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A C library for asynchronous DNS requests (grpc依赖)
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c-ares/docs/ares_gethostbyaddr.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.
.\"
.\" 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/
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_GETHOSTBYADDR 3 "24 July 1998"
.SH NAME
ares_gethostbyaddr \- Initiate a host query by address
.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>
typedef void (*ares_host_callback)(void *\fIarg\fP, int \fIstatus\fP,
int \fItimeouts\fP,
struct hostent *\fIhostent\fP)
void ares_gethostbyaddr(ares_channel \fIchannel\fP, const void *\fIaddr\fP,
int \fIaddrlen\fP, int \fIfamily\fP,
ares_host_callback \fIcallback\fP, void *\fIarg\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
.B ares_gethostbyaddr
function initiates a host query by address on the name service channel
identified by
.IR channel .
The parameters
.I addr
and
.I addrlen
give the address as a series of bytes, and
.I family
gives the type of address. When the query is complete or has failed, the ares
library will invoke \fIcallback\fP. Completion or failure of the query may
happen immediately, or may happen during a later call to
\fIares_process(3)\fP, \fIares_destroy(3)\fP or \fIares_cancel(3)\fP.
.PP
The callback argument
.I arg
is copied from the
.B ares_gethostbyaddr
argument
.IR arg .
The callback argument
.I status
indicates whether the query succeeded and, if not, how it failed. It
may have any of the following values:
.TP 19
.B ARES_SUCCESS
The host lookup completed successfully.
.TP 19
.B ARES_ENOTIMP
The ares library does not know how to look up addresses of type
.IR family .
.TP 19
.B ARES_ENOTFOUND
The address
.I addr
was not found.
.TP 19
.B ARES_ENOMEM
Memory was exhausted.
.TP 19
.B ARES_ECANCELLED
The query was cancelled.
.TP 19
.B ARES_EDESTRUCTION
The name service channel
.I channel
is being destroyed; the query will not be completed.
.PP
The callback argument
.I timeouts
reports how many times a query timed out during the execution of the
given request.
.PP
On successful completion of the query, the callback argument
.I hostent
points to a
.B struct hostent
containing the name of the host returned by the query. The callback
need not and should not attempt to free the memory pointed to by
.IR hostent ;
the ares library will free it when the callback returns. If the query
did not complete successfully,
.I hostent
will be
.BR NULL .
.SH SEE ALSO
.BR ares_process (3),
.BR ares_gethostbyname (3)
.SH AUTHOR
Greg Hudson, MIT Information Systems
.br
Copyright 1998 by the Massachusetts Institute of Technology.