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08504de718
The Linux kernel suppresses some ICMP error messages by default for UDP sockets. This commit enables full ICMP error reporting, hopefully resulting in faster failover to working name servers.
110 lines
4.6 KiB
C
110 lines
4.6 KiB
C
/* libresolv interfaces for internal use across glibc.
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Copyright (C) 2016-2019 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#ifndef _RESOLV_INTERNAL_H
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#define _RESOLV_INTERNAL_H 1
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#include <resolv.h>
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#include <stdbool.h>
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/* Resolver flags. Used for _flags in struct __res_state. */
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#define RES_F_VC 0x00000001 /* Socket is TCP. */
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#define RES_F_CONN 0x00000002 /* Socket is connected. */
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#define RES_F_EDNS0ERR 0x00000004 /* EDNS0 caused errors. */
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/* Internal version of RES_USE_INET6 which does not trigger a
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deprecation warning. */
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#define DEPRECATED_RES_USE_INET6 0x00002000
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static inline bool
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res_use_inet6 (void)
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{
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return _res.options & DEPRECATED_RES_USE_INET6;
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}
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enum
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{
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/* The advertized EDNS buffer size. The value 1200 is derived
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from the IPv6 minimum MTU (1280 bytes) minus some arbitrary
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space for tunneling overhead. If the DNS server does not react
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to ICMP Fragmentation Needed But DF Set messages, this should
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avoid all UDP fragments on current networks. Avoiding UDP
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fragments is desirable because it prevents fragmentation-based
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spoofing attacks because the randomness in a DNS packet is
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concentrated in the first fragment (with the headers) and does
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not protect subsequent fragments. */
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RESOLV_EDNS_BUFFER_SIZE = 1200,
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};
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struct resolv_context;
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/* Internal function for implementing res_nmkquery and res_mkquery.
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Also used by __res_context_query. */
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int __res_context_mkquery (struct resolv_context *, int op, const char *dname,
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int class, int type, const unsigned char *data,
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unsigned char *buf, int buflen) attribute_hidden;
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/* Main resolver query function for use within glibc. */
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int __res_context_search (struct resolv_context *, const char *, int, int,
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unsigned char *, int, unsigned char **,
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unsigned char **, int *, int *, int *);
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libresolv_hidden_proto (__res_context_search)
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/* Main resolver query function for use within glibc. */
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int __res_context_query (struct resolv_context *, const char *, int, int,
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unsigned char *, int, unsigned char **,
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unsigned char **, int *, int *, int *);
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libresolv_hidden_proto (__res_context_query)
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/* Internal function used to implement the query and search
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functions. */
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int __res_context_send (struct resolv_context *, const unsigned char *, int,
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const unsigned char *, int, unsigned char *,
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int, unsigned char **, unsigned char **,
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int *, int *, int *) attribute_hidden;
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/* Internal function similar to res_hostalias. */
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const char *__res_context_hostalias (struct resolv_context *,
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const char *, char *, size_t);
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libresolv_hidden_proto (__res_context_hostalias);
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/* Add an OPT record to a DNS query. */
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int __res_nopt (struct resolv_context *, int n0,
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unsigned char *buf, int buflen, int anslen) attribute_hidden;
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/* Convert from presentation format (which usually means ASCII
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printable) to network format (which is usually some kind of binary
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format). The input is in the range [SRC, SRC + SRCLEN). The
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output is written to DST (which has to be 4 or 16 bytes long,
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depending on AF). Return 0 for invalid input, 1 for success, -1
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for an invalid address family. */
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int __inet_pton_length (int af, const char *src, size_t srclen, void *);
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libc_hidden_proto (__inet_pton_length)
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/* Called as part of the thread shutdown sequence. */
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void __res_thread_freeres (void) attribute_hidden;
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/* The Linux kernel does not enable all ICMP messages on a UDP socket
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by default. A call this function enables full error reporting for
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the socket FD. FAMILY must be AF_INET or AF_INET6. Returns 0 on
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success, -1 on failure. */
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int __res_enable_icmp (int family, int fd) attribute_hidden;
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#endif /* _RESOLV_INTERNAL_H */
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