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glibc  2.9
Functions | Variables
hstcache.c File Reference
#include <alloca.h>
#include <assert.h>
#include <errno.h>
#include <error.h>
#include <libintl.h>
#include <netdb.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <arpa/nameser.h>
#include <sys/mman.h>
#include <stackinfo.h>
#include "nscd.h"
#include "dbg_log.h"

Go to the source code of this file.

Functions

static void cache_addhst (struct database_dyn *db, int fd, request_header *req, const void *key, struct hostent *hst, uid_t owner, struct hashentry *he, struct datahead *dh, int errval, int32_t ttl)
static int lookup (int type, void *key, struct hostent *resultbufp, char *buffer, size_t buflen, struct hostent **hst, int32_t *ttlp)
static void addhstbyX (struct database_dyn *db, int fd, request_header *req, void *key, uid_t uid, struct hashentry *he, struct datahead *dh)
void addhstbyname (struct database_dyn *db, int fd, request_header *req, void *key, uid_t uid)
void readdhstbyname (struct database_dyn *db, struct hashentry *he, struct datahead *dh)
void addhstbyaddr (struct database_dyn *db, int fd, request_header *req, void *key, uid_t uid)
void readdhstbyaddr (struct database_dyn *db, struct hashentry *he, struct datahead *dh)
void addhstbynamev6 (struct database_dyn *db, int fd, request_header *req, void *key, uid_t uid)
void readdhstbynamev6 (struct database_dyn *db, struct hashentry *he, struct datahead *dh)
void addhstbyaddrv6 (struct database_dyn *db, int fd, request_header *req, void *key, uid_t uid)
void readdhstbyaddrv6 (struct database_dyn *db, struct hashentry *he, struct datahead *dh)

Variables

static const hst_response_header disabled
static const hst_response_header notfound

Function Documentation

void addhstbyaddr ( struct database_dyn db,
int  fd,
request_header req,
void *  key,
uid_t  uid 
)

Definition at line 550 of file hstcache.c.

{
  addhstbyX (db, fd, req, key, uid, NULL, NULL);
}

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void addhstbyaddrv6 ( struct database_dyn db,
int  fd,
request_header req,
void *  key,
uid_t  uid 
)

Definition at line 594 of file hstcache.c.

{
  addhstbyX (db, fd, req, key, uid, NULL, NULL);
}

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void addhstbyname ( struct database_dyn db,
int  fd,
request_header req,
void *  key,
uid_t  uid 
)

Definition at line 528 of file hstcache.c.

{
  addhstbyX (db, fd, req, key, uid, NULL, NULL);
}

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void addhstbynamev6 ( struct database_dyn db,
int  fd,
request_header req,
void *  key,
uid_t  uid 
)

Definition at line 572 of file hstcache.c.

{
  addhstbyX (db, fd, req, key, uid, NULL, NULL);
}

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static void addhstbyX ( struct database_dyn db,
int  fd,
request_header req,
void *  key,
uid_t  uid,
struct hashentry he,
struct datahead dh 
) [static]

Definition at line 455 of file hstcache.c.

{
  /* Search for the entry matching the key.  Please note that we don't
     look again in the table whether the dataset is now available.  We
     simply insert it.  It does not matter if it is in there twice.  The
     pruning function only will look at the timestamp.  */
  int buflen = 1024;
  char *buffer = (char *) alloca (buflen);
  struct hostent resultbuf;
  struct hostent *hst;
  bool use_malloc = false;
  int errval = 0;
  int32_t ttl = INT32_MAX;

  if (__builtin_expect (debug_level > 0, 0))
    {
      const char *str;
      char buf[INET6_ADDRSTRLEN + 1];
      if (req->type == GETHOSTBYNAME || req->type == GETHOSTBYNAMEv6)
       str = key;
      else
       str = inet_ntop (req->type == GETHOSTBYADDR ? AF_INET : AF_INET6,
                      key, buf, sizeof (buf));

      if (he == NULL)
       dbg_log (_("Haven't found \"%s\" in hosts cache!"), (char *) str);
      else
       dbg_log (_("Reloading \"%s\" in hosts cache!"), (char *) str);
    }

