Implement Openflow 1.4 Vacancy Events for OFPT_TABLE_MOD.

OpenFlow 1.4 introduces the ability to turn on vacancy events with an
OFPT_TABLE_MOD message specifying OFPTC_VACANCY_EVENTS. This commit adds
support for the new feature in ovs-ofctl mod-table.
As per the openflow specification-1.4, vacancy event adds a mechanism
enabling the controller to get an early warning based on capacity
threshold chosen by the controller.

With this commit, vacancy events can be configured as:
ovs-ofctl -O OpenFlow14 mod-table <bridge> <table> vacancy:<low,high>
<low,high> specify vacancy threshold values in percentage for vacancy_down
and vacancy_up respectively.

To disable vacancy events, following command should be given:
ovs-ofctl -O OpenFlow14 mod-table <bridge> <table> novacancy

Signed-off-by: Saloni Jain <saloni.jain@tcs.com>
Co-authored-by: Shashwat Srivastava <shashwat.srivastava@tcs.com>
Signed-off-by: Shashwat Srivastava <shashwat.srivastava@tcs.com>
Co-authored-by: Sandeep Kumar <sandeep.kumar16@tcs.com>
Signed-off-by: Sandeep Kumar <sandeep.kumar16@tcs.com>
[blp@ovn.org fixed a few typos]
Signed-off-by: Ben Pfaff <blp@ovn.org>

NEWS

@@ -8,6 +8,7 @@ Post-v2.4.0
        now supported.
      * OpenFlow 1.4+ "importance" is now considered for flow eviction.
      * OpenFlow 1.4+ OFPTC_EVICTION is now implemented.
+     * OpenFlow 1.4+ OFPTC_VACANCY_EVENTS is now implemented.
      * OpenFlow 1.4+ OFPMP_TABLE_DESC is now implemented.
      * Allow modifying the ICMPv4/ICMPv6 type and code fields.
    - ovs-ofctl:

lib/ofp-parse.c

@@ -886,6 +886,49 @@ parse_ofp_flow_mod_str(struct ofputil_flow_mod *fm, const char *string,
     return error;
 }
 
