c-ares/docs/ares_dns_mapping.3

.\" Copyright (C) 2023 The c-ares project and its contributors.
.\" SPDX-License-Identifier: MIT
.\"
.TH ARES_DNS_MAPPINGS 3 "12 November 2023"
.SH NAME
ares_dns_class_fromstr, ares_dns_class_tostr, ares_dns_datatype_t, ares_dns_opcode_tostr,
ares_dns_opt_datatype_t, ares_dns_opt_get_datatype, ares_dns_opt_get_name,
ares_dns_rcode_tostr, ares_dns_rec_type_fromstr, ares_dns_rr_get_keys,
ares_dns_rr_key_datatype, ares_dns_rr_key_to_rec_type, ares_dns_rr_key_tostr,
ares_dns_section_tostr, ares_opt_param_t, ares_svcb_param_t \-
Helper functions for converting dns record identifiers to and from their
respective types, as well identifying datatypes for various records.
.SH SYNOPSIS
.nf
#include <ares.h>

const char *ares_dns_rec_type_tostr(ares_dns_rec_type_t type);

const char *ares_dns_class_tostr(ares_dns_class_t qclass);

const char *ares_dns_opcode_tostr(ares_dns_opcode_t opcode);

const char *ares_dns_rr_key_tostr(ares_dns_rr_key_t key);

const char *ares_dns_section_tostr(ares_dns_section_t section);

const char *ares_dns_rcode_tostr(ares_dns_rcode_t rcode);

ares_bool_t ares_dns_class_fromstr(ares_dns_class_t *qclass, const char *str);

ares_bool_t ares_dns_rec_type_fromstr(ares_dns_rec_type_t *qtype,
                                      const char *str);

const ares_dns_rr_key_t *ares_dns_rr_get_keys(ares_dns_rec_type_t type,
                                              size_t *cnt);

ares_dns_datatype_t ares_dns_rr_key_datatype(ares_dns_rr_key_t key);

ares_dns_rec_type_t ares_dns_rr_key_to_rec_type(ares_dns_rr_key_t key);

ares_dns_opt_datatype_t ares_dns_opt_get_datatype(ares_dns_rr_key_t key,
                                                  unsigned short opt);

const char *ares_dns_opt_get_name(ares_dns_rr_key_t key, unsigned short opt);

.fi
.SH ENUMERATIONS
.B ares_dns_datatype_t -
Data types associated with \fIares_dns_rr_key_t\fP:
.RS 4
.B ARES_DATATYPE_INADDR
- IPv4 address as \fIstruct in_addr *\fP. Use \fIares_dns_rr_set_addr(3)\fP to
set and \fIares_dns_rr_get_addr(3)\fP to get.
.br
.B ARES_DATATYPE_INADDR6
- IPv6 address as \fIstruct ares_in6_addr *\fP. Use \fIares_dns_rr_set_addr6(3)\fP to
set and \fIares_dns_rr_get_addr6(3)\fP to get.
.br
.B ARES_DATATYPE_U8
- 8bit unsigned integer. Use \fIares_dns_rr_set_u8(3)\fP to
set and \fIares_dns_rr_get_u8(3)\fP to get.
.br
.B ARES_DATATYPE_U16
- 16bit unsigned integer. Use \fIares_dns_rr_set_u16(3)\fP to
set and \fIares_dns_rr_get_u16(3)\fP to get.
.br
.B ARES_DATATYPE_U32
- 32bit unsigned integer. Use \fIares_dns_rr_set_u32(3)\fP to
set and \fIares_dns_rr_get_u32(3)\fP to get.
.br
.B ARES_DATATYPE_NAME
- Null-terminated string of a domain name (series of labels). Use \fIares_dns_rr_set_str(3)\fP to
set and \fIares_dns_rr_get_str(3)\fP to get.
.br
.B ARES_DATATYPE_STR
- Null-terminated string. Use \fIares_dns_rr_set_str(3)\fP to
set and \fIares_dns_rr_get_str(3)\fP to get.
.br
.B ARES_DATATYPE_BIN
- Binary Data. Use \fIares_dns_rr_set_bin(3)\fP to
set and \fIares_dns_rr_get_bin(3)\fP to get.
.br
.B ARES_DATATYPE_BINP
- Officially defined as binary data, but likely printable. Guaranteed to have
a NULL terminator for convenience (not included in length). Use \fIares_dns_rr_set_bin(3)\fP to
set and \fIares_dns_rr_get_bin(3)\fP to get.
.br
.B ARES_DATATYPE_OPT
- Array of options.  16bit identifier, Binary data. Use \fIares_dns_rr_set_opt(3)\fP to
set and \fIares_dns_rr_get_opt(3)\fP to get.
.br
.RE

