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put the evdns documentation into the header file. pathetic start of evdns manpage. a little bit

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more testing and debug output for the DNS regression test.   add a BSD copyright to evdns.h with
appropriate explanations.


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Niels Provos 2006-10-09 00:48:42 +00:00
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.\"
.\" Copyright (c) 2006 Niels Provos <provos@citi.umich.edu>
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\"
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 3. The name of the author may not be used to endorse or promote products
.\" derived from this software without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
.\" INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
.\" AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
.\" THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
.\" EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
.\" PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
.\" OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
.\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
.\" OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
.\" ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd October 7, 2006
.Dt EVDNS 3
.Os
.Sh NAME
.Nm evdns_init
.Nm evdns_shutdown
.Nm evdns_err_to_string
.Nm evdns_nameserver_add
.Nm evdns_count_nameservers
.Nm evdns_clear_nameservers_and_suspend
.Nm evdns_resume
.Nm evdns_nameserver_ip_add
.Nm evdns_resolve_ipv4
.Nm evdns_resolve_reverse
.Nm evdns_resolv_conf_parse
.Nm evdns_config_windows_nameservers
.Nm evdns_search_clear
.Nm evdns_search_add
.Nm evdns_search_ndots_set
.Nm evdns_set_log_fn
.Nd asynchronous functions for DNS resolution.
.Sh SYNOPSIS
.Fd #include <sys/time.h>
.Fd #include <event.h>
.Fd #include <evdns.h>
.Ft int
.Fn evdns_init
.Ft void
.Fn evdns_shutdown "int fail_requests"
.Ft "const char *"
.Fn evdns_err_to_string "int err"
.Ft int
.Fn evdns_nameserver_add "unsigned long int address"
.Ft int
.Fn evdns_count_nameservers
.Ft int
.Fn evdns_clear_nameservers_and_suspend
.Ft int
.Fn evdns_resume
.Ft int
.Fn evdns_nameserver_ip_add(const char *ip_as_string);
.Ft int
.Fn evdns_resolve_ipv4 "const char *name" "int flags" "evdns_callback_type callback" "void *ptr"
.Ft int
.Fn evdns_resolve_reverse "struct in_addr *in" "int flags" "evdns_callback_type callback" "void *ptr"
.Ft int
.Fn evdns_resolv_conf_parse "int flags" "const char *"
.Ft void
.Fn evdns_search_clear
.Ft void
.Fn evdns_search_add "const char *domain"
.Ft void
.Fn evdns_search_ndots_set "const int ndots"
.Ft void
.Fn evdns_set_log_fn "evdns_debug_log_fn_type fn"
.Ft int
.Fn evdns_config_windows_nameservers
.Sh DESCRIPTION
Welcome, gentle reader
.Pp
Async DNS lookups are really a whole lot harder than they should be,
mostly stemming from the fact that the libc resolver has never been
very good at them. Before you use this library you should see if libc
can do the job for you with the modern async call getaddrinfo_a
(see http://www.imperialviolet.org/page25.html#e498). Otherwise,
please continue.
.Pp
This code is based on libevent and you must call event_init before
any of the APIs in this file. You must also seed the OpenSSL random
source if you are using OpenSSL for ids (see below).
.Pp
This library is designed to be included and shipped with your source
code. You statically link with it. You should also test for the
existence of strtok_r and define HAVE_STRTOK_R if you have it.
.Pp
The DNS protocol requires a good source of id numbers and these
numbers should be unpredictable for spoofing reasons. There are
three methods for generating them here and you must define exactly
one of them. In increasing order of preference:
.Pp
DNS_USE_GETTIMEOFDAY_FOR_ID:
Using the bottom 16 bits of the usec result from gettimeofday. This
is a pretty poor solution but should work anywhere.
DNS_USE_CPU_CLOCK_FOR_ID:
Using the bottom 16 bits of the nsec result from the CPU's time
counter. This is better, but may not work everywhere. Requires
POSIX realtime support and you'll need to link against -lrt on
glibc systems at least.
DNS_USE_OPENSSL_FOR_ID:
Uses the OpenSSL RAND_bytes call to generate the data. You must
have seeded the pool before making any calls to this library.
