1/* Copyright (C) 1996 N.M. Maclaren 2 Copyright (C) 1996 The University of Cambridge 3 4This includes all of the code needed to handle Internet addressing. It is way 5outside current POSIX, unfortunately. It should be easy to convert to a system 6that uses another mechanism. The signal handling is not necessary for its 7function, but is an attempt to avoid the program hanging when the name server 8is inaccessible. */ 9 10 11 12#include "header.h" 13#include "internet.h" 14 15#include <netdb.h> 16#include <arpa/inet.h> 17 18#define INTERNET 19#include "kludges.h" 20#undef INTERNET 21 22 23/* Used to force dns resolving to ipv4 or ipv6 addresses. */ 24static int pref_family; 25 26/* There needs to be some disgusting grobble for handling timeouts, which is 27identical to the grobble in socket.c. */ 28 29static jmp_buf jump_buffer; 30 31static void jump_handler (int sig) { 32 longjmp(jump_buffer,1); 33} 34 35static void clear_alarm (void) { 36 int k; 37 38 k = errno; 39 alarm(0); 40 errno = 0; 41 if (signal(SIGALRM,SIG_DFL) == SIG_ERR) 42 fatal(1,"unable to reset signal handler",NULL); 43 errno = k; 44} 45 46void preferred_family(int fam) { 47 switch(fam) { 48 case PREF_FAM_INET: 49 pref_family = AF_INET; 50 break; 51#ifdef HAVE_IPV6 52 case PREF_FAM_INET6: 53 pref_family = AF_INET6; 54 break; 55#endif 56 default: 57 fatal(0,"unable to set the preferred family", NULL); 58 break; 59 } 60} 61 62#ifdef HAVE_IPV6 63 64void find_address (struct sockaddr_storage *address, 65 struct sockaddr_storage *anywhere, 66 int *port, char *hostname, int timespan) { 67 68/* Locate the specified NTP server and return its Internet address and port 69number. */ 70 71 int family, rval; 72 struct addrinfo hints; 73 struct addrinfo *res; 74 75 res = NULL; 76 memset(address, 0, sizeof(struct sockaddr_storage)); 77 memset(anywhere, 0, sizeof(struct sockaddr_storage)); 78 79 if (setjmp(jump_buffer)) 80 fatal(0,"unable to set up access to NTP server %s",hostname); 81 errno = 0; 82 if (signal(SIGALRM,jump_handler) == SIG_ERR) 83 fatal(1,"unable to set up signal handler",NULL); 84 alarm((unsigned int)timespan); 85 86/* Look up the Internet name or IP number. */ 87 memset(&hints, 0, sizeof(hints)); 88 hints.ai_socktype = SOCK_DGRAM; 89 hints.ai_family = pref_family; 90 rval = getaddrinfo(hostname, "ntp", &hints, &res); 91 if (rval != 0) 92 fatal(0, "getaddrinfo(hostname, ntp) failed with %s", 93 gai_strerror(rval)); 94 95/* Now clear the timer and check the result. */ 96 97 clear_alarm(); 98 /* There can be more than one address in the list, but for now only 99 use the first. */ 100 memcpy(address, res->ai_addr, res->ai_addrlen); 101 family = res->ai_family; 102 freeaddrinfo(res); 103 104 switch(family) { 105 case AF_INET: 106 hints.ai_family = AF_INET; 107 hints.ai_flags = AI_PASSIVE; 108 rval = getaddrinfo(NULL, "ntp", &hints, &res); 109 if (rval != 0) 110 fatal(0, "getaddrinfo(NULL, ntp) failed with %s", 111 gai_strerror(rval)); 112 memcpy(anywhere, res->ai_addr, res->ai_addrlen); 113 freeaddrinfo(res); 114 break; 115 case AF_INET6: 116 hints.ai_family = AF_INET6; 117 hints.ai_flags = AI_PASSIVE; 118 rval = getaddrinfo(NULL, "ntp", &hints, &res); 119 if (rval != 0) 120 fatal(0, "getaddrinfo(NULL, ntp, INET6, AI_PASSIVE) failed with %s", 121 gai_strerror(rval)); 122 memcpy(anywhere, res->ai_addr, res->ai_addrlen); 123 freeaddrinfo(res); 124 break; 125 } 126} 127 128#else 129 130void find_address (struct in_addr *address, struct in_addr *anywhere, 131 int *port, char *hostname, int timespan) { 132 133/* Locate the specified NTP server and return its Internet address and port 134number. */ 135 136 unsigned long ipaddr; 137 struct in_addr nowhere[1]; 138 struct hostent *host; 139 struct servent *service; 140 141/* Set up the reserved Internet addresses, attempting not to assume that 142addresses are 32 bits. */ 143 144 local_to_address(nowhere,INADDR_LOOPBACK); 145 local_to_address(anywhere,INADDR_ANY); 146 147/* Check the address, if any. This assumes that the DNS is reliable, or is at 148least checked by someone else. But it doesn't assume that it is accessible, so 149it needs to set up a timeout. */ 150 151 if (hostname == NULL) 152 *address = *anywhere; 153 else { 154 if (setjmp(jump_buffer)) 155 fatal(0,"unable to set up access to NTP server %s",hostname); 156 errno = 0; 157 if (signal(SIGALRM,jump_handler) == SIG_ERR) 158 fatal(1,"unable to set up signal handler",NULL); 159 alarm((unsigned int)timespan); 160 161/* Look up the Internet name or IP number. */ 162 163 if (! isdigit(hostname[0])) { 164 errno = 0; 165 host = gethostbyname(hostname); 166 } else { 167 if ((ipaddr = inet_addr(hostname)) == (unsigned long)-1) 168 fatal(0,"invalid IP number %s",hostname); 169 network_to_address(address,ipaddr); 170 errno = 0; 171 host = gethostbyaddr((void *)address,sizeof(struct in_addr), 172 AF_INET); 173 } 174 175/* Now clear the timer and check the result. */ 176 177 clear_alarm(); 178 if (host == NULL) fatal(1,"unable to locate IP address/number",NULL); 179 if (host->h_length != sizeof(struct in_addr)) 180 fatal(0,"the address does not seem to be an Internet one",NULL); 181 *address = *((struct in_addr **)host->h_addr_list)[0]; 182 if (memcmp(address,nowhere,sizeof(struct in_addr)) == 0 183 || memcmp(address,anywhere,sizeof(struct in_addr)) == 0) 184 fatal(0,"reserved IP numbers cannot be used",NULL); 185 if (verbose) 186 fprintf(stderr, 187 "%s: using NTP server %s (%s)\n", 188 argv0,host->h_name,inet_ntoa(*address)); 189 } 190 191/* Find out the port number (usually from /etc/services), and leave it in 192network format. This is assumed not to be obtained from a network service! 193Note that a port number is not assumed to be 16 bits. */ 194 195 if ((service = getservbyname("ntp","udp")) != NULL) { 196 *port = service->s_port; 197 if (verbose > 2) 198 fprintf(stderr,"Using port %d for NTP\n",port_to_integer(*port)); 199 } else { 200 *port = NTP_PORT; 201 if (verbose) 202 fprintf(stderr, 203 "%s: assuming port %d for NTP - check /etc/services\n", 204 argv0,port_to_integer(*port)); 205 } 206} 207#endif 208