+/* Convert 'setting' (as described for the "mod-table" command
+ * in ovs-ofctl man page) into 'tm->table_vacancy->vacancy_up' and
+ * 'tm->table_vacancy->vacancy_down' threshold values.
+ * For the two threshold values, value of vacancy_up is always greater
+ * than value of vacancy_down.
+ *
+ * Returns NULL if successful, otherwise a malloc()'d string describing the
+ * error.  The caller is responsible for freeing the returned string. */
+char * OVS_WARN_UNUSED_RESULT
+parse_ofp_table_vacancy(struct ofputil_table_mod *tm, const char *setting)
+{
+    char *save_ptr = NULL;
+    char *vac_up, *vac_down;
+    char *value = strdup(setting);
+    int vacancy_up, vacancy_down;
+
+    strtok_r(value, ":", &save_ptr);
+    vac_down = strtok_r(NULL, ",", &save_ptr);
+    if (!vac_down) {
+        return xasprintf("Vacancy down value missing");
+    }
+    if (!str_to_int(vac_down, 0, &vacancy_down) ||
+        vacancy_down < 0 || vacancy_down > 100) {
+        return xasprintf("Invalid vacancy down value \"%s\"", vac_down);
+    }
+    vac_up = strtok_r(NULL, ",", &save_ptr);
+    if (!vac_up) {
+        return xasprintf("Vacancy up value missing");
+    }
+    if (!str_to_int(vac_up, 0, &vacancy_up) ||
+        vacancy_up < 0 || vacancy_up > 100) {
+        return xasprintf("Invalid vacancy up value \"%s\"", vac_up);
+    }
+    if (vacancy_down > vacancy_up) {
+        return xasprintf("Invalid vacancy range, vacancy up should be greater"
+                         " than vacancy down ""(%s)",
+                         ofperr_to_string(OFPERR_OFPBPC_BAD_VALUE));
+    }
+    tm->table_vacancy.vacancy_down = vacancy_down;
+    tm->table_vacancy.vacancy_up = vacancy_up;
+    return NULL;
+}
+
 /* Convert 'table_id' and 'setting' (as described for the "mod-table" command
  * in the ovs-ofctl man page) into 'tm' for sending a table_mod command to a
  * switch.
@@ -912,13 +955,13 @@ parse_ofp_table_mod(struct ofputil_table_mod *tm, const char *table_id,
     tm->miss = OFPUTIL_TABLE_MISS_DEFAULT;
     tm->eviction = OFPUTIL_TABLE_EVICTION_DEFAULT;
     tm->eviction_flags = UINT32_MAX;
-
+    tm->vacancy = OFPUTIL_TABLE_VACANCY_DEFAULT;
+    tm->table_vacancy.vacancy_down = 0;
+    tm->table_vacancy.vacancy_up = 0;
+    tm->table_vacancy.vacancy = 0;
     /* Only OpenFlow 1.1 and 1.2 can configure table-miss via table_mod.
-     * Only OpenFlow 1.4+ can configure eviction via table_mod.
+     * Only OpenFlow 1.4+ can configure eviction and vacancy events
-     *
+     * via table_mod.
-     * (OpenFlow 1.4+ can also configure vacancy events via table_mod, but OVS
-     * doesn't support those yet and they're also logically a per-OpenFlow
-     * session setting so it wouldn't make sense to support them here anyway.)
      */
     if (!strcmp(setting, "controller")) {
         tm->miss = OFPUTIL_TABLE_MISS_CONTROLLER;
@@ -935,6 +978,16 @@ parse_ofp_table_mod(struct ofputil_table_mod *tm, const char *table_id,
     } else if (!strcmp(setting, "noevict")) {
         tm->eviction = OFPUTIL_TABLE_EVICTION_OFF;
         *usable_versions = (1 << OFP14_VERSION) | (1u << OFP15_VERSION);
+    } else if (!strncmp(setting, "vacancy", strcspn(setting, ":"))) {
+        tm->vacancy = OFPUTIL_TABLE_VACANCY_ON;
+        *usable_versions = (1 << OFP14_VERSION) | (1u << OFP15_VERSION);
+        char *error = parse_ofp_table_vacancy(tm, setting);
+        if (error) {
+            return error;
+        }
+    } else if (!strcmp(setting, "novacancy")) {
+        tm->vacancy = OFPUTIL_TABLE_VACANCY_OFF;
+        *usable_versions = (1 << OFP14_VERSION) | (1u << OFP15_VERSION);
     } else {
         return xasprintf("invalid table_mod setting %s", setting);
     }

lib/ofp-parse.h

@@ -100,5 +100,8 @@ char *str_to_be64(const char *str, ovs_be64 *valuep) OVS_WARN_UNUSED_RESULT;
 char *str_to_mac(const char *str, struct eth_addr *mac) OVS_WARN_UNUSED_RESULT;
 char *str_to_ip(const char *str, ovs_be32 *ip) OVS_WARN_UNUSED_RESULT;
 char *str_to_connhelper(const char *str, uint16_t *alg) OVS_WARN_UNUSED_RESULT;
+char *parse_ofp_table_vacancy(struct ofputil_table_mod *,
+                              const char *flow_miss_handling)
+    OVS_WARN_UNUSED_RESULT;
 
 #endif /* ofp-parse.h */

lib/ofp-print.c

@@ -990,6 +990,18 @@ ofputil_put_eviction_flags(struct ds *string, uint32_t eviction_flags)
     }
 }
 
+static const char *
+ofputil_table_vacancy_to_string(enum ofputil_table_vacancy vacancy)
+{
+    switch (vacancy) {
+    case OFPUTIL_TABLE_VACANCY_DEFAULT: return "default";
+    case OFPUTIL_TABLE_VACANCY_ON: return "on";
+    case OFPUTIL_TABLE_VACANCY_OFF: return "off";
+    default: return "***error***";
+    }
+
+}
+
 static void
 ofp_print_table_mod(struct ds *string, const struct ofp_header *oh)
 {
@@ -1020,6 +1032,15 @@ ofp_print_table_mod(struct ds *string, const struct ofp_header *oh)
         ds_put_cstr(string, "eviction_flags=");
         ofputil_put_eviction_flags(string, pm.eviction_flags);
     }
+    if (pm.vacancy != OFPUTIL_TABLE_VACANCY_DEFAULT) {
+        ds_put_format(string, ", vacancy=%s",
+                      ofputil_table_vacancy_to_string(pm.vacancy));
+        if (pm.vacancy == OFPUTIL_TABLE_VACANCY_ON) {
+            ds_put_format(string, " vacancy:%"PRIu8""
+                          ",%"PRIu8"", pm.table_vacancy.vacancy_down,
+                          pm.table_vacancy.vacancy_up);
+        }
+    }
 }
 
