resolv/resolv-internal.h

   1 /* libresolv interfaces for internal use across glibc.
   2    Copyright (C) 2016-2022 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #ifndef _RESOLV_INTERNAL_H
  20 #define _RESOLV_INTERNAL_H 1
  21
  22 #include <resolv.h>
  23 #include <stdbool.h>
  24
  25 /* Resolver flags.  Used for _flags in struct __res_state.  */
  26 #define RES_F_VC        0x00000001 /* Socket is TCP.  */
  27 #define RES_F_CONN      0x00000002 /* Socket is connected.  */
  28 #define RES_F_EDNS0ERR  0x00000004 /* EDNS0 caused errors.  */
  29
  30 /* The structure HEADER is normally aligned on a word boundary.  In
  31    some code, we need to access this structure when it may be aligned
  32    on a byte boundary.  To avoid unaligned accesses, we need a typedef
  33    with alignment one.  This ensures the fields are accessed with byte
  34    loads and stores.  */
  35 typedef HEADER __attribute__ ((__aligned__(1))) UHEADER;
  36
  37 /* Legacy function.  This needs to be removed once all NSS modules
  38    have been adjusted.  */
  39 static inline bool
  40 res_use_inet6 (void)
  41 {
  42   return false;
  43 }
  44
  45 enum
  46   {
  47     /* The advertized EDNS buffer size.  The value 1200 is derived
  48        from the IPv6 minimum MTU (1280 bytes) minus some arbitrary
  49        space for tunneling overhead.  If the DNS server does not react
  50        to ICMP Fragmentation Needed But DF Set messages, this should
  51        avoid all UDP fragments on current networks.  Avoiding UDP
  52        fragments is desirable because it prevents fragmentation-based
  53        spoofing attacks because the randomness in a DNS packet is
  54        concentrated in the first fragment (with the headers) and does
  55        not protect subsequent fragments.  */
  56     RESOLV_EDNS_BUFFER_SIZE = 1200,
  57   };
  58
  59 struct resolv_context;
  60
  61 /* Internal function for implementing res_nmkquery and res_mkquery.
  62    Also used by __res_context_query.  */
  63 int __res_context_mkquery (struct resolv_context *, int op, const char *dname,
  64                            int class, int type, const unsigned char *data,
  65                            unsigned char *buf, int buflen);
  66 libc_hidden_proto (__res_context_mkquery)
  67
  68 /* Main resolver query function for use within glibc.  */
  69 int __res_context_search (struct resolv_context *, const char *, int, int,
  70                           unsigned char *, int, unsigned char **,
  71                           unsigned char **, int *, int *, int *);
  72 libc_hidden_proto (__res_context_search)
  73
  74 /* Main resolver query function for use within glibc.  */
  75 int __res_context_query (struct resolv_context *, const char *, int, int,
  76                          unsigned char *, int, unsigned char **,
  77                          unsigned char **, int *, int *, int *);
  78 libc_hidden_proto (__res_context_query)
  79
  80 /* Internal function used to implement the query and search
  81    functions.  */
  82 int __res_context_send (struct resolv_context *, const unsigned char *, int,
  83                         const unsigned char *, int, unsigned char *,
  84                         int, unsigned char **, unsigned char **,
  85                         int *, int *, int *);
  86 libc_hidden_proto (__res_context_send)
  87
  88 /* Return true if the query has been handled in RES_NOAAAA mode.  For
  89    that, RES_NOAAAA must be active, and the question type must be AAAA.
  90    The caller is expected to return *RESULT as the return value.  */
  91 bool __res_handle_no_aaaa (struct resolv_context *ctx,
  92                            const unsigned char *buf, int buflen,
  93                            unsigned char *ans, int anssiz, int *result)
  94   attribute_hidden;
  95
  96 /* Internal function similar to res_hostalias.  */
  97 const char *__res_context_hostalias (struct resolv_context *,
  98                                      const char *, char *, size_t);
  99 libc_hidden_proto (__res_context_hostalias);
 100
 101 /* Add an OPT record to a DNS query.  */
 102 int __res_nopt (struct resolv_context *, int n0,
 103                 unsigned char *buf, int buflen, int anslen);
 104 libc_hidden_proto (__res_nopt)
 105
 106 /* Convert from presentation format (which usually means ASCII
 107    printable) to network format (which is usually some kind of binary
 108    format).  The input is in the range [SRC, SRC + SRCLEN).  The
 109    output is written to DST (which has to be 4 or 16 bytes long,
 110    depending on AF).  Return 0 for invalid input, 1 for success, -1
 111    for an invalid address family.  */
 112 int __inet_pton_length (int af, const char *src, size_t srclen, void *);
 113 libc_hidden_proto (__inet_pton_length)
 114
 115 /* Called as part of the thread shutdown sequence.  */
 116 void __res_thread_freeres (void) attribute_hidden;
 117
 118 /* The Linux kernel does not enable all ICMP messages on a UDP socket
 119    by default.  A call this function enables full error reporting for
 120    the socket FD.  FAMILY must be AF_INET or AF_INET6.  Returns 0 on
 121    success, -1 on failure.  */
 122 int __res_enable_icmp (int family, int fd) attribute_hidden;
 123
 124
 125 /* Returns the name server address for the indicated index.  */
 126 struct sockaddr *__res_get_nsaddr (res_state statp, unsigned int n);
 127 libc_hidden_proto (__res_get_nsaddr)
 128
 129
 130 #endif  /* _RESOLV_INTERNAL_H */