port: show how many MAC addresses each port has learned

The switch keeps a count of the dynamic L2 entries learned on every
port in L2_LRN_PORT_CONSTRT_CNT (0x53ac + 4 * port, 13 bits). `stat`
prints it in a new MACs column and /status.json carries it as "macs".

On a SWTGW218AS the count matched the L2 table port by port, static
entries are not included, and taking a port down drops it to 0.

httpd/page_impl.c

@@ -1032,6 +1032,9 @@ void send_status(void)
 		slen += strtox(outbuf + slen, "\",\"rxB\":\"0x");
 		STAT_GET(STAT_COUNTER_ERR_PKTS, i);
 		reg_to_html(RTL837X_STAT_V_HIGH);	// 32bit RX packet errors
+
+		slen += strtox(outbuf + slen, "\",\"macs\":\"0x");
+		reg_to_html(RTL837X_L2_LRN_PORT_CONSTRT_CNT + (i << 2));
 		slen += strtox(outbuf + slen, "\"}");
 		if (i < machine.max_port)
 			char_to_html(',');

rtl837x_port.c

@@ -510,7 +510,7 @@ void port_media_show(uint8_t port) __banked
 
 void port_stats_print(void) __banked
 {
-	print_string("\nPort\tState\tLink\tTxGood\t\tTxBad\t\tRxGood\t\tRxBad\n");
+	print_string("\nPort\tState\tLink\tTxGood\t\tTxBad\t\tRxGood\t\tRxBad\t\tMACs\n");
 	for (uint8_t i = machine.min_port; i <= machine.max_port; i++) {
 		print_phys_port(i); write_char('\t');
 
@@ -584,6 +584,9 @@ void port_stats_print(void) __banked
 
 		STAT_GET(STAT_COUNTER_ERR_PKTS, i);
 		print_reg(RTL837X_STAT_V_HIGH); write_char('\t');
+
+		reg_read(RTL837X_L2_LRN_PORT_CONSTRT_CNT + (i << 2));
+		itoa_short(SFR_DATA_U16 & L2_LRN_PORT_CNT_MASK);
 		print_string("\n");
 	}
 }

rtl837x_regs.h

@@ -214,6 +214,8 @@
 #define RTL837x_L2_TBL_FLUSH_CNF	0x53dc
 #define RTL837X_L2_LRN_PORT_CONSTRAINT	0x5384
 #define RTL837X_L2_LRN_PORT_CONSTRT_ACT	0x4f80
+#define RTL837X_L2_LRN_PORT_CONSTRT_CNT	0x53ac
+#define L2_LRN_PORT_CNT_MASK		0x1fff
 #define	RTL8373_REG_MAC_L2_PORT_MAX_LEN	0x1250
 
 /*

test/test_page_json.c

@@ -185,6 +185,23 @@ static void t_l2_page(void)
 	CHECK(balanced(), "every page is valid JSON");
 }
 
+static void t_status_macs(void)
+{
+	const char *p1, *end, *mac;
+
+	printf("[test] /status.json reports the MAC addresses learned on each port\n");
+	hw_reset(); out_reset();
+	hw_reg_set(RTL837X_L2_LRN_PORT_CONSTRT_CNT + (1 << 2), 0x21);
+	send_status();
+	p1 = strstr(body(), "\"logPort\":1,");
+	end = p1 ? strchr(p1, '}') : NULL;
+	mac = p1 ? strstr(p1, "\"macs\":\"0x21\"") : NULL;
+	CHECK(mac && mac < end, "port 1 shows its learned count");
+	CHECK(has("\"macs\":\"0x0\""), "a port without learned addresses shows 0");
+	CHECK(slen <= TCP_OUTBUF_SIZE, "fits the buffer");
+	CHECK(balanced(), "valid JSON");
+}
+
 static void t_status_counters(void)
 {
 	printf("[test] /status.json prints 64-bit packet counters in full\n");
@@ -211,6 +228,7 @@ int main(void)
 	t_l2();
 	t_l2_page();
 	t_status_counters();
+	t_status_macs();
 	printf("\n%d checks, %d failed\n", tests_run, tests_failed);
 	return tests_failed ? 1 : 0;
 }