 /* This function will print the Table description properties. */

lib/ofp-util.c

@@ -53,10 +53,13 @@ VLOG_DEFINE_THIS_MODULE(ofp_util);
  * in the peer and so there's not much point in showing a lot of them. */
 static struct vlog_rate_limit bad_ofmsg_rl = VLOG_RATE_LIMIT_INIT(1, 5);
 
+static enum ofputil_table_vacancy ofputil_decode_table_vacancy(
+    ovs_be32 config, enum ofp_version);
 static enum ofputil_table_eviction ofputil_decode_table_eviction(
     ovs_be32 config, enum ofp_version);
 static ovs_be32 ofputil_encode_table_config(enum ofputil_table_miss,
                                             enum ofputil_table_eviction,
+                                            enum ofputil_table_vacancy,
                                             enum ofp_version);
 
 struct ofp_prop_header {
@@ -4999,10 +5002,62 @@ ofputil_append_table_desc_reply(const struct ofputil_table_desc *td,
     otd->length = htons(reply->size - start_otd);
     otd->table_id = td->table_id;
     otd->config = ofputil_encode_table_config(OFPUTIL_TABLE_MISS_DEFAULT,
-                                              td->eviction, version);
+                                              td->eviction, td->vacancy,
+                                              version);
     ofpmp_postappend(replies, start_otd);
 }
 
+/* This function parses Vacancy property, and decodes the
+ * ofp14_table_mod_prop_vacancy in ofputil_table_mod.
+ * Returns OFPERR_OFPBPC_BAD_VALUE error code when vacancy_down is
+ * greater than vacancy_up and also when current vacancy has non-zero
+ * value. Returns 0 on success. */
+static enum ofperr
+parse_table_mod_vacancy_property(struct ofpbuf *property,
+                                 struct ofputil_table_mod *tm)
+{
+    struct ofp14_table_mod_prop_vacancy *otv = property->data;
+
+    if (property->size != sizeof *otv) {
+        return OFPERR_OFPBPC_BAD_LEN;
+    }
+    tm->table_vacancy.vacancy_down = otv->vacancy_down;
+    tm->table_vacancy.vacancy_up = otv->vacancy_up;
+    if (tm->table_vacancy.vacancy_down > tm->table_vacancy.vacancy_up) {
+        log_property(false, "Value of vacancy_down is greater than "
+                     "vacancy_up");
+        return OFPERR_OFPBPC_BAD_VALUE;
+    }
+    if (tm->table_vacancy.vacancy_down > 100 ||
+        tm->table_vacancy.vacancy_up > 100) {
+        log_property(false, "Vacancy threshold percentage should not be"
+                     "greater than 100");
+        return OFPERR_OFPBPC_BAD_VALUE;
+    }
+    tm->table_vacancy.vacancy = otv->vacancy;
+    if (tm->table_vacancy.vacancy) {
+        log_property(false, "Vacancy value should be zero for table-mod "
+                     "messages");
+        return OFPERR_OFPBPC_BAD_VALUE;
+    }
+    return 0;
+}
+
+/* Given 'config', taken from an OpenFlow 'version' message that specifies
+ * table configuration (a table mod, table stats, or table features message),
+ * returns the table vacancy configuration that it specifies.
+ *
+ * Only OpenFlow 1.4 and later specify table vacancy configuration this way,
+ * so for other 'version' this function always returns
+ * OFPUTIL_TABLE_VACANCY_DEFAULT. */
+static enum ofputil_table_vacancy
+ofputil_decode_table_vacancy(ovs_be32 config, enum ofp_version version)
+{
+    return (version < OFP14_VERSION ? OFPUTIL_TABLE_VACANCY_DEFAULT
+            : config & htonl(OFPTC14_VACANCY_EVENTS) ? OFPUTIL_TABLE_VACANCY_ON
+            : OFPUTIL_TABLE_VACANCY_OFF);
+}
+
 static enum ofperr
 parse_table_mod_eviction_property(struct ofpbuf *property,
                                   struct ofputil_table_mod *tm)
@@ -5038,8 +5093,10 @@ ofputil_decode_table_eviction(ovs_be32 config, enum ofp_version version)
 static ovs_be32
 ofputil_encode_table_config(enum ofputil_table_miss miss,
                             enum ofputil_table_eviction eviction,
+                            enum ofputil_table_vacancy vacancy,
                             enum ofp_version version)
 {
+    uint32_t config = 0;
     /* See the section "OFPTC_* Table Configuration" in DESIGN.md for more
      * information on the crazy evolution of this field. */
     switch (version) {
@@ -5072,10 +5129,15 @@ ofputil_encode_table_config(enum ofputil_table_miss miss,
 
