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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/
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_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>
const is fine on ares__channel_[un]lock (#758) at https://github.com/c-ares/c-ares/pull/601#issuecomment-1801935063 you chose not to scatter `const` on the public interface because of the plan - now realised - to add threading to c-ares, and in the expectation that even read operations would need to lock the mutex. But the threading implementation has a _pointer_ to a mutex inside the ares channel and as I understand it, that means that it is just fine to mark `ares__channel_lock` (and `ares__channel_unlock`) as taking a `const` channel. It is the pointed-to mutex that is not constant, but C does not propagate `const`-ness through pointers. This PR sprinkles const where appropriate on public interfaces. Fix By: David Hotham (@dimbleby)
6 months ago
int ares_fds(const 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)
10 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)
10 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)
10 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)
10 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)