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c-ares/docs/ares_fds.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 1998 by the Massachusetts Institute of Technology.
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/
2 years 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_FDS 3 "23 July 1998"
.SH NAME
Event Subsystem: No longer require integrators to have their own (#696) This PR implements an event thread to process all events on file descriptors registered by c-ares. Prior to this feature, integrators were required to understand the internals of c-ares and how to monitor file descriptors and timeouts and process events. Implements OS-specific efficient polling such as epoll(), kqueue(), or IOCP, and falls back to poll() or select() if otherwise unsupported. At this point, it depends on basic threading primitives such as pthreads or windows threads. If enabled via the ARES_OPT_EVENT_THREAD option passed to ares_init_options(), then socket callbacks cannot be used. Fixes Bug: #611 Fix By: Brad House (@bradh352)
10 months ago
ares_fds \- return file descriptors to select on (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
#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_fds(ares_channel_t *\fIchannel\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
fd_set *\fIread_fds\fP,
man ares_fds(3): mark as deprecated and add explanation (#691) ares_fds(3) is not safe to use, mark as deprecated. Fixes Issue: #687 Fix By: Brad House (@bradh352)
11 months ago
fd_set *\fIwrite_fds\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
man ares_fds(3): mark as deprecated and add explanation (#691) ares_fds(3) is not safe to use, mark as deprecated. Fixes Issue: #687 Fix By: Brad House (@bradh352)
11 months ago
See the \fBNOTES\fP section on issues with this function and alternatives.
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
The \fBares_fds(3)\fP function retrieves the set of file descriptors which the
man ares_fds(3): mark as deprecated and add explanation (#691) ares_fds(3) is not safe to use, mark as deprecated. Fixes Issue: #687 Fix By: Brad House (@bradh352)
11 months ago
calling application should \fBselect(2)\fP on for reading and writing for the
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
processing of name service queries pending on the name service channel
Event Subsystem: No longer require integrators to have their own (#696) This PR implements an event thread to process all events on file descriptors registered by c-ares. Prior to this feature, integrators were required to understand the internals of c-ares and how to monitor file descriptors and timeouts and process events. Implements OS-specific efficient polling such as epoll(), kqueue(), or IOCP, and falls back to poll() or select() if otherwise unsupported. At this point, it depends on basic threading primitives such as pthreads or windows threads. If enabled via the ARES_OPT_EVENT_THREAD option passed to ares_init_options(), then socket callbacks cannot be used. Fixes Bug: #611 Fix By: Brad House (@bradh352)
10 months ago
identified by \fIchannel\fP. Should not be used with \fBARES_OPT_EVENT_THREAD\fP
is passed to \fIares_init_options(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
File descriptors will be set in the file descriptor sets pointed to by
\fIread_fds\fP and \fIwrite_fds\fP as appropriate. File descriptors already
set in \fIread_fds\fP and \fIwrite_fds\fP will remain set; initialization of
the file descriptor sets (using \fBFD_ZERO\fP) is the responsibility of the
caller.
.SH RETURN VALUES
\fBares_fds(3)\fP returns a value that is one greater than the number of the
highest socket set in either \fIread_fds\fP or \fIwrite_fds\fP. If no queries
are active, \fBares_fds(3)\fP returns 0.
man ares_fds(3): mark as deprecated and add explanation (#691) ares_fds(3) is not safe to use, mark as deprecated. Fixes Issue: #687 Fix By: Brad House (@bradh352)
11 months ago
.SH NOTES
The \fBselect(2)\fP call which takes the \fIfd_set\fP parameter has significant
limitations which can impact modern systems. The limitations can vary from
system to system, but in general if the file descriptor value itself is greater
than 1024 (not the count but the actual value), this can lead to
\fBares_fds(3)\fP writing out of bounds which will cause a system crash. In
modern networking clients, it is not unusual to have file descriptor values
above 1024, especially when a library is pulled in as a dependency into a larger
project.
c-ares does not attempt to detect this condition to prevent crashes due to both
implementation-defined behavior in the OS as well as integrator-controllable
tunables which may impact the limits.
Event Subsystem: No longer require integrators to have their own (#696) This PR implements an event thread to process all events on file descriptors registered by c-ares. Prior to this feature, integrators were required to understand the internals of c-ares and how to monitor file descriptors and timeouts and process events. Implements OS-specific efficient polling such as epoll(), kqueue(), or IOCP, and falls back to poll() or select() if otherwise unsupported. At this point, it depends on basic threading primitives such as pthreads or windows threads. If enabled via the ARES_OPT_EVENT_THREAD option passed to ares_init_options(), then socket callbacks cannot be used. Fixes Bug: #611 Fix By: Brad House (@bradh352)
10 months ago
It is recommended to use \fBARES_OPT_EVENT_THREAD\fP passed to
\fIares_init_options(3)\fP, or socket state callbacks
(\fBARES_OPT_SOCK_STATE_CB\fP) registered via \fIares_init_options(3)\fP and use
more modern methods to check for socket readable/writable state such as
\fIpoll(2)\fP, \fIepoll(2)\fP, or \fIkqueue(2)\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 SEE ALSO
Event Subsystem: No longer require integrators to have their own (#696) This PR implements an event thread to process all events on file descriptors registered by c-ares. Prior to this feature, integrators were required to understand the internals of c-ares and how to monitor file descriptors and timeouts and process events. Implements OS-specific efficient polling such as epoll(), kqueue(), or IOCP, and falls back to poll() or select() if otherwise unsupported. At this point, it depends on basic threading primitives such as pthreads or windows threads. If enabled via the ARES_OPT_EVENT_THREAD option passed to ares_init_options(), then socket callbacks cannot be used. Fixes Bug: #611 Fix By: Brad House (@bradh352)
10 months ago
.BR ares_init_options (3),
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
.BR ares_timeout (3),
.BR ares_process (3)
.SH AUTHOR
Greg Hudson, MIT Information Systems
.br
Copyright 1998 by the Massachusetts Institute of Technology.