From b5d7f091ef4ac1156a3918cc5bef1d251ee40ec0 Mon Sep 17 00:00:00 2001
From: Pierre LALET <pierre.lalet@cea.fr>
Date: Mon, 28 Mar 2016 20:12:51 +0200
Subject: [PATCH] Fix TCP & UDP checksums when IP layer has options
Reported by Runa Barik on Scapy ML.
---
scapy/layers/inet.py | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/scapy/layers/inet.py b/scapy/layers/inet.py
index e26c4ef2..1807d19d 100644
--- a/scapy/layers/inet.py
+++ b/scapy/layers/inet.py
@@ -457,7 +457,12 @@ class TCP(Packet):
if self.chksum is None:
if isinstance(self.underlayer, IP):
if self.underlayer.len is not None:
- ln = self.underlayer.len-20
+ if self.underlayer.ihl is None:
+ olen = sum(len(x) for x in self.underlayer.options)
+ ihl = 5 + olen / 4 + (1 if olen % 4 else 0)
+ else:
+ ihl = self.underlayer.ihl
+ ln = self.underlayer.len - 4 * ihl
else:
ln = len(p)
psdhdr = struct.pack("!4s4sHH",
@@ -511,7 +516,12 @@ class UDP(Packet):
if self.chksum is None:
if isinstance(self.underlayer, IP):
if self.underlayer.len is not None:
- ln = self.underlayer.len-20
+ if self.underlayer.ihl is None:
+ olen = sum(len(x) for x in self.underlayer.options)
+ ihl = 5 + olen / 4 + (1 if olen % 4 else 0)
+ else:
+ ihl = self.underlayer.ihl
+ ln = self.underlayer.len - 4 * ihl
else:
ln = len(p)
psdhdr = struct.pack("!4s4sHH",
--
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