Interpret sl3a_uport == 0 in SVP_R_VL3_ACK to indicate the VL3 IP is a
next-hop router.

*** 72,82 ****
          SVP_S_BADL3TYPE = 0x03, /* Unknown svp_vl3_type_t */
          SVP_S_BADBULK   = 0x04  /* Unknown svp_bulk_type_t */
  } svp_status_t;
  
  /*
!  * A client issues the SVP_R_VL2_REQ whenever it needs to perform a VLS->UL3
   * lookup. Requests have the following structure:
   */
  typedef struct svp_vl2_req {
          uint8_t         sl2r_mac[ETHERADDRL];
          uint8_t         sl2r_pad[2];
--- 72,82 ----
          SVP_S_BADL3TYPE = 0x03, /* Unknown svp_vl3_type_t */
          SVP_S_BADBULK   = 0x04  /* Unknown svp_bulk_type_t */
  } svp_status_t;
  
  /*
!  * A client issues the SVP_R_VL2_REQ whenever it needs to perform a VL2->UL3
   * lookup. Requests have the following structure:
   */
  typedef struct svp_vl2_req {
          uint8_t         sl2r_mac[ETHERADDRL];
          uint8_t         sl2r_pad[2];
*** 251,260 ****
--- 251,261 ----
  /*
   * The far-remote Triton Data Center will answer with the requisite information
   * to send overlay packets to the appropriate far-remote CNs.
   */
  typedef struct svp_route_ack {
+         uint32_t        sra_status;     /* Status. */
          uint32_t        sra_dcid;       /* Far-remote Data Center ID. */
          uint32_t        sra_vnetid;     /* Far-remote vnet ID. */
          uint16_t        sra_vlan;       /* Far-remote VLAN ID. */
          uint16_t        sra_port;       /* Destination UL3 port. */
          uint8_t         sra_ip[16];     /* Destination UL3 address. */