IPv4收发实验 ipv4

#include "sysInclude.h"

extern void ip_DiscardPkt(char* pBuffer,inttype);

extern void ip_SendtoLower(char*pBuffer,int length);

extern void ip_SendtoUp(char *pBuffer,int length);

extern unsigned int getIpv4Address();

// implemented by students


int stud_ip_recv(char *pBuffer,unsigned short length)
{
intVersion=(int)pBuffer[0]>>4;
intIHL=(int)pBuffer[0]&0xf;
int TTL=(int)pBuffer[8];
int Head_Checksum=ntohs(*(short unsignedint*)(pBuffer+10));
int Dst_IP=ntohl(*(intunsigned*)(pBuffer+16));

if(Version!=4)
{
ip_DiscardPkt(pBuffer,STUD_IP_TEST_VERSION_ERROR);
return 1;
}

if(IHL<5)
{
ip_DiscardPkt(pBuffer,STUD_IP_TEST_HEADLEN_ERROR);
return 1;
}

if(TTL==0)
{
ip_DiscardPkt(pBuffer,STUD_IP_TEST_TTL_ERROR);
return 1;
}
if(Dst_IP!=getIpv4Address()&&Dst_IP!=0xffffffff)
{
ip_DiscardPkt(pBuffer,STUD_IP_TEST_DESTINATION_ERROR);
return1;
}
int sum =0;
unsignedshort int localCheckSum = 0;
unsignedshort int field;
intoffset;
for(int i =1;i <=10;i++)//计算校验和
{
offset = (i-1)*2;
if(i != 6)
{
field =(pBuffer[offset])<<8;
field += pBuffer[offset+1];
sum += field;
sum %= 65535;
}
}
localCheckSum = 0xffff - (unsigned shortint)sum;
if(localCheckSum!=Head_Checksum)//检验校验和
{
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 intsrcAddr,//unsigned short len最大2^16=64k字节;
unsigned int dstAddr,byte protocol,bytettl)//地址刚好为32位;byte类型为一个字节,是通过网络传输信息的单位
{
char* DstBuffer=new char(len+20);
memset(DstBuffer,0,len+20);

DstBuffer[0]=0x45;
unsigned short Total_len=htons(len+20);
memcpy(DstBuffer+2,&Total_len,16);
DstBuffer[8]=ttl;
DstBuffer[9]=protocol;

unsigned int Scr_IP=htonl(srcAddr);
unsigned int Dst_IP=htonl(dstAddr);
memcpy(DstBuffer+12,&Scr_IP,32);
memcpy(DstBuffer+16,&Dst_IP,32);

intsum=0;
unsignedshort int localCheckSum = 0;
IPv4收发实验 ipv4
for(inti=0;i<10;i++)
{
sum=sum+(DstBuffer[i*2]<<8)+(DstBuffer[i*2+1]);
sum%=65535;
}
localCheckSum=htons(0xffff-(unsigned shortint)sum);

memcpy(DstBuffer+10,&localCheckSum,sizeof(unsignedshort int));
memcpy(DstBuffer+20,pBuffer,len);
ip_SendtoLower(DstBuffer,len+20);
return 0;
}

  

爱华网本文地址 » http://www.413yy.cn/a/25101013/168697.html

更多阅读

怎样设置OUTLOOK来收发邮件? outlook收发邮件很慢

设置Outlook Express软件来收发邮件以中文版Outlook Express 6为例怎样设置OUTLOOK来收发邮件?——步骤/方法怎样设置OUTLOOK来收发邮件? 1、打开Outlook Express后,单击窗口中的“工具”菜单,选择“帐户怎样设置OUTLOOK来收发邮件? 2、

ipv6无网络访问权限怎么办 ipv4 ipv6无网络权限

ipv6无网络访问权限怎么办——简介有时IP4和IP6都正常连接,但突然又出现“IPV6无网络访问权限” 这是Win7系统下经常发生的事情,如下图。ipv6无网络访问权限怎么办——方法/步骤

声明:《IPv4收发实验 ipv4》为网友长欢尽分享!如侵犯到您的合法权益请联系我们删除