Back to index

glibc  2.9
Classes | Defines | Typedefs | Enumerations | Functions
dns-network.c File Reference
#include <ctype.h>
#include <errno.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "nsswitch.h"
#include <arpa/inet.h>

Go to the source code of this file.

Classes

union  querybuf

Defines

#define MAX_NR_ALIASES   48
#define MAXPACKET   65536
#define NS_MAXCDNAME   255 /* maximum compressed domain name */
#define offsetof(Type, Member)   ((size_t) &((Type *) NULL)->Member)

Typedefs

typedef union querybuf querybuf

Enumerations

enum  lookup_method { BYADDR, BYNAME }

Functions

int __ns_name_ntop (extern int __ns_name_unpack(const u_char const u_char *, char *, size_t)
enum nss_status _nss_dns_getnetbyaddr_r (uint32_t net, int type, struct netent *result, char *buffer, size_t buflen, int *errnop, int *herrnop)
static enum nss_status getanswer_r (const querybuf *answer, int anslen, struct netent *result, char *buffer, size_t buflen, int *errnop, int *h_errnop, lookup_method net_i)

Class Documentation

union querybuf

Definition at line 36 of file dns-canon.c.

Collaboration diagram for querybuf:
Class Members
unsigned char buf
u_char buf
HEADER hdr

Define Documentation

#define MAX_NR_ALIASES   48

Definition at line 71 of file dns-network.c.

#define MAXPACKET   65536

Definition at line 77 of file dns-network.c.

#define NS_MAXCDNAME   255 /* maximum compressed domain name */

Definition at line 96 of file dns-network.c.

#define offsetof (   Type,
  Member 
)    ((size_t) &((Type *) NULL)->Member)

Definition at line 242 of file dns-network.c.


Typedef Documentation

typedef union querybuf querybuf

Enumeration Type Documentation

Enumerator:
BYADDR 
BYNAME 

Definition at line 81 of file dns-network.c.


Function Documentation

int __ns_name_ntop ( extern int __ns_name_unpack (const u_char  const u_char *,
char *  ,
size_t   
)

Definition at line 97 of file dns-network.c.

{
  /* Return entry for network with NAME.  */
  union
  {
    querybuf *buf;
    u_char *ptr;
  } net_buffer;
  querybuf *orig_net_buffer;
  int anslen;
  char *qbuf;
  enum nss_status status;

  if (__res_maybe_init (&_res, 0) == -1)
    return NSS_STATUS_UNAVAIL;

  qbuf = strdupa (name);

  net_buffer.buf = orig_net_buffer = (querybuf *) alloca (1024);

  anslen = __libc_res_nsearch (&_res, qbuf, C_IN, T_PTR, net_buffer.buf->buf,
                            1024, &net_buffer.ptr, NULL, NULL, NULL);
  if (anslen < 0)
    {
      /* Nothing found.  */
      *errnop = errno;
      if (net_buffer.buf != orig_net_buffer)
       free (net_buffer.buf);
      return (errno == ECONNREFUSED
             || errno == EPFNOSUPPORT
             || errno == EAFNOSUPPORT)
       ? NSS_STATUS_UNAVAIL : NSS_STATUS_NOTFOUND;
    }

  status = getanswer_r (net_buffer.buf, anslen, result, buffer, buflen,
                     errnop, herrnop, BYNAME);
  if (net_buffer.buf != orig_net_buffer)
    free (net_buffer.buf);
  return status;
}

Here is the call graph for this function:

enum nss_status _nss_dns_getnetbyaddr_r ( uint32_t  net,
int  type,
struct netent result,
char *  buffer,
size_t  buflen,
int errnop,
int herrnop 
)

Definition at line 155 of file dns-network.c.

{
  /* Return entry for network with NAME.  */
  enum nss_status status;
  union
  {
    querybuf *buf;
    u_char *ptr;
  } net_buffer;
  querybuf *orig_net_buffer;
  unsigned int net_bytes[4];
  char qbuf[MAXDNAME];
  int cnt, anslen;
  u_int32_t net2;
  int olderr = errno;

