_add_msg bam = {
+        .bundle_id = ctrl.bundle_id,
+        .flags = ctrl.flags,
+        .msg = fm_msg->data,
+    };
+    struct ofpbuf *msg = ofputil_encode_bundle_add(OFP15_VERSION, &bam);
+
+    feature->xid = ((struct ofp_header *) msg->data)->xid;
+    rconn_send(swconn, msg, NULL);
+
+    ctrl.type = OFPBCT_DISCARD_REQUEST;
+    rconn_send(swconn,
+               ofputil_encode_bundle_ctrl_request(OFP15_VERSION, &ctrl), NULL);
+
+    minimatch_destroy(&fm.match);
+    ofpbuf_delete(fm_msg);
+}
+
+static bool
+sample_with_reg_handle_response(struct ovs_openflow_feature *feature,
+                                enum ofptype type, const struct ofp_header *oh)
+{
+    if (type != OFPTYPE_ERROR) {
+        log_unexpected_reply(feature, oh);
+    }
+
+    return false;
+}
+
+static bool
+sample_with_reg_handle_barrier(struct ovs_openflow_feature *feature OVS_UNUSED)
+{
+    return true;
+}
+
 static struct ovs_openflow_feature all_openflow_features[] = {
         {
             .value = OVS_DP_METER_SUPPORT,
@@ -199,6 +282,13 @@  static struct ovs_openflow_feature all_openflow_features[] = {
             .send_request = group_features_send_request,
             .handle_response = group_features_handle_response,
             .handle_barrier = default_barrier_response_handle,
+        },
+        {
+            .value = OVS_SAMPLE_REG_SUPPORT,
+            .name = "sample_action_with_registers",
+            .send_request = sample_with_reg_send_request,
+            .handle_response = sample_with_reg_handle_response,
+            .handle_barrier = sample_with_reg_handle_barrier,
         }
 };
 
@@ -271,6 +361,7 @@  ovs_feature_is_valid(enum ovs_feature_value feature)
     case OVS_CT_TUPLE_FLUSH_SUPPORT:
     case OVS_DP_HASH_L4_SYM_SUPPORT:
     case OVS_OF_GROUP_SUPPORT:
+    case OVS_SAMPLE_REG_SUPPORT:
         return true;
     default:
         return false;
diff --git a/northd/en-global-config.c b/northd/en-global-config.c
index d7607aa074..0ce7f83083 100644
--- a/northd/en-global-config.c
+++ b/northd/en-global-config.c
@@ -381,6 +381,7 @@  northd_enable_all_features(struct ed_type_global_config *data)
         .ls_dpg_column = true,
         .ct_commit_nat_v2 = true,
         .ct_commit_to_zone = true,
+        .sample_with_reg = true,
     };
 }
 
@@ -442,6 +443,15 @@  build_chassis_features(const struct sbrec_chassis_table *sbrec_chassis_table,
             chassis_features->ct_commit_to_zone) {
             chassis_features->ct_commit_to_zone = false;
         }
+
+        bool sample_with_reg =
+                smap_get_bool(&chassis->other_config,
+                              OVN_FEATURE_SAMPLE_WITH_REGISTERS,
+                              false);
+        if (!sample_with_reg &&
+            chassis_features->sample_with_reg) {
+            chassis_features->sample_with_reg = false;
+        }
     }
 }
 
diff --git a/northd/en-global-config.h b/northd/en-global-config.h
index 8a1c35fc8f..0cf34482af 100644
--- a/northd/en-global-config.h
+++ b/northd/en-global-config.h
@@ -19,6 +19,7 @@  struct chassis_features {
     bool ls_dpg_column;
     bool ct_commit_nat_v2;
     bool ct_commit_to_zone;
+    bool sample_with_reg;
 };
 
 struct global_config_tracked_data {