dhcpmon: support dual tor scenario (#7471)

src/dhcp_device.c

@@ -130,7 +130,7 @@ static void handle_dhcp_option_53(dhcp_device_context_t *context,
     case DHCP_MESSAGE_TYPE_INFORM:
         giaddr = ntohl(dhcphdr[DHCP_GIADDR_OFFSET] << 24 | dhcphdr[DHCP_GIADDR_OFFSET + 1] << 16 |
                        dhcphdr[DHCP_GIADDR_OFFSET + 2] << 8 | dhcphdr[DHCP_GIADDR_OFFSET + 3]);
-        if ((context->vlan_ip == giaddr && context->is_uplink && dir == DHCP_TX) ||
+        if ((context->giaddr_ip == giaddr && context->is_uplink && dir == DHCP_TX) ||
             (!context->is_uplink && dir == DHCP_RX && iphdr->ip_dst.s_addr == INADDR_BROADCAST)) {
             context->counters[DHCP_COUNTERS_CURRENT][dir][dhcp_option[2]]++;
             aggregate_dev.counters[DHCP_COUNTERS_CURRENT][dir][dhcp_option[2]]++;
@@ -140,7 +140,7 @@ static void handle_dhcp_option_53(dhcp_device_context_t *context,
     case DHCP_MESSAGE_TYPE_OFFER:
     case DHCP_MESSAGE_TYPE_ACK:
     case DHCP_MESSAGE_TYPE_NAK:
-        if ((context->vlan_ip == iphdr->ip_dst.s_addr && context->is_uplink && dir == DHCP_RX) ||
+        if ((context->giaddr_ip == iphdr->ip_dst.s_addr && context->is_uplink && dir == DHCP_RX) ||
             (!context->is_uplink && dir == DHCP_TX)) {
             context->counters[DHCP_COUNTERS_CURRENT][dir][dhcp_option[2]]++;
             aggregate_dev.counters[DHCP_COUNTERS_CURRENT][dir][dhcp_option[2]]++;
@@ -438,7 +438,7 @@ static int init_socket(dhcp_device_context_t *context, const char *intf)
  *
  * @return 0 on success, otherwise for failure
  */
-static int initialize_intf_mac_and_ip_addr(dhcp_device_context_t *context)
+int initialize_intf_mac_and_ip_addr(dhcp_device_context_t *context)
 {
     int rv = -1;
 
@@ -543,14 +543,14 @@ int dhcp_device_init(dhcp_device_context_t **context, const char *intf, uint8_t
 }
 
 /**
- * @code dhcp_device_start_capture(context, snaplen, base, vlan_ip);
+ * @code dhcp_device_start_capture(context, snaplen, base, giaddr_ip);
  *
  * @brief starts packet capture on this interface
  */
 int dhcp_device_start_capture(dhcp_device_context_t *context,
                               size_t snaplen,
                               struct event_base *base,
-                              in_addr_t vlan_ip)
+                              in_addr_t giaddr_ip)
 {
     int rv = -1;
 
@@ -565,7 +565,7 @@ int dhcp_device_start_capture(dhcp_device_context_t *context,
             break;
         }
 
-        context->vlan_ip = vlan_ip;
+        context->giaddr_ip = giaddr_ip;
 
         context->buffer = (uint8_t *) malloc(snaplen);
         if (context->buffer == NULL) {

src/dhcp_device.h

@@ -73,7 +73,7 @@ typedef struct
     int sock;                       /** Raw socket associated with this device/interface */
     in_addr_t ip;                   /** network address of this device (interface) */
     uint8_t mac[ETHER_ADDR_LEN];    /** hardware address of this device (interface) */
-    in_addr_t vlan_ip;              /** Vlan IP address */
+    in_addr_t giaddr_ip;            /** Gateway IP address */
     uint8_t is_uplink;              /** north interface? */
     char intf[IF_NAMESIZE];         /** device (interface) name */
     uint8_t *buffer;                /** buffer used to read socket data */
@@ -82,6 +82,17 @@ typedef struct
                                     /** current/snapshot counters of DHCP packets */
 } dhcp_device_context_t;
 
+/**
+ * @code initialize_intf_mac_and_ip_addr(context);
+ *
+ * @brief initializes device (interface) mac/ip addresses
+ *
+ * @param context           pointer to device (interface) context
+ *
+ * @return 0 on success, otherwise for failure
+ */
+int initialize_intf_mac_and_ip_addr(dhcp_device_context_t *context);
+
 /**
  * @code dhcp_device_get_ip(context, ip);
  *
@@ -119,21 +130,21 @@ int dhcp_device_init(dhcp_device_context_t **context,
                      uint8_t is_uplink);
 
 /**
- * @code dhcp_device_start_capture(context, snaplen, base, vlan_ip);
+ * @code dhcp_device_start_capture(context, snaplen, base, giaddr_ip);
  *
  * @brief starts packet capture on this interface
  *
  * @param context           pointer to device (interface) context
  * @param snaplen           length of packet capture
  * @param base              pointer to libevent base
- * @param vlan_ip           vlan IP address
+ * @param giaddr_ip         gateway IP address
  *
  * @return 0 on success, otherwise for failure
  */
 int dhcp_device_start_capture(dhcp_device_context_t *context,
                               size_t snaplen,
                               struct event_base *base,
-                              in_addr_t vlan_ip);
+                              in_addr_t giaddr_ip);
 
