ovn-controller: Detect and use L4_SYM dp-hash if available.

Regular dp-hash is not a canonical L4 hash (at least with the netlink
datapath).  If the datapath supports l4 symmetrical dp-hash use that one
instead.

Reported-at: ovn-org#112
Reported-at: https://bugzilla.redhat.com/show_bug.cgi?id=2188679
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
Acked-by: Ales Musil <amusil@redhat.com>

include/ovn/features.h

@@ -34,12 +34,14 @@ enum ovs_feature_support_bits {
     OVS_CT_ZERO_SNAT_SUPPORT_BIT,
     OVS_DP_METER_SUPPORT_BIT,
     OVS_CT_TUPLE_FLUSH_BIT,
+    OVS_DP_HASH_L4_SYM_BIT,
 };
 
 enum ovs_feature_value {
     OVS_CT_ZERO_SNAT_SUPPORT = (1 << OVS_CT_ZERO_SNAT_SUPPORT_BIT),
     OVS_DP_METER_SUPPORT = (1 << OVS_DP_METER_SUPPORT_BIT),
     OVS_CT_TUPLE_FLUSH_SUPPORT = (1 << OVS_CT_TUPLE_FLUSH_BIT),
+    OVS_DP_HASH_L4_SYM_SUPPORT = (1 << OVS_DP_HASH_L4_SYM_BIT),
 };
 
 void ovs_feature_support_destroy(void);

lib/actions.c

@@ -1625,6 +1625,12 @@ encode_SELECT(const struct ovnact_select *select,
     struct ds ds = DS_EMPTY_INITIALIZER;
     ds_put_format(&ds, "type=select,selection_method=dp_hash");
 
+    if (ovs_feature_is_supported(OVS_DP_HASH_L4_SYM_SUPPORT)) {
+        /* Select dp-hash l4_symmetric by setting the upper 32bits of
+         * selection_method_param to value 1 (1 << 32): */
+        ds_put_cstr(&ds, ",selection_method_param=0x100000000");
+    }
+
     struct mf_subfield sf = expr_resolve_field(&select->res_field);
 
     for (size_t bucket_id = 0; bucket_id < select->n_dsts; bucket_id++) {

lib/features.c

@@ -21,6 +21,7 @@
 #include "lib/dirs.h"
 #include "socket-util.h"
 #include "lib/vswitch-idl.h"
+#include "odp-netlink.h"
 #include "openvswitch/vlog.h"
 #include "openvswitch/ofpbuf.h"
 #include "openvswitch/rconn.h"
@@ -33,20 +34,48 @@ VLOG_DEFINE_THIS_MODULE(features);
 
 #define FEATURES_DEFAULT_PROBE_INTERVAL_SEC 5
 
+/* Parses 'cap_name' from 'ovs_capabilities' and returns whether the
+ * type of capability is supported or not. */
+typedef bool ovs_feature_parse_func(const struct smap *ovs_capabilities,
+                                    const char *cap_name);
+
 struct ovs_feature {
     enum ovs_feature_value value;
     const char *name;
+    ovs_feature_parse_func *parse;
 };
 
+static bool
+bool_parser(const struct smap *ovs_capabilities, const char *cap_name)
+{
+    return smap_get_bool(ovs_capabilities, cap_name, false);
+}
+
+static bool
+dp_hash_l4_sym_support_parser(const struct smap *ovs_capabilities,
+                              const char *cap_name OVS_UNUSED)
+{
+    int max_hash_alg = smap_get_int(ovs_capabilities, "max_hash_alg", 0);
+
+    return max_hash_alg == OVS_HASH_ALG_SYM_L4;
+}
+
 static struct ovs_feature all_ovs_features[] = {
     {
         .value = OVS_CT_ZERO_SNAT_SUPPORT,
-        .name = "ct_zero_snat"
+        .name = "ct_zero_snat",
+        .parse = bool_parser,
     },
     {
         .value = OVS_CT_TUPLE_FLUSH_SUPPORT,
-        .name = "ct_flush"
-    }
+        .name = "ct_flush",
+        .parse = bool_parser,
+    },
+    {
+        .value = OVS_DP_HASH_L4_SYM_SUPPORT,
+        .name = "dp_hash_l4_sym_support",
+        .parse = dp_hash_l4_sym_support_parser,
+    },
 };
 
 /* A bitmap of OVS features that have been detected as 'supported'. */
@@ -65,6 +94,7 @@ ovs_feature_is_valid(enum ovs_feature_value feature)
     case OVS_CT_ZERO_SNAT_SUPPORT:
     case OVS_DP_METER_SUPPORT:
     case OVS_CT_TUPLE_FLUSH_SUPPORT:
+    case OVS_DP_HASH_L4_SYM_SUPPORT:
         return true;
     default:
         return false;
@@ -183,18 +213,17 @@ ovs_feature_support_run(const struct smap *ovs_capabilities,
     }
 
     for (size_t i = 0; i < ARRAY_SIZE(all_ovs_features); i++) {
-        enum ovs_feature_value value = all_ovs_features[i].value;
-        const char *name = all_ovs_features[i].name;
-        bool old_state = supported_ovs_features & value;
-        bool new_state = smap_get_bool(ovs_capabilities, name, false);
+        struct ovs_feature *feature = &all_ovs_features[i];
+        bool old_state = supported_ovs_features & feature->value;
+        bool new_state = feature->parse(ovs_capabilities, feature->name);
         if (new_state != old_state) {
             updated = true;
             if (new_state) {
-                supported_ovs_features |= value;
+                supported_ovs_features |= feature->value;
             } else {
-                supported_ovs_features &= ~value;
+                supported_ovs_features &= ~feature->value;
             }
-            VLOG_INFO_RL(&rl, "OVS Feature: %s, state: %s", name,
+            VLOG_INFO_RL(&rl, "OVS Feature: %s, state: %s", feature->name,
                          new_state ? "supported" : "not supported");
         }
     }