.Pp
The library keeps track of the state of nameservers and will avoid
them when they go down. Otherwise it will round robin between them.
.Pp
Quick start guide:
#include "evdns.h"
void callback(int result, char type, int count, int ttl,
void *addresses, void *arg);
evdns_resolv_conf_parse(DNS_OPTIONS_ALL, "/etc/resolv.conf");
evdns_resolve("www.hostname.com", 0, callback, NULL);
.Pp
When the lookup is complete the callback function is called. The
first argument will be one of the DNS_ERR_* defines in evdns.h.
Hopefully it will be DNS_ERR_NONE, in which case type will be
DNS_IPv4_A, count will be the number of IP addresses, ttl is the time
which the data can be cached for (in seconds), addresses will point
to an array of uint32_t's and arg will be whatever you passed to
evdns_resolve.
.Pp
Searching:
.Pp
In order for this library to be a good replacement for glibc's resolver it
supports searching. This involves setting a list of default domains, in
which names will be queried for. The number of dots in the query name
determines the order in which this list is used.
.Pp
Searching appears to be a single lookup from the point of view of the API,
although many DNS queries may be generated from a single call to
evdns_resolve. Searching can also drastically slow down the resolution
of names.
.Pp
To disable searching:
1. Never set it up. If you never call evdns_resolv_conf_parse or
evdns_search_add then no searching will occur.
.Pp
2. If you do call evdns_resolv_conf_parse then don't pass
DNS_OPTION_SEARCH (or DNS_OPTIONS_ALL, which implies it).
.Pp
3. When calling evdns_resolve, pass the DNS_QUERY_NO_SEARCH flag.
.Pp
The order of searches depends on the number of dots in the name. If the
number is greater than the ndots setting then the names is first tried
globally. Otherwise each search domain is appended in turn.
.Pp
The ndots setting can either be set from a resolv.conf, or by calling
evdns_search_ndots_set.
.Pp
For example, with ndots set to 1 (the default) and a search domain list of
["myhome.net"]:
Query: www
Order: www.myhome.net, www.
.Pp
Query: www.abc
Order: www.abc., www.abc.myhome.net
.Pp
API reference:
.Pp
int evdns_nameserver_add(unsigned long int address)
Add a nameserver. The address should be an IP address in
network byte order. The type of address is chosen so that
it matches in_addr.s_addr.
Returns non-zero on error.
.Pp
int evdns_nameserver_ip_add(const char *ip_as_string)
This wraps the above function by parsing a string as an IP
address and adds it as a nameserver.
Returns non-zero on error
.Pp
int evdns_resolve(const char *name, int flags,
evdns_callback_type callback,
void *ptr)
Resolve a name. The name parameter should be a DNS name.
The flags parameter should be 0, or DNS_QUERY_NO_SEARCH
which disables searching for this query. (see defn of
searching above).
.Pp
The callback argument is a function which is called when
this query completes and ptr is an argument which is passed
to that callback function.
.Pp
Returns non-zero on error
.Pp
void evdns_search_clear()
Clears the list of search domains
.Pp
void evdns_search_add(const char *domain)
Add a domain to the list of search domains
.Pp
void evdns_search_ndots_set(int ndots)
Set the number of dots which, when found in a name, causes
the first query to be without any search domain.
.Pp
int evdns_count_nameservers(void)
Return the number of configured nameservers (not necessarily the
number of running nameservers). This is useful for double-checking
whether our calls to the various nameserver configuration functions
have been successful.
.Pp
int evdns_clear_nameservers_and_suspend(void)
Remove all currently configured nameservers, and suspend all pending
resolves. Resolves will not necessarily be re-attempted until
evdns_resume() is called.
.Pp
int evdns_resume(void)
Re-attempt resolves left in limbo after an earlier call to
evdns_clear_nameservers_and_suspend().
.Pp
int evdns_config_windows_nameservers(void)
Attempt to configure a set of nameservers based on platform settings on
a win32 host. Preferentially tries to use GetNetworkParams; if that fails,
looks in the registry. Returns 0 on success, nonzero on failure.