  while (lookup (req->type, key, &resultbuf, buffer, buflen, &hst, &ttl) != 0
        && h_errno == NETDB_INTERNAL
        && (errval = errno) == ERANGE)
    {
      errno = 0;

      if (__builtin_expect (buflen > 32768, 0))
       {
         char *old_buffer = buffer;
         buflen *= 2;
         buffer = (char *) realloc (use_malloc ? buffer : NULL, buflen);
         if (buffer == NULL)
           {
             /* We ran out of memory.  We cannot do anything but
               sending a negative response.  In reality this should
               never happen.  */
             hst = NULL;
             buffer = old_buffer;

             /* We set the error to indicate this is (possibly) a
               temporary error and that it does not mean the entry
               is not available at all.  */
             errval = EAGAIN;
             break;
           }
         use_malloc = true;
       }
      else
       /* Allocate a new buffer on the stack.  If possible combine it
          with the previously allocated buffer.  */
       buffer = (char *) extend_alloca (buffer, buflen, 2 * buflen);
    }

  cache_addhst (db, fd, req, key, hst, uid, he, dh,
              h_errno == TRY_AGAIN ? errval : 0, ttl);

  if (use_malloc)
    free (buffer);
}

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static void cache_addhst ( struct database_dyn db,
int  fd,
request_header req,
const void *  key,
struct hostent hst,
uid_t  owner,
struct hashentry he,
struct datahead dh,
int  errval,
int32_t  ttl 
) [static]

Definition at line 81 of file hstcache.c.

{
  bool all_written = true;
  time_t t = time (NULL);

  /* We allocate all data in one memory block: the iov vector,
     the response header and the dataset itself.  */
  struct dataset
  {
    struct datahead head;
    hst_response_header resp;
    char strdata[0];
  } *dataset;

  assert (offsetof (struct dataset, resp) == offsetof (struct datahead, data));

  if (hst == NULL)
    {
      if (he != NULL && errval == EAGAIN)
       {
         /* If we have an old record available but cannot find one
            now because the service is not available we keep the old
            record and make sure it does not get removed.  */
         if (reload_count != UINT_MAX)
           /* Do not reset the value if we never not reload the record.  */
           dh->nreloads = reload_count - 1;
       }
      else
       {
         /* We have no data.  This means we send the standard reply for this
            case.  */
         ssize_t total = sizeof (notfound);

         if (fd != -1 &&
             TEMP_FAILURE_RETRY (send (fd, &notfound, total,
                                   MSG_NOSIGNAL)) != total)
           all_written = false;

         dataset = mempool_alloc (db, sizeof (struct dataset) + req->key_len,
                               IDX_result_data);
         /* If we cannot permanently store the result, so be it.  */
         if (dataset != NULL)
           {
             dataset->head.allocsize = sizeof (struct dataset) + req->key_len;
             dataset->head.recsize = total;
             dataset->head.notfound = true;
             dataset->head.nreloads = 0;
             dataset->head.usable = true;

             /* Compute the timeout time.  */
             dataset->head.timeout = t + (ttl == INT32_MAX
                                      ? db->negtimeout : ttl);

             /* This is the reply.  */
             memcpy (&dataset->resp, &notfound, total);

             /* Copy the key data.  */
             memcpy (dataset->strdata, key, req->key_len);

             /* If necessary, we also propagate the data to disk.  */
             if (db->persistent)
              {
                // XXX async OK?
                uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1;
                msync ((void *) pval,
                      ((uintptr_t) dataset & pagesize_m1)
                      + sizeof (struct dataset) + req->key_len, MS_ASYNC);
              }

             /* Now get the lock to safely insert the records.  */
             pthread_rwlock_rdlock (&db->lock);

             (void) cache_add (req->type, &dataset->strdata, req->key_len,
                            &dataset->head, true, db, owner, he == NULL);

             pthread_rwlock_unlock (&db->lock);