     case OFP14_VERSION:
     case OFP15_VERSION:
-        /* OpenFlow 1.4 introduced OFPTC14_EVICTION and OFPTC14_VACANCY_EVENTS
+        /* OpenFlow 1.4 introduced OFPTC14_EVICTION and
-         * and we don't support the latter yet. */
+         * OFPTC14_VACANCY_EVENTS. */
-        return htonl(eviction == OFPUTIL_TABLE_EVICTION_ON
+        if (eviction == OFPUTIL_TABLE_EVICTION_ON) {
-                     ? OFPTC14_EVICTION : 0);
+            config |= OFPTC14_EVICTION;
+        }
+        if (vacancy == OFPUTIL_TABLE_VACANCY_ON) {
+            config |= OFPTC14_VACANCY_EVENTS;
+        }
+        return htonl(config);
     }
 
     OVS_NOT_REACHED();
@@ -5126,6 +5188,7 @@ ofputil_decode_table_mod(const struct ofp_header *oh,
     pm->miss = OFPUTIL_TABLE_MISS_DEFAULT;
     pm->eviction = OFPUTIL_TABLE_EVICTION_DEFAULT;
     pm->eviction_flags = UINT32_MAX;
+    pm->vacancy = OFPUTIL_TABLE_VACANCY_DEFAULT;
     ofpbuf_use_const(&b, oh, ntohs(oh->length));
     raw = ofpraw_pull_assert(&b);
 
@@ -5140,6 +5203,7 @@ ofputil_decode_table_mod(const struct ofp_header *oh,
         pm->table_id = otm->table_id;
         pm->miss = ofputil_decode_table_miss(otm->config, oh->version);
         pm->eviction = ofputil_decode_table_eviction(otm->config, oh->version);
+        pm->vacancy = ofputil_decode_table_vacancy(otm->config, oh->version);
         while (b.size > 0) {
             struct ofpbuf property;
             enum ofperr error;
@@ -5155,6 +5219,10 @@ ofputil_decode_table_mod(const struct ofp_header *oh,
                 error = parse_table_mod_eviction_property(&property, pm);
                 break;
 
+            case OFPTMPT14_VACANCY:
+                error = parse_table_mod_vacancy_property(&property, pm);
+                break;
+
             default:
                 error = OFPERR_OFPBRC_BAD_TYPE;
                 break;
@@ -5196,19 +5264,20 @@ ofputil_encode_table_mod(const struct ofputil_table_mod *tm,
         otm = ofpbuf_put_zeros(b, sizeof *otm);
         otm->table_id = tm->table_id;
         otm->config = ofputil_encode_table_config(tm->miss, tm->eviction,
-                                                  ofp_version);
+                                                  tm->vacancy, ofp_version);
         break;
     }
     case OFP14_VERSION:
     case OFP15_VERSION: {
         struct ofp14_table_mod *otm;
         struct ofp14_table_mod_prop_eviction *ote;
+        struct ofp14_table_mod_prop_vacancy *otv;
 
         b = ofpraw_alloc(OFPRAW_OFPT14_TABLE_MOD, ofp_version, 0);
         otm = ofpbuf_put_zeros(b, sizeof *otm);
         otm->table_id = tm->table_id;
         otm->config = ofputil_encode_table_config(tm->miss, tm->eviction,
-                                                  ofp_version);
+                                                  tm->vacancy, ofp_version);
 
