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A C library for asynchronous DNS requests (grpc依赖)
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c-ares/docs/ares_getnameinfo.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 2005 by Dominick Meglio.
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_GETNAMEINFO 3 "1 May 2009"
.SH NAME
ares_getnameinfo \- Address-to-nodename translation in protocol-independent manner
.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_nameinfo_callback)(void *\fIarg\fP, int \fIstatus\fP,
int \fItimeouts\fP, char *\fInode\fP,
char *\fIservice\fP)
`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_getnameinfo(ares_channel_t *\fIchannel\fP, const struct sockaddr *\fIsa\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_socklen_t \fIsalen\fP, int \fIflags\fP,
ares_nameinfo_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_getnameinfo
function is defined for protocol-independent address translation. The function
is a combination of \fIares_gethostbyaddr(3)\fP and \fIgetservbyport(3)\fP. The function will
translate the address either by executing a host query on the name service channel
identified by
.IR channel
or it will attempt to resolve it locally if possible.
The parameters
.I sa
and
.I len
give the address as a sockaddr structure, and
.I flags
gives the options that the function will use. Valid flags are listed below:
.TP 19
.B ARES_NI_NOFQDN
Only the nodename portion of the FQDN is returned for local hosts.
.TP 19
.B ARES_NI_NUMERICHOST
The numeric form of the hostname is returned rather than the name.
.TP 19
.B ARES_NI_NAMEREQD
An error is returned if the hostname cannot be found in the DNS.
.TP 19
.B ARES_NI_NUMERICSERV
The numeric form of the service is returned rather than the name.
.TP 19
.B ARES_NI_TCP
The service name is to be looked up for the TCP protocol.
.TP 19
.B ARES_NI_UDP
The service name is to be looked up for the UDP protocol.
.TP 19
.B ARES_NI_SCTP
The service name is to be looked up for the SCTP protocol.
.TP 19
.B ARES_NI_DCCP
The service name is to be looked up for the DCCP protocol.
.TP 19
.B ARES_NI_NUMERICSCOPE
The numeric form of the scope ID is returned rather than the name.
.TP 19
.B ARES_NI_LOOKUPHOST
A hostname lookup is being requested.
.TP 19
.B ARES_NI_LOOKUPSERVICE
A service name lookup is being requested.
.PP
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
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
When the associated callback is called, it is called with a channel lock so care
must be taken to ensure any processing is minimal to prevent DNS channel stalls.
The callback may be triggered from a different thread than the one which
called \fIares_getnameinfo(3)\fP.
For integrators running their own event loops and not using \fBARES_OPT_EVENT_THREAD\fP,
care needs to be taken to ensure any file descriptor lists are updated immediately
within the eventloop when notified.
Basic Thread Safety (#636) c-ares does not have any concept of thread-safety. It has always been 100% up to the implementor to ensure they never call c-ares from more than one thread at a time. This patch adds basic thread-safety support, which can be disabled at compile time if not desired. It uses a single recursive mutex per channel, which should be extremely quick when uncontested so overhead should be minimal. Fixes Bug: #610 Also sets the stage to implement #611 Fix By: Brad House (@bradh352)
1 year ago
.PP
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 callback argument
.I arg
is copied from the
.B ares_getnameinfo
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.
.TP 19
.B ARES_EBADFLAGS
The
.I flags
parameter contains an illegal value.
.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 node
contains a string representing the hostname (assuming
.B ARES_NI_LOOKUPHOST
was specified). Additionally,
.I service
contains a string representing the service name (assuming
.B ARES_NI_LOOKUPSERVICE
was specified).
If the query did not complete successfully, or one of the values
was not requested,
.I node
or
.I service
will be
.BR NULL .
.SH SEE ALSO
.BR ares_process (3),
.SH AUTHOR
Dominick Meglio
.br
Copyright 2005 by Dominick Meglio.