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特定のUDPポート用に独自のハンドラーを登録したいトンネリングカーネルモジュールを書いています。これを行うための最良の方法は何ですか？そのポートのトラフィックが到着したときにLinuxスタックが私のハンドラーを呼び出すように、そのハンドラーを登録するという考え方です。

[編集1]

ソケットAPIを使用する方法は、次のようなソケットにバインドすることです。

sin.sin_family = AF_INET;
sin.sin_addr.s_addr = htonl(INADDR_ANY);
sin.sin_port = htons(my_port);

err = kernel_bind(rcv_socket, (struct sockaddr *)&sin,
        sizeof(struct sockaddr_in));

udp_sk(rcv_socket->sk)->encap_rcv = my_handler;

問題は、このソケットが関連付けられてINADDR_ANYおり、マシン上の任意のホストIPに対応していることです。パケットに入ってくるIPに対してこれを実行したいですか？どうすればそれを達成できますか？

この場合、ソケットは使用できないと思います。どのIPでも、スタック内でパケットが。ip_forwardではなくパスを通過することを意味するためですip_local_delivery。そのようなパケット用に作成されたソケットはありません。この条件下でそれを達成する方法は？

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2 に答える 2

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反対票を投じる方へ: この試行錯誤した回答に反対票を投じた理由についてコメントしてください。

次の例が役に立ちます。必要に応じてフィルタを追加して、例を変更できます。

UDP の場合、以下の例に次の変更を加える必要があります。

sock_raw = socket(AF_INET , SOCK_RAW , IPPROTO_UDP);

http://www.binarytides.com/packet-sniffer-code-in-c-using-linux-sockets-bsd/ http://www.binarytides.com/packet-sniffer-code-in-c-using- linux-sockets-bsd-part-2/ [関連性]

参考までにコードをリストします

#include<netinet/in.h>
#include<errno.h>
#include<netdb.h>
#include<stdio.h> //For standard things
#include<stdlib.h>    //malloc
#include<string.h>    //strlen

#include<netinet/ip_icmp.h>   //Provides declarations for icmp header
#include<netinet/udp.h>   //Provides declarations for udp header
#include<netinet/tcp.h>   //Provides declarations for tcp header
#include<netinet/ip.h>    //Provides declarations for ip header
#include<netinet/if_ether.h>  //For ETH_P_ALL
#include<net/ethernet.h>  //For ether_header
#include<sys/socket.h>
#include<arpa/inet.h>
#include<sys/ioctl.h>
#include<sys/time.h>
#include<sys/types.h>
#include<unistd.h>

void ProcessPacket(unsigned char* , int);
void print_ip_header(unsigned char* , int);
void print_tcp_packet(unsigned char * , int );
void print_udp_packet(unsigned char * , int );
void print_icmp_packet(unsigned char* , int );
void PrintData (unsigned char* , int);

FILE *logfile;
struct sockaddr_in source,dest;
int tcp=0,udp=0,icmp=0,others=0,igmp=0,total=0,i,j; 

int main()
{
    int saddr_size , data_size;
    struct sockaddr saddr;

    unsigned char *buffer = (unsigned char *) malloc(65536); //Its Big!

    logfile=fopen("log.txt","w");
    if(logfile==NULL) 
    {
        printf("Unable to create log.txt file.");
    }
    printf("Starting...\n");

    int sock_raw = socket( AF_PACKET , SOCK_RAW , htons(ETH_P_ALL)) ;
    //setsockopt(sock_raw , SOL_SOCKET , SO_BINDTODEVICE , "eth0" , strlen("eth0")+ 1 );

    if(sock_raw < 0)
    {
        //Print the error with proper message
        perror("Socket Error");
        return 1;
    }
    while(1)
    {
        saddr_size = sizeof saddr;
        //Receive a packet
        data_size = recvfrom(sock_raw , buffer , 65536 , 0 , &saddr , (socklen_t*)&saddr_size);
        if(data_size <0 )
        {
            printf("Recvfrom error , failed to get packets\n");
            return 1;
        }
        //Now process the packet
        ProcessPacket(buffer , data_size);
    }
    close(sock_raw);
    printf("Finished");
    return 0;
}

