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c-ares/docs/ares_set_socket_functions.3

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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
.\" Copyright (C) Daniel Stenberg
.\" 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_SOCKET_FUNCTIONS 3 "13 Dec 2016"
.SH NAME
ares_set_socket_functions \- Set socket io callbacks
.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>
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
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
struct ares_socket_functions {
ares_socket_t (*\fIasocket\fP)(int, int, int, void *);
int (*\fIaclose\fP)(ares_socket_t, void *);
int (*\fIaconnect\fP)(ares_socket_t, const struct sockaddr *, ares_socklen_t, void *);
ares_ssize_t (*\fIarecvfrom\fP)(ares_socket_t, void *, size_t, int,
struct sockaddr *, ares_socklen_t *, void *);
ares_ssize_t (*\fIasendv\fP)(ares_socket_t, const struct iovec *, int, void *);
};
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
`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
void ares_set_socket_functions(ares_channel_t *\fIchannel\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
const struct ares_socket_functions * \fIfunctions\fP,
void *\fIuser_data\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
.PP
This function sets a set of callback \fIfunctions\fP in the given ares channel handle.
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
Cannot be used when \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
These callback functions will be invoked to create/destroy socket objects and perform
io, instead of the normal system calls. A client application can override normal network
Fix for TCP back to back queries (#552) As per #266, TCP queries are basically broken. If we get a partial reply, things just don't work, but unlike UDP, TCP may get fragmented and we need to properly handle that. I've started creating a basic parser/buffer framework for c-ares for memory safety reasons, but it also helps for things like this where we shouldn't be manually tracking positions and fetching only a couple of bytes at a time from a socket. This parser/buffer will be expanded and used more in the future. This also resolves #206 by allowing NULL to be specified for some socket callbacks so they will auto-route to the built-in c-ares functions. Fixes: #206, #266 Fix By: Brad House (@bradh352)
1 year ago
operation fully through this functionality, and provide its own transport layer. You
can choose to only implement some of the socket functions, and provide NULL to any
others and c-ares will use its built-in system functions in that case.
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
All callback functions are expected to operate like their system equivalents, and to
set
.BR errno(3)
to an appropriate error code on failure. C-ares also expects all io functions to behave
asynchronously, i.e. as if the socket object has been set to non-blocking mode. Thus
read/write calls (for TCP connections) are expected to often generate
.BR EAGAIN
or
.BR EWOULDBLOCK.
.PP
The \fIuser_data\fP value is provided to each callback function invocation to serve as
context.
.PP
The
.B ares_socket_functions
must provide the following callbacks:
.TP 18
.B \fIasocket\fP
.B ares_socket_t(*)(int \fIdomain\fP, int \fItype\fP, int \fIprotocol\fP, void * \fIuser_data\fP)
.br
Creates an endpoint for communication and returns a descriptor. \fIdomain\fP, \fItype\fP, and \fIprotocol\fP
each correspond to the parameters of
.BR socket(2).
Returns ahandle to the newly created socket, or -1 on error.
.TP 18
.B \fIaclose\fP
.B int(*)(ares_socket_t \fIfd\fP, void * \fIuser_data\fP)
.br
Closes the socket endpoint indicated by \fIfd\fP. See
.BR close(2)
.TP 18
.B \fIaconnect\fP
.B int(*)(ares_socket_t \fIfd\fP, const struct sockaddr * \fIaddr\fP, ares_socklen_t \fIaddr_len\fP, void * \fIuser_data\fP)
.br
Initiate a connection to the address indicated by \fIaddr\fP on a socket. See
.BR connect(2)
.TP 18
.B \fIarecvfrom\fP
.B ares_ssize_t(*)(ares_socket_t \fIfd\fP, void * \fIbuffer\fP, size_t \fIbuf_size\fP, int \fIflags\fP, struct sockaddr * \fIaddr\fP, ares_socklen_t * \fIaddr_len\fP, void * \fIuser_data\fP)
.br
Receives data from remote socket endpoint, if available. If the \fIaddr\fP parameter is not NULL and the connection protocol provides the source address, the callback should fill this in. See
.BR recvfrom(2)
.TP 18
.B \fIasendv\fP
.B ares_ssize_t(*)(ares_socket_t \fIfd\fP, const struct iovec * \fIdata\fP, int \fIlen\fP, void * \fIuser_data\fP)
.br
Send data, as provided by the iovec array \fIdata\fP, to the socket endpoint. See
.BR writev(2),
.PP
The
.B ares_socket_functions
struct provided is not copied but directly referenced,
and must thus remain valid through out the channels and any created socket's lifetime.
.SH AVAILABILITY
Added in c-ares 1.13.0
.SH SEE ALSO
.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 socket (2),
.BR close (2),
.BR connect (2),
.BR recv (2),
.BR recvfrom (2),
.BR send (2),
.BR writev (2)