發送arp資料包

代碼來自busybox,函數詢問TEST_IP的mac位址。read_interface函數通過ioctl來擷取接口interface相關資訊，arpping用于發送arp資料包。 也可以使用s = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ARP)); 則位址則變成了struct sockaddr_ll addr; 在arpping中調用以下函數，則也可以發送 # include < unistd. h> # include < errno . h> # include < netdb. h> # include < signal . h> # include < sys/ socket . h> # include < sys/ poll. h> # include < sys/ ioctl. h> # include < netinet/ if_ether. h> # include < net/ if_arp. h> # include < netinet/ udp. h> # include < netinet/ ip. h> # include < stdio. h> # include < stdarg. h> # include < net/ if . h> enum {     ARP_MSG_SIZE = 0x2a } ; char * strncpy_IFNAMSIZ( char * dst, const char * src) { # ifndef IFNAMSIZ         enum { IFNAMSIZ = 16 } ; # endif             return strncpy ( dst, src, IFNAMSIZ) ; } struct arpMsg {          uint8_t h_dest[ 6] ;     uint8_t h_source[ 6] ;     uint16_t h_proto;          uint16_t htype;     uint16_t ptype;     uint8_t hlen;     uint8_t plen;     uint16_t operation;     uint8_t sHaddr[ 6] ;     uint8_t sInaddr[ 4] ;     uint8_t tHaddr[ 6] ;     uint8_t tInaddr[ 4] ;     uint8_t pad[ 18] ; } PACKED; const int const_int_1 = 1; int setsockopt_broadcast( int fd) {     return setsockopt ( fd, SOL_SOCKET, SO_BROADCAST, & const_int_1, sizeof ( const_int_1) ) ; } char * safe_strncpy( char * dst, const char * src, size_t size) {     if ( ! size) return dst;     dst[ - - size] = '/0' ;     return strncpy ( dst, src, size) ; } int arpping( uint32_t test_ip, uint32_t from_ip, uint8_t * from_mac, const char * interface) {     int timeout_ms;     int s;     int rv = 1;     struct sockaddr addr;     struct arpMsg arp;     s = socket ( PF_PACKET , SOCK_PACKET , htons ( ETH_P_ARP) ) ;     if ( s = = - 1) {         perror ( "raw_socket" ) ;         return - 1;     }     if ( setsockopt_broadcast( s) = = - 1) {         perror ( "cannot enable bcast on raw socket" ) ;         goto ret;     }          memset ( & arp, 0, sizeof ( arp) ) ;     memset ( arp. h_dest, 0xff, 6) ;     memcpy ( arp. h_source, from_mac, 6) ;     arp. h_proto = htons ( ETH_P_ARP) ;     arp. htype = htons ( ARPHRD_ETHER) ;     arp. ptype = htons ( ETH_P_IP) ;     arp. hlen = 6;     arp. plen = 4;     arp. operation = htons ( ARPOP_REQUEST) ;     memcpy ( arp. sHaddr, from_mac, 6) ;     memcpy ( arp. sInaddr, & from_ip, sizeof ( from_ip) ) ;          memcpy ( arp. tInaddr, & test_ip, sizeof ( test_ip) ) ;     memset ( & addr, 0, sizeof ( addr) ) ;     safe_strncpy( addr. sa_data, interface, sizeof ( addr. sa_data) ) ;     if ( sendto ( s, & arp, sizeof ( arp) , 0, & addr, sizeof ( addr) ) < 0) {         // TODO: error message? caller didn't expect us to fail,         // just returning 1 "no reply received" misleads it.           } ret:     close ( s) ;     return rv; } int read_interface( const char * interface, int * ifindex, uint32_t * addr, uint8_t * arp) {     int fd;     struct ifreq ifr;     struct sockaddr_in * our_ip;     memset ( & ifr, 0, sizeof ( ifr) ) ;     fd = socket ( AF_INET , SOCK_RAW , IPPROTO_RAW ) ;     ifr. ifr_addr. sa_family = AF_INET ;     strncpy_IFNAMSIZ( ifr. ifr_name, interface) ;     if ( addr) {         if ( ioctl( fd, SIOCGIFADDR , & ifr) ! = 0) {             perror ( "ioctl" ) ;             close ( fd) ;             return - 1;         }         our_ip = ( struct sockaddr_in * ) & ifr. ifr_addr;         * addr = our_ip- > sin_addr. s_addr;         printf ( "ip of %s = %s /n" , interface, inet_ntoa( our_ip- > sin_addr) ) ;     }     if ( ifindex) {         if ( ioctl( fd, SIOCGIFINDEX , & ifr) ! = 0) {             close ( fd) ;             return - 1;         }         printf ( "adapter index %d" , ifr. ifr_ifindex) ;         * ifindex = ifr. ifr_ifindex;     }     if ( arp) {         if ( ioctl( fd, SIOCGIFHWADDR , & ifr) ! = 0) {             close ( fd) ;             return - 1;         }         memcpy ( arp, ifr. ifr_hwaddr. sa_data, 6) ;         printf ( "adapter hardware address %02x:%02x:%02x:%02x:%02x:%02x/n" ,             arp[ 0] , arp[ 1] , arp[ 2] , arp[ 3] , arp[ 4] , arp[ 5] ) ;     }     close ( fd) ;     return 0; } int main( void ) {     uint32_t TEST_IP = inet_addr( "191.192.193.194" ) ;     char interface[ ] = "eth0" ;     uint32_t ip;     uint8_t mac[ 6] ;     read_interface( interface, NULL , & ip, mac) ;            while ( 1) {         arpping( TEST_IP, ip, mac, interface) ;         sleep ( 1) ;     }     return 0; }