         if (tm->eviction_flags != UINT32_MAX) {
             ote = ofpbuf_put_zeros(b, sizeof *ote);
@@ -5216,6 +5285,13 @@ ofputil_encode_table_mod(const struct ofputil_table_mod *tm,
             ote->length = htons(sizeof *ote);
             ote->flags = htonl(tm->eviction_flags);
         }
+        if (tm->vacancy == OFPUTIL_TABLE_VACANCY_ON) {
+            otv = ofpbuf_put_zeros(b, sizeof *otv);
+            otv->type = htons(OFPTMPT14_VACANCY);
+            otv->length = htons(sizeof *otv);
+            otv->vacancy_down = tm->table_vacancy.vacancy_down;
+            otv->vacancy_up = tm->table_vacancy.vacancy_up;
+        }
         break;
     }
     default:
@@ -5682,6 +5758,7 @@ ofputil_put_ofp12_table_stats(const struct ofputil_table_stats *stats,
         features->nonmiss.instructions, OFP12_VERSION);
     out->config = ofputil_encode_table_config(features->miss_config,
                                               OFPUTIL_TABLE_EVICTION_DEFAULT,
+                                              OFPUTIL_TABLE_VACANCY_DEFAULT,
                                               OFP12_VERSION);
     out->max_entries = htonl(features->max_entries);
     out->active_count = htonl(stats->active_count);

lib/ofp-util.h

@@ -628,6 +628,33 @@ enum ofputil_table_eviction {
     OFPUTIL_TABLE_EVICTION_OFF      /* Disable eviction. */
 };
 
+/* Abstract version of OFPTC14_VACANCY_EVENTS.
+ *
+ * OpenFlow 1.0 through 1.3 don't know anything about vacancy events, so
+ * decoding a message for one of these protocols always yields
+ * OFPUTIL_TABLE_VACANCY_DEFAULT. */
+enum ofputil_table_vacancy {
+    OFPUTIL_TABLE_VACANCY_DEFAULT, /* No value. */
+    OFPUTIL_TABLE_VACANCY_ON,      /* Enable vacancy events. */
+    OFPUTIL_TABLE_VACANCY_OFF      /* Disable vacancy events. */
+};
+
+/* Abstract version of OFPTMPT_VACANCY.
+ *
+ * Openflow 1.4+ defines vacancy events.
+ * The fields vacancy_down and vacancy_up are the threshold for generating
+ * vacancy events that should be configured on the flow table, expressed as
+ * a percent.
+ * The vacancy field is only used when this property in included in a
+ * OFPMP_TABLE_DESC multipart reply or a OFPT_TABLE_STATUS message and
+ * represent the current vacancy of the table, expressed as a percent. In
+ * OFP_TABLE_MOD requests, this field must be set to 0 */
+struct ofputil_table_mod_prop_vacancy {
+    uint8_t vacancy_down;    /* Vacancy threshold when space decreases (%). */
+    uint8_t vacancy_up;      /* Vacancy threshold when space increases (%). */
+    uint8_t vacancy;         /* Current vacancy (%). */
+};
+
 /* Abstract ofp_table_mod. */
 struct ofputil_table_mod {
     uint8_t table_id;         /* ID of the table, 0xff indicates all tables. */
@@ -644,6 +671,16 @@ struct ofputil_table_mod {
      * absence.  For other versions, ignored on encoding, decoded to
      * UINT32_MAX.*/
     uint32_t eviction_flags;    /* OFPTMPEF14_*. */
+
+    /* OpenFlow 1.4+ only. For other versions, ignored on encoding, decoded to
+     * OFPUTIL_TABLE_VACANCY_DEFAULT. */
+    enum ofputil_table_vacancy vacancy;
+
+    /* Openflow 1.4+ only. Defines threshold values of vacancy expressed as
+     * percent, value of current vacancy is set to zero for table-mod.
+     * For other versions, ignored on encoding, all values decoded to
+     * zero. */
+    struct ofputil_table_mod_prop_vacancy table_vacancy;
 };
 