void ProcessPacket(unsigned char* buffer, int size)
{
    //Get the IP Header part of this packet , excluding the ethernet header
    struct iphdr *iph = (struct iphdr*)(buffer + sizeof(struct ethhdr));
    ++total;
    switch (iph->protocol) //Check the Protocol and do accordingly...
    {
        case 1:  //ICMP Protocol
            ++icmp;
            print_icmp_packet( buffer , size);
            break;

        case 2:  //IGMP Protocol
            ++igmp;
            break;

        case 6:  //TCP Protocol
            ++tcp;
            print_tcp_packet(buffer , size);
            break;

        case 17: //UDP Protocol
            ++udp;
            print_udp_packet(buffer , size);
            break;

        default: //Some Other Protocol like ARP etc.
            ++others;
            break;
    }
    printf("TCP : %d   UDP : %d   ICMP : %d   IGMP : %d   Others : %d   Total : %d\r", tcp , udp , icmp , igmp , others , total);
}

void print_ethernet_header(unsigned char* Buffer, int Size)
{
    struct ethhdr *eth = (struct ethhdr *)Buffer;

    fprintf(logfile , "\n");
    fprintf(logfile , "Ethernet Header\n");
    fprintf(logfile , "   |-Destination Address : %.2X-%.2X-%.2X-%.2X-%.2X-%.2X \n", eth->h_dest[0] , eth->h_dest[1] , eth->h_dest[2] , eth->h_dest[3] , eth->h_dest[4] , eth->h_dest[5] );
    fprintf(logfile , "   |-Source Address      : %.2X-%.2X-%.2X-%.2X-%.2X-%.2X \n", eth->h_source[0] , eth->h_source[1] , eth->h_source[2] , eth->h_source[3] , eth->h_source[4] , eth->h_source[5] );
    fprintf(logfile , "   |-Protocol            : %u \n",(unsigned short)eth->h_proto);
}

void print_ip_header(unsigned char* Buffer, int Size)
{
    print_ethernet_header(Buffer , Size);

    unsigned short iphdrlen;

    struct iphdr *iph = (struct iphdr *)(Buffer  + sizeof(struct ethhdr) );
    iphdrlen =iph->ihl*4;

    memset(&source, 0, sizeof(source));
    source.sin_addr.s_addr = iph->saddr;

    memset(&dest, 0, sizeof(dest));
    dest.sin_addr.s_addr = iph->daddr;

    fprintf(logfile , "\n");
    fprintf(logfile , "IP Header\n");
    fprintf(logfile , "   |-IP Version        : %d\n",(unsigned int)iph->version);
    fprintf(logfile , "   |-IP Header Length  : %d DWORDS or %d Bytes\n",(unsigned int)iph->ihl,((unsigned int)(iph->ihl))*4);
    fprintf(logfile , "   |-Type Of Service   : %d\n",(unsigned int)iph->tos);
    fprintf(logfile , "   |-IP Total Length   : %d  Bytes(Size of Packet)\n",ntohs(iph->tot_len));
    fprintf(logfile , "   |-Identification    : %d\n",ntohs(iph->id));
    //fprintf(logfile , "   |-Reserved ZERO Field   : %d\n",(unsigned int)iphdr->ip_reserved_zero);
    //fprintf(logfile , "   |-Dont Fragment Field   : %d\n",(unsigned int)iphdr->ip_dont_fragment);
    //fprintf(logfile , "   |-More Fragment Field   : %d\n",(unsigned int)iphdr->ip_more_fragment);
    fprintf(logfile , "   |-TTL      : %d\n",(unsigned int)iph->ttl);
    fprintf(logfile , "   |-Protocol : %d\n",(unsigned int)iph->protocol);
    fprintf(logfile , "   |-Checksum : %d\n",ntohs(iph->check));
    fprintf(logfile , "   |-Source IP        : %s\n",inet_ntoa(source.sin_addr));
    fprintf(logfile , "   |-Destination IP   : %s\n",inet_ntoa(dest.sin_addr));
}