.B ares_dns_opt_datatype_t -
Data types associated with \fIARES_DATATYPE_OPT\fP parameters if known as returned
by \fIares_dns_opt_get_datatype(3)\fP:
.RS 4
.B ARES_OPT_DATATYPE_NONE
- No value allowed for this parameter
.br
.B ARES_OPT_DATATYPE_STR_LIST
- List of strings, each prefixed with a single octet representing the length as
defined by RFC 1035. Can use \fIares_expand_string(3)\fP until buffer is consumed.
.br
.B ARES_OPT_DATATYPE_U8_LIST
- List of 8bit unsigned integers, concatenated
.br
.B ARES_OPT_DATATYPE_U16
- 16bit unsigned integer in network byte order
.br
.B ARES_OPT_DATATYPE_U16_LIST
- list of 16bit unsigned integers in network byte order, concatenated.
.br
.B ARES_OPT_DATATYPE_U32
- 32bit unsigned integer in network byte order
.br
.B ARES_OPT_DATATYPE_U32_LIST
- list of 16bit unsigned integers in network byte order, concatenated.
.br
.B ARES_OPT_DATATYPE_INADDR4_LIST
- List of ipv4 addresses in network byte order, concatenated
.br
.B ARES_OPT_DATATYPE_INADDR6_LIST
- List of ipv6 addresses in network byte order, concatenated
.br
.B ARES_OPT_DATATYPE_BIN
- Binary Data
.br
.B ARES_OPT_DATATYPE_NAME
- DNS Domain Name binary format as defined in RFC1035, can use \fIares_expand_name(3)\fP
.br
.RE

.B ares_svcb_param_t -
SVCB (and HTTPS) RR known parameters as returned by \fIares_dns_opt_get_datatype(3)\fP
with \fIARES_RR_SVCB_PARAMS\fP or \fIARES_RR_HTTPS_PARAMS\fP:
.RS 4
.B ARES_SVCB_PARAM_MANDATORY
- Mandatory keys in this RR (RFC 9460 Section 8). Datatype: \fIARES_OPT_DATATYPE_U16_LIST\fP
.br
.B ARES_SVCB_PARAM_ALPN
- Additional supported protocols (RFC 9460 Section 7.1). Datatype: \fIARES_OPT_DATATYPE_STR_LIST\fP
.br
.B ARES_SVCB_PARAM_NO_DEFAULT_ALPN
- No support for default protocol (RFC 9460 Section 7.1). Datatype: \fIARES_OPT_DATATYPE_NONE\fP
.br
.B ARES_SVCB_PARAM_PORT
- Port for alternative endpoint (RFC 9460 Section 7.2). Datatype: \fIARES_OPT_DATATYPE_U16\fP
.br
.B ARES_SVCB_PARAM_IPV4HINT
- IPv4 address hints (RFC 9460 Section 7.3). Datatype: \fIARES_OPT_DATATYPE_INADDR4_LIST\fP
.br
.B ARES_SVCB_PARAM_ECH
- RESERVED (held for Encrypted ClientHello)
.br
.B ARES_SVCB_PARAM_IPV6HINT
- IPv6 address hints (RFC 9460 Section 7.3). Datatype: \fIARES_OPT_DATATYPE_INADDR6_LIST\fP
.br

.RE

.B ares_opt_param_t -
OPT RR known parameters as returned by \fIares_dns_opt_get_datatype(3)\fP
with \fIARES_RR_OPT_OPTIONS\fB:
.RS 4
.B ARES_OPT_PARAM_LLQ
- RFC 8764. Apple's DNS Long-Lived Queries Protocol. Datatype: \fIARES_OPT_DATATYPE_BIN\fP
.br
.B ARES_OPT_PARAM_UL
- http://files.dns-sd.org/draft-sekar-dns-ul.txt: Update Lease. Datatype: \fIARES_OPT_DATATYPE_U32\fP
.br
.B ARES_OPT_PARAM_NSID
- RFC 5001. Name Server Identification. Datatype: \fIARES_OPT_DATATYPE_BIN\fP
.br
.B ARES_OPT_PARAM_DAU
- RFC 6975. DNSSEC Algorithm Understood. Datatype: \fIARES_OPT_DATATYPE_U8_LIST\fP
.br
.B ARES_OPT_PARAM_DHU
- RFC 6975. DS Hash Understood. Datatype: \fIARES_OPT_DATATYPE_U8_LIST\fP
.br
.B ARES_OPT_PARAM_N3U
- RFC 6975. NSEC3 Hash Understood. Datatype: \fIARES_OPT_DATATYPE_U8_LIST\fP
.br
.B ARES_OPT_PARAM_EDNS_CLIENT_SUBNET
- RFC 7871. Client Subnet. Datatype: \fIARES_OPT_DATATYPE_BIN\fP
.br
.B ARES_OPT_PARAM_EDNS_EXPIRE
- RFC 7314. Expire Timer. Datatype: \fIARES_OPT_DATATYPE_U32\fP
.br
.B ARES_OPT_PARAM_COOKIE
- RFC 7873. Client and Server Cookies. Datatype: \fIARES_OPT_DATATYPE_BIN\fP
.br
.B ARES_OPT_PARAM_EDNS_TCP_KEEPALIVE
- RFC 7828. TCP Keepalive timeout. Datatype: \fIARES_OPT_DATATYPE_U16\fP
.br
.B ARES_OPT_PARAM_PADDING
- RFC 7830. Padding. Datatype: \fIARES_OPT_DATATYPE_BIN\fP
.br
.B ARES_OPT_PARAM_CHAIN
- RFC 7901. Chain query requests. Datatype: \fIARES_OPT_DATATYPE_NAME\fP
.br
.B ARES_OPT_PARAM_EDNS_KEY_TAG
- RFC 8145. Signaling Trust Anchor Knowledge in DNSSEC. Datatype: \fIARES_OPT_DATATYPE_U16_LIST\fP
.br
.B ARES_OPT_PARAM_EXTENDED_DNS_ERROR
- RFC 8914. Extended ERROR code and message. Datatype: \fIARES_OPT_DATATYPE_BIN\fP
.br
.RE

