rawsocket发送dns包

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#include 
#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;

char g_testDomain[32] = "www.baidu.com.";
int g_dstPort = 53;

struct IPHeader
{
    unsigned char headerLen:4;
    unsigned char version:4;
    unsigned char tos; //服务类型
    unsigned short totalLen; //总长度
    unsigned short id; //标识
    unsigned short flagOffset; //3位标志+13位片偏移
    unsigned char ttl; //TTL
    unsigned char protocol; //协议
    unsigned short checksum; //首部检验和
    unsigned int srcIP; //源IP地址
    unsigned int dstIP; //目的IP地址
};

struct UDPHeader //定义UDP首部
{
    unsigned short srcPort;    //16位源端口
    unsigned short dstPort;    //16位目的端口
    unsigned short dataLen;//16位UDP包长度
    unsigned short checksum;//16位校验和
};

struct DNSHeader
{
    unsigned short id;//
    unsigned short bitHeader; //协议头
    unsigned short questionCount;//请求问题总数
    unsigned short answerCount;//回答总数
    unsigned short authorityCount;//授权总数
    unsigned short additionalCount;//附加总数
};

struct DNSQuery
{
    unsigned short queryType; //查询的资源记录类型。
    unsigned short queryClass; //指定信息的协议组。
};

struct DNS
{
    DNSHeader header;
    char* domainStr;
    DNSQuery query;
};

enum DNSType //查询的资源记录类型。
{
    DNSType_A=0x01,//指定计算机 IP 地址
    DNSType_NS=0x02, //指定用于命名区域的 DNS 名称服务器。
    DNSType_MD=0x03, //指定邮件接收站（此类型已经过时了，使用MX代替）
    DNSType_MF=0x04, //指定邮件中转站（此类型已经过时了，使用MX代替）
    DNSType_CNAME=0x05, //指定用于别名的规范名称。
    DNSType_SOA=0x06, //指定用于 DNS 区域的“起始授权机构”。
    DNSType_MB=0x07, //指定邮箱域名。
    DNSType_MG=0x08, //指定邮件组成员。
    DNSType_MR=0x09, //指定邮件重命名域名。
    DNSType_NULL=0x0A, //指定空的资源记录
    DNSType_WKS=0x0B, //描述已知服务。
    DNSType_PTR=0x0C, //如果查询是 IP 地址，则指定计算机名；否则指定指向其它信息的指针。
    DNSType_HINFO=0x0D, //指定计算机 CPU 以及操作系统类型。
    DNSType_MINFO=0x0E, //指定邮箱或邮件列表信息。
    DNSType_MX=0x0F, //指定邮件交换器。
    DNSType_TXT=0x10, //指定文本信息。
    DNSType_UINFO=0x64, //指定用户信息。
    DNSType_UID=0x65, //指定用户标识符。
    DNSType_GID=0x66, //指定组名的组标识符。
    DNSType_ANY=0xFF //指定所有数据类型。
};

enum DNSClass //指定信息的协议组。
{
    DNSClass_IN=0x01, //指定 Internet 类别。
    DNSClass_CSNET=0x02, //指定 CSNET 类别。（已过时）
    DNSClass_CHAOS=0x03, //指定 Chaos 类别。
    DNSClass_HESIOD=004,//指定 MIT Athena Hesiod 类别。
    DNSClass_ANY=0xFF //指定任何以前列出的通配符。
};

//udp校验和
unsigned short udpChecksum(unsigned short* buffer, int size)
{
    unsigned long cksum = 0;
    while(size>1)
    {
        cksum += *buffer++;
        size -= sizeof(unsigned short);
    }
    if(size)
    {
        cksum += *(unsigned char*)buffer;
    }
    cksum = (cksum>>16) + (cksum&0xffff); //将高16bit与低16bit相加

    cksum += (cksum>>16); //将进位到高位的16bit与低16bit 再相加

    return (unsigned short)(~cksum);
}

//ip数字转字符串
void ipLLToStr(long long ip_num,char* ip_str)
{
    unsigned int iptok1 = (ip_num & 0xFF000000) >> 24;
    unsigned int iptok2 = (ip_num & 0x00FF0000) >> 16;
    unsigned int iptok3 = (ip_num & 0x0000FF00) >> 8;
    unsigned int iptok4 = ip_num & 0x000000FF;
    char ip[32];
    bzero(ip,sizeof(ip));
    snprintf(ip,sizeof(ip),"%d.%d.%d.%d",iptok1,iptok2,iptok3,iptok4);
    strcpy(ip_str,ip);
}

//发送DNS报文
void sendDnsPacket(int sockfd,sockaddr_in* dstAddr,bool useEDns)
{
    char sendBuf[1024] = "";

