/* sends a DHCPDISCOVER broadcast message in an attempt to find DHCP servers */
int send_dhcp_discover(int sock){
dhcp_packet discover_packet;
struct sockaddr_in sockaddr_broadcast;
unsigned short opts;
/* clear the packet data structure */
bzero(&discover_packet,sizeof(discover_packet));
/* boot request flag (backward compatible with BOOTP servers) */
discover_packet.op=BOOTREQUEST;
/* hardware address type */
discover_packet.htype=ETHERNET_HARDWARE_ADDRESS;
/* length of our hardware address */
discover_packet.hlen=ETHERNET_HARDWARE_ADDRESS_LENGTH;
/*
* transaction ID is supposed to be random.
* This allows for proper randomness if the system supports it, and fallback to
* srand & random if not.
*/
int randfd = open("/dev/urandom", O_RDONLY);
if (randfd > 2 && read(randfd, (char *)&packet_xid, sizeof(uint32_t)) >= 0) {
/* no-op as we have successfully filled packet_xid */
}
else {
/* fallback bad rand */
srand(time(NULL));
packet_xid=random();
}
if (randfd > 2) close(randfd);
discover_packet.xid=htonl(packet_xid);
/**** WHAT THE HECK IS UP WITH THIS?!? IF I DON'T MAKE THIS CALL, ONLY ONE SERVER RESPONSE IS PROCESSED!!!! ****/
/* downright bizzarre... */
ntohl(discover_packet.xid);
/*discover_packet.secs=htons(65535);*/
discover_packet.secs=0xFF;
/*
* server needs to know if it should broadcast or unicast its response:
* 0x8000L == 32768 == 1 << 15 == broadcast, 0 == unicast
*/
discover_packet.flags = unicast ? 0 : htons(DHCP_BROADCAST_FLAG);
/* our hardware address */
memcpy(discover_packet.chaddr,client_hardware_address,ETHERNET_HARDWARE_ADDRESS_LENGTH);
/* first four bytes of options field is magic cookie (as per RFC 2132) */
discover_packet.options[0]='\x63';
discover_packet.options[1]='\x82';
discover_packet.options[2]='\x53';
discover_packet.options[3]='\x63';
opts = 4;
/* DHCP message type is embedded in options field */
discover_packet.options[opts++]=DHCP_OPTION_MESSAGE_TYPE; /* DHCP message type option identifier */
discover_packet.options[opts++]='\x01'; /* DHCP message option length in bytes */
discover_packet.options[opts++]=DHCPDISCOVER;
/* the IP address we're requesting */
if(request_specific_address==TRUE){
discover_packet.options[opts++]=DHCP_OPTION_REQUESTED_ADDRESS;
discover_packet.options[opts++]='\x04';
memcpy(&discover_packet.options[opts],&requested_address,sizeof(requested_address));
opts += sizeof(requested_address);
}
discover_packet.options[opts++]=DHCP_OPTION_END;
/* unicast fields */
if(unicast)
discover_packet.giaddr.s_addr = my_ip.s_addr;
/* see RFC 1542, 4.1.1 */
discover_packet.hops = unicast ? 1 : 0;
/* send the DHCPDISCOVER packet to broadcast address */
sockaddr_broadcast.sin_family=AF_INET;
sockaddr_broadcast.sin_port=htons(DHCP_SERVER_PORT);
sockaddr_broadcast.sin_addr.s_addr = unicast ? dhcp_ip.s_addr : INADDR_BROADCAST;
bzero(&sockaddr_broadcast.sin_zero,sizeof(sockaddr_broadcast.sin_zero));
if(verbose){
printf(_("DHCPDISCOVER to %s port %d\n"),inet_ntoa(sockaddr_broadcast.sin_addr),ntohs(sockaddr_broadcast.sin_port));
printf("DHCPDISCOVER XID: %u (0x%X)\n",ntohl(discover_packet.xid),ntohl(discover_packet.xid));
printf("DHCDISCOVER ciaddr: %s\n",inet_ntoa(discover_packet.ciaddr));
