# HG changeset patch
# User Kim Alvefur <zash@zash.se>
# Date 1685534899 -7200
# Node ID 332e95f75dbb91b5a15e988e0486015bf39a955b
# Parent  d5f322dd424b497ed6f0e1cfa729524377fba780
util.prosodyctl.check: Fix error where hostname can't be turned into A label

Where gethostname or tohostname returns an invalid name, e.g. containing
underscores or something, to_ascii would reject this and return nil,
which triggers an error in the dns lookup.

Reported by prova2 in the chat, for whom tohostname returned a long name
containing underscores.

diff -r d5f322dd424b -r 332e95f75dbb util/prosodyctl/check.lua
--- a/util/prosodyctl/check.lua	Thu Aug 18 03:26:32 2022 +0200
+++ b/util/prosodyctl/check.lua	Wed May 31 14:08:19 2023 +0200
@@ -751,16 +751,17 @@
 
 		local fqdn = socket.dns.tohostname(socket.dns.gethostname());
 		if fqdn then
-			do
-				local res = dns.lookup(idna.to_ascii(fqdn), "A");
+			local fqdn_a = idna.to_ascii(fqdn);
+			if fqdn_a then
+				local res = dns.lookup(fqdn_a, "A");
 				if res then
 					for _, record in ipairs(res) do
 						external_addresses:add(record.a);
 					end
 				end
 			end
-			do
-				local res = dns.lookup(idna.to_ascii(fqdn), "AAAA");
+			if fqdn_a then
+				local res = dns.lookup(fqdn_a, "AAAA");
 				if res then
 					for _, record in ipairs(res) do
 						external_addresses:add(record.aaaa);