prg13_1.c

《unix网络编程技术与分析》一书的C源程序

// File: prg13_1.c
 #include <pcap.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <errno.h>
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>

 #define BUFSIZ  1000 
 #define PCAP_ERRBUF_SIZE  200
 void Display( const u_char * packet, const size_t length );

 /* list all packets be filtered      */
 void my_callback ( u_char * none, const struct pcap_pkthdr * pkthdr, const u_char * packet )
 {
 Display( ( u_char * )packet, ( size_t )( pkthdr->caplen ) );
 return;
 }  

 int main(int argc,char **argv)
 { 
 int i;
 char *dev; 
 char errbuf[PCAP_ERRBUF_SIZE];
 pcap_t* descr;
 const u_char *packet;
 struct pcap_pkthdr hdr;     
 struct ether_header *eptr; 
 struct bpf_program fp;     
 bpf_u_int32 maskp;          
 bpf_u_int32 netp;           

 if(argc != 2){ 
   fprintf(stdout,"Usage: %s \"filter program\"\n"  ,argv[0]);
   return 0;
   }

 /* grab a device */
 dev = pcap_lookupdev(errbuf);
 if(dev == NULL) { 
   fprintf(stderr,"%s\n",errbuf); 
   exit(1); 
   }

 /* ask pcap for the network address and mask of the device */
 pcap_lookupnet(dev,&netp,&maskp,errbuf);

 /* open device for reading this time lets set it in promiscuous
 * mode so we can monitor traffic to another machine             */
 descr = pcap_open_live(dev,BUFSIZ,1,-1,errbuf);
 if(descr == NULL) { 
   printf("pcap_open_live(): %s\n",errbuf); 
   exit(1);
   }

 /* Lets try and compile the program.. non-optimized */
 if(pcap_compile(descr,&fp,argv[1],0,netp) == -1) { 
   fprintf(stderr,"Error calling pcap_compile\n"); 
   exit(1);
   }

 /* set the compiled program as the filter */
 if(pcap_setfilter(descr,&fp) == -1) { 
   fprintf(stderr,"Error setting filter\n"); 
   exit(1); 
   }

 /* capture packets */ 
 pcap_loop(descr,-1,my_callback,NULL);

 return 0;
 }

 void Display ( const u_char * packet, const size_t length )
 {
 u_long offset;
 int    i, j, k;

 printf( "packet [ %lu bytes ]: \n", ( long unsigned int )length );
 if ( length <= 0 ) {
 return;
 }
 i   = 0;
 offset = 0;
 for ( k = length / 16; k > 0; k--, offset += 16 ){
   printf( "%08X ", ( unsigned int )offset );
   for ( j = 0; j < 16; j++, i++ ) {
     if ( j == 8 ){
       printf( "-%02X", packet[i] );
       }
    else  printf( " %02X", packet[i] );
    }
   printf( "    " );
   i -= 16;
   for ( j = 0; j < 16; j++, i++ ) {
     /* if ( isprint( (int)packet[i] ) ) */
     if ( ( packet[i] >= ' ' ) && ( packet[i] <= 255 ) )  {
     printf( "%c", packet[i] ); 
     }
     else   printf( "." ); 
     }
   printf( "\n" );
   } 
 k = length - i;
 if ( k <= 0 ){
   return;
   }
 printf( "%08X ", ( unsigned int )offset );
 for ( j = 0 ; j < k; j++, i++ ){
   if ( j == 8 ){
     printf( "-%02X", packet[i] );
     }
   else  printf( " %02X", packet[i] );
   }
 i -= k;
 for ( j = 16 - k; j > 0; j-- )  {
   printf( "   " );
   }
 printf( "    " );
 for ( j = 0; j < k; j++, i++ ){
   if ( ( packet[i] >= ' ' ) && ( packet[i] <= 255 ) ) {
     printf( "%c", packet[i] ); 
     }
   else   {
     printf( "." ); 
     }
   }
 printf( "\n" );
 return;
 }