�[experiment-3]Add the code and report

experiment-3/code/ipv4.cpp

@@ -0,0 +1,116 @@
+/*
+* THIS FILE IS FOR IP TEST
+*/
+// system support
+#include "sysInclude.h"
+
+extern void ip_DiscardPkt(char* pBuffer,int type);
+
+extern void ip_SendtoLower(char*pBuffer,int length);
+
+extern void ip_SendtoUp(char *pBuffer,int length);
+
+extern unsigned int getIpv4Address();
+
+// implemented by students
+
+struct Ipv4
+{
+  char version_ihl;
+  char type_of_service;
+  short total_length;
+  short identification;
+  short fragment_offset;
+  char time_to_live;
+  char protocol;
+  short header_checksum;
+  unsigned int source_address;
+  unsigned int destination_address;
+  Ipv4() {
+    memset(this,0,sizeof(Ipv4));
+  }
+  Ipv4(unsigned int len,unsigned int srcAddr,unsigned int dstAddr,
+    byte _protocol,byte ttl) {
+    memset(this,0,sizeof(Ipv4));
+    version_ihl = 0x45;
+    total_length = htons(len+20);
+    time_to_live = ttl;
+    protocol = _protocol;
+    source_address = htonl(srcAddr);
+    destination_address = htonl(dstAddr);
+
+    char *pBuffer;
+    memcpy(pBuffer,this,sizeof(Ipv4));
+    int sum = 0;
+    for(int i = 0; i < 10; i++) {
+        if(i != 5) {
+          sum += (int)((unsigned char)pBuffer[i*2] << 8);
+          sum += (int)((unsigned char)pBuffer[i*2+1]);
+        }
+    }
+    while((sum & 0xffff0000) != 0) {
+      sum = (sum & 0xffff) + ((sum >> 16) & 0xffff);
+    }
+    unsigned short int ssum = sum;
+    header_checksum = htons(~ssum);
+  }
+};
+
+int stud_ip_recv(char *pBuffer,unsigned short length)
+{
+  Ipv4 *ipv4 = new Ipv4();
+  *ipv4 = *(Ipv4*)pBuffer;
+  int version = 0xf & ((ipv4->version_ihl)>> 4);
+  if(version != 4)  {
+    ip_DiscardPkt(pBuffer,STUD_IP_TEST_VERSION_ERROR);
+    return 1;
+  }
+  int ihl = 0xf & ipv4->version_ihl;
+  if(ihl < 5) {
+    ip_DiscardPkt(pBuffer,STUD_IP_TEST_HEADLEN_ERROR);
+    return 1;
+  }
+  int ttl = (int)ipv4->time_to_live;
+  if(ttl == 0) {
+    ip_DiscardPkt(pBuffer,STUD_IP_TEST_TTL_ERROR);
+    return 1;
+  }
+  int destination_address = ntohl(ipv4->destination_address);  
+  if(destination_address != getIpv4Address() && destination_address != 0xffffffff) {
+    ip_DiscardPkt(pBuffer,STUD_IP_TEST_DESTINATION_ERROR);
+    return 1;
+  }
+  int header_checksum = ntohs(ipv4->header_checksum);
+  int sum = 0;
+  for(int i = 0; i < ihl*2; i++) {
+    if(i!=5)
+    {
+      sum += (int)((unsigned char)pBuffer[i*2] << 8);
+      sum += (int)((unsigned char)pBuffer[i*2+1]);
+    }
+  }
+
+  while((sum & 0xffff0000) != 0) {
+    sum = (sum & 0xffff) + ((sum >> 16) & 0xffff);
+  }
+  unsigned short int ssum = (~sum) & 0xffff;
+  if(ssum != header_checksum) {
+    ip_DiscardPkt(pBuffer,STUD_IP_TEST_CHECKSUM_ERROR);
+    return 1;
+  }
+  ip_SendtoUp(pBuffer,length);
+  return 0;
+}
+
+int stud_ip_Upsend(char *pBuffer,unsigned short len,unsigned int srcAddr,
+           unsigned int dstAddr,byte protocol,byte ttl)
+{
+  char *pack_to_sent = new char[len+20];
+  memset(pack_to_sent,0,len+20);
+  *((Ipv4*)pack_to_sent) = Ipv4(len,srcAddr,dstAddr,protocol,ttl);
+  memcpy(pack_to_sent+20,pBuffer,len);
+  ip_SendtoLower(pack_to_sent,len+20);
+  delete[] pack_to_sent;
+
+  return 0;
+}