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A C library for asynchronous DNS requests (grpc依赖)
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c-ares/docs/ares_set_servers.3

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Avoid buffer overflow in RC4 loop comparison (#336) The rc4 function iterates over a buffer of size buffer_len who's maximum value is INT_MAX with a counter of type short that is not guaranteed to have maximum size INT_MAX. In circumstances where short is narrower than int and where buffer_len is larger than the maximum value of a short, it may be possible to loop infinitely as counter will overflow and never be greater than or equal to buffer_len. The solution is to make the comparison be between types of equal width. This commit defines counter as an int. Fix By: Fionn Fitzmaurice (@fionn)
4 years ago
.\"
.\" Copyright 2010 by Ben Greear <greearb@candelatech.com>
.\"
.\" Permission to use, copy, modify, and distribute this
.\" software and its documentation for any purpose and without
.\" fee is hereby granted, provided that the above copyright
.\" notice appear in all copies and that both that copyright
.\" notice and this permission notice appear in supporting
.\" documentation, and that the name of M.I.T. not be used in
.\" advertising or publicity pertaining to distribution of the
.\" software without specific, written prior permission.
.\" M.I.T. makes no representations about the suitability of
.\" this software for any purpose. It is provided "as is"
.\" without express or implied warranty.
.\"
provide SPDX identifiers and a REUSE CI job to verify All files have their licence and copyright information clearly identifiable. If not in the file header, they are set separately in .reuse/dep5. All used license texts are provided in LICENSES/
1 year ago
.\" SPDX-License-Identifier: MIT
.\"
Avoid buffer overflow in RC4 loop comparison (#336) The rc4 function iterates over a buffer of size buffer_len who's maximum value is INT_MAX with a counter of type short that is not guaranteed to have maximum size INT_MAX. In circumstances where short is narrower than int and where buffer_len is larger than the maximum value of a short, it may be possible to loop infinitely as counter will overflow and never be greater than or equal to buffer_len. The solution is to make the comparison be between types of equal width. This commit defines counter as an int. Fix By: Fionn Fitzmaurice (@fionn)
4 years ago
.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
tag some functions as deprecated in docs
12 months ago
for an ares channel. (deprecated)
Avoid buffer overflow in RC4 loop comparison (#336) The rc4 function iterates over a buffer of size buffer_len who's maximum value is INT_MAX with a counter of type short that is not guaranteed to have maximum size INT_MAX. In circumstances where short is narrower than int and where buffer_len is larger than the maximum value of a short, it may be possible to loop infinitely as counter will overflow and never be greater than or equal to buffer_len. The solution is to make the comparison be between types of equal width. This commit defines counter as an int. Fix By: Fionn Fitzmaurice (@fionn)
4 years ago
.SH SYNOPSIS
.nf
docs: reformat/cleanup man pages SYNOPSIS sections (#494) To make them render "nicer" in both terminals and on the website. - Removes the bold - Removes .PP lines - Indents them more like proper code style Fix By: Daniel Stenberg (@bagder)
2 years ago
#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,
Mark a couple of parameters as const in the public API
1 year ago
const struct ares_addr_node *\fIservers\fP)
docs: reformat/cleanup man pages SYNOPSIS sections (#494) To make them render "nicer" in both terminals and on the website. - Removes the bold - Removes .PP lines - Indents them more like proper code style Fix By: Daniel Stenberg (@bagder)
2 years ago
`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,
Mark a couple of parameters as const in the public API
1 year ago
const struct ares_addr_port_node *\fIservers\fP)
Avoid buffer overflow in RC4 loop comparison (#336) The rc4 function iterates over a buffer of size buffer_len who's maximum value is INT_MAX with a counter of type short that is not guaranteed to have maximum size INT_MAX. In circumstances where short is narrower than int and where buffer_len is larger than the maximum value of a short, it may be possible to loop infinitely as counter will overflow and never be greater than or equal to buffer_len. The solution is to make the comparison be between types of equal width. This commit defines counter as an int. Fix By: Fionn Fitzmaurice (@fionn)
4 years ago
.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
ares_set_servers_*() should allow an empty server list For historic reasons, we have users depending on ares_set_servers_*() to return ARES_SUCCESS when passing no servers and actually *clear* the server list. It appears they do this for test cases to simulate DNS unavailable or similar. Presumably they could achieve the same effect in other ways (point to localhost on a port that isn't in use). But it seems like this might be wide-spread enough to cause headaches so we just will document and test for this behavior, clearly it hasn't caused "issues" for anyone with the old behavior. See: https://github.com/nodejs/node/pull/50800 Fix By: Brad House (@bradh352)
1 year ago
The \fBares_set_servers_ports(3)\fP function also allows the specification of UDP and
Avoid buffer overflow in RC4 loop comparison (#336) The rc4 function iterates over a buffer of size buffer_len who's maximum value is INT_MAX with a counter of type short that is not guaranteed to have maximum size INT_MAX. In circumstances where short is narrower than int and where buffer_len is larger than the maximum value of a short, it may be possible to loop infinitely as counter will overflow and never be greater than or equal to buffer_len. The solution is to make the comparison be between types of equal width. This commit defines counter as an int. Fix By: Fionn Fitzmaurice (@fionn)
4 years ago
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
ares_set_servers_*() should allow an empty server list For historic reasons, we have users depending on ares_set_servers_*() to return ARES_SUCCESS when passing no servers and actually *clear* the server list. It appears they do this for test cases to simulate DNS unavailable or similar. Presumably they could achieve the same effect in other ways (point to localhost on a port that isn't in use). But it seems like this might be wide-spread enough to cause headaches so we just will document and test for this behavior, clearly it hasn't caused "issues" for anyone with the old behavior. See: https://github.com/nodejs/node/pull/50800 Fix By: Brad House (@bradh352)
1 year ago
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.
