1/* libresolv interfaces for internal use across glibc.
2 Copyright (C) 2016-2024 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#define RES_F_SNGLKUP 0x00200000 /* Private version of RES_SNGLKUP. */
30#define RES_F_SNGLKUPREOP 0x00400000 /* Private version of RES_SNGLKUPREOP. */
31
32/* The structure HEADER is normally aligned on a word boundary. In
33 some code, we need to access this structure when it may be aligned
34 on a byte boundary. To avoid unaligned accesses, we need a typedef
35 with alignment one. This ensures the fields are accessed with byte
36 loads and stores. */
37typedef HEADER __attribute__ ((__aligned__(1))) UHEADER;
38
39/* List of known interfaces. */
40struct netaddr
41{
42 int addrtype;
43 union
44 {
45 struct
46 {
47 uint32_t addr;
48 uint32_t mask;
49 } ipv4;
50 } u;
51};
52
53/* Legacy function. This needs to be removed once all NSS modules
54 have been adjusted. */
55static inline bool
56res_use_inet6 (void)
57{
58 return false;
59}
60
61enum
62 {
63 /* The advertised EDNS buffer size. The value 1200 is derived
64 from the IPv6 minimum MTU (1280 bytes) minus some arbitrary
65 space for tunneling overhead. If the DNS server does not react
66 to ICMP Fragmentation Needed But DF Set messages, this should
67 avoid all UDP fragments on current networks. Avoiding UDP
68 fragments is desirable because it prevents fragmentation-based
69 spoofing attacks because the randomness in a DNS packet is
70 concentrated in the first fragment (with the headers) and does
71 not protect subsequent fragments. */
72 RESOLV_EDNS_BUFFER_SIZE = 1200,
73 };
74
75struct resolv_context;
76
77/* Internal function for implementing res_nmkquery and res_mkquery.
78 Also used by __res_context_query. */
79int __res_context_mkquery (struct resolv_context *, int op, const char *dname,
80 int class, int type, const unsigned char *data,
81 unsigned char *buf, int buflen);
82libc_hidden_proto (__res_context_mkquery)
83
84/* Main resolver query function for use within glibc. */
85int __res_context_search (struct resolv_context *, const char *, int, int,
86 unsigned char *, int, unsigned char **,
87 unsigned char **, int *, int *, int *);
88libc_hidden_proto (__res_context_search)
89
90/* Main resolver query function for use within glibc. */
91int __res_context_query (struct resolv_context *, const char *, int, int,
92 unsigned char *, int, unsigned char **,
93 unsigned char **, int *, int *, int *);
94libc_hidden_proto (__res_context_query)
95
96/* Internal function used to implement the query and search
97 functions. */
98int __res_context_send (struct resolv_context *, const unsigned char *, int,
99 const unsigned char *, int, unsigned char *,
100 int, unsigned char **, unsigned char **,
101 int *, int *, int *);
102libc_hidden_proto (__res_context_send)
103
104/* Return true if the query has been handled in RES_NOAAAA mode. For
105 that, RES_NOAAAA must be active, and the question type must be AAAA.
106 The caller is expected to return *RESULT as the return value. */
107bool __res_handle_no_aaaa (struct resolv_context *ctx,
108 const unsigned char *buf, int buflen,
109 unsigned char *ans, int anssiz, int *result)
110 attribute_hidden;
111
112/* Internal function similar to res_hostalias. */
113const char *__res_context_hostalias (struct resolv_context *,
114 const char *, char *, size_t);
115libc_hidden_proto (__res_context_hostalias);
116
117/* Add an OPT record to a DNS query. */
118int __res_nopt (struct resolv_context *, int n0,
119 unsigned char *buf, int buflen, int anslen);
120libc_hidden_proto (__res_nopt)
121
122/* Convert from presentation format (which usually means ASCII
123 printable) to network format (which is usually some kind of binary
124 format). The input is in the range [SRC, SRC + SRCLEN). The
125 output is written to DST (which has to be 4 or 16 bytes long,
126 depending on AF). Return 0 for invalid input, 1 for success, -1
127 for an invalid address family. */
128int __inet_pton_length (int af, const char *src, size_t srclen, void *);
129libc_hidden_proto (__inet_pton_length)
130
131/* Called as part of the thread shutdown sequence. */
132void __res_thread_freeres (void) attribute_hidden;
133
134/* The Linux kernel does not enable all ICMP messages on a UDP socket
135 by default. A call this function enables full error reporting for
136 the socket FD. FAMILY must be AF_INET or AF_INET6. Returns 0 on
137 success, -1 on failure. */
138int __res_enable_icmp (int family, int fd) attribute_hidden;
139
140
141/* Returns the name server address for the indicated index. */
142struct sockaddr *__res_get_nsaddr (res_state statp, unsigned int n);
143libc_hidden_proto (__res_get_nsaddr)
144
145
146#endif /* _RESOLV_INTERNAL_H */
147

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source code of glibc/resolv/resolv-internal.h