Linux下的ping程序源代码(2)

uint16_t ICMP::checksum(uint16_t *addr, int len)
{
    int nleft = len;
    int sum =0;
    unsigned short *w = addr;
    unsigned short answer = 0;

while(nleft > 1)
    {
    sum += *w++;
    nleft -=2;
    }

if(nleft == 1)
    {
    *(unsigned char *) (&answer) = *(unsigned char *) w;
    sum += answer;
    }

sum = (sum >> 16) + (sum & 0xffff);
    sum += (sum >> 16);
    answer = ~sum;
    return (answer);
}

int ICMP:: send_icmp(char *host, void *buf, int len)
{
    memcpy(packet->icmp_data, buf, len);
    packet->icmp_cksum =0;
    packet->icmp_cksum = checksum((uint16_t *)packet, ICMPHEAD + 6);
    int err = send(packet, MAXICMPLEN, host);
    return err;

}

int ICMP:: recv_icmp(sockaddr *from)
{
    char buf[MAXICMPLEN + 100];
    int hlen1, icmplen;
    struct ip *ip;
    struct icmp *icmp;

if( Error() )
    {
    printf("Error() = %d\n", Error());
    return -1;
    }
   
   socklen_t addrlen = 0;
    int len = receive(buf, MAXICMPLEN+100, from , &addrlen);

if ( len == -1)
    {
    cout<<"Receive Failed\n";
    return -1;
    }

ip = (struct ip *)buf;
    hlen1 = ip->ip_hl << 2;

icmp = (struct icmp *) (buf + hlen1);

if( (icmplen = len -hlen1) < 8)
    {
    cout<<"Receive Fail\n";
    return -1;
    }

memcpy(packet, icmp , icmplen);
   // printf("11111\n");
    return 0;
}

main(int argc, char *argv[])
{
    ICMP icmp;
    struct sockaddr from;
    char *host;
    int count;

if(argc < 2)
    {
    printf("can shu you wu\n");
    exit(1);
    }
    if(argc == 2)
    {
    host = argv[1];
    count = 5;
    }
    if( argc == 3)
    {
    host = argv[1];
    count = 3;
    }

for( int i=0; i<=count; i++)
    {
    icmp.setId(getpid());
    icmp.setSeq(i);
    char *test_data = "abcde";
    icmp.send_icmp(host, test_data, strlen(test_data));
    printf("count = %d\n", count);
    }

int num = 1;
    while(1)
    {
    if(icmp.recv_icmp(&from) < 0)
        continue;
    if(icmp.packet->icmp_type == ICMP_ECHOREPLY)
    {
           if( icmp.packet->icmp_id == getpid())
        {
        printf("%d bypes form %s: seq=%u, data=%s\n",
            icmp.length, host, icmp.packet->icmp_seq, icmp.packet->icmp_data);
        num++;
        if(num > count)
            break;
        }

}
    }
}