             /* Mark the old entry as obsolete.  */
             if (dh != NULL)
              dh->usable = false;
           }
         else
           ++db->head->addfailed;
       }
    }
  else
    {
      /* Determine the I/O structure.  */
      size_t h_name_len = strlen (hst->h_name) + 1;
      size_t h_aliases_cnt;
      uint32_t *h_aliases_len;
      size_t h_addr_list_cnt;
      int addr_list_type;
      char *addresses;
      char *aliases;
      char *key_copy = NULL;
      char *cp;
      size_t cnt;
      ssize_t total;

      /* Determine the number of aliases.  */
      h_aliases_cnt = 0;
      for (cnt = 0; hst->h_aliases[cnt] != NULL; ++cnt)
       ++h_aliases_cnt;
      /* Determine the length of all aliases.  */
      h_aliases_len = (uint32_t *) alloca (h_aliases_cnt * sizeof (uint32_t));
      total = 0;
      for (cnt = 0; cnt < h_aliases_cnt; ++cnt)
       {
         h_aliases_len[cnt] = strlen (hst->h_aliases[cnt]) + 1;
         total += h_aliases_len[cnt];
       }

      /* Determine the number of addresses.  */
      h_addr_list_cnt = 0;
      while (hst->h_addr_list[h_addr_list_cnt] != NULL)
       ++h_addr_list_cnt;

      if (h_addr_list_cnt == 0)
       /* Invalid entry.  */
       return;

      total += (sizeof (struct dataset)
              + h_name_len
              + h_aliases_cnt * sizeof (uint32_t)
              + h_addr_list_cnt * hst->h_length);

      /* If we refill the cache, first assume the reconrd did not
        change.  Allocate memory on the cache since it is likely
        discarded anyway.  If it turns out to be necessary to have a
        new record we can still allocate real memory.  */
      bool alloca_used = false;
      dataset = NULL;

      /* If the record contains more than one IP address (used for
        load balancing etc) don't cache the entry.  This is something
        the current cache handling cannot handle and it is more than
        questionable whether it is worthwhile complicating the cache
        handling just for handling such a special case. */
      if (he == NULL && h_addr_list_cnt == 1)
       {
         dataset = (struct dataset *) mempool_alloc (db,
                                                total + req->key_len,
                                                IDX_result_data);
         if (dataset == NULL)
           ++db->head->addfailed;
       }

      if (dataset == NULL)
       {
         /* We cannot permanently add the result in the moment.  But
            we can provide the result as is.  Store the data in some
            temporary memory.  */
         dataset = (struct dataset *) alloca (total + req->key_len);

         /* We cannot add this record to the permanent database.  */
         alloca_used = true;
       }

      dataset->head.allocsize = total + req->key_len;
      dataset->head.recsize = total - offsetof (struct dataset, resp);
      dataset->head.notfound = false;
      dataset->head.nreloads = he == NULL ? 0 : (dh->nreloads + 1);
      dataset->head.usable = true;

      /* Compute the timeout time.  */
      dataset->head.timeout = t + (ttl == INT32_MAX ? db->postimeout : ttl);

      dataset->resp.version = NSCD_VERSION;
      dataset->resp.found = 1;
      dataset->resp.h_name_len = h_name_len;
      dataset->resp.h_aliases_cnt = h_aliases_cnt;
      dataset->resp.h_addrtype = hst->h_addrtype;
      dataset->resp.h_length = hst->h_length;
      dataset->resp.h_addr_list_cnt = h_addr_list_cnt;
      dataset->resp.error = NETDB_SUCCESS;

      /* Make sure there is no gap.  */
      assert ((char *) (&dataset->resp.error + 1) == dataset->strdata);

      cp = dataset->strdata;

      cp = mempcpy (cp, hst->h_name, h_name_len);
      cp = mempcpy (cp, h_aliases_len, h_aliases_cnt * sizeof (uint32_t));

      /* The normal addresses first.  */
      addresses = cp;
      for (cnt = 0; cnt < h_addr_list_cnt; ++cnt)
       cp = mempcpy (cp, hst->h_addr_list[cnt], hst->h_length);

      /* Then the aliases.  */
      aliases = cp;
      for (cnt = 0; cnt < h_aliases_cnt; ++cnt)
       cp = mempcpy (cp, hst->h_aliases[cnt], h_aliases_len[cnt]);

      assert (cp
             == dataset->strdata + total - offsetof (struct dataset,
                                                strdata));

