unix4lyfe git - darkstat/blob - localip.c

   1 /* darkstat 3
   2  * copyright (c) 2001-2008 Emil Mikulic.
   3  *
   4  * localip.c: determine local IP of our capture interface
   5  *
   6  * You may use, modify and redistribute this file under the terms of the
   7  * GNU General Public License version 2. (see COPYING.GPL)
   8  */
   9
  10 #include "darkstat.h"
  11 #include "conv.h" /* for strlcpy */
  12 #include "decode.h" /* for ip_to_str, ip6_to_str */
  13 #include "err.h"
  14 #include "localip.h"
  15
  16 #include <net/if.h>
  17 #include <ifaddrs.h>
  18 #include <errno.h>
  19 #include <string.h>
  20 #include <unistd.h>
  21
  22 static const char *iface = NULL;
  23
  24 in_addr_t localip = 0;
  25 static in_addr_t last_localip = 0;
  26
  27 struct in6_addr localip6;
  28 static struct in6_addr last_localip6;
  29
  30 void
  31 localip_init(const char *interface)
  32 {
  33    iface = interface;
  34    localip_update();
  35 }
  36
  37 void
  38 localip_update(void)
  39 {
  40    struct ifaddrs *ifas, *ifa;
  41    int flags = 0;
  42
  43 #define HAS_IPV4  0x01
  44 #define HAS_IPV6  0x02
  45
  46    if (iface == NULL) {
  47       /* reading from capfile */
  48       localip = 0;
  49       memset(&localip6, '\0', sizeof(localip6));
  50       return;
  51    }
  52
  53    if (getifaddrs(&ifas) < 0)
  54       err(1, "can't get own IP address on interface \"%s\"", iface);
  55
  56    for (ifa = ifas; ifa; ifa = ifa->ifa_next) {
  57       if (flags == (HAS_IPV4 | HAS_IPV6))
  58          break;   /* Task is already complete. */
  59
  60       if (strncmp(ifa->ifa_name, iface, IFNAMSIZ))
  61          continue;   /* Wrong interface. */
  62
  63       /* The first IPv4 name is always functional. */
  64       if ( (ifa->ifa_addr->sa_family == AF_INET)
  65             && ! (flags & HAS_IPV4) ) {
  66          /* Good IPv4 address. */
  67          localip = ((struct sockaddr_in *) ifa->ifa_addr)->sin_addr.s_addr;
  68          flags |= HAS_IPV4;
  69          continue;
  70       }
  71
  72       /* IPv6 needs some obvious exceptions. */
  73       if( ifa->ifa_addr->sa_family == AF_INET6 ) {
  74          struct sockaddr_in6 *sa6 = (struct sockaddr_in6 *) ifa->ifa_addr;
  75
  76          if( IN6_IS_ADDR_LINKLOCAL(&(sa6->sin6_addr.s6_addr))
  77             || IN6_IS_ADDR_SITELOCAL(&(sa6->sin6_addr.s6_addr)) )
  78             continue;
  79          else
  80             /* Only standard IPv6 can reach this point. */
  81             memcpy(&localip6, &sa6->sin6_addr, sizeof(localip6));
  82             flags |= HAS_IPV6;
  83       }
  84    }
  85
  86    freeifaddrs(ifas);
  87
  88    /* Repport an error if IPv4 address could not be found. */
  89    if ( !(flags & HAS_IPV4) )
  90        err(1, "can't get own IPv4 address on interface \"%s\"", iface);
  91
  92    /* struct sockaddr {
  93     *      sa_family_t     sa_family;      * address family, AF_xxx
  94     *      char            sa_data[14];    * 14 bytes of protocol address
  95     *
  96     * struct sockaddr_in {
  97     *      sa_family_t           sin_family;     * Address family
  98     *      unsigned short int    sin_port;       * Port number
  99     *      struct in_addr        sin_addr;       * Internet address
 100     *
 101     * struct in_addr {
 102     *      __u32   s_addr;
 103     */
 104
 105    if (last_localip != localip) {
 106       verbosef("local_ip update(%s) = %s", iface, ip_to_str(localip));
 107       last_localip = localip;
 108    }
 109    if (memcmp(&last_localip6, &localip6, sizeof(localip6))) {
 110       verbosef("local_ip6 update(%s) = %s", iface, ip6_to_str(&localip6));
 111       memcpy(&last_localip6, &localip6, sizeof(localip6));
 112    }
 113 }
 114
 115 /* vim:set ts=3 sw=3 tw=78 expandtab: */