void print_tcp_packet(unsigned char* Buffer, int Size)
{
    unsigned short iphdrlen;

    struct iphdr *iph = (struct iphdr *)( Buffer  + sizeof(struct ethhdr) );
    iphdrlen = iph->ihl*4;

    struct tcphdr *tcph=(struct tcphdr*)(Buffer + iphdrlen + sizeof(struct ethhdr));

    int header_size =  sizeof(struct ethhdr) + iphdrlen + tcph->doff*4;

    fprintf(logfile , "\n\n***********************TCP Packet*************************\n");  

    print_ip_header(Buffer,Size);

    fprintf(logfile , "\n");
    fprintf(logfile , "TCP Header\n");
    fprintf(logfile , "   |-Source Port      : %u\n",ntohs(tcph->source));
    fprintf(logfile , "   |-Destination Port : %u\n",ntohs(tcph->dest));
    fprintf(logfile , "   |-Sequence Number    : %u\n",ntohl(tcph->seq));
    fprintf(logfile , "   |-Acknowledge Number : %u\n",ntohl(tcph->ack_seq));
    fprintf(logfile , "   |-Header Length      : %d DWORDS or %d BYTES\n" ,(unsigned int)tcph->doff,(unsigned int)tcph->doff*4);
    //fprintf(logfile , "   |-CWR Flag : %d\n",(unsigned int)tcph->cwr);
    //fprintf(logfile , "   |-ECN Flag : %d\n",(unsigned int)tcph->ece);
    fprintf(logfile , "   |-Urgent Flag          : %d\n",(unsigned int)tcph->urg);
    fprintf(logfile , "   |-Acknowledgement Flag : %d\n",(unsigned int)tcph->ack);
    fprintf(logfile , "   |-Push Flag            : %d\n",(unsigned int)tcph->psh);
    fprintf(logfile , "   |-Reset Flag           : %d\n",(unsigned int)tcph->rst);
    fprintf(logfile , "   |-Synchronise Flag     : %d\n",(unsigned int)tcph->syn);
    fprintf(logfile , "   |-Finish Flag          : %d\n",(unsigned int)tcph->fin);
    fprintf(logfile , "   |-Window         : %d\n",ntohs(tcph->window));
    fprintf(logfile , "   |-Checksum       : %d\n",ntohs(tcph->check));
    fprintf(logfile , "   |-Urgent Pointer : %d\n",tcph->urg_ptr);
    fprintf(logfile , "\n");
    fprintf(logfile , "                        DATA Dump                         ");
    fprintf(logfile , "\n");

    fprintf(logfile , "IP Header\n");
    PrintData(Buffer,iphdrlen);

    fprintf(logfile , "TCP Header\n");
    PrintData(Buffer+iphdrlen,tcph->doff*4);

    fprintf(logfile , "Data Payload\n");    
    PrintData(Buffer + header_size , Size - header_size );

    fprintf(logfile , "\n###########################################################");
}

void print_udp_packet(unsigned char *Buffer , int Size)
{

    unsigned short iphdrlen;

    struct iphdr *iph = (struct iphdr *)(Buffer +  sizeof(struct ethhdr));
    iphdrlen = iph->ihl*4;

    struct udphdr *udph = (struct udphdr*)(Buffer + iphdrlen  + sizeof(struct ethhdr));

    int header_size =  sizeof(struct ethhdr) + iphdrlen + sizeof udph;

    fprintf(logfile , "\n\n***********************UDP Packet*************************\n");

    print_ip_header(Buffer,Size);           

    fprintf(logfile , "\nUDP Header\n");
    fprintf(logfile , "   |-Source Port      : %d\n" , ntohs(udph->source));
    fprintf(logfile , "   |-Destination Port : %d\n" , ntohs(udph->dest));
    fprintf(logfile , "   |-UDP Length       : %d\n" , ntohs(udph->len));
    fprintf(logfile , "   |-UDP Checksum     : %d\n" , ntohs(udph->check));

    fprintf(logfile , "\n");
    fprintf(logfile , "IP Header\n");
    PrintData(Buffer , iphdrlen);

    fprintf(logfile , "UDP Header\n");
    PrintData(Buffer+iphdrlen , sizeof udph);

    fprintf(logfile , "Data Payload\n");    

