434 lines
15 KiB
Groff
434 lines
15 KiB
Groff
.TH "libunbound" "3" "Jun 17, 2019" "NLnet Labs" "unbound 1.9.2"
|
|
.\"
|
|
.\" libunbound.3 -- unbound library functions manual
|
|
.\"
|
|
.\" Copyright (c) 2007, NLnet Labs. All rights reserved.
|
|
.\"
|
|
.\" See LICENSE for the license.
|
|
.\"
|
|
.\"
|
|
.SH "NAME"
|
|
.B libunbound,
|
|
.B unbound.h,
|
|
.B ub_ctx,
|
|
.B ub_result,
|
|
.B ub_callback_type,
|
|
.B ub_ctx_create,
|
|
.B ub_ctx_delete,
|
|
.B ub_ctx_set_option,
|
|
.B ub_ctx_get_option,
|
|
.B ub_ctx_config,
|
|
.B ub_ctx_set_fwd,
|
|
.B ub_ctx_set_stub,
|
|
.B ub_ctx_set_tls,
|
|
.B ub_ctx_resolvconf,
|
|
.B ub_ctx_hosts,
|
|
.B ub_ctx_add_ta,
|
|
.B ub_ctx_add_ta_autr,
|
|
.B ub_ctx_add_ta_file,
|
|
.B ub_ctx_trustedkeys,
|
|
.B ub_ctx_debugout,
|
|
.B ub_ctx_debuglevel,
|
|
.B ub_ctx_async,
|
|
.B ub_poll,
|
|
.B ub_wait,
|
|
.B ub_fd,
|
|
.B ub_process,
|
|
.B ub_resolve,
|
|
.B ub_resolve_async,
|
|
.B ub_cancel,
|
|
.B ub_resolve_free,
|
|
.B ub_strerror,
|
|
.B ub_ctx_print_local_zones,
|
|
.B ub_ctx_zone_add,
|
|
.B ub_ctx_zone_remove,
|
|
.B ub_ctx_data_add,
|
|
.B ub_ctx_data_remove
|
|
\- Unbound DNS validating resolver 1.9.2 functions.
|
|
.SH "SYNOPSIS"
|
|
.B #include <unbound.h>
|
|
.LP
|
|
\fIstruct ub_ctx *\fR
|
|
\fBub_ctx_create\fR(\fIvoid\fR);
|
|
.LP
|
|
\fIvoid\fR
|
|
\fBub_ctx_delete\fR(\fIstruct ub_ctx*\fR ctx);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_ctx_set_option\fR(\fIstruct ub_ctx*\fR ctx, \fIchar*\fR opt, \fIchar*\fR val);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_ctx_get_option\fR(\fIstruct ub_ctx*\fR ctx, \fIchar*\fR opt, \fIchar**\fR val);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_ctx_config\fR(\fIstruct ub_ctx*\fR ctx, \fIchar*\fR fname);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_ctx_set_fwd\fR(\fIstruct ub_ctx*\fR ctx, \fIchar*\fR addr);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_ctx_set_stub\fR(\fIstruct ub_ctx*\fR ctx, \fIchar*\fR zone,
|
|
\fIchar*\fR addr,
|
|
.br
|
|
\fIint\fR isprime);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_ctx_set_tls\fR(\fIstruct ub_ctx*\fR ctx, \fIint\fR tls);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_ctx_resolvconf\fR(\fIstruct ub_ctx*\fR ctx, \fIchar*\fR fname);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_ctx_hosts\fR(\fIstruct ub_ctx*\fR ctx, \fIchar*\fR fname);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_ctx_add_ta\fR(\fIstruct ub_ctx*\fR ctx, \fIchar*\fR ta);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_ctx_add_ta_autr\fR(\fIstruct ub_ctx*\fR ctx, \fIchar*\fR fname);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_ctx_add_ta_file\fR(\fIstruct ub_ctx*\fR ctx, \fIchar*\fR fname);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_ctx_trustedkeys\fR(\fIstruct ub_ctx*\fR ctx, \fIchar*\fR fname);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_ctx_debugout\fR(\fIstruct ub_ctx*\fR ctx, \fIFILE*\fR out);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_ctx_debuglevel\fR(\fIstruct ub_ctx*\fR ctx, \fIint\fR d);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_ctx_async\fR(\fIstruct ub_ctx*\fR ctx, \fIint\fR dothread);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_poll\fR(\fIstruct ub_ctx*\fR ctx);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_wait\fR(\fIstruct ub_ctx*\fR ctx);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_fd\fR(\fIstruct ub_ctx*\fR ctx);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_process\fR(\fIstruct ub_ctx*\fR ctx);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_resolve\fR(\fIstruct ub_ctx*\fR ctx, \fIchar*\fR name,