.Pp
int evdns_resolv_conf_parse(int flags, const char *filename)
Parse a resolv.conf like file from the given filename.
.Pp
See the man page for resolv.conf for the format of this file.
The flags argument determines what information is parsed from
this file:
DNS_OPTION_SEARCH - domain, search and ndots options
DNS_OPTION_NAMESERVERS - nameserver lines
DNS_OPTION_MISC - timeout and attempts options
DNS_OPTIONS_ALL - all of the above
The following directives are not parsed from the file:
sortlist, rotate, no-check-names, inet6, debug
.Pp
Returns non-zero on error:
0 no errors
1 failed to open file
2 failed to stat file
3 file too large
4 out of memory
5 short read from file
.Pp
Internals:
.Pp
Requests are kept in two queues. The first is the inflight queue. In
this queue requests have an allocated transaction id and nameserver.
They will soon be transmitted if they haven't already been.
.Pp
The second is the waiting queue. The size of the inflight ring is
limited and all other requests wait in waiting queue for space. This
bounds the number of concurrent requests so that we don't flood the
nameserver. Several algorithms require a full walk of the inflight
queue and so bounding its size keeps thing going nicely under huge
(many thousands of requests) loads.
.Pp
If a nameserver loses too many requests it is considered down and we
try not to use it. After a while we send a probe to that nameserver
(a lookup for google.com) and, if it replies, we consider it working
again. If the nameserver fails a probe we wait longer to try again
with the next probe.
.Sh SEE ALSO
.Xr event 3 ,
.Xr gethostbyname 3 ,
.Xr resolv.conf 5
.Sh HISTORY
The
.Nm evdns
API was developed by Adam Langley on top of the
.Nm libevent
API.
The code was integrate into
.Nm Tor
by Nick Mathewson and finally put into
.Nm libevent
itself by Niels Provos.
.Sh AUTHORS
The
.Nm evdns
API and code was written by Adam Langley with significant
contributions by Nick Mathewson.
.Sh BUGS
This documentation is neither complete nor authoritative.
If you are in doubt about the usage of this API then
check the source code to find out how it works, write
up the missing piece of documentation and send it to
me for inclusion in this man page.

186
evdns.c
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@ -32,192 +32,6 @@
* the source verbatim in their source distributions) * the source verbatim in their source distributions)
* *
* Version: 0.1b * Version: 0.1b
*
*
* Welcome, gentle reader
*
* Async DNS lookups are really a whole lot harder than they should be,
* mostly stemming from the fact that the libc resolver has never been
* very good at them. Before you use this library you should see if libc
* can do the job for you with the modern async call getaddrinfo_a
* (see http://www.imperialviolet.org/page25.html#e498). Otherwise,
* please continue.
*
* This code is based on libevent and you must call event_init before
* any of the APIs in this file. You must also seed the OpenSSL random
* source if you are using OpenSSL for ids (see below).
*
* This library is designed to be included and shipped with your source
* code. You statically link with it. You should also test for the
* existence of strtok_r and define HAVE_STRTOK_R if you have it.
*
* The DNS protocol requires a good source of id numbers and these
* numbers should be unpredictable for spoofing reasons. There are
* three methods for generating them here and you must define exactly
* one of them. In increasing order of preference:
*
* DNS_USE_GETTIMEOFDAY_FOR_ID:
* Using the bottom 16 bits of the usec result from gettimeofday. This
* is a pretty poor solution but should work anywhere.
* DNS_USE_CPU_CLOCK_FOR_ID:
* Using the bottom 16 bits of the nsec result from the CPU's time
* counter. This is better, but may not work everywhere. Requires
* POSIX realtime support and you'll need to link against -lrt on
* glibc systems at least.
* DNS_USE_OPENSSL_FOR_ID:
* Uses the OpenSSL RAND_bytes call to generate the data. You must
* have seeded the pool before making any calls to this library.
*
* The library keeps track of the state of nameservers and will avoid
* them when they go down. Otherwise it will round robin between them.
