ping命令

    unix网络编程里面的ping命令的源代码挺长的，为了加深理解，比照书上的内容，自己写了一个简化版，代码比较粗糙，没有怎么修饰，而且只能ping IPV4的，但是可以ping网站的名字和地址。

    环境是ubuntu12.04+codelite

    执行时需要超级用户权限，如果以后想直接只用这个，可以设置一个suid位。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <stdlib.h>
#include <signal.h>
#include <sys/types.h>
#include <netdb.h>
#include <netinet/ip_icmp.h>
#include <sys/time.h>

int sockfd;
int size;
struct addrinfo *addr_info;
int send_msg(int sockfd, struct addrinfo *addr);
void sig_alarm(int signo){
    if(send_msg(sockfd, addr_info)<0){
        puts("send_msg error");
    }
    alarm(1);
}

uint16_t in_cksum(uint16_t *addr, int len);

int nsend   = 0;
int datalen = 56;
#define BUFSIZE 1500
char sendbuf[BUFSIZE];
char recvbuf[BUFSIZE];



int main(int argc ,char *argv[]){

    if((sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP)) == -1){
            perror("socket");
            exit(1);
    }

    if(signal(SIGALRM, sig_alarm) < 0){
            perror("sigalrm");
            exit(1);
    }

    //获取ip地址
    struct sockaddr_in sock_addr;
    if(getaddrinfo(argv[1], NULL, NULL, &addr_info) ！= 0){
            perror("getaddrinfo");
            exit(1);
    }
    setsockopt(sockfd, SOL_SOCKET, SO_RCVBUF, &size, sizeof(size));//把套接口缓存设置为61440，防止多个ping产生溢出

    //输出一些ping的信息
    char hostname[20];//主机名字
    printf("ping %s (%s): %d data bytes\n", addr_info->ai_canonname?addr_info->ai_canonname:argv[1],\
                                            inet_ntop(AF_INET, &((struct sockaddr_in *)(addr_info->ai_addr))->sin_addr, hostname, sizeof(hostname)), \
                                            datalen);


    //发送icmp消息
    sig_alarm(SIGALRM);
    if(setuid(getuid())<0){
            perror("setuid(getuid())");
            return 0;
    }

    int           hlen1;
    char          controlbuf[BUFSIZE];
    struct msghdr msg;
    struct iovec  iov;
    ssize_t        n;
    struct timeval tval;
    size = 61440;


    iov.iov_base = recvbuf;
    iov.iov_len    = sizeof(recvbuf);
    msg.msg_iov    = &iov;
    msg.msg_iovlen    = 1;
    msg.msg_name    = calloc(1,addr_info->ai_addrlen);
    msg.msg_namelen    = addr_info->ai_addrlen;
    msg.msg_control    = controlbuf;
    for(;;){
        if(recvmsg(sockfd, &msg, 0) < 0){
            perror("recvmsg");
            return 0;
        }
        //解析icmp消息
        if(gettimeofday(&tval, NULL) < 0){
                perror("gettimeofday");
                return 0;
        }

        int icmplen;
        double rtt;
        struct ip  *ip_pkag = NULL;
        struct icmp *icmp_pkg;
        struct timeval *tvsend;
        ip_pkag = (struct ip *)recvbuf;
        hlen1 = ip_pkag->ip_hl<<2;
        if(ip_pkag->ip_p != IPPROTO_ICMP){
                printf("get addr not icmp");
                return 0;
        }
        icmp_pkg = (struct icmp *)(recvbuf + hlen1);
        if(icmp_pkg->icmp_type != ICMP_ECHOREPLY){
                printf("not icmp reply");
                return 0;
        }
        //计算时间差
        tvsend = (struct timeval *)(icmp_pkg->icmp_data);
        if((tval.tv_usec -= tvsend->tv_usec) < 0){
            tval.tv_sec;
            tval.tv_usec += 1000000;
        }
        tval.tv_sec -= tvsend->tv_sec;
        rtt = tval.tv_sec*1000.0 + tval.tv_usec/1000.0;

        printf("%d bytes from %s: seq= %u, ttl=%d, rtt=%.3fms\n",icmplen,  inet_ntop(AF_INET, &((struct sockaddr_in *)(addr_info->ai_addr))->sin_addr,hostname, sizeof(hostname)), icmp_pkg->icmp_seq, ip_pkag->ip_ttl, rtt);
    }
    return 0;
}

int send_msg(int sockfd, struct addrinfo *addr_info){
    struct icmp *icmp_pkg = (struct icmp *)sendbuf;
    icmp_pkg->icmp_type = ICMP_ECHO;
    icmp_pkg->icmp_code = 0;
    icmp_pkg->icmp_id   = getpid()&0xffff;
    icmp_pkg->icmp_seq  = nsend++;
    memset(icmp_pkg->icmp_data, 0xa5, datalen);
    if(gettimeofday((struct timeval *)icmp_pkg->icmp_data, NULL) < 0){
            perror("gettimeofday");
            return 1;
    }

    int len;
    len = 8 + datalen;
    icmp_pkg->icmp_cksum = 0;
     icmp_pkg->icmp_cksum = in_cksum((u_short *)icmp_pkg, len);

    if(sendto(sockfd, sendbuf, len, 0, addr_info->ai_addr, addr_info->ai_addrlen ) < 0){
        perror("sendto");
        return 2;
    }
    return 0;
}

uint16_t in_cksum(uint16_t *addr, int len){
    int nleft=len;
    uint32_t sum = 0;
    uint16_t *w = addr;
    uint16_t 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); //add hi 16 to low 16
    sum  += (sum>>16); //add carry
    answer = ~sum; //truncate to 16 bits
    return answer;
}

 myping.txt