    DNS requestDNS;
    bzero(&requestDNS,sizeof(requestDNS));
    int domainLen = strlen(g_testDomain)+1;
    int dnsDataLen = sizeof(requestDNS.header)+sizeof(requestDNS.query)+domainLen;

    int totalLen = sizeof(IPHeader) + sizeof(UDPHeader) + dnsDataLen;
    int pos = 0;
    IPHeader* ipHeader = (IPHeader *)sendBuf;
    ipHeader->headerLen = sizeof(IPHeader)>>2;
    ipHeader->version = IPVERSION;
    //服务类型
    ipHeader->tos = 0;
    ipHeader->totalLen = totalLen;
    ipHeader->id=0;
    //设置flag标记为0
    ipHeader->flagOffset=0;
    //运用的协议为DNS协议
    ipHeader->protocol=IPPROTO_UDP;
    //一个封包在网络上可以存活的时间
    ipHeader->ttl=64;
    //目的地址
    //ipHeader->srcIP = inet_addr("1.1.1.1"); //如果想要伪造源IP的话...
    ipHeader->dstIP = dstAddr->sin_addr.s_addr;
    pos = sizeof(IPHeader);

    UDPHeader* udpHeader = (UDPHeader*)(sendBuf+pos);
    udpHeader->srcPort = htons(21000);
    udpHeader->dstPort = htons(g_dstPort);
    udpHeader->dataLen = htons(totalLen-sizeof(IPHeader));
    pos+= sizeof(UDPHeader);


    requestDNS.header.id = 10;
    requestDNS.header.bitHeader = htons(0x0100);
    requestDNS.header.questionCount = htons(1);
    if(useEDns){
        requestDNS.header.additionalCount = htons(1);
    }

    requestDNS.domainStr = new char[domainLen];
    bzero(requestDNS.domainStr,domainLen);
    char *priorPtr = g_testDomain;
    char *currPtr = strstr(g_testDomain,".");
    int dotPos = 0;
    while(currPtr!=NULL)
    {
        int size = currPtr - priorPtr;
        requestDNS.domainStr[dotPos] = size;
        dotPos++;
        memcpy(requestDNS.domainStr+dotPos,priorPtr,size);
        dotPos += size;
        currPtr++;
        priorPtr = currPtr;
        currPtr = strstr(g_testDomain+dotPos,".");
        if(currPtr==NULL)
        {
            size = strlen(g_testDomain) - dotPos;
            requestDNS.domainStr[dotPos] = size;
            dotPos++;
            memcpy(requestDNS.domainStr+dotPos,priorPtr,size);
            requestDNS.domainStr[domainLen-1] = '\0';
        }
    }
    requestDNS.query.queryType = htons(1);
    requestDNS.query.queryClass = htons(1);

    memcpy(sendBuf+pos,&requestDNS.header,sizeof(requestDNS.header));
    pos += sizeof(requestDNS.header);

    memcpy(sendBuf+pos,requestDNS.domainStr,domainLen);
    pos += domainLen;

    memcpy(sendBuf+pos,&requestDNS.query,sizeof(requestDNS.query));

    udpHeader->checksum = udpChecksum((unsigned short*)(sendBuf+sizeof(IPHeader) + sizeof(UDPHeader)), dnsDataLen);

    if(sendto(sockfd,sendBuf,totalLen,0,(struct sockaddr *)dstAddr,sizeof(*dstAddr))<0){
        perror("sendto error");
    }
}

//解析dns result
bool decodeDNSResult(const char *buf, int& index,char* dst)
{
    if (buf == NULL){
        return false;
    }

    int i = 0;
    unsigned char len = 0;
    bool skip0x = true;
    while ( (len = buf[index]) != 0x00)
    {
        if ((len & 0xc0) == 0) //普通格式，LabelDataLen + Label
        {
            index++;//跳过len
            memcpy(dst+i,buf+index,len);
            i += len;
            index += len;
            strcat(dst,".");
            i++;
            continue;
        }
        //消息压缩格式，11000000 00000000，两个字节，前2位为跳转标志，后14位为跳转的偏移
        short test = 0;
        memcpy(&test,buf+index,2);
        int jumpIndex = ntohs(test) & 0x3fff;
        index++;
        index++;//跳过len
        skip0x = false;
        if (!decodeDNSResult(buf,jumpIndex,dst+i)){
            return false;
        }
        break;
    }
    if(skip0x){
        index++;//跳过0x00
    }
    return true;
}

//解析dns question
void parseDNSQuestion(const char* recvBuf,int& pos,int questionCount)
{
    char contentStr[2048] = "";
    for(int i = 0;i0){
        cout << contentStr << endl;
    }
}