*
* Quick start guide:
* #include "evdns.h"
* void callback(int result, char type, int count, int ttl,
* void *addresses, void *arg);
* evdns_resolv_conf_parse(DNS_OPTIONS_ALL, "/etc/resolv.conf");
* evdns_resolve("www.hostname.com", 0, callback, NULL);
*
* When the lookup is complete the callback function is called. The
* first argument will be one of the DNS_ERR_* defines in evdns.h.
* Hopefully it will be DNS_ERR_NONE, in which case type will be
* DNS_IPv4_A, count will be the number of IP addresses, ttl is the time
* which the data can be cached for (in seconds), addresses will point
* to an array of uint32_t's and arg will be whatever you passed to
* evdns_resolve.
*
* Searching:
*
* In order for this library to be a good replacement for glibc's resolver it
* supports searching. This involves setting a list of default domains, in
* which names will be queried for. The number of dots in the query name
* determines the order in which this list is used.
*
* Searching appears to be a single lookup from the point of view of the API,
* although many DNS queries may be generated from a single call to
* evdns_resolve. Searching can also drastically slow down the resolution
* of names.
*
* To disable searching:
* 1. Never set it up. If you never call evdns_resolv_conf_parse or
* evdns_search_add then no searching will occur.
*
* 2. If you do call evdns_resolv_conf_parse then don't pass
* DNS_OPTION_SEARCH (or DNS_OPTIONS_ALL, which implies it).
*
* 3. When calling evdns_resolve, pass the DNS_QUERY_NO_SEARCH flag.
*
* The order of searches depends on the number of dots in the name. If the
* number is greater than the ndots setting then the names is first tried
* globally. Otherwise each search domain is appended in turn.
*
* The ndots setting can either be set from a resolv.conf, or by calling
* evdns_search_ndots_set.
*
* For example, with ndots set to 1 (the default) and a search domain list of
* ["myhome.net"]:
* Query: www
* Order: www.myhome.net, www.
*
* Query: www.abc
* Order: www.abc., www.abc.myhome.net
*
* API reference:
*
* int evdns_nameserver_add(unsigned long int address)
* Add a nameserver. The address should be an IP address in
* network byte order. The type of address is chosen so that
* it matches in_addr.s_addr.
* Returns non-zero on error.
*
* int evdns_nameserver_ip_add(const char *ip_as_string)
* This wraps the above function by parsing a string as an IP
* address and adds it as a nameserver.
* Returns non-zero on error
*
* int evdns_resolve(const char *name, int flags,
* evdns_callback_type callback,
* void *ptr)
* Resolve a name. The name parameter should be a DNS name.
* The flags parameter should be 0, or DNS_QUERY_NO_SEARCH
* which disables searching for this query. (see defn of
* searching above).
*
* The callback argument is a function which is called when
* this query completes and ptr is an argument which is passed
* to that callback function.
*
* Returns non-zero on error
*
* void evdns_search_clear()
* Clears the list of search domains
*
* void evdns_search_add(const char *domain)
* Add a domain to the list of search domains
*
* void evdns_search_ndots_set(int ndots)
* Set the number of dots which, when found in a name, causes
* the first query to be without any search domain.
*
* int evdns_count_nameservers(void)
* Return the number of configured nameservers (not necessarily the
* number of running nameservers). This is useful for double-checking
* whether our calls to the various nameserver configuration functions
* have been successful.
*
* int evdns_clear_nameservers_and_suspend(void)
* Remove all currently configured nameservers, and suspend all pending
* resolves. Resolves will not necessarily be re-attempted until
* evdns_resume() is called.
*
* int evdns_resume(void)
* Re-attempt resolves left in limbo after an earlier call to
* evdns_clear_nameservers_and_suspend().
*
* int evdns_config_windows_nameservers(void)
* Attempt to configure a set of nameservers based on platform settings on
* a win32 host. Preferentially tries to use GetNetworkParams; if that fails,
* looks in the registry. Returns 0 on success, nonzero on failure.
*
* int evdns_resolv_conf_parse(int flags, const char *filename)
* Parse a resolv.conf like file from the given filename.
*
* See the man page for resolv.conf for the format of this file.