|
|
.br
|
|
\fIint\fR rrtype, \fIint\fR rrclass, \fIstruct ub_result**\fR result);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_resolve_async\fR(\fIstruct ub_ctx*\fR ctx, \fIchar*\fR name,
|
|
.br
|
|
\fIint\fR rrtype, \fIint\fR rrclass, \fIvoid*\fR mydata,
|
|
.br
|
|
\fIub_callback_type\fR callback, \fIint*\fR async_id);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_cancel\fR(\fIstruct ub_ctx*\fR ctx, \fIint\fR async_id);
|
|
.LP
|
|
\fIvoid\fR
|
|
\fBub_resolve_free\fR(\fIstruct ub_result*\fR result);
|
|
.LP
|
|
\fIconst char *\fR
|
|
\fBub_strerror\fR(\fIint\fR err);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_ctx_print_local_zones\fR(\fIstruct ub_ctx*\fR ctx);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_ctx_zone_add\fR(\fIstruct ub_ctx*\fR ctx, \fIchar*\fR zone_name, \fIchar*\fR zone_type);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_ctx_zone_remove\fR(\fIstruct ub_ctx*\fR ctx, \fIchar*\fR zone_name);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_ctx_data_add\fR(\fIstruct ub_ctx*\fR ctx, \fIchar*\fR data);
|
|
.LP
|
|
\fIint\fR
|
|
\fBub_ctx_data_remove\fR(\fIstruct ub_ctx*\fR ctx, \fIchar*\fR data);
|
|
.SH "DESCRIPTION"
|
|
.B Unbound
|
|
is an implementation of a DNS resolver, that does caching and
|
|
DNSSEC validation. This is the library API, for using the \-lunbound library.
|
|
The server daemon is described in \fIunbound\fR(8).
|
|
The library works independent from a running unbound server, and
|
|
can be used to convert hostnames to ip addresses, and back,
|
|
and obtain other information from the DNS. The library performs public\-key
|
|
validation of results with DNSSEC.
|
|
.P
|
|
The library uses a variable of type \fIstruct ub_ctx\fR to keep context
|
|
between calls. The user must maintain it, creating it with
|
|
.B ub_ctx_create
|
|
and deleting it with
|
|
.B ub_ctx_delete\fR.
|
|
It can be created and deleted at any time. Creating it anew removes any
|
|
previous configuration (such as trusted keys) and clears any cached results.
|
|
.P
|
|
The functions are thread\-safe, and a context can be used in a threaded (as
|
|
well as in a non\-threaded) environment. Also resolution (and validation)
|
|
can be performed blocking and non\-blocking (also called asynchronous).
|
|
The async method returns from the call immediately, so that processing
|
|
can go on, while the results become available later.
|
|
.P
|
|
The functions are discussed in turn below.
|
|
.SH "FUNCTIONS"
|
|
.TP
|
|
.B ub_ctx_create
|
|
Create a new context, initialised with defaults.
|
|
The information from /etc/resolv.conf and /etc/hosts is not utilised
|
|
by default. Use
|
|
.B ub_ctx_resolvconf
|
|
and
|
|
.B ub_ctx_hosts
|
|
to read them.
|
|
Before you call this, use the openssl functions CRYPTO_set_id_callback and
|
|
CRYPTO_set_locking_callback to set up asynchronous operation if you use
|
|
lib openssl (the application calls these functions once for initialisation).
|
|
Openssl 1.0.0 or later uses the CRYPTO_THREADID_set_callback function.
|
|
.TP
|
|
.B ub_ctx_delete
|
|
Delete validation context and free associated resources.
|
|
Outstanding async queries are killed and callbacks are not called for them.
