dns: show the last lookup with the servers

The answer to a lookup arrives after the command has returned, so the
console of the web interface never shows it. Plain "dns" now prints the
name and the address, or whether it is still pending or failed.

dns.c

@@ -200,6 +200,18 @@ void dns_show(void) __banked
 	print_string(", from DHCP ");
 	print_ip(dhcp_state.dns);
 	write_char('\n');
+	if (!dns_state.name[0])
+		return;
+	print_string("Last lookup ");
+	print_string_x(dns_state.name);
+	print_string(": ");
+	if (dns_state.status == DNS_DONE)
+		print_ip(dns_state.addr);
+	else if (dns_state.status == DNS_PENDING)
+		print_string("pending");
+	else
+		print_string("failed");
+	write_char('\n');
 }
 
 

doc/dns.md

@@ -6,9 +6,13 @@ for anything else that is given a name instead of an address.
 ```
 dns server <ip> [<ip>]   # one or two servers, 0.0.0.0 removes them
 dns lookup <name>        # resolve a name and print the address
-dns                      # show the servers
+dns                      # show the servers and the last lookup
 ```
 
+The answer to a lookup arrives after the command has returned, so it is
+printed on the serial console and in the syslog. In the console of the web
+interface, run `dns` afterwards to see it.
+
 Without a configured server the resolver uses the one handed out by DHCP.
 Only address records are looked up; a query goes to the servers in turn,
 every two seconds, and gives up after six tries. A name that already is a