lldp: announce shutdown with a TTL of 0

lldp off and port <n> lldp block went silent and left the neighbour
holding our entry until its TTL ran out, 120 s later. Send one LLDPDU
with a TTL of 0 on the ports that stop, the shutdown form 802.1AB
defines for this, before the transmit mask changes.

cmd_parser.c

@@ -920,6 +920,8 @@ void parse_port(void)
 		print_string("\"\n");
 	} else if (cmd_compare(2, "lldp")) {
 		if (cmd_compare(3, "block")){
+			if (lldp_enabled)
+				lldp_shutdown((uint16_t)1 << phy_settings.port);
 			lldp_logical_port_status &= ~((uint16_t)1 << phy_settings.port);
 		} else if (cmd_compare(3, "permit")) {
 			lldp_logical_port_status |= (uint16_t)1 << phy_settings.port;
@@ -2046,6 +2048,8 @@ void cmd_parser(void) __banked
 				lldp_enabled = 1;
 			} else {
 				print_string("LLDP disabled\n");
+				if (lldp_enabled)
+					lldp_shutdown(lldp_logical_port_status);
 				lldp_enabled = 0;
 			}
 		}

rtl837x_lldp.c

@@ -54,7 +54,7 @@ struct lldp_pkt {
 // the length at any point
 #define LLDP_TYPE(value) (value << 1)
 
-void lldp_send(void) __banked __reentrant
+static void lldp_send_ports(uint16_t ttl, uint16_t ports) __reentrant
 {
     __xdata uint8_t *p;
     uint8_t port_position;
@@ -84,8 +84,8 @@ void lldp_send(void) __banked __reentrant
     //TTL
     *p++ = LLDP_TYPE(LLDP_TTL_TLV_TYPE);
     *p++ = LLDP_TTL_TLV_LENGTH;
-    *p++ = 0x00; //padding
+    *p++ = ttl >> 8;
-    *p++ = LLDP_TTL_TTL_SECONDS;
+    *p++ = ttl & 0xff;
 
     p += lldp_sysname(p);
     p += lldp_sysdesc(p);
@@ -136,7 +136,7 @@ void lldp_send(void) __banked __reentrant
 
     for (uint8_t port = machine.min_port; port <= machine.max_port; port++) {
 
-        if ((1 << port) & lldp_logical_port_status) {
+        if ((1 << port) & ports) {
             LLDP_O->payload[port_position] = '0' + machine.log_to_phys_port[port];
             LLDP_O->rtl_tag.pmask = HTONS((uint16_t)1 << port);
 
@@ -145,6 +145,16 @@ void lldp_send(void) __banked __reentrant
     }
 }
 
+void lldp_send(void) __banked __reentrant
+{
+    lldp_send_ports(LLDP_TTL_TTL_SECONDS, lldp_logical_port_status);
+}
+
+void lldp_shutdown(uint16_t ports) __banked __reentrant
+{
+    lldp_send_ports(0, ports);
+}
+
 void lldp_set_addresses(void) __banked {
     // LLDP destination multicast addr: 01:80:c2:00:00:0e
     memcpyc(LLDP_O->dst.addr, "\x01\x80\xc2\x00\x00\x0e", MAC_ADDR_LEN);

rtl837x_lldp.h

@@ -42,6 +42,7 @@
 void lldp_init(void) __banked;
 void lldp_tick(void) __banked;
 void lldp_send(void) __banked;
+void lldp_shutdown(uint16_t ports) __banked;
 void lldp_set_addresses(void) __banked;
 void lldp_set_rtl_wrapper(void) __banked;
 uint8_t lldp_sysname(__xdata uint8_t *p) __banked;