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 */
  13 #include "err.h"
  14 #include "localip.h"
  15
  16 #include <sys/socket.h>
  17 #include <net/if.h>
  18 #include <ifaddrs.h>
  19 #include <errno.h>
  20 #include <string.h>
  21 #include <unistd.h>
  22
  23 static const char *iface = NULL;
  24
  25 struct in_addr localip = { 0 };
  26 static struct in_addr last_localip = { 0 };
  27
  28 struct in6_addr localip6;
  29 static struct in6_addr last_localip6;
  30
  31 void
  32 localip_init(const char *interface)
  33 {
  34    iface = interface;
  35    localip_update();
  36 }
  37
  38 void
  39 localip_update(void)
  40 {
  41    struct ifaddrs *ifas, *ifa;
  42    int flags = 0;
  43
  44 #define HAS_IPV4  0x01
  45 #define HAS_IPV6  0x02
  46
  47    if (iface == NULL) {
  48       /* reading from capfile */
  49       memset(&localip, 0, sizeof(localip));
  50       memset(&localip6, 0, sizeof(localip6));
  51       return;
  52    }
  53
  54    if (getifaddrs(&ifas) < 0)
  55       err(1, "can't get own IP address on interface \"%s\"", iface);
  56
  57    for (ifa = ifas; ifa; ifa = ifa->ifa_next) {
  58       if (flags == (HAS_IPV4 | HAS_IPV6))
  59          break;   /* Task is already complete. */
  60
  61       if (strncmp(ifa->ifa_name, iface, IFNAMSIZ))
  62          continue;   /* Wrong interface. */
  63
  64       /* The first IPv4 name is always functional. */
  65       if ( (ifa->ifa_addr->sa_family == AF_INET)
  66             && ! (flags & HAS_IPV4) ) {
  67          /* Good IPv4 address. */
  68          localip.s_addr = ((struct sockaddr_in *) ifa->ifa_addr)->sin_addr.s_addr;
  69          flags |= HAS_IPV4;
  70          continue;
  71       }
  72
  73       /* IPv6 needs some obvious exceptions. */
  74       if ( ifa->ifa_addr->sa_family == AF_INET6 ) {
  75          struct sockaddr_in6 *sa6 = (struct sockaddr_in6 *) ifa->ifa_addr;
  76
  77          if ( IN6_IS_ADDR_LINKLOCAL(&(sa6->sin6_addr))
  78               || IN6_IS_ADDR_SITELOCAL(&(sa6->sin6_addr)) )
  79             continue;
  80          else
  81             /* Only standard IPv6 can reach this point. */
  82             memcpy(&localip6, &sa6->sin6_addr, sizeof(localip6));
  83             flags |= HAS_IPV6;
  84       }
  85    }
  86
  87    freeifaddrs(ifas);
  88
  89    /* Repport an error if IPv4 address could not be found. */
  90    if ( !(flags & HAS_IPV4) )
  91        err(1, "can't get own IPv4 address on interface \"%s\"", iface);
  92
  93    /* struct sockaddr {
  94     *      sa_family_t     sa_family;      * address family, AF_xxx
  95     *      char            sa_data[14];    * 14 bytes of protocol address
  96     *
  97     * struct sockaddr_in {
  98     *      sa_family_t           sin_family;     * Address family
  99     *      unsigned short int    sin_port;       * Port number
 100     *      struct in_addr        sin_addr;       * Internet address
 101     *
 102     * struct in_addr {
 103     *      __u32   s_addr;
 104     */
 105
 106    if (last_localip.s_addr != localip.s_addr) {
 107       verbosef("local_ip update(%s) = %s", iface,
 108                ip_to_str_af(&localip, AF_INET));
 109       memcpy(&last_localip, &localip, sizeof(last_localip));
 110    }
 111    if (memcmp(&last_localip6, &localip6, sizeof(localip6))) {
 112       verbosef("local_ip6 update(%s) = %s", iface,
 113                ip_to_str_af(&localip6, AF_INET6));
 114       memcpy(&last_localip6, &localip6, sizeof(localip6));
 115    }
 116 }
 117
 118 /* vim:set ts=3 sw=3 tw=78 expandtab: */