stp: use the front panel number as the port ID

The port ID in the BPDUs was the chip port plus one, so on most boards
it did not match the port label, neither on the Spanning Tree page nor
on the neighbour. Send the front panel number instead, and 101 and up
for the LAGs, the same numbers the page already uses for the Port
column. A returned BPDU of our own is mapped back to the port by that
number.

Scenario 66 gives one port a front panel number that differs from its
chip port.

test/stp/stp_sim.c

@@ -17,7 +17,7 @@ uint8_t uip_buf[UIP_CONF_BUFFER_ALLOC_SIZE];
 uint16_t uip_len;
 struct uip_eth_addr uip_ethaddr = { .addr = { 0x1c, 0x2a, 0xa3, 0x1a, 0x72, 0x4e } };
 const struct machine machine = {
-	.log_to_phys_port = { 1, 2, 3, 4, 5, 6, 7, 8, 9 }
+	.log_to_phys_port = { 1, 2, 3, 4, 5, 6, 10, 8, 9 }
 };
 struct machine_runtime machine_detected = { .isRTL8373 = 1 };
 uint8_t sfr_data[4];
@@ -2049,7 +2049,7 @@ static void scen_lag(void)
 	t.legacy = 2;
 	bpdu_in(&t);
 	check(tx_frames[1] == 1 && tx_frames[2] == 0, "a reply leaves through the lowest member");
-	check(last_tx[1].port_id == STP_LAG_BASE + 1, "with the group's own port id");
+	check(last_tx[1].port_id == 101, "with the group's own port id");
 
 	memset(flush_count, 0, sizeof(flush_count));
 	links_set((1 << 2) | (1 << 8));
@@ -2292,6 +2292,24 @@ static void scen_mikrotik_wire_capture(void)
 	check(attributed, "both VLAN layouts select the captured root and change RX and edge status only on the ingress port");
 }
 
+static void scen_port_id_panel(void)
+{
+	struct sim_bpdu own = {
+		.port = 0, .root_prio = 0x40, .root_cost = 20000,
+		.br_prio = 0x80, .port_id = 10
+	};
+
+	printf("66. the port ID is the front panel number, not the chip port\n");
+	reset_all();
+	links_set((1 << 0) | (1 << 6) | (1 << 8));
+	follow_root(5);
+	check(last_tx[6].port_id == 10, "chip port 6 sends front panel number 10");
+	memcpy(own.root_mac, ROOT_MAC, 6);
+	memcpy(own.br_mac, uip_ethaddr.addr, 6);
+	bpdu_in(&own);
+	check_state(6, 1, "its BPDU coming back on another port blocks chip port 6");
+}
+
 int main(int argc, char **argv)
 {
 	verbose = argc > 1 && argv[1][0] == '-' ? (argv[1][1] == 'd' ? 2 : 1) : 0;
@@ -2353,6 +2371,7 @@ int main(int argc, char **argv)
 	scen_loop_peer_heard_bpdu();
 	scen_loop_peer_autoedge_off();
 	scen_mikrotik_wire_capture();
+	scen_port_id_panel();
 	if (failures) {
 		printf("\n%d check(s) failed\n", failures);
 		return 1;