From 4a53c18869b0519046fdd8b59cde8e9c7479a023 Mon Sep 17 00:00:00 2001
From: Dobrica Pavlinusic <dpavlin@rot13.org>
Date: Sun, 4 Oct 2020 10:21:58 +0200
Subject: [PATCH] correctly parse Upstream return write parameter frame

---
 Protocol.pm | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/Protocol.pm b/Protocol.pm
index 829b7f0..3ec521d 100644
--- a/Protocol.pm
+++ b/Protocol.pm
@@ -210,12 +210,16 @@ sub protocol_decode {
 
 		} elsif ( $up_down eq 'down' && $function_code == 0x03 ) {
 			# type A
+			# 0x03 => 'Downstream read parameter frame',
 
 			$data_range = substr($data,0,1);
 			$data = substr($data,1);
 
 		} elsif ( $up_down eq 'up'   && ( $function_code == 0x07 || $function_code == 0x08 || $function_code == 0x03 ) ) {
 			# type B
+			# 0x07 => 'Upstream Heartbeat Frame',
+			# 0x08 => 'Upstream alarm frame',
+			# 0x03 => 'Upstream Read Parameter Frame',
 
 			$data_len = unpack('C', substr($data,1,1));
 			$data_range = substr($data,2, $data_len);
@@ -224,6 +228,7 @@ sub protocol_decode {
 
 		} elsif ( $up_down eq 'down' && $function_code == 0x06 ) {
 			# type B
+			# 0x06 => 'Downstream write parameter frame',
 
 			$data_len = unpack('C', substr($data,1,1));
 			$data_range = substr($data,2, $data_len);
@@ -232,15 +237,21 @@ sub protocol_decode {
 
 		} elsif ( $up_down eq 'up' && $function_code == 0x06 ) {
 			# type C
+			# 0x06 => 'Upstream return write parameter frame',
 
-			# FIXME check first byte?
-			my $data_range = substr($data,1,1);
+			$data_len = unpack('C', substr($data,1,1));
+			$data_range = substr($data,2, $data_len);
+			if ( $data_len == 1 ) {
+				# XXX return is OK/not OK
+				$pack_fmt = 'C';
+			}
 
-			$data = substr($data,2);
+			$data = substr($data,2 + $data_len);
 
 		} else {
 			$hash->{error}->{function_code_unknown} = $function_code;
-			warn "ERROR unknown function_code = $function_code";
+			print STDERR "ERROR unknown function_code = $function_code\n";
+			return $hash;
 		}
 
 		my @v = unpack($pack_fmt, $data_range);
-- 
2.20.1