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.\"
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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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`ares_channel` -> `ares_channel_t *`: don't bury the pointer (#595)
`ares_channel` is defined as `typedef struct ares_channeldata *ares_channel;`. The problem with this, is it embeds the pointer into the typedef, which means an `ares_channel` can never be declared as `const` as if you write `const ares_channel channel`, that expands to `struct ares_channeldata * const ares_channel` and not `const struct ares_channeldata *channel`.
We will now typedef `ares_channel_t` as `typedef struct ares_channeldata ares_channel_t;`, so if you write `const ares_channel_t *channel`, it properly expands to `const struct ares_channeldata *channel`.
We are maintaining the old typedef for API compatibility with existing integrations, and due to typedef expansion this should not even cause any compiler warnings for existing code. There are no ABI implications with this change. I could be convinced to keep existing public functions as `ares_channel` if a sufficient argument exists, but internally we really need make this change for modern best practices.
This change will allow us to internally use `const ares_channel_t *` where appropriate. Whether or not we decide to change any public interfaces to use `const` may require further discussion on if there might be ABI implications (I don't think so, but I'm also not 100% sure what a compiler internally does with `const` when emitting machine code ... I think more likely ABI implications would occur going the opposite direction).
FYI, This PR was done via a combination of sed and clang-format, the only manual code change was the addition of the new typedef, and a couple doc fixes :)
Fix By: Brad House (@bradh352)
1 year ago
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int ares_set_servers_csv(ares_channel_t *\fIchannel\fP, const char* \fIservers\fP)
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`ares_channel` -> `ares_channel_t *`: don't bury the pointer (#595)
`ares_channel` is defined as `typedef struct ares_channeldata *ares_channel;`. The problem with this, is it embeds the pointer into the typedef, which means an `ares_channel` can never be declared as `const` as if you write `const ares_channel channel`, that expands to `struct ares_channeldata * const ares_channel` and not `const struct ares_channeldata *channel`.
We will now typedef `ares_channel_t` as `typedef struct ares_channeldata ares_channel_t;`, so if you write `const ares_channel_t *channel`, it properly expands to `const struct ares_channeldata *channel`.
We are maintaining the old typedef for API compatibility with existing integrations, and due to typedef expansion this should not even cause any compiler warnings for existing code. There are no ABI implications with this change. I could be convinced to keep existing public functions as `ares_channel` if a sufficient argument exists, but internally we really need make this change for modern best practices.
This change will allow us to internally use `const ares_channel_t *` where appropriate. Whether or not we decide to change any public interfaces to use `const` may require further discussion on if there might be ABI implications (I don't think so, but I'm also not 100% sure what a compiler internally does with `const` when emitting machine code ... I think more likely ABI implications would occur going the opposite direction).
FYI, This PR was done via a combination of sed and clang-format, the only manual code change was the addition of the new typedef, and a couple doc fixes :)
Fix By: Brad House (@bradh352)
1 year ago
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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. Each server
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entry may contain these forms:
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ip[:port][%iface]
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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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For example:
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192.168.1.100,192.168.1.101:53,[1:2:3::4]:53,[fe80::1]:53%eth0
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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 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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