  /* No net address lookup for IPv6 yet.  */
  if (type != AF_INET)
    return NSS_STATUS_UNAVAIL;

  if (__res_maybe_init (&_res, 0) == -1)
    return NSS_STATUS_UNAVAIL;

  net2 = (u_int32_t) net;
  for (cnt = 4; net2 != 0; net2 >>= 8)
    net_bytes[--cnt] = net2 & 0xff;

  switch (cnt)
    {
    case 3:
      /* Class A network.  */
      sprintf (qbuf, "0.0.0.%u.in-addr.arpa", net_bytes[3]);
      break;
    case 2:
      /* Class B network.  */
      sprintf (qbuf, "0.0.%u.%u.in-addr.arpa", net_bytes[3], net_bytes[2]);
      break;
    case 1:
      /* Class C network.  */
      sprintf (qbuf, "0.%u.%u.%u.in-addr.arpa", net_bytes[3], net_bytes[2],
              net_bytes[1]);
      break;
    case 0:
      /* Class D - E network.  */
      sprintf (qbuf, "%u.%u.%u.%u.in-addr.arpa", net_bytes[3], net_bytes[2],
              net_bytes[1], net_bytes[0]);
      break;
    }

  net_buffer.buf = orig_net_buffer = (querybuf *) alloca (1024);

  anslen = __libc_res_nquery (&_res, qbuf, C_IN, T_PTR, net_buffer.buf->buf,
                           1024, &net_buffer.ptr, NULL, NULL, NULL);
  if (anslen < 0)
    {
      /* Nothing found.  */
      int err = errno;
      __set_errno (olderr);
      if (net_buffer.buf != orig_net_buffer)
       free (net_buffer.buf);
      return (err == ECONNREFUSED
             || err == EPFNOSUPPORT
             || err == EAFNOSUPPORT)
       ? NSS_STATUS_UNAVAIL : NSS_STATUS_NOTFOUND;
    }

  status = getanswer_r (net_buffer.buf, anslen, result, buffer, buflen,
                     errnop, herrnop, BYADDR);
  if (net_buffer.buf != orig_net_buffer)
    free (net_buffer.buf);
  if (status == NSS_STATUS_SUCCESS)
    {
      /* Strip trailing zeros.  */
      unsigned int u_net = net;    /* Maybe net should be unsigned?  */

      while ((u_net & 0xff) == 0 && u_net != 0)
       u_net >>= 8;
      result->n_net = u_net;
    }

  return status;
}

Here is the call graph for this function:

static enum nss_status getanswer_r ( const querybuf answer,
int  anslen,
struct netent result,
char *  buffer,
size_t  buflen,
int errnop,
int h_errnop,
lookup_method  net_i 
) [static]

Definition at line 245 of file dns-network.c.

{
  /*
   * Find first satisfactory answer
   *
   *      answer --> +------------+  ( MESSAGE )
   *                 |   Header   |
   *                 +------------+
   *                 |  Question  | the question for the name server
   *                 +------------+
   *                 |   Answer   | RRs answering the question
   *                 +------------+
   *                 | Authority  | RRs pointing toward an authority
   *                 | Additional | RRs holding additional information
   *                 +------------+
   */
  struct net_data
  {
    char *aliases[MAX_NR_ALIASES];
    char linebuffer[0];
  } *net_data;

  uintptr_t pad = -(uintptr_t) buffer % __alignof__ (struct net_data);
  buffer += pad;

  if (__builtin_expect (buflen < sizeof (*net_data) + pad, 0))
    {
      /* The buffer is too small.  */
    too_small:
      *errnop = ERANGE;
      *h_errnop = NETDB_INTERNAL;
      return NSS_STATUS_TRYAGAIN;
    }
  buflen -= pad;

  net_data = (struct net_data *) buffer;
  int linebuflen = buflen - offsetof (struct net_data, linebuffer);
  if (buflen - offsetof (struct net_data, linebuffer) != linebuflen)
    linebuflen = INT_MAX;
  const unsigned char *end_of_message = &answer->buf[anslen];
  const HEADER *header_pointer = &answer->hdr;
  /* #/records in the answer section.  */
  int answer_count =  ntohs (header_pointer->ancount);
  /* #/entries in the question section.  */
  int question_count = ntohs (header_pointer->qdcount);
  char *bp = net_data->linebuffer;
  const unsigned char *cp = &answer->buf[HFIXEDSZ];
  char **alias_pointer;
  int have_answer;
  char *ans;
  u_char packtmp[NS_MAXCDNAME];

  if (question_count == 0)
    {
      /* FIXME: the Sun version uses for host name lookup an additional
        parameter for pointing to h_errno.  this is missing here.
        OSF/1 has a per-thread h_errno variable.  */
      if (header_pointer->aa != 0)
       {
         __set_h_errno (HOST_NOT_FOUND);
         return NSS_STATUS_NOTFOUND;
       }
      else
       {
         __set_h_errno (TRY_AGAIN);
         return NSS_STATUS_TRYAGAIN;
       }
    }