    //Move the pointer ahead and reduce the size of string
    PrintData(Buffer + header_size , Size - header_size);

    fprintf(logfile , "\n###########################################################");
}

void print_icmp_packet(unsigned char* Buffer , int Size)
{
    unsigned short iphdrlen;

    struct iphdr *iph = (struct iphdr *)(Buffer  + sizeof(struct ethhdr));
    iphdrlen = iph->ihl * 4;

    struct icmphdr *icmph = (struct icmphdr *)(Buffer + iphdrlen  + sizeof(struct ethhdr));

    int header_size =  sizeof(struct ethhdr) + iphdrlen + sizeof icmph;

    fprintf(logfile , "\n\n***********************ICMP Packet*************************\n"); 

    print_ip_header(Buffer , Size);

    fprintf(logfile , "\n");

    fprintf(logfile , "ICMP Header\n");
    fprintf(logfile , "   |-Type : %d",(unsigned int)(icmph->type));

    if((unsigned int)(icmph->type) == 11)
    {
        fprintf(logfile , "  (TTL Expired)\n");
    }
    else if((unsigned int)(icmph->type) == ICMP_ECHOREPLY)
    {
        fprintf(logfile , "  (ICMP Echo Reply)\n");
    }

    fprintf(logfile , "   |-Code : %d\n",(unsigned int)(icmph->code));
    fprintf(logfile , "   |-Checksum : %d\n",ntohs(icmph->checksum));
    //fprintf(logfile , "   |-ID       : %d\n",ntohs(icmph->id));
    //fprintf(logfile , "   |-Sequence : %d\n",ntohs(icmph->sequence));
    fprintf(logfile , "\n");

    fprintf(logfile , "IP Header\n");
    PrintData(Buffer,iphdrlen);

    fprintf(logfile , "UDP Header\n");
    PrintData(Buffer + iphdrlen , sizeof icmph);

    fprintf(logfile , "Data Payload\n");    

    //Move the pointer ahead and reduce the size of string
    PrintData(Buffer + header_size , (Size - header_size) );

    fprintf(logfile , "\n###########################################################");
}

void PrintData (unsigned char* data , int Size)
{
    int i , j;
    for(i=0 ; i < Size ; i++)
    {
        if( i!=0 && i%16==0)   //if one line of hex printing is complete...
        {
            fprintf(logfile , "         ");
            for(j=i-16 ; j<i ; j++)
            {
                if(data[j]>=32 && data[j]<=128)
                    fprintf(logfile , "%c",(unsigned char)data[j]); //if its a number or alphabet

                else fprintf(logfile , "."); //otherwise print a dot
            }
            fprintf(logfile , "\n");
        } 

        if(i%16==0) fprintf(logfile , "   ");
            fprintf(logfile , " %02X",(unsigned int)data[i]);

        if( i==Size-1)  //print the last spaces
        {
            for(j=0;j<15-i%16;j++) 
            {
              fprintf(logfile , "   "); //extra spaces
            }

            fprintf(logfile , "         ");

            for(j=i-i%16 ; j<=i ; j++)
            {
                if(data[j]>=32 && data[j]<=128) 
                {
                  fprintf(logfile , "%c",(unsigned char)data[j]);
                }
                else
                {
                  fprintf(logfile , ".");
                }
            }

            fprintf(logfile ,  "\n" );
        }
    }
}

Linux では、プレフィックス「sudo」を付けてコードを実行します。:)

于 2013-04-19T16:40:04.363 に答える
-1

相対的なカーネルレベルの機能はわかりませんが、レイヤー2フレームをリッスンするRAW SOCKETにバインドし、IPパケット用のフィルターを追加することをお勧めします。

このような：

fd = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_IP));

フレームを分析し、必要な udp パケットのみを抽出するのはあなた次第です。

レイヤー 2 で作業すると、ホストを通過する 100% の IP パケットの配信が許可されます。

于 2013-01-11T09:36:14.037 に答える