//解析dns结果
void parseResult( const char *recvBuf, int &pos,int count)
{
    char contentStr[2048] = "";
    for(int i=0;i0){
        cout << contentStr << endl;
    }
}

//解析dns包
void parseDnsPacket(int sockfd,sockaddr_in* dstAddr)
{
    char recvBuf[10240] = "";
    socklen_t cliLen = sizeof(dstAddr);
    int recvLen = recvfrom(sockfd,recvBuf,sizeof(recvBuf),0,(sockaddr*)&dstAddr,&cliLen);
    if( recvLen > 0)
    {
        int pos = 0;
        IPHeader* ipHeader = (IPHeader *)recvBuf;
        pos += sizeof(IPHeader);
        char srcIPStr[64] = "",dstIPStr[64]="";
        ipLLToStr(ntohl(ipHeader->srcIP),srcIPStr);
        ipLLToStr(ntohl(ipHeader->dstIP),dstIPStr);
        int totalLen = ntohs(ipHeader->totalLen);
        char ipHeaderStr[256] = "";
        snprintf(ipHeaderStr,sizeof(ipHeaderStr),"response ip header info: version:%d,tos:%d,protocol:%d,ttl:%d,srcIP:%s,dstIP:%s,totalLen:%d"
                 ,ipHeader->version,ipHeader->tos,ipHeader->protocol,ipHeader->ttl,srcIPStr,dstIPStr,totalLen);
        cout << ipHeaderStr << endl;
        UDPHeader* udpHeader = (UDPHeader*)(recvBuf+pos);
        pos += sizeof(UDPHeader);
        unsigned short  udpSrcPort = ntohs(udpHeader->srcPort);
        unsigned short  udpDstPort = ntohs(udpHeader->dstPort);
        unsigned short  udpLen = ntohs(udpHeader->dataLen);
        char udpHeaderStr[256] = "";
        snprintf(udpHeaderStr,sizeof(udpHeaderStr),"response udp header:srcPort:%d,dstPort:%d,udpLen:%d",udpSrcPort,udpDstPort,udpLen);
        cout << udpHeaderStr << endl;
        DNSHeader* dnsHeader = (DNSHeader*)(recvBuf+pos);
        dnsHeader->bitHeader = ntohs(dnsHeader->bitHeader);
        dnsHeader->answerCount = ntohs(dnsHeader->answerCount);
        dnsHeader->additionalCount = ntohs(dnsHeader->additionalCount);
        dnsHeader->authorityCount = ntohs(dnsHeader->authorityCount);
        dnsHeader->questionCount = ntohs(dnsHeader->questionCount);

        int dnsStartPos = sizeof(DNSHeader);
        //解析question
        parseDNSQuestion(recvBuf+pos,dnsStartPos,dnsHeader->questionCount);
        //解析answer
        parseResult(recvBuf+pos,dnsStartPos,dnsHeader->answerCount);
        //解析授权
        parseResult(recvBuf+pos,dnsStartPos,dnsHeader->authorityCount);
        //解析additional
        parseResult(recvBuf+pos,dnsStartPos,dnsHeader->additionalCount);
    }

}

int main()
{
    int sockfd = socket(AF_INET,SOCK_RAW,IPPROTO_UDP);
    if( sockfd < 0)
    {
        cout << strerror(errno) << endl;
        return -1;
    }

    int bufSize=50*1024;
    setsockopt(sockfd,SOL_SOCKET,SO_RCVBUF,&bufSize,sizeof(bufSize) );

    //IPPROTO_TP说明用户自己填写IP报文
    //IP_HDRINCL表示由内核来计算IP报文的头部校验和，和填充那个IP的id
    int on = 1;
    setsockopt(sockfd,IPPROTO_IP,IP_HDRINCL,&on,sizeof(on));

    char dstStr[32] = "114.114.114.114";
    sockaddr_in dstAddr;
    bzero(&dstAddr,sizeof(dstAddr));
    dstAddr.sin_family=AF_INET;
    dstAddr.sin_addr.s_addr = inet_addr(dstStr);
    dstAddr.sin_port = htons(g_dstPort);
    sendDnsPacket(sockfd,&dstAddr,false);
    parseDnsPacket(sockfd,&dstAddr);

    close(sockfd);
    return 0;
}

response ip header info: version:4,tos:0,protocol:17,ttl:142,srcIP:114.114.114.114,dstIP:172.16.96.52,totalLen:118
response udp header:srcPort:53,dstPort:21000,udpLen:98
www.baidu.com. type:1 class:1

www.baidu.com. ttl:0 type:5 class:1 www.a.shifen.com.
www.a.shifen.com. ttl:164 type:1 class:1 220.181.112.244
www.a.shifen.com. ttl:164 type:1 class:1 220.181.111.188