 /* Abstract ofp14_table_desc. */
@@ -651,6 +688,8 @@ struct ofputil_table_desc {
     uint8_t table_id;         /* ID of the table. */
     enum ofputil_table_eviction eviction;
     uint32_t eviction_flags;    /* UINT32_MAX if not present. */
+    enum ofputil_table_vacancy vacancy;
+    struct ofputil_table_mod_prop_vacancy table_vacancy;
 };
 
 enum ofperr ofputil_decode_table_mod(const struct ofp_header *,

ofproto/ofproto-provider.h

@@ -256,6 +256,15 @@ struct oftable {
 #define EVICTION_OPENFLOW (1 << 1) /* Set to 1 if OpenFlow enables eviction. */
     unsigned int eviction;
 
+    /* If true, vacancy events are enabled; otherwise they are disabled. */
+    bool vacancy_enabled;
+
+    /* Non-zero values for vacancy_up and vacancy_down indicates that vacancy
+     * is enabled by table-mod, else these values are set to zero when
+     * vacancy is disabled */
+    uint8_t vacancy_down; /* Vacancy threshold when space decreases (%). */
+    uint8_t vacancy_up;   /* Vacancy threshold when space increases (%). */
+
     atomic_ulong n_matched;
     atomic_ulong n_missed;
 };

ofproto/ofproto.c

@@ -6646,20 +6646,20 @@ ofproto_table_get_miss_config(const struct ofproto *ofproto, uint8_t table_id)
 
 static void
 table_mod__(struct oftable *oftable,
-            enum ofputil_table_miss miss, enum ofputil_table_eviction eviction)
+            const struct ofputil_table_mod *tm)
 {
-    if (miss == OFPUTIL_TABLE_MISS_DEFAULT) {
+    if (tm->miss == OFPUTIL_TABLE_MISS_DEFAULT) {
         /* This is how an OFPT_TABLE_MOD decodes if it doesn't specify any
          * table-miss configuration (because the protocol used doesn't have
          * such a concept), so there's nothing to do. */
     } else {
-        atomic_store_relaxed(&oftable->miss_config, miss);
+        atomic_store_relaxed(&oftable->miss_config, tm->miss);
     }
 
     unsigned int new_eviction = oftable->eviction;
-    if (eviction == OFPUTIL_TABLE_EVICTION_ON) {
+    if (tm->eviction == OFPUTIL_TABLE_EVICTION_ON) {
         new_eviction |= EVICTION_OPENFLOW;
-    } else if (eviction == OFPUTIL_TABLE_EVICTION_OFF) {
+    } else if (tm->eviction == OFPUTIL_TABLE_EVICTION_OFF) {
         new_eviction &= ~EVICTION_OPENFLOW;
     }
 
@@ -6670,6 +6670,16 @@ table_mod__(struct oftable *oftable,
                                    oftable->n_eviction_fields);
         ovs_mutex_unlock(&ofproto_mutex);
     }
+
+    if (tm->vacancy != OFPUTIL_TABLE_VACANCY_DEFAULT) {
+        ovs_mutex_lock(&ofproto_mutex);
+        oftable->vacancy_enabled = (tm->vacancy == OFPUTIL_TABLE_VACANCY_ON
+                                    ? OFPTC14_VACANCY_EVENTS
+                                    : 0);
+        oftable->vacancy_down = tm->table_vacancy.vacancy_down;
+        oftable->vacancy_up = tm->table_vacancy.vacancy_up;
+        ovs_mutex_unlock(&ofproto_mutex);
+    }
 }
 
 static enum ofperr
@@ -6693,7 +6703,7 @@ table_mod(struct ofproto *ofproto, const struct ofputil_table_mod *tm)
         struct oftable *oftable;
         OFPROTO_FOR_EACH_TABLE (oftable, ofproto) {
             if (!(oftable->flags & (OFTABLE_HIDDEN | OFTABLE_READONLY))) {
-                table_mod__(oftable, tm->miss, tm->eviction);
+                table_mod__(oftable, tm);
             }
         }
     } else {
@@ -6701,7 +6711,7 @@ table_mod(struct ofproto *ofproto, const struct ofputil_table_mod *tm)
         if (oftable->flags & OFTABLE_READONLY) {
             return OFPERR_OFPTMFC_EPERM;
         }
-        table_mod__(oftable, tm->miss, tm->eviction);
+        table_mod__(oftable, tm);
     }
 
