prosodyctl: check turn: warn about external port mismatches behind NAT

Some NATs don't preserve port numbers, which can cause the TURN server's
reported relay address to be incorrect (the TURN server has no way to predict
what the external port is, so it can't be corrected in config like an IP
mismatch can).

1 files changed, 11 insertions, 5 deletions

diff --git a/util/prosodyctl/check.lua b/util/prosodyctl/check.lua
index 354cc3c3..71bbc222 100644
--- a/util/prosodyctl/check.lua
+++ b/util/prosodyctl/check.lua
@@ -62,9 +62,7 @@ local function check_probe(base_url, probe_module, target)
 end
 
 local function check_turn_service(turn_service, ping_service)
-	local array = require "util.array";
 	local ip = require "util.ip";
-	local set = require "util.set";
 	local stun = require "net.stun";
 
 	-- Create UDP socket for communication with the server
@@ -251,9 +249,17 @@ local function check_turn_service(turn_service, ping_service)
 		return result;
 	end
 
-	local relayed_address_set = set.new(array.pluck(result.relayed_addresses, "address"));
-	if not relayed_address_set:contains(result.external_ip_pong.address) then
+	local relay_address_found, relay_port_matches;
+	for _, relayed_address in ipairs(result.relayed_addresses) do
+		if relayed_address.address == result.external_ip_pong.address then
+			relay_address_found = true;
+			relay_port_matches = result.external_ip_pong.port == relayed_address.port;
+		end
+	end
+	if not relay_address_found then
 		table.insert(result.warnings, "TURN external IP vs relay address mismatch! Is the TURN server behind a NAT and misconfigured?");
+	elseif not relay_port_matches then
+		table.insert(result.warnings, "External port does not match reported relay port! This is probably caused by a NAT in front of the TURN server.");
 	end
 
 	--
@@ -1284,7 +1290,7 @@ local function check(arg)
 					end
 				end
 				if result.external_ip_pong then
-					print(("TURN external IP: %s"):format(result.external_ip_pong.address));
+					print(("TURN external address: %s:%d"):format(result.external_ip_pong.address, result.external_ip_pong.port));
 				end
 			end