lldp: send the port name as the port description

A port named in the CLI or the web UI (port <n> name ...) now carries
that name in a Port Description TLV, so a neighbour sees "Uplink" next
to "Port 9". The tail of the frame is built per port, since the TLV
length differs from port to port; ports without a name send no TLV.

rtl837x_lldp.c

@@ -63,6 +63,7 @@ struct lldp_pkt {
 static void lldp_send_ports(uint16_t ttl, uint16_t ports) __reentrant
 {
     __xdata uint8_t *p;
+    __xdata uint8_t *tail;
     uint8_t port_position;
 
     lldp_set_addresses();
@@ -120,25 +121,7 @@ static void lldp_send_ports(uint16_t ttl, uint16_t ports) __reentrant
         *p++ = 0; //OID length
     }
 
-    // End of LLDPDU TLV
-    *p++ = 0x00; //padding
-    *p++ = 0x00; //padding
-
-    while (p < (LLDP_O->payload + LLDP_MIN_ETHERNET_PAYLOAD_LENGTH))
-        *p++ = 0x00;
-
-    /*
-     * uip_len is the Ethernet frame length excluding FCS.
-     *
-     * The frame consists of:
-     *
-     *     dst mac
-     *     src mac
-     *     rtl_tag  sizeof(struct rtl_tag)
-     *     EtherType (2 bytes)
-     *     payload (how far we've moved p pointer)
-     */
-    uip_len = MAC_ADDR_LEN + MAC_ADDR_LEN + sizeof(struct rtl_tag) + LLDP_ETHERTYPE_LENGTH + (p - LLDP_O->payload);
+    tail = p;
 
     for (uint8_t port = MACHINE_MIN_PORT; port <= MACHINE_MAX_PORT; port++) {
 
@@ -146,6 +129,29 @@ static void lldp_send_ports(uint16_t ttl, uint16_t ports) __reentrant
             LLDP_O->payload[port_position] = '0' + machine.log_to_phys_port[port];
             LLDP_O->rtl_tag.pmask = HTONS((uint16_t)1 << port);
 
+            p = tail;
+            p += lldp_portdesc(p, port);
+
+            // End of LLDPDU TLV
+            *p++ = 0x00; //padding
+            *p++ = 0x00; //padding
+
+            while (p < (LLDP_O->payload + LLDP_MIN_ETHERNET_PAYLOAD_LENGTH))
+                *p++ = 0x00;
+
+            /*
+             * uip_len is the Ethernet frame length excluding FCS.
+             *
+             * The frame consists of:
+             *
+             *     dst mac
+             *     src mac
+             *     rtl_tag  sizeof(struct rtl_tag)
+             *     EtherType (2 bytes)
+             *     payload (how far we've moved p pointer)
+             */
+            uip_len = MAC_ADDR_LEN + MAC_ADDR_LEN + sizeof(struct rtl_tag) + LLDP_ETHERTYPE_LENGTH + (p - LLDP_O->payload);
+
             tcpip_output();
         }
     }
@@ -205,3 +211,15 @@ uint8_t lldp_sysdesc(__xdata uint8_t *p) __banked
     memcpyc(p, VERSION_SW, version_length);
     return machine_name_length + 1 + version_length + 2;
 }
+
+uint8_t lldp_portdesc(__xdata uint8_t *p, uint8_t port) __banked
+{
+    uint8_t name_length = strlen_x(port_names[port]);
+
+    if (!name_length)
+        return 0;
+    *p++ = LLDP_TYPE(LLDP_PORT_DESC_TLV_TYPE);
+    *p++ = name_length;
+    memcpy(p, port_names[port], name_length);
+    return name_length + 2;
+}

rtl837x_lldp.h

@@ -24,6 +24,7 @@
 #define LLDP_CHASSIS_ID_TLV_LENGTH 7
 #define LLDP_CHASSIS_ID_TLV_SUBTYPE 4
 
+#define LLDP_PORT_DESC_TLV_TYPE 4
 #define LLDP_SYSNAME_TLV_TYPE 5
 #define LLDP_SYSDESC_TLV_TYPE 6
 
@@ -47,5 +48,6 @@ void lldp_set_addresses(void) __banked;
 void lldp_set_rtl_wrapper(void) __banked;
 uint8_t lldp_sysname(__xdata uint8_t *p) __banked;
 uint8_t lldp_sysdesc(__xdata uint8_t *p) __banked;
+uint8_t lldp_portdesc(__xdata uint8_t *p, uint8_t port) __banked;
 
 #endif