mirror of https://github.com/nodejs/node.git
164 lines
5.2 KiB
Groff
164 lines
5.2 KiB
Groff
.\"
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.\" Copyright 2010 by Ben Greear <greearb@candelatech.com>
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.\" SPDX-License-Identifier: MIT
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.\"
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.TH ARES_SET_SERVERS_CSV 3 "5 Dec 2023"
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.SH NAME
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ares_set_servers_csv, ares_set_servers_ports_csv, ares_get_servers_csv \- Set
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or Get a list of DNS servers used for queries.
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.SH SYNOPSIS
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.nf
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#include <ares.h>
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int ares_set_servers_csv(ares_channel_t *\fIchannel\fP, const char* \fIservers\fP)
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int ares_set_servers_ports_csv(ares_channel_t *\fIchannel\fP, const char* \fIservers\fP)
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char *ares_get_servers_csv(const ares_channel_t *\fIchannel\fP)
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.fi
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.SH DESCRIPTION
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The \fBares_set_servers_csv\fP and \fBares_set_servers_ports_csv\fP functions set
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the list of DNS servers that c-ares will query. As of v1.22.0 this function can
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be called on an active channel with running queries, previously it would return
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ARES_ENOTIMP.
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Though not recommended, passing NULL for servers will clear all configured
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servers and make an inoperable channel, this may be advantageous for test
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simulation but unlikely to be useful in production.
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The \fBares_get_servers_csv\fP retrieves the list of servers in comma delimited
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format.
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The input and output format is a comma separated list of servers. Two formats
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are available, the typical \fBresolv.conf(5)\fP \fInameserver\fP format, as
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well as a \fIURI\fP format. Both formats can be used at the same time in the
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provided CSV string.
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The \fInameserver\fP format is:
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.nf
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ip[:port][%iface]
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.fi
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.RS 4
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The \fBip\fP may be encapsulated in square brackets ([ ]), and must be if
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using ipv6 and also specifying a port.
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The \fBport\fP is optional, and will default to 53 or the value specified in
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\fBares_init_options(3)\fP.
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The \fBiface\fP is specific to IPv6 link-local servers (fe80::/10) and should
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not otherwise be used.
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.RE
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\fInameserver\fP format examples:
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.nf
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192.168.1.100
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192.168.1.101:53
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[1:2:3::4]:53
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[fe80::1]:53%eth0
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.fi
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.PP
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The \fIURI\fP format is is made up of these defined schemes:
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.RS 4
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\fIdns://\fP - Normal DNS server (UDP + TCP). We need to be careful not to
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conflict with query params defined in RFC4501 since we'd technically be
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extending this URI scheme. Port defaults to 53.
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\fIdns+tls://\fP - DNS over TLS. Port defaults to 853.
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\fIdns+https://\fP - DNS over HTTPS. Port defaults to 443.
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.RE
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.PP
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Query parameters are defined as below. Additional parameters may be defined
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in the future.
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.RS 4
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\fItcpport\fP - TCP port to use, only for \fIdns://\fP scheme. The port
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specified as part of the authority component of the URI will be used for both
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UDP and TCP by default, this option will override the TCP port.
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\fIipaddr\fP - Only for \fIdns+tls://\fP and \fIdns+https://\fP. If the
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authority component of the URI contains a hostname, this is used to specify the
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ip address of the hostname. If not specified, will need to use a non-secure
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server to perform a DNS lookup to retrieve this information. It is always
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recommended to have both the ip address and fully qualified domain name
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specified.
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\fIhostname\fP - Only for \fIdns+tls://\fP and \fIdns+https://\fP. If the
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authority component of the URI contains an ip address, this is used to specify
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the fully qualified domain name of the server. If not specified, will need to
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use a non-secure server to perform a DNS reverse lookup to retrieve this
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information. It is always recommended to have both the ip address and fully
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qualified domain name specified.
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\fIdomain\fP - If specified, this server is a domain-specific server. Any
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queries for this domain will be routed to this server. Multiple servers may be
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tagged with the same domain.
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.RE
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\fIURI\fP format Examples:
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.nf
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dns://8.8.8.8
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dns://[2001:4860:4860::8888]
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dns://[fe80::b542:84df:1719:65e3%en0]
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dns://192.168.1.1:55
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dns://192.168.1.1?tcpport=1153
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dns://10.0.1.1?domain=myvpn.com
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dns+tls://8.8.8.8?hostname=dns.google
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dns+tls://one.one.one.one?ipaddr=1.1.1.1
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.fi
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\fBNOTE\fP: While we are defining the scheme for things like domain-specific
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servers, DNS over TLS and DNS over HTTPS, the underlying implementations for
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those features do not yet exist and therefore will result in errors if they are
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attempted to be used.
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.PP
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As of c-ares 1.24.0, \fBares_set_servers_csv\fP and \fBares_set_servers_ports_csv\fP
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are identical. Prior versions would simply omit ports in \fBares_set_servers_csv\fP
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but due to the addition of link local interface support, this difference was
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removed.
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.SH EXAMPLE
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.nf
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192.168.1.100,[fe80::1]:53%eth0,dns://192.168.1.1?tcpport=1153
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.fi
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.SH RETURN VALUES
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.B ares_set_servers_csv(3)
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and
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.B ares_set_servers_ports_csv(3)
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may return any of the following values:
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.TP 15
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.B ARES_SUCCESS
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The name servers configuration was successfully initialized.
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.TP 15
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.B ARES_ENOMEM
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The process's available memory was exhausted.
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.TP 15
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.B ARES_ENODATA
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The channel data identified by
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.IR channel
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was invalid.
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.TP 15
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.B ARES_ENOTINITIALIZED
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c-ares library initialization not yet performed.
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.PP
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.B ares_get_servers_csv(3)
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returns a string representing the servers configured which must be freed with
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\fBares_free_string(3)\fP. If it returns NULL, this is an out of memory condition.
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.SH SEE ALSO
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.BR ares_set_servers (3)
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.SH AVAILABILITY
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\fBares_set_servers_csv\fP was added in c-ares 1.7.2
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\fBares_set_servers_ports_csv\fP was added in c-ares 1.11.0.
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\fBares_get_servers_csv\fP was added in c-ares 1.24.0.
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\fIURI\fP support was added in c-ares 1.34.0.
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