* The flags argument determines what information is parsed from
* this file:
* DNS_OPTION_SEARCH - domain, search and ndots options
* DNS_OPTION_NAMESERVERS - nameserver lines
* DNS_OPTION_MISC - timeout and attempts options
* DNS_OPTIONS_ALL - all of the above
* The following directives are not parsed from the file:
* sortlist, rotate, no-check-names, inet6, debug
*
* Returns non-zero on error:
* 0 no errors
* 1 failed to open file
* 2 failed to stat file
* 3 file too large
* 4 out of memory
* 5 short read from file
*
* Internals:
*
* Requests are kept in two queues. The first is the inflight queue. In
* this queue requests have an allocated transaction id and nameserver.
* They will soon be transmitted if they haven't already been.
*
* The second is the waiting queue. The size of the inflight ring is
* limited and all other requests wait in waiting queue for space. This
* bounds the number of concurrent requests so that we don't flood the
* nameserver. Several algorithms require a full walk of the inflight
* queue and so bounding its size keeps thing going nicely under huge
* (many thousands of requests) loads.
*
* If a nameserver loses too many requests it is considered down and we
* try not to use it. After a while we send a probe to that nameserver
* (a lookup for google.com) and, if it replies, we consider it working
* again. If the nameserver fails a probe we wait longer to try again
* with the next probe.
*/ */
#include <sys/types.h> #include <sys/types.h>

231
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@ -1,4 +1,38 @@
/* This software is Public Domain. To view a copy of the public domain dedication, /*
* Copyright (c) 2006 Niels Provos <provos@citi.umich.edu>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* The original DNS code is due to Adam Langley with heavy
* modifications by Nick Mathewson. Adam put his DNS software in the
* public domain. You can find his original copyright below. Please,
* aware that the code as part of libevent is governed by the 3-clause
* BSD license above.
*
* This software is Public Domain. To view a copy of the public domain dedication,
* visit http://creativecommons.org/licenses/publicdomain/ or send a letter to * visit http://creativecommons.org/licenses/publicdomain/ or send a letter to
* Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA. * Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA.
* *
@ -13,6 +47,194 @@
* the source verbatim in their source distributions) * the source verbatim in their source distributions)
*/ */
/*
*
* Welcome, gentle reader
*
* Async DNS lookups are really a whole lot harder than they should be,
* mostly stemming from the fact that the libc resolver has never been
* very good at them. Before you use this library you should see if libc
* can do the job for you with the modern async call getaddrinfo_a
* (see http://www.imperialviolet.org/page25.html#e498). Otherwise,
* please continue.
*
* This code is based on libevent and you must call event_init before
* any of the APIs in this file. You must also seed the OpenSSL random
* source if you are using OpenSSL for ids (see below).
*
* This library is designed to be included and shipped with your source
* code. You statically link with it. You should also test for the
* existence of strtok_r and define HAVE_STRTOK_R if you have it.
*
* The DNS protocol requires a good source of id numbers and these
* numbers should be unpredictable for spoofing reasons. There are
* three methods for generating them here and you must define exactly
* one of them. In increasing order of preference:
*
* DNS_USE_GETTIMEOFDAY_FOR_ID:
* Using the bottom 16 bits of the usec result from gettimeofday. This
* is a pretty poor solution but should work anywhere.
* DNS_USE_CPU_CLOCK_FOR_ID:
* Using the bottom 16 bits of the nsec result from the CPU's time
* counter. This is better, but may not work everywhere. Requires
* POSIX realtime support and you'll need to link against -lrt on
* glibc systems at least.
* DNS_USE_OPENSSL_FOR_ID:
* Uses the OpenSSL RAND_bytes call to generate the data. You must
* have seeded the pool before making any calls to this library.
*
* The library keeps track of the state of nameservers and will avoid
* them when they go down. Otherwise it will round robin between them.
*
* Quick start guide:
* #include "evdns.h"
* void callback(int result, char type, int count, int ttl,
* void *addresses, void *arg);
* evdns_resolv_conf_parse(DNS_OPTIONS_ALL, "/etc/resolv.conf");
* evdns_resolve("www.hostname.com", 0, callback, NULL);
*
* When the lookup is complete the callback function is called. The
* first argument will be one of the DNS_ERR_* defines in evdns.h.
