From 6c976d8b561fe50de34c5453213861b1fdf8584f Mon Sep 17 00:00:00 2001
From: retu2libc <christheyankee@gmail.com>
Date: Thu, 7 Mar 2024 00:05:39 -0500
Subject: [PATCH] Offload FCS to driver specific code

---
 src/Home/Net/Drivers/PCNet.ZC      | 8 +++++++-
 src/Home/Net/Protocols/Ethernet.ZC | 7 +++----
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/src/Home/Net/Drivers/PCNet.ZC b/src/Home/Net/Drivers/PCNet.ZC
index bf84da61..637956de 100755
--- a/src/Home/Net/Drivers/PCNet.ZC
+++ b/src/Home/Net/Drivers/PCNet.ZC
@@ -635,7 +635,13 @@ I64 PCNetPacketReceive(U8 **packet_buffer_out, U16 *packet_length_out)
 	NetDebug("PCNET RECEIVE PACKET: de_index incremented = 0x%0X", pcnet.current_rx_de_index);
 
 	*packet_buffer_out = pcnet.rx_buffer_addr_phys + de_index * ETHERNET_FRAME_SIZE;
-	*packet_length_out = packet_length;
+
+	// ASTRPRCV causes 802.3 packets to be stripped and FCS to be checked
+	U16 ethertype = (*packet_buffer_out)[ETHERNET_ETHERTYPE_OFFSET + 1] | (*packet_buffer_out)[ETHERNET_ETHERTYPE_OFFSET] << 8;
+	if (ethertype < ETHERNET_v2_MTU)
+		*packet_length_out = ethertype;
+	else
+		*packet_length_out = packet_length - FCS_LENGTH;  // ethertype ii TODO: Validate FCS
 
 	return de_index;
 }
diff --git a/src/Home/Net/Protocols/Ethernet.ZC b/src/Home/Net/Protocols/Ethernet.ZC
index 611b3b34..cdd54b33 100755
--- a/src/Home/Net/Protocols/Ethernet.ZC
+++ b/src/Home/Net/Protocols/Ethernet.ZC
@@ -29,6 +29,8 @@ U0 EthernetGlobalsInit()
 
 U0 EthernetFrameParse(CEthernetFrame *frame_out, U8 *frame, U16 length)
 {
+	// length is assumed to NOT include the FCS.
+
 	// Shrine says MemCopy has a high overhead.
 	// Almost tempted to say that means that a lot
 	// of the current system should be done with 
@@ -45,10 +47,7 @@ U0 EthernetFrameParse(CEthernetFrame *frame_out, U8 *frame, U16 length)
 
 	frame_out->data		 = frame + ETHERNET_DATA_OFFSET;
 
-	if (frame_out->ethertype <= ETHERNET_v2_MTU) // check if the field is a length or an ethertype
-		frame_out->length = frame_out->ethertype;
-	else
-		frame_out->length = length - ETHERNET_MAC_HEADER_LENGTH - FCS_LENGTH;
+	frame_out->length	 = length - ETHERNET_MAC_HEADER_LENGTH;
 }
 
 U0 EthernetFrameFinish(I64 de_index)