From 34dad826201af2954615737c1c2d3b29d4cca167 Mon Sep 17 00:00:00 2001
From: Florent Kermarrec <florent@enjoy-digital.fr>
Date: Wed, 4 Feb 2015 19:35:38 +0100
Subject: [PATCH] ip: add checksum computation on ip tx (maybe not optimal on
 ressources)

---
 liteeth/generic/depacketizer.py |  6 +++---
 liteeth/generic/packetizer.py   |  8 ++++----
 liteeth/ip/__init__.py          | 27 +++++++++++++++++++++++++++
 3 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/liteeth/generic/depacketizer.py b/liteeth/generic/depacketizer.py
index 0713b36e8..64a1974ef 100644
--- a/liteeth/generic/depacketizer.py
+++ b/liteeth/generic/depacketizer.py
@@ -12,15 +12,15 @@ class LiteEthDepacketizer(Module):
 	def __init__(self, sink_description, source_description, header_type, header_length):
 		self.sink = sink = Sink(sink_description)
 		self.source = source = Source(source_description)
+		self.header = Signal(header_length*8)
 		###
 		shift = Signal()
-		header = Signal(header_length*8)
 		counter = Counter(max=header_length)
 		self.submodules += counter
 
 		self.sync += \
 			If(shift,
-				header.eq(Cat(header[8:], sink.data))
+				self.header.eq(Cat(self.header[8:], sink.data))
 			)
 
 		fsm = FSM(reset_state="IDLE")
@@ -54,7 +54,7 @@ class LiteEthDepacketizer(Module):
 			source.eop.eq(sink.eop),
 			source.data.eq(sink.data),
 			source.error.eq(sink.error),
-			_decode_header(header_type, header, source)
+			_decode_header(header_type, self.header, source)
 		]
 		fsm.act("COPY",
 			sink.ack.eq(source.ack),
diff --git a/liteeth/generic/packetizer.py b/liteeth/generic/packetizer.py
index ebd42c0cf..ac9cc6207 100644
--- a/liteeth/generic/packetizer.py
+++ b/liteeth/generic/packetizer.py
@@ -12,18 +12,18 @@ class LiteEthPacketizer(Module):
 	def __init__(self, sink_description, source_description, header_type, header_length):
 		self.sink = sink = Sink(sink_description)
 		self.source = source = Source(source_description)
+		self.header = Signal(header_length*8)
 		###
-		header = Signal(header_length*8)
 		header_reg = Signal(header_length*8)
 		load = Signal()
 		shift = Signal()
 		counter = Counter(max=header_length)
 		self.submodules += counter
 
-		self.comb += _encode_header(header_type, header, sink)
+		self.comb += _encode_header(header_type, self.header, sink)
 		self.sync += [
 			If(load,
-				header_reg.eq(header)
+				header_reg.eq(self.header)
 			).Elif(shift,
 				header_reg.eq(Cat(header_reg[8:], Signal(8)))
 			)
@@ -40,7 +40,7 @@ class LiteEthPacketizer(Module):
 				source.stb.eq(1),
 				source.sop.eq(1),
 				source.eop.eq(0),
-				source.data.eq(header[:8]),
+				source.data.eq(self.header[:8]),
 				If(source.stb & source.ack,
 					load.eq(1),
 					NextState("SEND_HEADER"),
diff --git a/liteeth/ip/__init__.py b/liteeth/ip/__init__.py
index 973423563..84fd81773 100644
--- a/liteeth/ip/__init__.py
+++ b/liteeth/ip/__init__.py
@@ -18,6 +18,26 @@ class LiteEthIPV4Packetizer(LiteEthPacketizer):
 			ipv4_header,
 			ipv4_header_len)
 
+class LiteEthIPV4Checksum(Module):
+	def __init__(self, skip_header=False):
+		self.header = Signal(ipv4_header_len*8)
+		self.value = Signal(16)
+
+		s = Signal(17)
+		r = Signal(17)
+		for i in range(ipv4_header_len//2):
+			if skip_header and i == 5:
+				pass
+			else:
+				s_next = Signal(17)
+				r_next = Signal(17)
+				self.comb += [
+					s_next.eq(r + self.header[i*16:(i+1)*16]),
+					r_next.eq(Cat(s_next[:16]+s_next[16], Signal()))
+				]
+				s, r = s_next, r_next
+		self.comb += self.value.eq(~Cat(r[8:16], r[:8]))
+
 class LiteEthIPTX(Module):
 	def __init__(self, mac_address, ip_address, arp_table):
 		self.sink = Sink(eth_ipv4_user_description(8))
@@ -45,6 +65,13 @@ class LiteEthIPTX(Module):
 		]
 		sink = packetizer.source
 
+		checksum = LiteEthIPV4Checksum(skip_header=True)
+		self.submodules += checksum
+		self.comb += [
+			checksum.header.eq(packetizer.header),
+			packetizer.sink.header_checksum.eq(checksum.value)
+		]
+
 		destination_mac_address = Signal(48)
 
 		fsm = FSM(reset_state="IDLE")