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