      /* If we are adding a GETHOSTBYNAME{,v6} entry we must be prepared
        that the answer we get from the NSS does not contain the key
        itself.  This is the case if the resolver is used and the name
        is extended by the domainnames from /etc/resolv.conf.  Therefore
        we explicitly add the name here.  */
      key_copy = memcpy (cp, key, req->key_len);

      assert ((char *) &dataset->resp + dataset->head.recsize == cp);

      /* Now we can determine whether on refill we have to create a new
        record or not.  */
      if (he != NULL)
       {
         assert (fd == -1);

         if (total + req->key_len == dh->allocsize
             && total - offsetof (struct dataset, resp) == dh->recsize
             && memcmp (&dataset->resp, dh->data,
                      dh->allocsize - offsetof (struct dataset, resp)) == 0)
           {
             /* The data has not changed.  We will just bump the
               timeout value.  Note that the new record has been
               allocated on the stack and need not be freed.  */
             assert (h_addr_list_cnt == 1);
             dh->timeout = dataset->head.timeout;
             ++dh->nreloads;
           }
         else
           {
             if (h_addr_list_cnt == 1)
              {
                /* We have to create a new record.  Just allocate
                   appropriate memory and copy it.  */
                struct dataset *newp
                  = (struct dataset *) mempool_alloc (db,
                                                 total + req->key_len,
                                                 IDX_result_data);
                if (newp != NULL)
                  {
                    /* Adjust pointers into the memory block.  */
                    addresses = (char *) newp + (addresses
                                             - (char *) dataset);
                    aliases = (char *) newp + (aliases - (char *) dataset);
                    assert (key_copy != NULL);
                    key_copy = (char *) newp + (key_copy - (char *) dataset);

                    dataset = memcpy (newp, dataset, total + req->key_len);
                    alloca_used = false;
                  }
                else
                  ++db->head->addfailed;
              }

             /* Mark the old record as obsolete.  */
             dh->usable = false;
           }
       }
      else
       {
         /* We write the dataset before inserting it to the database
            since while inserting this thread might block and so would
            unnecessarily keep the receiver waiting.  */
         assert (fd != -1);

#ifdef HAVE_SENDFILE
         if (__builtin_expect (db->mmap_used, 1) && !alloca_used)
           {
             assert (db->wr_fd != -1);
             assert ((char *) &dataset->resp > (char *) db->data);
             assert ((char *) &dataset->resp - (char *) db->head
                    + total
                    <= (sizeof (struct database_pers_head)
                       + db->head->module * sizeof (ref_t)
                       + db->head->data_size));
             ssize_t written = sendfileall (fd, db->wr_fd,
                                        (char *) &dataset->resp
                                        - (char *) db->head,
                                        dataset->head.recsize);
             if (written != dataset->head.recsize)
              {
# ifndef __ASSUME_SENDFILE
                if (written == -1 && errno == ENOSYS)
                  goto use_write;
# endif
                all_written = false;
              }
           }
         else
# ifndef __ASSUME_SENDFILE
         use_write:
# endif
#endif
           if (writeall (fd, &dataset->resp, dataset->head.recsize)
              != dataset->head.recsize)
             all_written = false;
       }

      /* Add the record to the database.  But only if it has not been
        stored on the stack.

        If the record contains more than one IP address (used for
        load balancing etc) don't cache the entry.  This is something
        the current cache handling cannot handle and it is more than
        questionable whether it is worthwhile complicating the cache
        handling just for handling such a special case. */
      if (! alloca_used)
       {
         /* If necessary, we also propagate the data to disk.  */
         if (db->persistent)
           {
             // XXX async OK?
             uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1;
             msync ((void *) pval,
                   ((uintptr_t) dataset & pagesize_m1)
                   + total + req->key_len, MS_ASYNC);
           }

         addr_list_type = (hst->h_length == NS_INADDRSZ
                         ? GETHOSTBYADDR : GETHOSTBYADDRv6);

         /* Now get the lock to safely insert the records.  */
         pthread_rwlock_rdlock (&db->lock);

