1/* libresolv interfaces for internal use across glibc.
2 Copyright (C) 2016-2021 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/* Legacy function. This needs to be removed once all NSS modules
31 have been adjusted. */
32static inline bool
33res_use_inet6 (void)
34{
35 return false;
36}
37
38enum
39 {
40 /* The advertized EDNS buffer size. The value 1200 is derived
41 from the IPv6 minimum MTU (1280 bytes) minus some arbitrary
42 space for tunneling overhead. If the DNS server does not react
43 to ICMP Fragmentation Needed But DF Set messages, this should
44 avoid all UDP fragments on current networks. Avoiding UDP
45 fragments is desirable because it prevents fragmentation-based
46 spoofing attacks because the randomness in a DNS packet is
47 concentrated in the first fragment (with the headers) and does
48 not protect subsequent fragments. */
49 RESOLV_EDNS_BUFFER_SIZE = 1200,
50 };
51
52struct resolv_context;
53
54/* Internal function for implementing res_nmkquery and res_mkquery.
55 Also used by __res_context_query. */
56int __res_context_mkquery (struct resolv_context *, int op, const char *dname,
57 int class, int type, const unsigned char *data,
58 unsigned char *buf, int buflen) attribute_hidden;
59
60/* Main resolver query function for use within glibc. */
61int __res_context_search (struct resolv_context *, const char *, int, int,
62 unsigned char *, int, unsigned char **,
63 unsigned char **, int *, int *, int *);
64libresolv_hidden_proto (__res_context_search)
65
66/* Main resolver query function for use within glibc. */
67int __res_context_query (struct resolv_context *, const char *, int, int,
68 unsigned char *, int, unsigned char **,
69 unsigned char **, int *, int *, int *);
70libresolv_hidden_proto (__res_context_query)
71
72/* Internal function used to implement the query and search
73 functions. */
74int __res_context_send (struct resolv_context *, const unsigned char *, int,
75 const unsigned char *, int, unsigned char *,
76 int, unsigned char **, unsigned char **,
77 int *, int *, int *) attribute_hidden;
78
79/* Internal function similar to res_hostalias. */
80const char *__res_context_hostalias (struct resolv_context *,
81 const char *, char *, size_t);
82libresolv_hidden_proto (__res_context_hostalias);
83
84/* Add an OPT record to a DNS query. */
85int __res_nopt (struct resolv_context *, int n0,
86 unsigned char *buf, int buflen, int anslen) attribute_hidden;
87
88/* Convert from presentation format (which usually means ASCII
89 printable) to network format (which is usually some kind of binary
90 format). The input is in the range [SRC, SRC + SRCLEN). The
91 output is written to DST (which has to be 4 or 16 bytes long,
92 depending on AF). Return 0 for invalid input, 1 for success, -1
93 for an invalid address family. */
94int __inet_pton_length (int af, const char *src, size_t srclen, void *);
95libc_hidden_proto (__inet_pton_length)
96
97/* Called as part of the thread shutdown sequence. */
98void __res_thread_freeres (void) attribute_hidden;
99
100/* The Linux kernel does not enable all ICMP messages on a UDP socket
101 by default. A call this function enables full error reporting for
102 the socket FD. FAMILY must be AF_INET or AF_INET6. Returns 0 on
103 success, -1 on failure. */
104int __res_enable_icmp (int family, int fd) attribute_hidden;
105
106#endif /* _RESOLV_INTERNAL_H */
107