.SH DESCRIPTION
The \fIares_dns_rec_type_tostr(3)\fP function outputs a human readable DNS record
type from its numeric form passed in
.IR type .

The \fIares_dns_class_tostr(3)\fP function outputs a human readable DNS class
from its numeric form passed in
.IR qclass .

The \fIares_dns_opcode_tostr(3)\fP function outputs a human readable DNS opcode
from its numeric form in
.IR opcode .

The \fIares_dns_rr_key_tostr(3)\fP function outputs a human readable DNS Resource
Record parameter name from its numeric form in
.IR key .

The \fIares_dns_section_tostr(3)\fP function outputs a human readable DNS
message section from its numeric form in
.IR section .

The \fIares_dns_rcode_tostr(3)\fP function outputs a human readable DNS
response code from its numeric form in
.IR rcode .

The \fIares_dns_class_fromstr(3)\fP function outputs the DNS class in numeric
from from its string representation in
.IR str .
The result is stored into the variable pointed to by
.IR qclass .

The \fIares_dns_rec_type_fromstr(3)\fP function outputs the DNS record type in
numeric from from its string representation in
.IR str .
The result is stored into the variable pointed to by
.IR qtype .

The \fIares_dns_rr_get_keys(3)\fP function retrieves a list of parameters that
may be set or retrieved for the provided
.IR type .
The count of returned keys is stored into the variable pointed to by
.IR cnt .

The \fIares_dns_rr_key_datatype(3)\fP function retrieves the associated datatype
for an RR parameter specified by
.IR key .

The \fIares_dns_rr_key_to_rec_type(3)\fP function dereferences the provided RR
parameter specified by
.IR key
to the DNS Record Type it belongs.

The \fIares_dns_opt_get_datatype(3)\fP function is used in association with
\fIares_dns_rr_set_opt(3)\fP and \fIares_dns_rr_get_opt(3)\fP to retrieve the
datatype of an option record contained within an RR as specified in
.IR key
if it is known.  The raw option record identifier is provided by
.IR opt .

The \fIares_dns_opt_get_name(3)\fP function is used in association with
\fIares_dns_rr_set_opt(3)\fP and \fIares_dns_rr_get_opt(3)\fP to retrieve human
readable parameter name of an option record contained within an RR as specified
in
.IR key
if it is known.  The raw option record identifier is provided by
.IR opt .

.SH RETURN VALUES
\fIares_dns_rec_type_tostr(3)\fP, \fIares_dns_class_tostr(3)\fP,
\fIares_dns_opcode_tostr(3)\fP, \fIares_dns_rr_key_tostr(3)\fP,
\fIares_dns_section_tostr(3)\fP, \fIares_dns_rcode_tostr(3)\fP, and
\fIares_dns_opt_get_name(3)\fP all return a human printable ASCII string, or
NULL on error.

\fIares_dns_class_fromstr(3)\fP and \fIares_dns_rec_type_fromstr(3)\fP return
.B ARES_TRUE
on successful conversion, otherwise
.B ARES_FALSE.

\fIares_dns_rr_get_keys(3)\fP returns an array of keys or NULL on failure.

\fIares_dns_rr_key_datatype(3)\fP, \fIares_dns_rr_key_to_rec_type(3)\fP, and
\fIares_dns_opt_get_datatype(3)\fP return their respective integer values, or
0 on failure.

.SH AVAILABILITY
These functions were first introduced in c-ares version 1.22.0.
.SH SEE ALSO
.BR ares_dns_record (3),
.BR ares_dns_rr (3),
.BR ares_init (3)