 /**
  * @code dhcp_device_shutdown(context);

src/dhcp_devman.c

@@ -37,6 +37,12 @@ static uint32_t dhcp_num_mgmt_intf = 0;
  *  This IP is used to filter Offer/Ack packet coming from DHCP server */
 static in_addr_t vlan_ip = 0;
 
+/* Device loopback interface ip, which will be used as the giaddr in dual tor setup. */
+static in_addr_t loopback_ip = 0;
+
+/* Whether the device is in dual tor mode, 0 as default for single tor mode. */
+static int dual_tor_mode = 0;
+
 /** mgmt interface */
 static struct intf *mgmt_intf = NULL;
 
@@ -148,6 +154,37 @@ int dhcp_devman_add_intf(const char *name, char intf_type)
     return rv;
 }
 
+/**
+ * @code dhcp_devman_setup_dual_tor_mode(name);
+ *
+ * @brief set up dual tor mode: 1) set dual_tor_mode flag and 2) retrieve loopback_ip.
+ */
+int dhcp_devman_setup_dual_tor_mode(const char *name)
+{
+    int rv = -1;
+
+    dhcp_device_context_t loopback_intf_context;
+
+    if (strlen(name) < sizeof(loopback_intf_context.intf)) {
+        strncpy(loopback_intf_context.intf, name, sizeof(loopback_intf_context.intf) - 1);
+        loopback_intf_context.intf[sizeof(loopback_intf_context.intf) - 1] = '\0';
+    } else {
+        syslog(LOG_ALERT, "loopback interface name (%s) is too long", name);
+        return rv;
+    }
+
+    if (initialize_intf_mac_and_ip_addr(&loopback_intf_context) == 0 &&
+        dhcp_device_get_ip(&loopback_intf_context, &loopback_ip) == 0) {
+            dual_tor_mode = 1;
+    } else {
+        syslog(LOG_ALERT, "failed to retrieve ip addr for loopback interface (%s)", name);
+        return rv;
+    }
+
+    rv = 0;
+    return rv;
+}
+
 /**
  * @code dhcp_devman_start_capture(snaplen, base);
  *
@@ -160,7 +197,7 @@ int dhcp_devman_start_capture(size_t snaplen, struct event_base *base)
 
     if ((dhcp_num_south_intf == 1) && (dhcp_num_north_intf >= 1)) {
         LIST_FOREACH(int_ptr, &intfs, entry) {
-            rv = dhcp_device_start_capture(int_ptr->dev_context, snaplen, base, vlan_ip);
+            rv = dhcp_device_start_capture(int_ptr->dev_context, snaplen, base, dual_tor_mode ? loopback_ip : vlan_ip);
             if (rv == 0) {
                 syslog(LOG_INFO,
                        "Capturing DHCP packets on interface %s, ip: 0x%08x, mac [%02x:%02x:%02x:%02x:%02x:%02x] \n",

src/dhcp_devman.h

@@ -63,6 +63,17 @@ dhcp_device_context_t* dhcp_devman_get_mgmt_dev();
  */
 int dhcp_devman_add_intf(const char *name, char intf_type);
 
+/**
+ * @code dhcp_devman_setup_dual_tor_mode(name);
+ *
+ * @brief set up dual tor mode: 1) set dual_tor_mode flag and 2) retrieve loopback_ip.
+ *
+ * @param name              interface name
+ *
+ * @return 0 on success, nonzero otherwise
+ */
+int dhcp_devman_setup_dual_tor_mode(const char *name);
+
 /**
  * @code dhcp_devman_start_capture(snaplen, base);
  *

src/main.c

@@ -40,11 +40,12 @@ static const uint32_t dhcpmon_default_unhealthy_max_count = 10;
  */
 static void usage(const char *prog)
 {
-    printf("Usage: %s -id <south interface> {-iu <north interface>}+ -im <mgmt interface> [-w <snapshot window in sec>]"
-            "[-c <unhealthy status count>] [-s <snap length>] [-d]\n", prog);
+    printf("Usage: %s -id <south interface> {-iu <north interface>}+ -im <mgmt interface> [-u <loopback interface>]"
+            "[-w <snapshot window in sec>] [-c <unhealthy status count>] [-s <snap length>] [-d]\n", prog);
     printf("where\n");
     printf("\tsouth interface: is a vlan interface,\n");
     printf("\tnorth interface: is a TOR-T1 interface,\n");
+    printf("\tloopback interface: is the loopback interface for dual tor setup,\n");
     printf("\tsnapshot window: during which DHCP counters are gathered and DHCP status is validated (default %d),\n",
             dhcpmon_default_health_check_window);
     printf("\tunhealthy status count: count of consecutive unhealthy status before writing an alert to syslog "
@@ -132,6 +133,12 @@ int main(int argc, char **argv)
             }
             i += 2;
             break;
+        case 'u':
+            if (dhcp_devman_setup_dual_tor_mode(argv[i + 1]) != 0) {
+                usage(basename(argv[0]));
+            }
+            i += 2;
+            break;
         case 'd':
             make_daemon = 1;
             i++;