* Hopefully it will be DNS_ERR_NONE, in which case type will be
* DNS_IPv4_A, count will be the number of IP addresses, ttl is the time
* which the data can be cached for (in seconds), addresses will point
* to an array of uint32_t's and arg will be whatever you passed to
* evdns_resolve.
*
* Searching:
*
* In order for this library to be a good replacement for glibc's resolver it
* supports searching. This involves setting a list of default domains, in
* which names will be queried for. The number of dots in the query name
* determines the order in which this list is used.
*
* Searching appears to be a single lookup from the point of view of the API,
* although many DNS queries may be generated from a single call to
* evdns_resolve. Searching can also drastically slow down the resolution
* of names.
*
* To disable searching:
* 1. Never set it up. If you never call evdns_resolv_conf_parse or
* evdns_search_add then no searching will occur.
*
* 2. If you do call evdns_resolv_conf_parse then don't pass
* DNS_OPTION_SEARCH (or DNS_OPTIONS_ALL, which implies it).
*
* 3. When calling evdns_resolve, pass the DNS_QUERY_NO_SEARCH flag.
*
* The order of searches depends on the number of dots in the name. If the
* number is greater than the ndots setting then the names is first tried
* globally. Otherwise each search domain is appended in turn.
*
* The ndots setting can either be set from a resolv.conf, or by calling
* evdns_search_ndots_set.
*
* For example, with ndots set to 1 (the default) and a search domain list of
* ["myhome.net"]:
* Query: www
* Order: www.myhome.net, www.
*
* Query: www.abc
* Order: www.abc., www.abc.myhome.net
*
* API reference:
*
* int evdns_nameserver_add(unsigned long int address)
* Add a nameserver. The address should be an IP address in
* network byte order. The type of address is chosen so that
* it matches in_addr.s_addr.
* Returns non-zero on error.
*
* int evdns_nameserver_ip_add(const char *ip_as_string)
* This wraps the above function by parsing a string as an IP
* address and adds it as a nameserver.
* Returns non-zero on error
*
* int evdns_resolve(const char *name, int flags,
* evdns_callback_type callback,
* void *ptr)
* Resolve a name. The name parameter should be a DNS name.
* The flags parameter should be 0, or DNS_QUERY_NO_SEARCH
* which disables searching for this query. (see defn of
* searching above).
*
* The callback argument is a function which is called when
* this query completes and ptr is an argument which is passed
* to that callback function.
*
* Returns non-zero on error
*
* void evdns_search_clear()
* Clears the list of search domains
*
* void evdns_search_add(const char *domain)
* Add a domain to the list of search domains
*
* void evdns_search_ndots_set(int ndots)
* Set the number of dots which, when found in a name, causes
* the first query to be without any search domain.
*
* int evdns_count_nameservers(void)
* Return the number of configured nameservers (not necessarily the
* number of running nameservers). This is useful for double-checking
* whether our calls to the various nameserver configuration functions
* have been successful.
*
* int evdns_clear_nameservers_and_suspend(void)
* Remove all currently configured nameservers, and suspend all pending
* resolves. Resolves will not necessarily be re-attempted until
* evdns_resume() is called.
*
* int evdns_resume(void)
* Re-attempt resolves left in limbo after an earlier call to
* evdns_clear_nameservers_and_suspend().
*
* int evdns_config_windows_nameservers(void)
* Attempt to configure a set of nameservers based on platform settings on
* a win32 host. Preferentially tries to use GetNetworkParams; if that fails,
* looks in the registry. Returns 0 on success, nonzero on failure.
*
* int evdns_resolv_conf_parse(int flags, const char *filename)
* Parse a resolv.conf like file from the given filename.
*
* See the man page for resolv.conf for the format of this file.
