From: Florent Kermarrec <florent@enjoy-digital.fr>
Date: Wed, 4 Feb 2015 18:03:49 +0000 (+0100)
Subject: ip: add checksum functions to model
X-Git-Tag: 24jan2021_ls180~2604^2~94
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=99323b4e87911384b99f9769cfca663b65714ba0;p=litex.git

ip: add checksum functions to model
---

diff --git a/liteeth/common.py b/liteeth/common.py
index 09972a99..1d32885e 100644
--- a/liteeth/common.py
+++ b/liteeth/common.py
@@ -52,7 +52,7 @@ arp_header = {
 	"destination_ip_address":	HField(24,  0, 32)
 }
 
-ipv4_header_len = 24
+ipv4_header_len = 20
 ipv4_header = {
 	"version":					HField(0,  0, 4),
 	"ihl":						HField(0,  4, 4),
@@ -66,8 +66,7 @@ ipv4_header = {
 	"protocol":					HField(9,  0, 8),
 	"header_checksum":			HField(10,  0, 16),
 	"source_ip_address":		HField(12,  0, 32),
-	"destination_ip_address":	HField(16,  0, 32),
-	"options":					HField(20,  0, 32)
+	"destination_ip_address":	HField(16,  0, 32)
 }
 
 udp_header_len = 8
diff --git a/liteeth/ip/__init__.py b/liteeth/ip/__init__.py
index 1ffb5293..97342356 100644
--- a/liteeth/ip/__init__.py
+++ b/liteeth/ip/__init__.py
@@ -41,8 +41,7 @@ class LiteEthIPTX(Module):
 			packetizer.sink.flags.eq(0),
 			packetizer.sink.fragment_offset.eq(0),
 			packetizer.sink.time_to_live.eq(0x80),
-			packetizer.sink.source_ip_address.eq(ip_address),
-			packetizer.sink.options.eq(0)
+			packetizer.sink.source_ip_address.eq(ip_address)
 		]
 		sink = packetizer.source
 
diff --git a/liteeth/test/model/arp.py b/liteeth/test/model/arp.py
index 1dc84626..65f006f3 100644
--- a/liteeth/test/model/arp.py
+++ b/liteeth/test/model/arp.py
@@ -87,7 +87,7 @@ class ARP(Module):
 			self.process_request(packet)
 		elif packet.operation == arp_opcode_reply:
 			self.process_reply(packet)
-	
+
 	def process_request(self, request):
 		if request.destination_ip_address == self.ip_address:
 			reply = ARPPacket([0]*(arp_packet_length-arp_header_len))
diff --git a/liteeth/test/model/ip.py b/liteeth/test/model/ip.py
index 3b5aa6d5..61a861be 100644
--- a/liteeth/test/model/ip.py
+++ b/liteeth/test/model/ip.py
@@ -10,11 +10,28 @@ def print_ip(s):
 
 preamble = split_bytes(eth_preamble, 8)
 
+def carry_around_add(a, b):
+    c = a + b
+    return (c & 0xffff) + (c >> 16)
+
+def checksum(msg):
+    s = 0
+    for i in range(0, len(msg), 2):
+        w = msg[i] + (msg[i+1] << 8)
+        s = carry_around_add(s, w)
+    return ~s & 0xffff
+
 # IP model
 class IPPacket(Packet):
 	def __init__(self, init=[]):
 		Packet.__init__(self, init)
 
+	def get_checksum(self):
+		return self[10] | (self[11] << 8)
+
+	def check_checksum(self):
+		return checksum(self[:ipv4_header_len]) == 0
+
 	def decode(self):
 		header = []
 		for byte in self[:ipv4_header_len]:
@@ -30,6 +47,13 @@ class IPPacket(Packet):
 		for d in split_bytes(header, ipv4_header_len):
 			self.insert(0, d)
 
+	def insert_checksum(self):
+		self[10] = 0
+		self[11] = 0
+		c = checksum(self[:ipv4_header_len])
+		self[10] = c & 0xff
+		self[11] = (c >> 8) & 0xff
+
 	def __repr__(self):
 		r = "--------\n"
 		for k in sorted(ipv4_header.keys()):
@@ -56,6 +80,7 @@ class IP(Module):
 
 	def send(self, packet):
 		packet.encode()
+		packet.insert_checksum()
 		if self.debug:
 			print_ip(">>>>>>>>")
 			print_ip(packet)
@@ -67,6 +92,11 @@ class IP(Module):
 
 	def callback(self, packet):
 		packet = IPPacket(packet)
+		if not packet.check_checksum():
+			received = packet.get_checksum()
+			packet.insert_checksum()
+			expected = packet.get_checksum()
+			raise ValueError("Checksum error received %04x / expected %04x" %(received, expected)) # XXX maybe too restrictive
 		packet.decode()
 		if self.debug:
 			print_ip("<<<<<<<<")
@@ -78,7 +108,7 @@ class IP(Module):
 
 	def process(self, packet):
 		pass
-	
+
 if __name__ == "__main__":
 	from liteeth.test.model.dumps import *
 	from liteeth.test.model.mac import *
@@ -89,11 +119,14 @@ if __name__ == "__main__":
 	#print(packet)
 	packet = IPPacket(packet)
 	# check decoding
+	errors += not packet.check_checksum()
 	packet.decode()
 	#print(packet)
 	errors += verify_packet(packet, {})
 	# check encoding
 	packet.encode()
+	packet.insert_checksum()
+	errors += not packet.check_checksum()
 	packet.decode()
 	#print(packet)
 	errors += verify_packet(packet, {})