printf("DHCDISCOVER yiaddr: %s\n",inet_ntoa(discover_packet.yiaddr));
printf("DHCDISCOVER siaddr: %s\n",inet_ntoa(discover_packet.siaddr));
printf("DHCDISCOVER giaddr: %s\n",inet_ntoa(discover_packet.giaddr));
}
/* send the DHCPDISCOVER packet out */
send_dhcp_packet(&discover_packet,sizeof(discover_packet),sock,&sockaddr_broadcast);
if(verbose)
printf("\n\n");
return OK;
}
/* sends a DHCPDISCOVER broadcast message in an attempt to find DHCP servers */
int send_dhcp_discover(int sock){
dhcp_packet discover_packet;
struct sockaddr_in sockaddr_broadcast;
/* clear the packet data structure */
bzero(&discover_packet,sizeof(discover_packet));
/* boot request flag (backward compatible with BOOTP servers) */
discover_packet.op=BOOTREQUEST;
/* hardware address type */
discover_packet.htype=ETHERNET_HARDWARE_ADDRESS;
/* length of our hardware address */
discover_packet.hlen=ETHERNET_HARDWARE_ADDRESS_LENGTH;
discover_packet.hops=0;
/* transaction id is supposed to be random */
srand(time(NULL));
packet_xid=random();
discover_packet.xid=htonl(packet_xid);
/**** WHAT THE HECK IS UP WITH THIS?!? IF I DON'T MAKE THIS CALL, ONLY ONE SERVER RESPONSE IS PROCESSED!!!! ****/
/* downright bizzarre... */
ntohl(discover_packet.xid);
/*discover_packet.secs=htons(65535);*/
discover_packet.secs=0xFF;
/* tell server it should broadcast its response */
discover_packet.flags=htons(DHCP_BROADCAST_FLAG);
/* our hardware address */
memcpy(discover_packet.chaddr,client_hardware_address,ETHERNET_HARDWARE_ADDRESS_LENGTH);
/* first four bytes of options field is magic cookie (as per RFC 2132) */
discover_packet.options[0]='\x63';
discover_packet.options[1]='\x82';
discover_packet.options[2]='\x53';
discover_packet.options[3]='\x63';
/* DHCP message type is embedded in options field */
discover_packet.options[4]=DHCP_OPTION_MESSAGE_TYPE; /* DHCP message type option identifier */
discover_packet.options[5]='\x01'; /* DHCP message option length in bytes */
discover_packet.options[6]=DHCPDISCOVER;
/* the IP address we're requesting */
if(request_specific_address==TRUE){
discover_packet.options[7]=DHCP_OPTION_REQUESTED_ADDRESS;
discover_packet.options[8]='\x04';
memcpy(&discover_packet.options[9],&requested_address,sizeof(requested_address));
}
/* send the DHCPDISCOVER packet to broadcast address */
sockaddr_broadcast.sin_family=AF_INET;
sockaddr_broadcast.sin_port=htons(DHCP_SERVER_PORT);
sockaddr_broadcast.sin_addr.s_addr=INADDR_BROADCAST;
bzero(&sockaddr_broadcast.sin_zero,sizeof(sockaddr_broadcast.sin_zero));
#ifdef DEBUG
printf("DHCPDISCOVER to %s port %d\n",inet_ntoa(sockaddr_broadcast.sin_addr),ntohs(sockaddr_broadcast.sin_port));
printf("DHCPDISCOVER XID: %lu (0x%X)\n",ntohl(discover_packet.xid),ntohl(discover_packet.xid));
printf("DHCDISCOVER ciaddr: %s\n",inet_ntoa(discover_packet.ciaddr));
printf("DHCDISCOVER yiaddr: %s\n",inet_ntoa(discover_packet.yiaddr));
printf("DHCDISCOVER siaddr: %s\n",inet_ntoa(discover_packet.siaddr));
printf("DHCDISCOVER giaddr: %s\n",inet_ntoa(discover_packet.giaddr));
#endif
/* send the DHCPDISCOVER packet out */
send_dhcp_packet(&discover_packet,sizeof(discover_packet),sock,&sockaddr_broadcast);
#ifdef DEBUG
printf("\n\n");
#endif
return OK;
}
