dist/ntp/sntp/internet.c

   1 /*      $NetBSD: internet.c,v 1.3 2003/12/04 17:17:36 drochner Exp $    */
   2
   3 /*  Copyright (C) 1996 N.M. Maclaren
   4     Copyright (C) 1996 The University of Cambridge
   5
   6 This includes all of the code needed to handle Internet addressing.  It is way
   7 outside current POSIX, unfortunately.  It should be easy to convert to a system
   8 that uses another mechanism.  The signal handling is not necessary for its
   9 function, but is an attempt to avoid the program hanging when the name server
  10 is inaccessible. */
  11
  12
  13
  14 #include "header.h"
  15 #include "internet.h"
  16
  17 #include <netdb.h>
  18 #include <arpa/inet.h>
  19
  20 #define INTERNET
  21 #include "kludges.h"
  22 #undef INTERNET
  23
  24
  25 /* Used to force dns resolving to ipv4 or ipv6 addresses. */
  26 static int pref_family;
  27
  28 /* There needs to be some disgusting grobble for handling timeouts, which is
  29 identical to the grobble in socket.c. */
  30
  31 static jmp_buf jump_buffer;
  32
  33 static void jump_handler (int sig) {
  34     longjmp(jump_buffer,1);
  35 }
  36
  37 static void clear_alarm (void) {
  38     int k;
  39
  40     k = errno;
  41     alarm(0);
  42     errno = 0;
  43     if (signal(SIGALRM,SIG_DFL) == SIG_ERR)
  44         fatal(1,"unable to reset signal handler",NULL);
  45     errno = k;
  46 }
  47
  48 void preferred_family(int fam) {
  49         switch(fam) {
  50         case PREF_FAM_INET:
  51             pref_family = AF_INET;
  52             break;
  53 #ifdef HAVE_IPV6
  54         case PREF_FAM_INET6:
  55             pref_family = AF_INET6;
  56             break;
  57 #endif
  58         default:
  59             fatal(0,"unable to set the preferred family", NULL);
  60             break;
  61         }
  62 }
  63
  64 #ifdef HAVE_IPV6
  65
  66 void find_address (struct sockaddr_storage *address,
  67     struct sockaddr_storage *anywhere,
  68     int *port, char *hostname, int timespan) {
  69
  70 /* Locate the specified NTP server and return its Internet address and port
  71 number. */
  72
  73     int family, rval;
  74     struct addrinfo hints;
  75     struct addrinfo *res;
  76
  77     res = NULL;
  78     memset(address, 0, sizeof(struct sockaddr_storage));
  79     memset(anywhere, 0, sizeof(struct sockaddr_storage));
  80
  81     if (setjmp(jump_buffer))
  82         fatal(0,"unable to set up access to NTP server %s",hostname);
  83     errno = 0;
  84     if (signal(SIGALRM,jump_handler) == SIG_ERR)
  85         fatal(1,"unable to set up signal handler",NULL);
  86     alarm((unsigned int)timespan);
  87
  88 /* Look up the Internet name or IP number. */
  89     memset(&hints, 0, sizeof(hints));
  90     hints.ai_socktype = SOCK_DGRAM;
  91     hints.ai_family = pref_family;
  92     rval = getaddrinfo(hostname, "ntp", &hints, &res);
  93     if (rval != 0)
  94         fatal(0, "getaddrinfo(hostname, ntp)  failed with %s",
  95             gai_strerror(rval));
  96
  97 /* Now clear the timer and check the result. */
  98
  99     clear_alarm();
 100     /* There can be more than one address in the list, but for now only
 101     use the first. */
 102     memcpy(address, res->ai_addr, res->ai_addrlen);
 103     family = res->ai_family;
 104     freeaddrinfo(res);
 105
 106     switch(family) {
 107     case AF_INET:
 108         hints.ai_family = AF_INET;
 109         hints.ai_flags = AI_PASSIVE;
 110         rval = getaddrinfo(NULL, "ntp", &hints, &res);
 111         if (rval != 0)
 112             fatal(0, "getaddrinfo(NULL, ntp) failed with %s",
 113                 gai_strerror(rval));
 114         memcpy(anywhere, res->ai_addr, res->ai_addrlen);
