ofp-actions: Fix variable length meta-flow OXMs.

Previously, if a flow action that involves a tunnel metadata meta-flow
field is dumped from vswitchd, the replied field length in the OXM header
is filled with the maximum possible field length, instead of the length
configured in the tunnel TLV mapping table. To solve this issue, this patch
introduces the following changes.

In order to maintain the correct length of variable length mf_fields (i.e.
tun_metadata), this patch creates a per-switch based map (struct vl_mff_map)
that hosts the variable length mf_fields. This map is updated when a
controller adds/deletes tlv-mapping entries to/from a switch. Although the
per-swtch based vl_mff_map only hosts tun_metadata for now, it is able to
support new variable length mf_fields in the future.

With this commit, when a switch decodes a flow action with mf_field, the switch
firstly looks up the global mf_fields map to identify the mf_field type. For
the variable length mf_fields, the switch uses the vl_mff_map to get the
configured mf_field entries. By lookig up vl_mff_map, the switch can check
if the added flow action access beyond the configured size of a variable
length mf_field, and the switch reports an ofperr if the controller adds a flow
with unmapped variable length mf_field. Later on, when a controller request
flows from the switch, with the per-switch based mf_fields, the switch will
encode the OXM header with correct length for variable length mf_fields.

To use the vl_mff_map for decoding flow actions, extract-ofp-actions is
updated to pass the vl_mff_map to the required action decoding functions.
Also, a new error code is introduced to identify a flow with an invalid
variable length mf_field. Moreover, a testcase is added to prevent future
regressions.

Committer notes:
 - Factor out common code
 - Style fixups
 - Rename OFPERR_NXFMFC_INVALID_VL_MFF -> OFPERR_NXFMFC_INVALID_TLV_FIELD

VMWare-BZ: #1768370
Reported-by: Harold Lim <haroldl@vmware.com>
Suggested-by: Joe Stringer <joe@ovn.org>
Suggested-by: Jarno Rajahalme <jarno@ovn.org>
Signed-off-by: Yi-Hung Wei <yihung.wei@gmail.com>
Signed-off-by: Joe Stringer <joe@ovn.org>

lib/meta-flow.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2011, 2012, 2013, 2014, 2015, 2016 Nicira, Inc.
+ * Copyright (c) 2011-2017 Nicira, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -27,6 +27,7 @@
 #include "openvswitch/dynamic-string.h"
 #include "nx-match.h"
 #include "openvswitch/ofp-util.h"
+#include "ovs-rcu.h"
 #include "ovs-thread.h"
 #include "packets.h"
 #include "random.h"
@@ -2639,3 +2640,109 @@ field_array_set(enum mf_field_id id, const union mf_value *value,
 
     memcpy(fa->values + offset, value, value_size);
 }
+
+static inline uint32_t
+mf_field_hash(uint32_t key)
+{
+    return hash_int(key, 0);
+}
+
+void
+mf_vl_mff_map_clear(struct vl_mff_map *vl_mff_map)
+    OVS_REQUIRES(vl_mff_map->mutex)
+{
+    struct mf_field *mf;
+
+    CMAP_FOR_EACH (mf, cmap_node, &vl_mff_map->cmap) {
+        cmap_remove(&vl_mff_map->cmap, &mf->cmap_node, mf_field_hash(mf->id));
+        ovsrcu_postpone(free, mf);
+    }
+}
+
+static struct mf_field *
+mf_get_vl_mff__(uint32_t id, const struct vl_mff_map *vl_mff_map)
+{
+    struct mf_field *field;
+
+    CMAP_FOR_EACH_WITH_HASH (field, cmap_node, mf_field_hash(id),
+                             &vl_mff_map->cmap) {
+        if (field->id == id) {
+            return field;
+        }
+    }
+
+    return NULL;
+}
+
+/* If 'mff' is a variable length field, looks up 'vl_mff_map', returns a
+ * pointer to the variable length meta-flow field corresponding to 'mff'.
+ * Returns NULL if no mapping is existed for 'mff'. */
+const struct mf_field *
+mf_get_vl_mff(const struct mf_field *mff,
+              const struct vl_mff_map *vl_mff_map)
+{
+    if (mff && mff->variable_len && vl_mff_map) {
+        return mf_get_vl_mff__(mff->id, vl_mff_map);
+    }
+
+    return NULL;
+}
+
+/* Updates the tun_metadata mf_field in 'vl_mff_map' according to 'ttm'.
+ * This function is supposed to be invoked after tun_metadata_table_mod(). */
+enum ofperr
+mf_vl_mff_map_mod_from_tun_metadata(struct vl_mff_map *vl_mff_map,
+                                    const struct ofputil_tlv_table_mod *ttm)
+    OVS_REQUIRES(vl_mff_map->mutex)
+{
+    struct ofputil_tlv_map *tlv_map;
+
+    if (ttm->command == NXTTMC_CLEAR) {
+        mf_vl_mff_map_clear(vl_mff_map);
+        return 0;
+    }
+
+    LIST_FOR_EACH (tlv_map, list_node, &ttm->mappings) {
+        unsigned int idx = MFF_TUN_METADATA0 + tlv_map->index;
+        struct mf_field *mf;
+
+        if (idx >= MFF_TUN_METADATA0 + TUN_METADATA_NUM_OPTS) {
+            return OFPERR_NXTTMFC_BAD_FIELD_IDX;
+        }
+
+        switch (ttm->command) {
+        case NXTTMC_ADD:
+            mf = xmalloc(sizeof *mf);
+            *mf = mf_fields[idx];
+            mf->n_bytes = tlv_map->option_len;
+            mf->n_bits = tlv_map->option_len * 8;
+            mf->mapped = true;
+
+            cmap_insert(&vl_mff_map->cmap, &mf->cmap_node, mf_field_hash(idx));
+            break;
+
+        case NXTTMC_DELETE:
+            mf = mf_get_vl_mff__(idx, vl_mff_map);
+            if (mf) {
+                cmap_remove(&vl_mff_map->cmap, &mf->cmap_node,
+                            mf_field_hash(idx));
+                ovsrcu_postpone(free, mf);
+            }
+            break;
+
+        case NXTTMC_CLEAR:
+        default:
+            OVS_NOT_REACHED();
+        }
+    }
+
+    return 0;
+}
+
+/* Returns true if a variable length meta-flow field 'mff' is not mapped in
+ * the 'vl_mff_map'. */
+bool
+mf_vl_mff_invalid(const struct mf_field *mff, const struct vl_mff_map *map)
+{
+    return map && mff && mff->variable_len && !mff->mapped;
+}