[ovs-dev] ofproto-dpif: Allow IPv6 ND Extensions only if supported

diff --git a/lib/odp-util.c b/lib/odp-util.c
index 3a574bf9d..b9600b4d5 100644
--- a/lib/odp-util.c
+++ b/lib/odp-util.c
@@ -6206,23 +6206,24 @@  odp_flow_key_from_flow__(const struct odp_flow_key_parms *parms,
                 && (!export_mask || (data->tp_src == htons(0xff)
                                      && data->tp_dst == htons(0xff)))) {
                 struct ovs_key_nd *nd_key;
-                struct ovs_key_nd_extensions *nd_ext_key;
                 nd_key = nl_msg_put_unspec_uninit(buf, OVS_KEY_ATTR_ND,
                                                     sizeof *nd_key);
                 nd_key->nd_target = data->nd_target;
                 nd_key->nd_sll = data->arp_sha;
                 nd_key->nd_tll = data->arp_tha;
 
-                /* Add ND Extensions Attr only if reserved field
+                /* Add ND Extensions Attr only if supported and reserved field
                  * or options type is set. */
-                if (data->igmp_group_ip4 != 0 ||
-                    data->tcp_flags != 0) {
-                    nd_ext_key =
-                         nl_msg_put_unspec_uninit(buf,
+                if (parms->support.nd_ext) {
+                    struct ovs_key_nd_extensions *nd_ext_key;
+
+                    if (data->igmp_group_ip4 != 0 || data->tcp_flags != 0) {
+                        nd_ext_key = nl_msg_put_unspec_uninit(buf,
                                             OVS_KEY_ATTR_ND_EXTENSIONS,
                                             sizeof *nd_ext_key);
-                    nd_ext_key->nd_reserved = data->igmp_group_ip4;
-                    nd_ext_key->nd_options_type = ntohs(data->tcp_flags);
+                        nd_ext_key->nd_reserved = data->igmp_group_ip4;
+                        nd_ext_key->nd_options_type = ntohs(data->tcp_flags);
+                    }
                 }
             }
         }
diff --git a/lib/odp-util.h b/lib/odp-util.h
index a03e82532..f15e258e6 100644
--- a/lib/odp-util.h
+++ b/lib/odp-util.h
@@ -203,7 +203,11 @@  int odp_flow_from_string(const char *s, const struct simap *port_names,
                                                                              \
     /* Conntrack original direction tuple matching * supported. */           \
     ODP_SUPPORT_FIELD(bool, ct_orig_tuple, "CT orig tuple")                  \
-    ODP_SUPPORT_FIELD(bool, ct_orig_tuple6, "CT orig tuple for IPv6")
+    ODP_SUPPORT_FIELD(bool, ct_orig_tuple6, "CT orig tuple for IPv6")        \
+                                                                             \
+    /* If true, it means that the datapath supports the IPv6 Neigh           \
+     * Discovery Extension bits. */                                          \
+    ODP_SUPPORT_FIELD(bool, nd_ext, "IPv6 ND Extension")
 
 /* Indicates support for various fields. This defines how flows will be
  * serialised. */
diff --git a/ofproto/ofproto-dpif.c b/ofproto/ofproto-dpif.c
index c35ec3e61..1aa4dad2b 100644
--- a/ofproto/ofproto-dpif.c
+++ b/ofproto/ofproto-dpif.c
@@ -1470,6 +1470,55 @@  check_max_dp_hash_alg(struct dpif_backer *backer)
     return max_alg;
 }
 
+/* Tests whether 'backer''s datapath supports IPv6 ND extensions.
+ * Only userspace datapath support OVS_KEY_ATTR_ND_EXTENSIONS in keys.
+ *
+ * Returns false if 'backer' definitely does not support matching and
+ * setting reserved and options type, true if it seems to support. */
+static bool
+check_nd_extensions(struct dpif_backer *backer)
+{
+    struct eth_header *eth;
+    struct ofpbuf actions;
+    struct dpif_execute execute;
+    struct dp_packet packet;
+    struct flow flow;
+    int error;
+    struct ovs_key_nd_extensions key, mask;
+
+    ofpbuf_init(&actions, 64);
+    memset(&key, 0x53, sizeof key);
+    memset(&mask, 0x7f, sizeof mask);
+    commit_masked_set_action(&actions, OVS_KEY_ATTR_ND_EXTENSIONS, &key, &mask,
+                             sizeof key);
+
+    /* Compose a dummy ethernet packet. */
+    dp_packet_init(&packet, ETH_HEADER_LEN);
+    eth = dp_packet_put_zeros(&packet, ETH_HEADER_LEN);
+    eth->eth_type = htons(0x1234);
+
+    flow_extract(&packet, &flow);
+
+    /* Execute the actions.  On datapaths without support fails with EINVAL. */
+    execute.actions = actions.data;
+    execute.actions_len = actions.size;
+    execute.packet = &packet;
+    execute.flow = &flow;
+    execute.needs_help = false;
+    execute.probe = true;
+    execute.mtu = 0;
+
+    error = dpif_execute(backer->dpif, &execute);
+
+    dp_packet_uninit(&packet);
+    ofpbuf_uninit(&actions);
+
+    VLOG_INFO("%s: Datapath %s IPv6 ND Extensions", dpif_name(backer->dpif),
+              error ? "does not support" : "supports");
+
+    return !error;
+}
+
 #define CHECK_FEATURE__(NAME, SUPPORT, FIELD, VALUE, ETHTYPE)               \
 static bool                                                                 \
 check_##NAME(struct dpif_backer *backer)                                    \
@@ -1541,10 +1590,10 @@  check_support(struct dpif_backer *backer)
     backer->rt_support.odp.ct_zone = check_ct_zone(backer);
     backer->rt_support.odp.ct_mark = check_ct_mark(backer);
     backer->rt_support.odp.ct_label = check_ct_label(backer);
-
     backer->rt_support.odp.ct_state_nat = check_ct_state_nat(backer);
     backer->rt_support.odp.ct_orig_tuple = check_ct_orig_tuple(backer);
     backer->rt_support.odp.ct_orig_tuple6 = check_ct_orig_tuple6(backer);
+    backer->rt_support.odp.nd_ext = check_nd_extensions(backer);
 }
 
 static int
@@ -4551,6 +4600,14 @@  check_actions(const struct ofproto_dpif *ofproto,
                                        "ct original direction tuple");
                 return OFPERR_NXBAC_CT_DATAPATH_SUPPORT;
             }
+        } else if (!support->nd_ext && ofpact->type == OFPACT_SET_FIELD) {
+            const struct mf_field *dst = ofpact_get_mf_dst(ofpact);
+
+            if (dst->id == MFF_ND_RESERVED || dst->id == MFF_ND_OPTIONS_TYPE) {
+                report_unsupported_act("set field",
+                                       "setting IPv6 ND Extensions fields");
+                return OFPERR_OFPBAC_BAD_SET_ARGUMENT;
+            }
         }
     }
 
diff --git a/tests/test-odp.c b/tests/test-odp.c
index 09fec706a..0ddfd4070 100644
--- a/tests/test-odp.c
+++ b/tests/test-odp.c
@@ -65,6 +65,7 @@  parse_keys(bool wc_keys)
                     .ct_mark = true,
                     .ct_label = true,
                     .max_vlan_headers = SIZE_MAX,
+                    .nd_ext = true,
                 },
             };