icmp协议ping程序实现

#include <stdio.h> #include <stdlib.h> #include <netinet/ip_icmp.h> #include <string.h> #include "ping.h" #define ICMP_ECHOREPLY 0 #define ICMP_ECHOREQ 8 // statistics int nsend = 0, nrecv = 0; int rrt[10]; int packsize; void get_data(int rrt[], int size, int *min, int *max, int *avg); void tv_sub(struct timeval *out,struct timeval *in); // calculate checksum of icmp header uint16_t cal_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); sum += (sum >> 16); answer = ~sum; return(answer); } void print_head(char *ip) { packsize = sizeof(struct icmp) + sizeof(struct timeval); printf("Ping %s with %d bytes of data:\n", ip, packsize); } void print_stat(char *ip) { int min_rrt, max_rrt, avg_rrt; int lost; if(nsend < 1) return; get_data(rrt, nsend, &min_rrt, &max_rrt, &avg_rrt); lost = nsend - nrecv; printf("========================================================================\n"); printf("Ping Statistics for %s:\n", ip); printf("\tPackets: Send = %d, Received = %d, Lost = %d(%.1f%% lost),\n", nsend, nrecv, lost, (lost / (nsend * 1.0) * 100.0)); printf("Approximate round trip times in milli-seconds:\n"); printf("\tMinimum = %dms, Maximum = %dms, Average = %dms\n", min_rrt, max_rrt, avg_rrt); } void send_ping(int sockfd, struct sockaddr_in *dstaddr) { char buf[100]; size_t len = sizeof(struct icmp); socklen_t dstlen = sizeof(struct sockaddr_in); struct icmp *echo; memset(buf, 0, sizeof(buf)); echo = (struct icmp*)buf; echo = (struct icmp *)buf; echo->icmp_type = ICMP_ECHOREQ; echo->icmp_code = 0; echo->icmp_cksum = 0; echo->icmp_id = getpid(); echo->icmp_seq = nsend; struct timeval *tval= (struct timeval *)echo->icmp_data; gettimeofday(tval,NULL); echo->icmp_cksum = cal_cksum((uint16_t *)echo, packsize); // send ping message if(sendto(sockfd, buf, len, 0, (struct sockaddr*)dstaddr, dstlen) == -1) printf("Send Ping Message Error!\n"); nsend++; } void recv_ping(int sockfd, struct sockaddr_in *dstaddr) { char buf[100]; ssize_t n; struct ip *ip; struct icmp *icmp; socklen_t dstlen = sizeof(struct sockaddr_in); int ttl; fd_set rset; int maxfd = sockfd + 1; struct timeval timeo, *tvsend, tvrecv; unsigned char *p; unsigned char ipaddr[100]; int time; memset(buf, 0, sizeof(buf)); timeo.tv_sec = 3; timeo.tv_usec = 0; FD_ZERO(&rset); FD_SET(sockfd, &rset); gettimeofday(&tvrecv, NULL); while(1) { // set timeout 3s if((n = select(maxfd, &rset, NULL, NULL, &timeo)) == -1) { printf("Select Error!\n"); exit(1); } if(n <= 0) { printf("Request Time Out!\n"); fflush(stdout); break; } if((n = recvfrom(sockfd, buf, sizeof(buf), 0, (struct sockaddr *)dstaddr, &dstlen)) == -1) printf("Recv Ping Message Error!\n"); // check if icmp ip = (struct ip*)buf; ttl = ip->ip_ttl; // get src ip p = (unsigned char *)&ip->ip_src; sprintf(ipaddr, "%d.%d.%d.%d", p[0], p[1], p[2], p[3]); // check if loop if(strcmp(ipaddr, "127.0.0.1") == 0) { //perror("Loop!"); continue; } // check if icmp packet if(ip->ip_p != IPPROTO_ICMP) { //perror("Not ICMP Protocol!"); continue; } // check if icmp reply icmp = (struct icmp*)(buf + sizeof(struct ip)); if(icmp->icmp_type == ICMP_ECHOREPLY) { // check id if(icmp->icmp_id == getpid()) { tvsend = (struct timeval *)icmp->icmp_data; tv_sub(&tvrecv, tvsend); time = tvrecv.tv_sec * 1000 + tvrecv.tv_usec / 1000; nrecv++; printf("\tReply from %s: bytes = %d time = %dms TTL = %d\n", ipaddr, n, time, ttl); rrt[nsend - 1] = time; break; } else { //perror("Not Expected Identifier!"); continue; } } else { //perror("Not ICMP Reply Message!"); continue; } } } /* ================================================================ */ /* Auxiliary Function */ /* ================================================================ */ /* * Function: get_data * Purpose: get statistics from data rrt array, such as minimum rrt, * maximum rrt, average rrt * Parameters: rrt - round trip time * size - array size * min - store minimum time * max - store maximum time * avg - store average time * Return: none */ void get_data(int rrt[], int size, int *min, int *max, int *avg) { int sum = 0; int i; *min = rrt[0], *max = rrt[0]; for(i = 0; i < size; i++) { sum += rrt[i]; if(rrt[i] < *min) *min = rrt[i]; if(rrt[i] > *max) *max = rrt[i]; } *avg = sum / size; } void tv_sub(struct timeval *out,struct timeval *in) { if((out->tv_usec -= in->tv_usec) < 0) { --out->tv_sec; out->tv_usec += 1000000; } out->tv_sec -= in->tv_sec; }