A C library for asynchronous DNS requests (grpc依赖)
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.\"
.\" Copyright 2010 by Ben Greear <greearb@candelatech.com>
.\" SPDX-License-Identifier: MIT
.\"
.TH ARES_SET_SERVERS 3 "5 March 2010"
.SH NAME
`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
ares_set_servers, ares_set_servers_ports \- Initialize name server configuration
for an ares channel. (deprecated)
.SH SYNOPSIS
.nf
#include <ares.h>
`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
int ares_set_servers(ares_channel_t *\fIchannel\fP,
const struct ares_addr_node *\fIservers\fP)
`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
int ares_set_servers_ports(ares_channel_t *\fIchannel\fP,
const struct ares_addr_port_node *\fIservers\fP)
.fi
.SH DESCRIPTION
The \fBares_set_servers(3)\fP function initializes name servers configuration
for the channel data identified by
.IR channel ,
from a
.IR servers
pointer to a linked list of ares_addr_node structs holding name servers
address data.
.PP
The name server linked list pointer argument may be the result of a previous
call to \fBares_get_servers(3)\fP or a linked list of \fBares_addr_node\fP structs
set up by other means.
.PP
The \fBares_set_servers_ports(3)\fP function also allows the specification of UDP and
TCP ports to be used for communication on a per-server basis. The provided
linked list argument may be the result of a previous call to
\fBares_get_servers_ports(3)\fP or a linked list of \fBares_addr_port_node\fP structs
set up by other means.
.PP
This function replaces any potentially previously configured name servers
with the ones given in the linked list. So, in order to configure a channel
with more than one name server all the desired ones must be specified in a
single list. Though not recommended, passing NULL will clear all configured
servers and make an inoperable channel, this may be advantageous for test
simulation but unlikely to be useful in production.
.PP
The function does not take ownership of the linked list argument.
The caller is responsible for freeing the linked list when no longer needed.
.PP
This function is capable of handling IPv4 and IPv6 name server
addresses simultaneously, rendering \fBares_init_options(3)\fP with
optmask \fBARES_OPT_SERVERS\fP functionally obsolete except for
IPv4-only name server usage.
.PP
As of v1.22.0 this function can
be called on an active channel with running queries, previously it would return
ARES_ENOTIMP.
.SH RETURN VALUES
.B ares_set_servers(3)
may return any of the following values:
.TP 15
.B ARES_SUCCESS
The name servers configuration was successfully initialized.
.TP 15
.B ARES_ENOMEM
The process's available memory was exhausted.
.TP 15
.B ARES_ENODATA
The channel data identified by
.IR channel
was invalid.
.TP 15
.B ARES_ENOTINITIALIZED
c-ares library initialization not yet performed.
.SH SEE ALSO
.BR ares_set_servers_csv (3),
.BR ares_get_servers (3),
.BR ares_init_options (3),
.BR ares_dup (3)
.SH NOTES
Deprecated functions as of c-ares 1.24.0 due to inability to set all available
server options. Use \fBares_set_servers_csv(3)\fP.
.SH AVAILABILITY
\fBares_set_servers(3)\fP was added in c-ares 1.7.1;
\fBares_set_servers_ports(3)\fP was added in c-ares 1.11.0.