     return 0;

tests/ofp-print.at

@@ -1132,7 +1132,7 @@ AT_KEYWORDS([ofp-print])
 AT_CHECK([ovs-ofctl ofp-print "\
 05 11 00 10 00 00 00 02 02 00 00 00 00 00 00 00 \
 " 3], [0], [dnl
-OFPT_TABLE_MOD (OF1.4) (xid=0x2): table_id=2, eviction=off
+OFPT_TABLE_MOD (OF1.4) (xid=0x2): table_id=2, eviction=off, vacancy=off
 ])
 AT_CLEANUP
 

tests/ofproto.at

@@ -1936,6 +1936,13 @@ mv expout orig-expout
 sed -e '2s/eviction=off/eviction=on/' <orig-expout > expout
 AT_CHECK([ovs-ofctl -O OpenFlow14 dump-table-desc br0 | sed '/^$/d
 /^OFPST_TABLE_DESC/d'], [0], [expout])
+
+AT_CHECK([ovs-ofctl -O Openflow14 mod-table br0 0 vacancy:20,80])
+# Check that the configuration was updated.
+mv expout orig-expout
+sed -e '3s/vacancy=off/vacancy=on vacancy_down=20% vacancy_up=80% vacancy=0%/' <orig-expout > expout
+AT_CHECK([ovs-ofctl -O OpenFlow14 dump-table-desc br0 | sed '/^$/d
+/^OFPST_TABLE_DESC/d'], [0], [expout])
 OVS_VSWITCHD_STOP
 AT_CLEANUP
 

utilities/ovs-ofctl.8.in

@@ -96,8 +96,13 @@ algorithm described for the \fBFlow_Table\fR table in
 \fBovs-vswitchd.conf.db\fR(5).
 .IP \fBnoevict\fR
 Refuse to add the new flow.  (Eviction might still be enabled through
-the \fBoverflow_policy\fR oclumn in the \fBFlow_Table\fR table
+the \fBoverflow_policy\fR column in the \fBFlow_Table\fR table
 documented in \fBovs-vswitchd.conf.db\fR(5).)
+.IP \fBvacancy:\fIlow\fB,\fIhigh\fR
+Enables sending vacancy events to controllers using \fBTABLE_STATUS\fR
+messages, based on percentage thresholds \fIlow\fR and \fIhigh\fR.
+.IP \fBnovacancy\fR
+Disables vacancy events.
 .RE
 .
 .TP

utilities/ovs-ofctl.c

@@ -347,7 +347,7 @@ usage(void)
            "  mod-port SWITCH IFACE ACT   modify port behavior\n"
            "  mod-table SWITCH MOD        modify flow table behavior\n"
            "      OF1.1/1.2 MOD: controller, continue, drop\n"
-           "      OF1.4+ MOD: evict, noevict\n"
+           "      OF1.4+ MOD: evict, noevict, vacancy:low,high, novacancy\n"
            "  get-frags SWITCH            print fragment handling behavior\n"
            "  set-frags SWITCH FRAG_MODE  set fragment handling behavior\n"
            "      FRAG_MODE: normal, drop, reassemble, nx-match\n"
@@ -1934,6 +1934,70 @@ found:
     vconn_close(vconn);
 }
 