* The flags argument determines what information is parsed from
* this file:
* DNS_OPTION_SEARCH - domain, search and ndots options
* DNS_OPTION_NAMESERVERS - nameserver lines
* DNS_OPTION_MISC - timeout and attempts options
* DNS_OPTIONS_ALL - all of the above
* The following directives are not parsed from the file:
* sortlist, rotate, no-check-names, inet6, debug
*
* Returns non-zero on error:
* 0 no errors
* 1 failed to open file
* 2 failed to stat file
* 3 file too large
* 4 out of memory
* 5 short read from file
*
* Internals:
*
* Requests are kept in two queues. The first is the inflight queue. In
* this queue requests have an allocated transaction id and nameserver.
* They will soon be transmitted if they haven't already been.
*
* The second is the waiting queue. The size of the inflight ring is
* limited and all other requests wait in waiting queue for space. This
* bounds the number of concurrent requests so that we don't flood the
* nameserver. Several algorithms require a full walk of the inflight
* queue and so bounding its size keeps thing going nicely under huge
* (many thousands of requests) loads.
*
* If a nameserver loses too many requests it is considered down and we
* try not to use it. After a while we send a probe to that nameserver
* (a lookup for google.com) and, if it replies, we consider it working
* again. If the nameserver fails a probe we wait longer to try again
* with the next probe.
*/
#ifndef EVENTDNS_H #ifndef EVENTDNS_H
#define EVENTDNS_H #define EVENTDNS_H
@ -49,6 +271,13 @@
#define DNS_OPTION_MISC 4 #define DNS_OPTION_MISC 4
#define DNS_OPTIONS_ALL 7 #define DNS_OPTIONS_ALL 7
/*
* The callback that contains the results from a lookup.
* - type is either DNS_IPv4_A or DNS_PTR
* - count contains the number of addresses of form type
* - ttl is the number of seconds the resolution may be cached for.
* - addresses needs to be cast according to type
*/
typedef void (*evdns_callback_type) (int result, char type, int count, int ttl, void *addresses, void *arg); typedef void (*evdns_callback_type) (int result, char type, int count, int ttl, void *addresses, void *arg);
int evdns_init(void); int evdns_init(void);

3
evhttp.h
View File

@ -82,7 +82,8 @@ void evhttp_send_reply(struct evhttp_request *, int, const char *,
/* Interfaces for making requests */ /* Interfaces for making requests */
enum evhttp_cmd_type { EVHTTP_REQ_GET, EVHTTP_REQ_POST, EVHTTP_REQ_HEAD }; enum evhttp_cmd_type { EVHTTP_REQ_GET, EVHTTP_REQ_POST, EVHTTP_REQ_HEAD };
/* Creates a new request object that needs to be filled in with the request /*
* Creates a new request object that needs to be filled in with the request
* parameters. The callback is executed when the request completed or an * parameters. The callback is executed when the request completed or an
* error occurred. * error occurred.
*/ */

35
test/regress_dns.c
View File

@ -44,6 +44,7 @@
#include <sys/socket.h> #include <sys/socket.h>
#include <sys/signal.h> #include <sys/signal.h>
#include <netinet/in.h> #include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h> #include <unistd.h>
#endif #endif
#include <netdb.h> #include <netdb.h>
@ -63,8 +64,38 @@ void
dns_gethostbyname_cb(int result, char type, int count, int ttl, dns_gethostbyname_cb(int result, char type, int count, int ttl,
void *addresses, void *arg) void *addresses, void *arg)
{ {
if (result == DNS_ERR_NONE) dns_ok = 0;
dns_ok = 1;
if (result != DNS_ERR_NONE)
goto out;
fprintf(stderr, "type: %d, count: %d, ttl: %d: ", type, count, ttl);
switch (type) {
case DNS_IPv4_A: {
struct in_addr *in_addrs = addresses;
int i;
/* a resolution that's not valid does not help */
if (ttl < 0)
goto out;
for (i = 0; i < count; ++i)
fprintf(stderr, "%s ", inet_ntoa(in_addrs[0]));
break;
}
case DNS_PTR:
/* may get at most one PTR */
if (count != 1)
goto out;
fprintf(stderr, "%s ", *(char **)addresses);
break;
default:
goto out;
}
dns_ok = 1;
out:
event_loopexit(NULL); event_loopexit(NULL);
} }