1/* libresolv interfaces for internal use across glibc.
2 Copyright (C) 2016-2023 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. */
35typedef HEADER __attribute__ ((__aligned__(1))) UHEADER;
36
37/* Legacy function. This needs to be removed once all NSS modules
38 have been adjusted. */
39static inline bool
40res_use_inet6 (void)
41{
42 return false;
43}
44
45enum
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
59struct resolv_context;
60
61/* Internal function for implementing res_nmkquery and res_mkquery.
62 Also used by __res_context_query. */
63int __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);
66libc_hidden_proto (__res_context_mkquery)
67
68/* Main resolver query function for use within glibc. */
69int __res_context_search (struct resolv_context *, const char *, int, int,
70 unsigned char *, int, unsigned char **,
71 unsigned char **, int *, int *, int *);
72libc_hidden_proto (__res_context_search)
73
74/* Main resolver query function for use within glibc. */
75int __res_context_query (struct resolv_context *, const char *, int, int,
76 unsigned char *, int, unsigned char **,
77 unsigned char **, int *, int *, int *);
78libc_hidden_proto (__res_context_query)
79
80/* Internal function used to implement the query and search
81 functions. */
82int __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 *);
86libc_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. */
91bool __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. */
97const char *__res_context_hostalias (struct resolv_context *,
98 const char *, char *, size_t);
99libc_hidden_proto (__res_context_hostalias);
100
101/* Add an OPT record to a DNS query. */
102int __res_nopt (struct resolv_context *, int n0,
103 unsigned char *buf, int buflen, int anslen);
104libc_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. */
112int __inet_pton_length (int af, const char *src, size_t srclen, void *);
113libc_hidden_proto (__inet_pton_length)
114
115/* Called as part of the thread shutdown sequence. */
116void __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. */
122int __res_enable_icmp (int family, int fd) attribute_hidden;
123
124
125/* Returns the name server address for the indicated index. */
126struct sockaddr *__res_get_nsaddr (res_state statp, unsigned int n);
127libc_hidden_proto (__res_get_nsaddr)
128
129
130#endif /* _RESOLV_INTERNAL_H */
131