From 1c602981f0e8f91f9a6acd2a8e9b0dfc65603252 Mon Sep 17 00:00:00 2001
From: dowright <dowright@nationofnobodies.com>
Date: Wed, 25 Aug 2021 15:45:04 -0700
Subject: [PATCH] work on new packet

---
 new_packet.pxd |  4 ++--
 new_packet.pyx | 34 ++++++++++++++++++++++++----------
 2 files changed, 26 insertions(+), 12 deletions(-)

diff --git a/new_packet.pxd b/new_packet.pxd
index d68ad99..7204354 100644
--- a/new_packet.pxd
+++ b/new_packet.pxd
@@ -14,7 +14,7 @@ cdef enum:
 
 # cython define
 cdef struct iphdr:
-        u_int8_t  ihl_ver
+        u_int8_t  ver_ihl
         u_int8_t  tos
         u_int16_t tot_len
         u_int16_t id
@@ -32,7 +32,7 @@ cdef struct tcphdr:
     u_int32_t th_seq
     u_int32_t th_ack
 
-    u_int8_t th_off
+    u_int8_t  th_off
 
     u_int8_t  th_flags
     u_int16_t th_win
diff --git a/new_packet.pyx b/new_packet.pyx
index 3b300ad..2a28633 100644
--- a/new_packet.pyx
+++ b/new_packet.pyx
@@ -77,32 +77,46 @@ cdef class CPacket:
 
         self.ip_header = <iphdr*>self.data
 
-        cdef u_int8_t iphdr_len = (self.ip_header.tos & 15) * 4
+        cdef u_int8_t hdr_shift = 4
+        cdef u_int8_t hdr_multiplier = 4
+        cdef u_int8_t hdr_xand = 15
+        cdef u_int8_t iphdr_len
+
+        iphdr_len = self.ip_header.ver_ihl & hdr_xand
+        iphdr_len = iphdr_len * hdr_multiplier
+
+        printf('ip header length=%f\n', iphdr_len)
 
         cdef u_int8_t tcphdr_len
-        cdef u_int8_t udphdr_len
+        cdef u_int8_t udphdr_len  = 8
+        cdef u_int8_t icmphdr_len = 4
 
         cdef void *data = &self.data[iphdr_len]
+        cdef ptrdiff_t hdrptr = <u_int32_t*>data - <u_int32_t*>self.data
 
         if (self.ip_header.protocol == IPPROTO_TCP):
 
-            self.tcp_header = <tcphdr*>data
+            self.tcp_header = <tcphdr*>&hdrptr
 
-            tcphdr_len = (self.tcp_header.th_off & 15) * 4
+            tcphdr_len = self.tcp_header.th_off >> hdr_shift
+            tcphdr_len = tcphdr_len & hdr_xand
+            tcphdr_len = tcphdr_len * hdr_multiplier
+
+            printf('TCP HEADER LEN=%f\n', tcphdr_len)
 
             self.cmbhdr_len = iphdr_len + tcphdr_len
 
         elif (self.ip_header.protocol == IPPROTO_UDP):
 
-            self.udp_header = <udphdr*>data
-
-            udphdr_len = 8
+            self.udp_header = <udphdr*>&hdrptr
 
             self.cmbhdr_len = iphdr_len + udphdr_len
 
         elif (self.ip_header.protocol == IPPROTO_ICMP):
 
-            self.icmp_header = <icmphdr*>data
+            self.icmp_header = <icmphdr*>&hdrptr
+
+            self.cmbhdr_len = iphdr_len + icmphdr_len
 
     cdef void verdict(self, u_int32_t verdict):
         '''Call appropriate set_verdict function on packet.'''
@@ -245,7 +259,7 @@ cdef class CPacket:
         cdef tuple ip_header
 
         ip_header = (
-            self.ip_header.ihl_ver,
+            self.ip_header.ver_ihl,
             self.ip_header.tos,
             ntohs(self.ip_header.tot_len),
             ntohs(self.ip_header.id),
@@ -305,7 +319,7 @@ cdef class CPacket:
 
         cdef object payload
 
-        payload = self.data[self.cmbhdr_len:self.data_len]
+        payload = self.data[<Py_ssize_t>self.cmbhdr_len:self.data_len]
 
         return payload