Avoid buffer overflow in RC4 loop comparison (#336) The rc4 function iterates over a buffer of size buffer_len who's maximum value is INT_MAX with a counter of type short that is not guaranteed to have maximum size INT_MAX. In circumstances where short is narrower than int and where buffer_len is larger than the maximum value of a short, it may be possible to loop infinitely as counter will overflow and never be greater than or equal to buffer_len. The solution is to make the comparison be between types of equal width. This commit defines counter as an int. Fix By: Fionn Fitzmaurice (@fionn)
4 years ago
.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.
docs: document setting servers can be done live
1 year ago
.PP
As of v1.22.0 this function can
be called on an active channel with running queries, previously it would return
ARES_ENOTIMP.
Avoid buffer overflow in RC4 loop comparison (#336) The rc4 function iterates over a buffer of size buffer_len who's maximum value is INT_MAX with a counter of type short that is not guaranteed to have maximum size INT_MAX. In circumstances where short is narrower than int and where buffer_len is larger than the maximum value of a short, it may be possible to loop infinitely as counter will overflow and never be greater than or equal to buffer_len. The solution is to make the comparison be between types of equal width. This commit defines counter as an int. Fix By: Fionn Fitzmaurice (@fionn)
4 years ago
.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),
docs: provide better man page references When referring to another c-ares function use \fI function(3) \fP to let the webpage rendering find and cross-link them appropriately. SEE ALSO references should be ".BR name (3),", with a space before the open parenthesis. This helps the manpage to HTML renderer. Closes #565
1 year ago
.BR ares_dup (3)
Support ipv6 link-local servers and %iface syntax (#646) Some environments may send router advertisements on a link setting their link-local (fe80::/10) address as a valid DNS server to the remote system. This will cause a DNS entry to be created like `fe80::1%iface`, since all link-local network interfaces are technically part of the same /10 subnet, it must be told what interface to send packets through explicitly if there are multiple physical interfaces. This PR adds support for the %iface modifier when setting DNS servers via `/etc/resolv.conf` as well as via `ares_set_servers_csv()`. For MacOS and iOS it is assumed that libresolve will set the `sin6_scope_id` and should be supported, but my test systems don't seem to read the Router Advertisement for RDNSS link-local. Specifying the link-local dns server on MacOS via adig has been tested and confirmed working. For Windows, this is similar to MacOS in that the system doesn't seem to honor the RDNSS RA, but specifying manually has been tested to work. At this point, Android support does not exist. Fixes Bug #462 Supersedes PR #463 Fix By: Brad House (@bradh352) and Serhii Purik (@sergvpurik)
12 months ago
tag some functions as deprecated in docs
12 months ago
.SH NOTES
Support ipv6 link-local servers and %iface syntax (#646) Some environments may send router advertisements on a link setting their link-local (fe80::/10) address as a valid DNS server to the remote system. This will cause a DNS entry to be created like `fe80::1%iface`, since all link-local network interfaces are technically part of the same /10 subnet, it must be told what interface to send packets through explicitly if there are multiple physical interfaces. This PR adds support for the %iface modifier when setting DNS servers via `/etc/resolv.conf` as well as via `ares_set_servers_csv()`. For MacOS and iOS it is assumed that libresolve will set the `sin6_scope_id` and should be supported, but my test systems don't seem to read the Router Advertisement for RDNSS link-local. Specifying the link-local dns server on MacOS via adig has been tested and confirmed working. For Windows, this is similar to MacOS in that the system doesn't seem to honor the RDNSS RA, but specifying manually has been tested to work. At this point, Android support does not exist. Fixes Bug #462 Supersedes PR #463 Fix By: Brad House (@bradh352) and Serhii Purik (@sergvpurik)
12 months ago
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.
Avoid buffer overflow in RC4 loop comparison (#336) The rc4 function iterates over a buffer of size buffer_len who's maximum value is INT_MAX with a counter of type short that is not guaranteed to have maximum size INT_MAX. In circumstances where short is narrower than int and where buffer_len is larger than the maximum value of a short, it may be possible to loop infinitely as counter will overflow and never be greater than or equal to buffer_len. The solution is to make the comparison be between types of equal width. This commit defines counter as an int. Fix By: Fionn Fitzmaurice (@fionn)
4 years ago
.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.
.SH AUTHOR
Implementation of this function and associated library internals are based
on code, comments and feedback provided in November and December of 2008 by
Daniel Stenberg, Gregor Jasny, Phil Blundell and Yang Tse, December 2009
by Cedric Bail, February 2010 by Jakub Hrozek. On March 2010 Yang Tse
shuffled all the bits and this function popped out.
.br
Copyright 1998 by the Massachusetts Institute of Technology.
.br
Copyright (C) 2008-2010 by Daniel Stenberg