pingもどき

/* * sample program * ping test program */ #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/types.h> #include <sys/time.h> #include <sys/socket.h> #include <netinet/in.h> #include <netinet/ip.h> #include <netinet/ip_icmp.h> #include <arpa/inet.h> #include <net/ethernet.h> #include <netdb.h> #include <errno.h> int sequence; pid_t pid; struct in_addr addr; unsigned short calc_checksum(int , void *); int send_icmp_echo_request(int); int recv_icmp_echo_reply(int, struct timeval*); int main(int argc, char *argv[]) { char host[256] = {0}; int cnt = 0, ret = 0; struct addrinfo hints, *res; int recvfd = 0, sendfd = 0; struct timeval tv; if(argc != 2){ fprintf(stdout, "Usage: myping distination\n"); return -1; } strncpy(host, argv[1], 256); memset(&hints, 0, sizeof(struct addrinfo)); hints.ai_family = AF_INET; hints.ai_socktype = SOCK_DGRAM; ret = getaddrinfo(host, NULL, &hints, &res); if((ret != 0) || (res == NULL)){ fprintf(stdout, "distination not found!\n"); return -1; } addr.s_addr = ((struct sockaddr_in *)(res->ai_addr))->sin_addr.s_addr; pid = getpid(); /* create recv socket */ recvfd = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_IP)); if(recvfd < 0){ perror("socket error"); return -1; } /* create send socket */ sendfd = socket(PF_INET, SOCK_RAW, IPPROTO_RAW); if(sendfd < 0){ perror("socket error"); return -1; } for(cnt = 0; cnt < 3; cnt++){ if(send_icmp_echo_request(sendfd) < 0){ break; } gettimeofday(&tv, NULL); if(recv_icmp_echo_reply(recvfd, &tv) < 0){ fprintf(stdout, "Destination Host Unreachable\n"); } sleep(1); } close(recvfd); close(sendfd); return 0; } unsigned short calc_checksum(int len, void *start) { unsigned short *p; unsigned long sum = 0; p = (unsigned short *)start; while(len > 1){ sum += *p; p++; len -= sizeof(unsigned short); } if(len){ sum += *(uint8_t *)p; } sum = (sum & 0xffff) + (sum >> 16); sum += (sum >> 16); return (unsigned short)(~sum & 0xffff); } int send_icmp_echo_request(int sockfd) { struct packet { struct iphdr ip; struct icmphdr icmp; char data[64]; }packet; int datalen = 0, len = 0; struct sockaddr_in to; /* set icmp data */ memset(&packet, 0, sizeof(struct packet)); strcpy(packet.data, "1234567890qwertyuiopasdfghjklzxcvbnm"); datalen = strlen(packet.data); packet.icmp.type = ICMP_ECHO; packet.icmp.un.echo.id = htons(pid); packet.icmp.un.echo.sequence = htons(++sequence); datalen += sizeof(struct icmphdr); packet.icmp.checksum = calc_checksum(datalen, &(packet.icmp)); /* set ip header */ /* (id, tot_len, saddr and check are set automatically.) */ packet.ip.version = 4; packet.ip.ihl = 5; packet.ip.tos = 0; datalen += sizeof(struct iphdr); packet.ip.tot_len = 0; packet.ip.id = 0; packet.ip.frag_off = htons(0x02 << 13); packet.ip.ttl = 64; packet.ip.protocol = IPPROTO_ICMP; packet.ip.daddr = *(uint32_t *)&addr; packet.ip.saddr = 0; packet.ip.check = 0; /* send icmp */ memset(&to, 0, sizeof(struct sockaddr_in)); to.sin_family = PF_INET; to.sin_addr = addr; len = sendto(sockfd, &packet, datalen, 0, (struct sockaddr *)&to, sizeof(to)); if(len < 0){ perror("sendto error"); } return len; } int recv_icmp_echo_reply(int sockfd, struct timeval *tv) { struct iphdr *ip; struct icmphdr *icmp; char buf[ETHER_MAX_LEN] = {0}; char sip[16] = {0}; unsigned short icmpid, icmpseq; int len = 0, icmplen = 0, usec = 0; double msec; struct timeval now, tout; fd_set readfd; while(1){ gettimeofday(&now, NULL); if(now.tv_sec >= (tv->tv_sec + 2)){ return -1; /* timeout */ } memset(buf, 0, sizeof(buf)); FD_ZERO(&readfd); FD_SET(sockfd, &readfd); tout.tv_sec = 0; tout.tv_usec = 100000; if(select(sockfd +1, &readfd, NULL, NULL, &tout) <= 0){ continue; } if(FD_ISSET(sockfd, &readfd) == 0){ continue; } len = recv(sockfd, buf, sizeof(buf), 0); if(len < 0){ perror("recv error"); return -1; } gettimeofday(&now, NULL); ip = (struct iphdr *)(buf + sizeof(struct ether_header)); if((ip->protocol != IPPROTO_ICMP) || (ip->saddr != addr.s_addr)){ continue; } icmp = (struct icmphdr *)((char *)ip + sizeof(struct iphdr)); icmpid = ntohs(icmp->un.echo.id); if((icmp->type != ICMP_ECHOREPLY) || (icmpid != pid)){ continue; } icmpseq = ntohs(icmp->un.echo.sequence); icmplen = ntohs(ip->tot_len) - sizeof(struct iphdr); sprintf(sip, "%s", inet_ntoa(*(struct in_addr *)&(ip->saddr))); usec = ((now.tv_sec)&0x03) * 1000000 + now.tv_usec; usec = usec - ((tv->tv_sec)&0x03) * 1000000 - tv->tv_usec; msec = (double)usec / 1000; fprintf(stdout, "%d bytes from %s: icmp_seq=%d ttl=%d time=%.3f ms\n", icmplen, sip, icmpseq, ip->ttl, msec); break; } return len; }