global: support DNS search domains

This has been supported by Windows and Linux for quite some time. Add
support here for iOS and macOS.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

Sources/WireGuardApp/UI/TunnelViewModel.swift

@@ -139,8 +139,10 @@ class TunnelViewModel {
             if let mtu = config.mtu {
                 scratchpad[.mtu] = String(mtu)
             }
-            if !config.dns.isEmpty {
-                scratchpad[.dns] = config.dns.map { $0.stringRepresentation }.joined(separator: ", ")
+            if !config.dns.isEmpty || !config.dnsSearch.isEmpty {
+                var dns = config.dns.map { $0.stringRepresentation }
+                dns.append(contentsOf: config.dnsSearch)
+                scratchpad[.dns] = dns.joined(separator: ", ")
             }
             return scratchpad
         }
@@ -194,15 +196,16 @@ class TunnelViewModel {
             }
             if let dnsString = scratchpad[.dns] {
                 var dnsServers = [DNSServer]()
+                var dnsSearch = [String]()
                 for dnsServerString in dnsString.splitToArray(trimmingCharacters: .whitespacesAndNewlines) {
                     if let dnsServer = DNSServer(from: dnsServerString) {
                         dnsServers.append(dnsServer)
                     } else {
-                        fieldsWithError.insert(.dns)
-                        errorMessages.append(tr("alertInvalidInterfaceMessageDNSInvalid"))
+                        dnsSearch.append(dnsServerString)
                     }
                 }
                 config.dns = dnsServers
+                config.dnsSearch = dnsSearch
             }
 
             guard errorMessages.isEmpty else { return .error(errorMessages.first!) }

Sources/WireGuardApp/UI/macOS/View/highlighter.c

@@ -337,11 +337,6 @@ static bool is_valid_network(string_span_t s)
 	return is_valid_ipv4(s) || is_valid_ipv6(s);
 }
 
-static bool is_valid_dns(string_span_t s)
-{
-	return is_valid_ipv4(s) || is_valid_ipv6(s);
-}
-
 enum field {
 	InterfaceSection,
 	PrivateKey,
@@ -451,7 +446,12 @@ static void highlight_multivalue_value(struct highlight_span_array *ret, const s
 {
 	switch (section) {
 	case DNS:
-		append_highlight_span(ret, parent.s, s, is_valid_dns(s) ? HighlightIP : HighlightError);
+		if (is_valid_ipv4(s) || is_valid_ipv6(s))
+			append_highlight_span(ret, parent.s, s, HighlightIP);
+		else if (is_valid_hostname(s))
+			append_highlight_span(ret, parent.s, s, HighlightHost);
+		else
+			append_highlight_span(ret, parent.s, s, HighlightError);
 		break;
 	case Address:
 	case AllowedIPs: {