+/* This function uses OFPMP14_TABLE_DESC request to get the current
+ * table configuration from switch. The function then modifies
+ * only that table-config property, which has been requested. */
+static void
+fetch_table_desc(struct vconn *vconn, struct ofputil_table_mod *tm,
+                 struct ofputil_table_desc *td)
+{
+    struct ofpbuf *request;
+    ovs_be32 send_xid;
+    bool done = false;
+    bool found = false;
+
+    request = ofputil_encode_table_desc_request(vconn_get_version(vconn));
+    send_xid = ((struct ofp_header *) request->data)->xid;
+    send_openflow_buffer(vconn, request);
+    while (!done) {
+        ovs_be32 recv_xid;
+        struct ofpbuf *reply;
+
+        run(vconn_recv_block(vconn, &reply), "OpenFlow packet receive failed");
+        recv_xid = ((struct ofp_header *) reply->data)->xid;
+        if (send_xid == recv_xid) {
+            struct ofp_header *oh = reply->data;
+            enum ofptype type;
+            struct ofpbuf b;
+            uint16_t flags;
+
+            ofpbuf_use_const(&b, oh, ntohs(oh->length));
+            if (ofptype_pull(&type, &b)
+                || type != OFPTYPE_TABLE_DESC_REPLY) {
+                ovs_fatal(0, "received bad reply: %s",
+                          ofp_to_string(reply->data, reply->size,
+                                        verbosity + 1));
+            }
+            flags = ofpmp_flags(oh);
+            done = !(flags & OFPSF_REPLY_MORE);
+            if (found) {
+                /* We've already found the table desc consisting of current
+                 * table configuration, but we need to drain the queue of
+                 * any other replies for this request. */
+                continue;
+            }
+            while (!ofputil_decode_table_desc(&b, td, oh->version)) {
+                if (td->table_id == tm->table_id) {
+                    found = true;
+                    break;
+                }
+            }
+        } else {
+            VLOG_DBG("received reply with xid %08"PRIx32" "
+                     "!= expected %08"PRIx32, recv_xid, send_xid);
+        }
+        ofpbuf_delete(reply);
+    }
+    if (tm->eviction != OFPUTIL_TABLE_EVICTION_DEFAULT) {
+        tm->vacancy = td->vacancy;
+        tm->table_vacancy.vacancy_down = td->table_vacancy.vacancy_down;
+        tm->table_vacancy.vacancy_up = td->table_vacancy.vacancy_up;
+    } else if (tm->vacancy != OFPUTIL_TABLE_VACANCY_DEFAULT) {
+        tm->eviction = td->eviction;
+        tm->eviction_flags = td->eviction_flags;
+    }
+}
+
 static void
 ofctl_mod_table(struct ovs_cmdl_context *ctx)
 {
@@ -1941,6 +2005,7 @@ ofctl_mod_table(struct ovs_cmdl_context *ctx)
     struct ofputil_table_mod tm;
     struct vconn *vconn;
     char *error;
+    int i;
 
     error = parse_ofp_table_mod(&tm, ctx->argv[2], ctx->argv[3],
                                 &usable_versions);
@@ -1951,15 +2016,36 @@ ofctl_mod_table(struct ovs_cmdl_context *ctx)
     uint32_t allowed_versions = get_allowed_ofp_versions();
     if (!(allowed_versions & usable_versions)) {
         struct ds versions = DS_EMPTY_INITIALIZER;
-        ofputil_format_version_bitmap_names(&versions, allowed_versions);
+        ofputil_format_version_bitmap_names(&versions, usable_versions);
         ovs_fatal(0, "table_mod '%s' requires one of the OpenFlow "
-                  "versions %s but none is enabled (use -O)",
+                  "versions %s",
                   ctx->argv[3], ds_cstr(&versions));
     }
     mask_allowed_ofp_versions(usable_versions);
-
     enum ofputil_protocol protocol = open_vconn(ctx->argv[1], &vconn);
-    transact_noreply(vconn, ofputil_encode_table_mod(&tm, protocol));
+
+    /* For OpenFlow 1.4+, ovs-ofctl mod-table should not affect table-config
+     * properties that the user didn't ask to change, so it is necessary to
+     * restore the current configuration of table-config parameters using
+     * OFPMP14_TABLE_DESC request. */
+    if ((allowed_versions & (1u << OFP14_VERSION)) ||
+        (allowed_versions & (1u << OFP15_VERSION))) {
+        struct ofputil_table_desc td;
+
+        if (tm.table_id == OFPTT_ALL) {
+            for (i = 0; i < OFPTT_MAX; i++) {
+                tm.table_id = i;
+                fetch_table_desc(vconn, &tm, &td);
+                transact_noreply(vconn,
+                                 ofputil_encode_table_mod(&tm, protocol));
+            }
+        } else {
+            fetch_table_desc(vconn, &tm, &td);
+            transact_noreply(vconn, ofputil_encode_table_mod(&tm, protocol));
+        }
+    } else {
+        transact_noreply(vconn, ofputil_encode_table_mod(&tm, protocol));
+    }
     vconn_close(vconn);
 }