# HG changeset patch
# User Matthew Wild <mwild1@gmail.com>
# Date 1779712168 -3600
# Node ID 721823e085ecb7c8d8b477c48a9e408ff85f6ff6
# Parent  604bed81808ee86b6092dffd31e161726d06a9fd
net.stun: Fix parsing of STUN packets with 0-length attributes

Not sure where the '20' came from. RFC 8489 defines attributes as simple TLVs,
with the type+length header being always 16 bits (4 bytes).

The branch for non-zero lengths already uses the correct header size.

diff -r 604bed81808e -r 721823e085ec net/stun.lua
--- a/net/stun.lua	Mon May 25 13:23:03 2026 +0100
+++ b/net/stun.lua	Mon May 25 13:29:28 2026 +0100
@@ -185,7 +185,7 @@
 		local attr_type, attr_len = struct.unpack(">I2I2", attr_hdr); --luacheck: ignore 211/attr_type
 		if attr_len == 0 then
 			table.insert(self.attributes, attr_hdr);
-			pos = pos + 20;
+			pos = pos + 4;
 		else
 			local data = bytes:sub(pos + 4, pos + 3 + attr_len);
 			assert(#data == attr_len, "packet truncated in attribute value");