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glibc  2.9
Defines | Functions
opensock.c File Reference
#include <assert.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <kernel-features.h>
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Defines

#define nafs   (sizeof (afs) / sizeof (afs[0]))

Functions

int internal_function __opensock (void)

Define Documentation

#define nafs   (sizeof (afs) / sizeof (afs[0]))

Function Documentation

Definition at line 30 of file opensock.c.

{
  static int last_family;   /* Available socket family we will use.  */
  static int last_type;
  static const struct
  {
    int family;
    const char procname[15];
  } afs[] =
    {
      /* The 2.2 kernels cannot handle ioctl(SIOCGIFCONF) on AF_UNIX sockets.
        Give the kernel a chance to user inet sockets on old kernels.  */
#if __LINUX_KERNEL_VERSION < 132096
      { AF_INET, "" },
      { AF_UNIX, "net/unix" },
#else
      { AF_UNIX, "net/unix" },
      { AF_INET, "" },
#endif
      { AF_INET6, "net/if_inet6" },
      { AF_AX25, "net/ax25" },
      { AF_NETROM, "net/nr" },
      { AF_ROSE, "net/rose" },
      { AF_IPX, "net/ipx" },
      { AF_APPLETALK, "net/appletalk" },
      { AF_ECONET, "sys/net/econet" },
      { AF_ASH, "sys/net/ash" },
      { AF_X25, "net/x25" },
#ifdef NEED_AF_IUCV
      { AF_IUCV, "net/iucv" }
#endif
    };
#define nafs (sizeof (afs) / sizeof (afs[0]))
  char fname[sizeof "/proc/" + 14];
  int result;
  int has_proc;
  size_t cnt;

  /* We already know which family to use from the last call.  Use it
     again.  */
  if (last_family != 0)
    {
      assert (last_type != 0);

#ifdef SOCK_CLOEXEC
# ifndef __ASSUME_SOCK_CLOEXEC
      if (__have_sock_cloexec >= 0)
# endif
       {
         result = __socket (last_family, last_type | SOCK_CLOEXEC, 0);
# ifndef __ASSUME_SOCK_CLOEXEC
         if (__have_sock_cloexec == 0)
           __have_sock_cloexec = result != -1 || errno != EINVAL ? 1 : -1;
# endif
       }
#endif
#ifndef __ASSUME_SOCK_CLOEXEC
# ifdef SOCK_CLOEXEC
      if (__have_sock_cloexec < 0)
# endif
       result = __socket (last_family, last_type, 0);
#endif
      if (result != -1 || errno != EAFNOSUPPORT)
       /* Maybe the socket type isn't supported anymore (module is
          unloaded).  In this case again try to find the type.  */
       return result;

      /* Reset the values.  They seem not valid anymore.  */
      last_family = 0;
      last_type = 0;
    }

  /* Check whether the /proc filesystem is available.  */
  has_proc = __access ("/proc/net", R_OK) != -1;
  strcpy (fname, "/proc/");

  /* Iterate over the interface families and find one which is
     available.  */
  for (cnt = 0; cnt < nafs; ++cnt)
    {
      int type = SOCK_DGRAM;

      if (has_proc && afs[cnt].procname[0] != '\0')
       {
         strcpy (fname + 6, afs[cnt].procname);
         if (__access (fname, R_OK) == -1)
           /* The /proc entry is not available.  I.e., we cannot
              create a socket of this type (without loading the
              module).  Don't look for it since this might trigger
              loading the module.  */
           continue;
       }

      if (afs[cnt].family == AF_NETROM || afs[cnt].family == AF_X25)
       type = SOCK_SEQPACKET;

#ifdef SOCK_CLOEXEC
# ifndef __ASSUME_SOCK_CLOEXEC
      if (__have_sock_cloexec >= 0)
# endif
       {
         result = __socket (afs[cnt].family, type | SOCK_CLOEXEC, 0);
# ifndef __ASSUME_SOCK_CLOEXEC
         if (__have_sock_cloexec == 0)
           __have_sock_cloexec = result != -1 || errno != EINVAL ? 1 : -1;
# endif
       }
#endif
#ifndef __ASSUME_SOCK_CLOEXEC
# ifdef SOCK_CLOEXEC
      if (__have_sock_cloexec < 0)
# endif
       result = __socket (afs[cnt].family, type, 0);
#endif
      if (result != -1)
       {
         /* Found an available family.  */
         last_type = type;
         last_family = afs[cnt].family;
         return result;
       }
    }

  /* None of the protocol families is available.  It is unclear what kind
     of error is returned.  ENOENT seems like a reasonable choice.  */
  __set_errno (ENOENT);
  return -1;
}

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