Allowing commands like port 1 lldp block and port 2 lldp permit

so we are able to enable/disable lldp transmission on a specific
port.

cmd_parser.c

@@ -881,6 +881,7 @@ void parse_port(void)
 		cmd_error("\nUsage:" \
 					 "\nport <port> [show|on|off]" \
 					 "\nport <port> [10m|100m|1g|2g5|duplex] [half|full]" \
+					 "\nport <port> lldp [block|permit]" \
 					 "\nport <port> name [custom port name]\n");
 		return;
 	}
@@ -966,6 +967,14 @@ void parse_port(void)
 		else
 			phy_settings.duplex = PHY_DUPLEX_HALF;
 		phy_set_duplex();
+	} else if (cmd_compare(2, "lldp")) {
+		if (cmd_compare(3, "block")){
+			lldp_port_status &= ~(1 << phy_settings.port);
+		} else if (cmd_compare(3, "permit")) {
+			lldp_port_status |= 1 << phy_settings.port;
+		} else {
+			print_string ("Unknown port <port> lldp [block|permit] command\n");
+		}
 	} else {
 		cmd_error("Unknown port command\n");
 	}

rtl837x_common.h

@@ -131,6 +131,7 @@ struct flash_region_t {
 };
 
 extern __xdata char port_names[9][PORT_NAME_SIZE];
+extern __xdata uint16_t lldp_port_status;
 
 extern __xdata bool stp_enabled;
 

rtl837x_lldp.c

@@ -14,6 +14,7 @@ extern __xdata bool lldp_enabled;
 extern __code const struct machine machine;
 
 __xdata uint8_t lldp_seconds;
+__xdata uint16_t lldp_port_status = 0xffff;
 
 void lldp_init(void) __banked
 {
@@ -109,12 +110,14 @@ void lldp_send(void) __banked __reentrant
 
     for (uint8_t port = machine.min_port; port <= machine.max_port; port++) {
 
+        if ((1 << machine.log_to_phys_port[port]) & lldp_port_status) {
             LLDP_O->payload[port_position] = '0' + machine.log_to_phys_port[port];
             LLDP_O->rtl_tag.pmask = HTONS((uint16_t)1 << port);
 
             tcpip_output();
         }
     }
+}
 
 void lldp_set_addresses(void) __banked {
     // LLDP destination multicast addr: 01:80:c2:00:00:0e