source: vbox/trunk/src/VBox/HostDrivers/VBoxTAP/instance.c@ 161

/*
 *  TAP-Win32 -- A kernel driver to provide virtual tap device
 *               functionality on Windows.  Originally derived
 *               from the CIPE-Win32 project by Damion K. Wilson,
 *               with extensive modifications by James Yonan.
 *
 *  All source code which derives from the CIPE-Win32 project is
 *  Copyright (C) Damion K. Wilson, 2003, and is released under the
 *  GPL version 2 (see below).
 *
 *  All other source code is Copyright (C) 2002-2005 OpenVPN Solutions LLC,
 *  and is released under the GPL version 2 (see below).
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program (see the file COPYING included with this
 *  distribution); if not, write to the Free Software Foundation, Inc.,
 *  59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#define INSTANCE_KEY(a) ((PVOID)((a)->m_Extension.m_TapDevice))

#define N_INSTANCE_BUCKETS 256

typedef struct _INSTANCE {
  struct _INSTANCE *next;
  TapAdapterPointer m_Adapter;
} INSTANCE;

typedef struct {
  INSTANCE *list;
  MUTEX lock;
} INSTANCE_BUCKET;

typedef struct {
  INSTANCE_BUCKET buckets[N_INSTANCE_BUCKETS];
} INSTANCE_HASH;

INSTANCE_HASH *g_InstanceHash = NULL;

// must return a hash >= 0 and < N_INSTANCE_BUCKETS
int
InstanceHashValue (PVOID addr)
{
  UCHAR *p = (UCHAR *) &addr;

  if (sizeof (addr) == 4)
    return p[0] ^ p[1] ^ p[2] ^ p[3];
  else if (sizeof (addr) == 8)
    return p[0] ^ p[1] ^ p[2] ^ p[3] ^ p[4] ^ p[5] ^ p[6] ^ p[7];
  else
    {
      MYASSERT (0);
    }
}

BOOLEAN
InitInstanceList (VOID)
{
  MYASSERT (g_InstanceHash == NULL);
  g_InstanceHash = MemAlloc (sizeof (INSTANCE_HASH), TRUE);
  if (g_InstanceHash)
    {
      int i;
      for (i = 0; i < N_INSTANCE_BUCKETS; ++i)
        INIT_MUTEX (&g_InstanceHash->buckets[i].lock);
      return TRUE;
    }
  else
    return FALSE;
}

int
NInstances (VOID)
{
  int i, n = 0;

  if (g_InstanceHash)
    {
      for (i = 0; i < N_INSTANCE_BUCKETS; ++i)
        {
          BOOLEAN got_lock;
          INSTANCE_BUCKET *ib = &g_InstanceHash->buckets[i];
          ACQUIRE_MUTEX_ADAPTIVE (&ib->lock, got_lock);

          if (got_lock)
            {
              INSTANCE *current;
              for (current = ib->list; current != NULL; current = current->next)
                ++n;
              RELEASE_MUTEX (&ib->lock);
            }
          else
            return -1;
        }
    }

  return n;
}

int
InstanceMaxBucketSize (VOID)
{
  int i, n = 0;

  if (g_InstanceHash)
    {
      for (i = 0; i < N_INSTANCE_BUCKETS; ++i)
        {
          BOOLEAN got_lock;
          int bucket_size = 0;
          INSTANCE_BUCKET *ib = &g_InstanceHash->buckets[i];
          ACQUIRE_MUTEX_ADAPTIVE (&ib->lock, got_lock);

          if (got_lock)
            {
              INSTANCE *current;
              for (current = ib->list; current != NULL; current = current->next)
                  ++bucket_size;
              if (bucket_size > n)
                n = bucket_size;
              RELEASE_MUTEX (&ib->lock);
            }
          else
            return -1;
        }
    }

  return n;
}

VOID
FreeInstanceList (VOID)
{
  if (g_InstanceHash)
    {
      MYASSERT (NInstances() == 0);
      MemFree (g_InstanceHash, sizeof (INSTANCE_HASH));
      g_InstanceHash = NULL;
    }
}

BOOLEAN
AddAdapterToInstanceList (TapAdapterPointer p_Adapter)
{
  BOOLEAN got_lock;
  BOOLEAN ret = FALSE;
  const int hash = InstanceHashValue(INSTANCE_KEY(p_Adapter));
  INSTANCE_BUCKET *ib = &g_InstanceHash->buckets[hash];

  DEBUGP (("[TAP] AddAdapterToInstanceList hash=%d\n", hash));

  ACQUIRE_MUTEX_ADAPTIVE (&ib->lock, got_lock);

  if (got_lock)
    {
      INSTANCE *i = MemAlloc (sizeof (INSTANCE), FALSE);
      if (i)
        {
          MYASSERT (p_Adapter);
          i->m_Adapter = p_Adapter;
          i->next = ib->list;
          ib->list = i;
          ret = TRUE;
        }
      RELEASE_MUTEX (&ib->lock);
    }

  return ret;
}

BOOLEAN
RemoveAdapterFromInstanceList (TapAdapterPointer p_Adapter)
{
  BOOLEAN got_lock;
  BOOLEAN ret = FALSE;
  INSTANCE_BUCKET *ib = &g_InstanceHash->buckets[InstanceHashValue(INSTANCE_KEY(p_Adapter))];

  ACQUIRE_MUTEX_ADAPTIVE (&ib->lock, got_lock);

  if (got_lock)
    {
      INSTANCE *current, *prev=NULL;
      for (current = ib->list; current != NULL; current = current->next)
        {
          if (current->m_Adapter == p_Adapter) // found match
            {
              if (prev)
                prev->next = current->next;
              else
                ib->list = current->next;
              MemFree (current->m_Adapter, sizeof (TapAdapter));
              MemFree (current, sizeof (INSTANCE));
              ret = TRUE;
              break;
            }
          prev = current;
        }
      RELEASE_MUTEX (&ib->lock);
    }

  return ret;
}

TapAdapterPointer
LookupAdapterInInstanceList (PDEVICE_OBJECT p_DeviceObject)
{
  BOOLEAN got_lock;
  TapAdapterPointer ret = NULL;
  INSTANCE_BUCKET *ib = &g_InstanceHash->buckets[InstanceHashValue((PVOID)p_DeviceObject)];

  ACQUIRE_MUTEX_ADAPTIVE (&ib->lock, got_lock);

  if (got_lock)
    {
      INSTANCE *current, *prev=NULL;
      for (current = ib->list; current != NULL; current = current->next)
        {
          if (p_DeviceObject == INSTANCE_KEY (current->m_Adapter)) // found match
            {
              // move it to head of list
              if (prev)
                {
                  prev->next = current->next;
                  current->next = ib->list;
                  ib->list = current;
                }
              ret = ib->list->m_Adapter;
              break;
            }
          prev = current;
        }
      RELEASE_MUTEX (&ib->lock);
    }

  return ret;
}