dpif: Allow the port number to be requested when adding an interface.

The datapath allows requesting a specific port number for a port, but
the dpif interface didn't expose it.  This commit adds that support.

Signed-off-by: Justin Pettit <jpettit@nicira.com>

lib/dpif-linux.c

@@ -424,11 +424,13 @@ dpif_linux_port_add(struct dpif *dpif_, struct netdev *netdev,
         netdev_linux_ethtool_set_flag(netdev, ETH_FLAG_LRO, "LRO", false);
     }
 
-    /* Loop until we find a port that isn't used. */
+    /* Unless a specific port was requested, loop until we find a port
+     * that isn't used. */
     do {
         uint32_t upcall_pid;
 
-        request.port_no = ++dpif->alloc_port_no;
+        request.port_no = *port_nop != UINT16_MAX ? *port_nop
+                          : ++dpif->alloc_port_no;
         upcall_pid = dpif_linux_port_get_pid(dpif_, request.port_no);
         request.upcall_pid = &upcall_pid;
         error = dpif_linux_vport_transact(&request, &reply, &buf);
@@ -441,10 +443,13 @@ dpif_linux_port_add(struct dpif *dpif_, struct netdev *netdev,
             /* Older datapath has lower limit. */
             max_ports = dpif->alloc_port_no;
             dpif->alloc_port_no = 0;
+        } else if (error == EBUSY && *port_nop != UINT16_MAX) {
+            VLOG_INFO("%s: requested port %"PRIu16" is in use",
+                     dpif_name(dpif_), *port_nop);
         }
 
         ofpbuf_delete(buf);
-    } while ((i++ < max_ports)
+    } while ((*port_nop == UINT16_MAX) && (i++ < max_ports)
              && (error == EBUSY || error == EFBIG));
 
     return error;

lib/dpif-netdev.c

@@ -407,7 +407,16 @@ dpif_netdev_port_add(struct dpif *dpif, struct netdev *netdev,
     struct dp_netdev *dp = get_dp_netdev(dpif);
     int port_no;
 
+    if (*port_nop != UINT16_MAX) {
+        if (*port_nop >= MAX_PORTS) {
+            return EFBIG;
+        } else if (dp->ports[*port_nop]) {
+            return EBUSY;
+        }
+        port_no = *port_nop;
+    } else {
         port_no = choose_port(dpif, netdev);
+    }
     if (port_no >= 0) {
         *port_nop = port_no;
         return do_add_port(dp, netdev_get_name(netdev),

lib/dpif-provider.h

@@ -110,8 +110,12 @@ struct dpif_class {
     /* Retrieves statistics for 'dpif' into 'stats'. */
     int (*get_stats)(const struct dpif *dpif, struct dpif_dp_stats *stats);
 
-    /* Adds 'netdev' as a new port in 'dpif'.  If successful, sets '*port_no'
-     * to the new port's port number. */
+    /* Adds 'netdev' as a new port in 'dpif'.  If '*port_no' is not
+     * UINT16_MAX, attempts to use that as the port's port number.
+     *
+     * If port is successfully added, sets '*port_no' to the new port's
+     * port number.  Returns EBUSY if caller attempted to choose a port
+     * number, and it was in use. */
     int (*port_add)(struct dpif *dpif, struct netdev *netdev,
                     uint16_t *port_no);
 

lib/dpif.c

@@ -410,19 +410,27 @@ dpif_get_dp_stats(const struct dpif *dpif, struct dpif_dp_stats *stats)
     return error;
 }
 
-/* Attempts to add 'netdev' as a port on 'dpif'.  If successful, returns 0 and
- * sets '*port_nop' to the new port's port number (if 'port_nop' is non-null).
- * On failure, returns a positive errno value and sets '*port_nop' to
- * UINT16_MAX (if 'port_nop' is non-null). */
+/* Attempts to add 'netdev' as a port on 'dpif'.  If 'port_nop' is
+ * non-null and its value is not UINT16_MAX, then attempts to use the
+ * value as the port number.
+ *
+ * If successful, returns 0 and sets '*port_nop' to the new port's port
+ * number (if 'port_nop' is non-null).  On failure, returns a positive
+ * errno value and sets '*port_nop' to UINT16_MAX (if 'port_nop' is
+ * non-null). */
 int
 dpif_port_add(struct dpif *dpif, struct netdev *netdev, uint16_t *port_nop)
 {
     const char *netdev_name = netdev_get_name(netdev);
-    uint16_t port_no;
+    uint16_t port_no = UINT16_MAX;
     int error;
 
     COVERAGE_INC(dpif_port_add);
 
+    if (port_nop) {
+        port_no = *port_nop;
+    }
+
     error = dpif->dpif_class->port_add(dpif, netdev, &port_no);
     if (!error) {
         VLOG_DBG_RL(&dpmsg_rl, "%s: added %s as port %"PRIu16,

ofproto/ofproto-dpif.c

@@ -2514,7 +2514,7 @@ static int
 port_add(struct ofproto *ofproto_, struct netdev *netdev, uint16_t *ofp_portp)
 {
     struct ofproto_dpif *ofproto = ofproto_dpif_cast(ofproto_);
-    uint16_t odp_port;
+    uint16_t odp_port = UINT16_MAX;
     int error;
 
     error = dpif_port_add(ofproto->dpif, netdev, &odp_port);