         /* NB: the following code is really complicated.  It has
            seemlingly duplicated code paths which do the same.  The
            problem is that we always must add the hash table entry
            with the FIRST flag set first.  Otherwise we get dangling
            pointers in case memory allocation fails.  */
         assert (hst->h_addr_list[1] == NULL);

         /* Avoid adding names if more than one address is available.  See
            above for more info.  */
         assert (req->type == GETHOSTBYNAME
                || req->type == GETHOSTBYNAMEv6
                || req->type == GETHOSTBYADDR
                || req->type == GETHOSTBYADDRv6);

         (void) cache_add (req->type, key_copy, req->key_len,
                         &dataset->head, true, db, owner, he == NULL);

         pthread_rwlock_unlock (&db->lock);
       }
    }

  if (__builtin_expect (!all_written, 0) && debug_level > 0)
    {
      char buf[256];
      dbg_log (_("short write in %s: %s"),  __FUNCTION__,
              strerror_r (errno, buf, sizeof (buf)));
    }
}

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static int lookup ( int  type,
void *  key,
struct hostent resultbufp,
char *  buffer,
size_t  buflen,
struct hostent **  hst,
int32_t ttlp 
) [static]

Definition at line 437 of file hstcache.c.

{
  if (type == GETHOSTBYNAME)
    return __gethostbyname3_r (key, AF_INET, resultbufp, buffer, buflen, hst,
                            &h_errno, ttlp, NULL);
  if (type == GETHOSTBYNAMEv6)
    return __gethostbyname3_r (key, AF_INET6, resultbufp, buffer, buflen, hst,
                            &h_errno, ttlp, NULL);
  if (type == GETHOSTBYADDR)
    return __gethostbyaddr2_r (key, NS_INADDRSZ, AF_INET, resultbufp, buffer,
                            buflen, hst, &h_errno, ttlp);
  return __gethostbyaddr2_r (key, NS_IN6ADDRSZ, AF_INET6, resultbufp, buffer,
                          buflen, hst, &h_errno, ttlp);
}

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void readdhstbyaddr ( struct database_dyn db,
struct hashentry he,
struct datahead dh 
)

Definition at line 558 of file hstcache.c.

{
  request_header req =
    {
      .type = GETHOSTBYADDR,
      .key_len = he->len
    };

  addhstbyX (db, -1, &req, db->data + he->key, he->owner, he, dh);
}

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void readdhstbyaddrv6 ( struct database_dyn db,
struct hashentry he,
struct datahead dh 
)

Definition at line 602 of file hstcache.c.

{
  request_header req =
    {
      .type = GETHOSTBYADDRv6,
      .key_len = he->len
    };

  addhstbyX (db, -1, &req, db->data + he->key, he->owner, he, dh);
}

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void readdhstbyname ( struct database_dyn db,
struct hashentry he,
struct datahead dh 
)

Definition at line 536 of file hstcache.c.

{
  request_header req =
    {
      .type = GETHOSTBYNAME,
      .key_len = he->len
    };

  addhstbyX (db, -1, &req, db->data + he->key, he->owner, he, dh);
}

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void readdhstbynamev6 ( struct database_dyn db,
struct hashentry he,
struct datahead dh 
)

Definition at line 580 of file hstcache.c.

{
  request_header req =
    {
      .type = GETHOSTBYNAMEv6,
      .key_len = he->len
    };

  addhstbyX (db, -1, &req, db->data + he->key, he->owner, he, dh);
}

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Variable Documentation

Initial value:
{
  .version = NSCD_VERSION,
  .found = -1,
  .h_name_len = 0,
  .h_aliases_cnt = 0,
  .h_addrtype = -1,
  .h_length = -1,
  .h_addr_list_cnt = 0,
  .error = NETDB_INTERNAL
}

Definition at line 46 of file hstcache.c.

Initial value:
{
  .version = NSCD_VERSION,
  .found = 0,
  .h_name_len = 0,
  .h_aliases_cnt = 0,
  .h_addrtype = -1,
  .h_length = -1,
  .h_addr_list_cnt = 0,
  .error = HOST_NOT_FOUND
}

Definition at line 67 of file hstcache.c.