  /* Skip the question part.  */
  while (question_count-- > 0)
    {
      int n = __dn_skipname (cp, end_of_message);
      if (n < 0 || end_of_message - (cp + n) < QFIXEDSZ)
       {
         __set_h_errno (NO_RECOVERY);
         return NSS_STATUS_UNAVAIL;
       }
      cp += n + QFIXEDSZ;
    }

  alias_pointer = result->n_aliases = &net_data->aliases[0];
  *alias_pointer = NULL;
  have_answer = 0;
  ans = NULL;

  while (--answer_count >= 0 && cp < end_of_message)
    {
      int n = dn_expand (answer->buf, end_of_message, cp, bp, linebuflen);
      int type, class;

      n = __ns_name_unpack (answer->buf, end_of_message, cp,
                         packtmp, sizeof packtmp);
      if (n != -1 && __ns_name_ntop (packtmp, bp, linebuflen) == -1)
       {
         if (errno == EMSGSIZE)
           goto too_small;

         n = -1;
       }

      if (n > 0 && bp[0] == '.')
       bp[0] = '\0';

      if (n < 0 || res_dnok (bp) == 0)
       break;
      cp += n;
      ans = strdupa (bp);
      GETSHORT (type, cp);
      GETSHORT (class, cp);
      cp += INT32SZ;        /* TTL */
      GETSHORT (n, cp);

      if (class == C_IN && type == T_PTR)
       {
         n = __ns_name_unpack (answer->buf, end_of_message, cp,
                            packtmp, sizeof packtmp);
         if (n != -1 && __ns_name_ntop (packtmp, bp, linebuflen) == -1)
           {
             if (errno == EMSGSIZE)
              goto too_small;

             n = -1;
           }

         if (n < 0 || !res_hnok (bp))
           {
             /* XXX What does this mean?  The original form from bind
               returns NULL. Incrementing cp has no effect in any case.
               What should I return here. ??? */
             cp += n;
             return NSS_STATUS_UNAVAIL;
           }
         cp += n;
         if (alias_pointer + 2 < &net_data->aliases[MAX_NR_ALIASES])
           {
             *alias_pointer++ = bp;
             n = strlen (bp) + 1;
             bp += n;
             linebuflen -= n;
             result->n_addrtype = class == C_IN ? AF_INET : AF_UNSPEC;
             ++have_answer;
           }
       }
    }

  if (have_answer)
    {
      *alias_pointer = NULL;
      switch (net_i)
       {
       case BYADDR:
         result->n_name = *result->n_aliases++;
         result->n_net = 0L;
         return NSS_STATUS_SUCCESS;

       case BYNAME:
         {
           char **ap = result->n_aliases++;
           while (*ap != NULL)
             {
              /* Check each alias name for being of the forms:
                 4.3.2.1.in-addr.arpa            = net 1.2.3.4
                 3.2.1.in-addr.arpa              = net 0.1.2.3
                 2.1.in-addr.arpa         = net 0.0.1.2
                 1.in-addr.arpa           = net 0.0.0.1
              */
              uint32_t val = 0;    /* Accumulator for n_net value.  */
              unsigned int shift = 0; /* Which part we are parsing now.  */
              const char *p = *ap; /* Consuming the string.  */
              do
                {
                  /* Match the leading 0 or 0[xX] base indicator.  */
                  unsigned int base = 10;
                  if (*p == '0' && p[1] != '.')
                    {
                     base = 8;
                     ++p;
                     if (*p == 'x' || *p == 'X')
                       {
                         base = 16;
                         ++p;
                         if (*p == '.')
                           break; /* No digit here.  Give up on alias.  */
                       }
                     if (*p == '\0')
                       break;
                    }

                  uint32_t part = 0; /* Accumulates this part's number.  */
                  do
                    {
                     if (isdigit (*p) && (*p - '0' < base))
                       part = (part * base) + (*p - '0');
                     else if (base == 16 && isxdigit (*p))
                       part = (part << 4) + 10 + (tolower (*p) - 'a');
                     ++p;
                    } while (*p != '\0' && *p != '.');

                  if (*p != '.')
                    break;  /* Bad form.  Give up on this name.  */

                  /* Install this as the next more significant byte.  */
                  val |= part << shift;
                  shift += 8;
                  ++p;

                  /* If we are out of digits now, there are two cases:
                     1. We are done with digits and now see "in-addr.arpa".
                     2. This is not the droid we are looking for.  */
                  if (!isdigit (*p) && !strcasecmp (p, "in-addr.arpa"))
                    {
                     result->n_net = val;
                     return NSS_STATUS_SUCCESS;
                    }

                  /* Keep going when we have seen fewer than 4 parts.  */
                } while (shift < 32);
             }
         }
         break;
       }
    }

  __set_h_errno (TRY_AGAIN);
  return NSS_STATUS_TRYAGAIN;
}

Here is the call graph for this function:

Here is the caller graph for this function: