Exemple #1
0
//called if icmp packet comes in
void icmp_packet_in(char *buffer,unsigned int len) {
    int i;

    //we only support ICMP echo request (ping) packets:
    if (buffer[ICMP_POS_TYPE] == ICMP_TYPE_ECHO_REQUEST) {
        //reuse buffer for the ICMP echo reply:

        //*******************************
        //setup the eth packet:
        for(i=0; i<6; i++)
            buffer[i] = buffer[6+i];

        //packet source mac:
        nic_copy_mac_to_buf(&buffer[6]);

        //change type to ECHO REPLY
        buffer[ICMP_POS_TYPE] = ICMP_TYPE_ECHO_REPLY;

        //"calculate" checksum:
        //use quick & dirty hack, we change only the icmp type
        //so we can calculate the new checksum like this:
        if (buffer[ICMP_POS_CHECKSUM+0] > 0xFF-0x08)
            buffer[ICMP_POS_CHECKSUM+1] = buffer[ICMP_POS_CHECKSUM+1] + 1;

        buffer[ICMP_POS_CHECKSUM+0] = buffer[ICMP_POS_CHECKSUM+0] + 0x08;

        //set up dst ip (copy src to dest ip):
        for(i=0; i<4; i++) {
            buffer[IP_POS_DST_IP+i] = buffer[IP_POS_SRC_IP+i];
        }

        //set up src ip:
        nic_ip_to_buffer(&buffer[IP_POS_SRC_IP], nic_ip);

        nic_send_packet(buffer,len);
    }
}
Exemple #2
0
// Lab 6 network dirver
// Return number of data sent
int
sys_net_send(void *buf, size_t size)
{ 
	return nic_send_packet(buf, size);
}