 115         freeaddrinfo(res);
 116         break;
 117     case AF_INET6:
 118         hints.ai_family = AF_INET6;
 119         hints.ai_flags = AI_PASSIVE;
 120         rval = getaddrinfo(NULL, "ntp", &hints, &res);
 121         if (rval != 0)
 122             fatal(0, "getaddrinfo(NULL, ntp, INET6, AI_PASSIVE) failed with %s",
 123                 gai_strerror(rval));
 124         memcpy(anywhere, res->ai_addr, res->ai_addrlen);
 125         freeaddrinfo(res);
 126         break;
 127     }
 128 }
 129
 130 #else
 131
 132 void find_address (struct in_addr *address, struct in_addr *anywhere,
 133     int *port, char *hostname, int timespan) {
 134
 135 /* Locate the specified NTP server and return its Internet address and port
 136 number. */
 137
 138     unsigned long ipaddr;
 139     struct in_addr nowhere[1];
 140     struct hostent *host;
 141     struct servent *service;
 142
 143 /* Set up the reserved Internet addresses, attempting not to assume that
 144 addresses are 32 bits. */
 145
 146     local_to_address(nowhere,INADDR_LOOPBACK);
 147     local_to_address(anywhere,INADDR_ANY);
 148
 149 /* Check the address, if any.  This assumes that the DNS is reliable, or is at
 150 least checked by someone else.  But it doesn't assume that it is accessible, so
 151 it needs to set up a timeout. */
 152
 153     if (hostname == NULL)
 154         *address = *anywhere;
 155     else {
 156         if (setjmp(jump_buffer))
 157             fatal(0,"unable to set up access to NTP server %s",hostname);
 158         errno = 0;
 159         if (signal(SIGALRM,jump_handler) == SIG_ERR)
 160             fatal(1,"unable to set up signal handler",NULL);
 161         alarm((unsigned int)timespan);
 162
 163 /* Look up the Internet name or IP number. */
 164
 165         if (! isdigit(hostname[0])) {
 166             errno = 0;
 167             host = gethostbyname(hostname);
 168         } else {
 169             if ((ipaddr = inet_addr(hostname)) == (unsigned long)-1)
 170                 fatal(0,"invalid IP number %s",hostname);
 171             network_to_address(address,ipaddr);
 172             errno = 0;
 173             host = gethostbyaddr((void *)address,sizeof(struct in_addr),
 174                 AF_INET);
 175         }
 176
 177 /* Now clear the timer and check the result. */
 178
 179         clear_alarm();
 180         if (host == NULL) fatal(1,"unable to locate IP address/number",NULL);
 181         if (host->h_length != sizeof(struct in_addr))
 182             fatal(0,"the address does not seem to be an Internet one",NULL);
 183         *address = *((struct in_addr **)host->h_addr_list)[0];
 184         if (memcmp(address,nowhere,sizeof(struct in_addr)) == 0
 185             || memcmp(address,anywhere,sizeof(struct in_addr)) == 0)
 186             fatal(0,"reserved IP numbers cannot be used",NULL);
 187         if (verbose)
 188             fprintf(stderr,
 189                 "%s: using NTP server %s (%s)\n",
 190                 argv0,host->h_name,inet_ntoa(*address));
 191     }
 192
 193 /* Find out the port number (usually from /etc/services), and leave it in
 194 network format.  This is assumed not to be obtained from a network service!
 195 Note that a port number is not assumed to be 16 bits. */
 196
 197     if ((service = getservbyname("ntp","udp")) != NULL) {
 198         *port = service->s_port;
 199         if (verbose > 2)
 200             fprintf(stderr,"Using port %d for NTP\n",port_to_integer(*port));
 201     } else {
 202         *port = NTP_PORT;
 203         if (verbose)
 204             fprintf(stderr,
 205                 "%s: assuming port %d for NTP - check /etc/services\n",
 206                 argv0,port_to_integer(*port));
 207     }
 208 }
 209 #endif