[转] 原始UDP封包发送
源:
发送原始UDP封包时:
1 以IPPROTO_UDP 为协议类型创建一个原始套接字,打开原始套接字上的IP_HDRINCL选项
2 构建UDP封包,要先设置IP头,设置UDP头,最后UDP净荷数据。
3 初始化完整的UDP封包之后,调用sendto函数即可将他发送。
计算UDP封包校验和的过程如下:
void ComputeUdpPseudoHeaderChecksum(
IPHeader *pIphdr,
UDPHeader *pUdphdr,
char *payload,
int payloadlen
)
{
char buff[1024];
char *ptr = buff;
int chksumlen = 0;
ULONG zero = 0;
// 包含源IP地址和目的IP地址
memcpy(ptr, &pIphdr->ipSource, sizeof(pIphdr->ipSource));
ptr += sizeof(pIphdr->ipSource);
chksumlen += sizeof(pIphdr->ipSource);
memcpy(ptr, &pIphdr->ipDestination, sizeof(pIphdr->ipDestination));
ptr += sizeof(pIphdr->ipDestination);
chksumlen += sizeof(pIphdr->ipDestination);
// 包含8位0域
memcpy(ptr, &zero, 1);
ptr += 1;
chksumlen += 1;
// 协议
memcpy(ptr, &pIphdr->ipProtocol, sizeof(pIphdr->ipProtocol));
ptr += sizeof(pIphdr->ipProtocol);
chksumlen += sizeof(pIphdr->ipProtocol);
// UDP长度
memcpy(ptr, &pUdphdr->len, sizeof(pUdphdr->len));
ptr += sizeof(pUdphdr->len);
chksumlen += sizeof(pUdphdr->len);
// UDP源端口号
memcpy(ptr, &pUdphdr->sourcePort, sizeof(pUdphdr->sourcePort));
ptr += sizeof(pUdphdr->sourcePort);
chksumlen += sizeof(pUdphdr->sourcePort);
// UDP目的端口号
memcpy(ptr, &pUdphdr->destinationPort, sizeof(pUdphdr->destinationPort));
ptr += sizeof(pUdphdr->destinationPort);
chksumlen += sizeof(pUdphdr->destinationPort);
// 又是UDP长度
memcpy(ptr, &pUdphdr->len, sizeof(pUdphdr->len));
ptr += sizeof(pUdphdr->len);
chksumlen += sizeof(pUdphdr->len);
// 16位的UDP校验和,置为0
memcpy(ptr, &zero, sizeof(USHORT));
ptr += sizeof(USHORT);
chksumlen += sizeof(USHORT);
// 净荷
memcpy(ptr, payload, payloadlen);
ptr += payloadlen;
chksumlen += payloadlen;
// 补齐到下一个16位边界
for(int i=0; i<payloadlen%2; i++)
{
*ptr = 0;
ptr++;
chksumlen++;
}
// 计算这个校验和,将结果填充到UDP头
pUdphdr->checksum = checksum((USHORT*)buff, chksumlen);
}
发送原始UDP封包的过程如下:
int main()
{
// 输入参数信息
char szDestIp[] = "10.16.115.88"; // <<== 填写目的IP地址
char szSourceIp[] = "127.0.0.1"; // <<== 填写您自己的IP地址
USHORT nDestPort = 4567;
USHORT nSourcePort = 8888;
char szMsg[] = "This is a test \r\n";
int nMsgLen = strlen(szMsg);
// 创建原始套节字
SOCKET sRaw = ::socket(AF_INET, SOCK_RAW, IPPROTO_UDP);
// 有效IP头包含选项
BOOL bIncl = TRUE;
::setsockopt(sRaw, IPPROTO_IP, IP_HDRINCL, (char *)&bIncl, sizeof(bIncl));
char buff[1024] = { 0 };
// IP头
IPHeader *pIphdr = (IPHeader *)buff;
pIphdr->iphVerLen = (4<<4 | (sizeof(IPHeader)/sizeof(ULONG)));
pIphdr->ipLength = ::htons(sizeof(IPHeader) + sizeof(UDPHeader) + nMsgLen);
pIphdr->ipTTL = 128;
pIphdr->ipProtocol = IPPROTO_UDP;
pIphdr->ipSource = ::inet_addr(szSourceIp);
pIphdr->ipDestination = ::inet_addr(szDestIp);
pIphdr->ipChecksum = checksum((USHORT*)pIphdr, sizeof(IPHeader));
// UDP头
UDPHeader *pUdphdr = (UDPHeader *)&buff[sizeof(IPHeader)];
pUdphdr->sourcePort = htons(8888);
pUdphdr->destinationPort = htons(nDestPort);
pUdphdr->len = htons(sizeof(UDPHeader) + nMsgLen);
pUdphdr->checksum = 0;
char *pData = &buff[sizeof(IPHeader) + sizeof(UDPHeader)];
memcpy(pData, szMsg, nMsgLen);
ComputeUdpPseudoHeaderChecksum(pIphdr, pUdphdr, pData, nMsgLen);
// 设置目的地址
SOCKADDR_IN destAddr = { 0 };
destAddr.sin_family = AF_INET;
destAddr.sin_port = htons(nDestPort);
destAddr.sin_addr.S_un.S_addr = ::inet_addr(szDestIp);
// 发送原始UDP封包
int nRet;
for(int i=0; i<5; i++)
{
nRet = ::sendto(sRaw, buff,
sizeof(IPHeader) + sizeof(UDPHeader) + nMsgLen, 0, (sockaddr*)&destAddr, sizeof(destAddr));
if(nRet == SOCKET_ERROR)
{
printf(" sendto() failed: %d \n", ::WSAGetLastError());
break;
}
else
{
printf(" sent %d bytes \n", nRet);
}
}
::closesocket(sRaw);
getchar();
return 0;
}