|
|
.TP
|
|
.B ub_ctx_set_option
|
|
A power\-user interface that lets you specify one of the options from the
|
|
config file format, see \fIunbound.conf\fR(5). Not all options are
|
|
relevant. For some specific options, such as adding trust anchors, special
|
|
routines exist. Pass the option name with the trailing ':'.
|
|
.TP
|
|
.B ub_ctx_get_option
|
|
A power\-user interface that gets an option value. Some options cannot be
|
|
gotten, and others return a newline separated list. Pass the option name
|
|
without trailing ':'. The returned value must be free(2)d by the caller.
|
|
.TP
|
|
.B ub_ctx_config
|
|
A power\-user interface that lets you specify an unbound config file, see
|
|
\fIunbound.conf\fR(5), which is read for configuration. Not all options are
|
|
relevant. For some specific options, such as adding trust anchors, special
|
|
routines exist. This function is thread\-safe only if a single instance of
|
|
ub_ctx* exists in the application. If several instances exist the
|
|
application has to ensure that ub_ctx_config is not called in parallel by
|
|
the different instances.
|
|
.TP
|
|
.B ub_ctx_set_fwd
|
|
Set machine to forward DNS queries to, the caching resolver to use.
|
|
IP4 or IP6 address. Forwards all DNS requests to that machine, which
|
|
is expected to run a recursive resolver. If the proxy is not
|
|
DNSSEC capable, validation may fail. Can be called several times, in
|
|
that case the addresses are used as backup servers.
|
|
At this time it is only possible to set configuration before the
|
|
first resolve is done.
|
|
.TP
|
|
.B ub_ctx_set_stub
|
|
Set a stub zone, authoritative dns servers to use for a particular zone.
|
|
IP4 or IP6 address. If the address is NULL the stub entry is removed.
|
|
Set isprime true if you configure root hints with it. Otherwise similar to
|
|
the stub zone item from unbound's config file. Can be called several times,
|
|
for different zones, or to add multiple addresses for a particular zone.
|
|
At this time it is only possible to set configuration before the
|
|
first resolve is done.
|
|
.TP
|
|
.B ub_ctx_set_tls
|
|
Enable DNS over TLS (DoT) for machines set with
|
|
.B ub_ctx_set_fwd.
|
|
At this time it is only possible to set configuration before the
|
|
first resolve is done.
|
|
.TP
|
|
.B ub_ctx_resolvconf
|
|
By default the root servers are queried and full resolver mode is used, but
|
|
you can use this call to read the list of nameservers to use from the
|
|
filename given.
|
|
Usually "/etc/resolv.conf". Uses those nameservers as caching proxies.
|
|
If they do not support DNSSEC, validation may fail.
|
|
Only nameservers are picked up, the searchdomain, ndots and other
|
|
settings from \fIresolv.conf\fR(5) are ignored.
|
|
If fname NULL is passed, "/etc/resolv.conf" is used (if on Windows,
|
|
the system\-wide configured nameserver is picked instead).
|
|
At this time it is only possible to set configuration before the
|
|
first resolve is done.
|
|
.TP
|
|
.B ub_ctx_hosts
|
|
Read list of hosts from the filename given.
|
|
Usually "/etc/hosts". When queried for, these addresses are not marked
|
|
DNSSEC secure. If fname NULL is passed, "/etc/hosts" is used
|
|
(if on Windows, etc/hosts from WINDIR is picked instead).
|
|
At this time it is only possible to set configuration before the
|
|
first resolve is done.
|
|
.TP
|
|
.B
|
|
ub_ctx_add_ta
|
|
Add a trust anchor to the given context.
|
|
At this time it is only possible to add trusted keys before the
|
|
first resolve is done.
|
|
The format is a string, similar to the zone\-file format,
|
|
[domainname] [type] [rdata contents]. Both DS and DNSKEY records are accepted.
|
|
.TP
|
|
.B ub_ctx_add_ta_autr
|
|
Add filename with automatically tracked trust anchor to the given context.
|
|
Pass name of a file with the managed trust anchor. You can create this
|
|
file with \fIunbound\-anchor\fR(8) for the root anchor. You can also
|
|
create it with an initial file with one line with a DNSKEY or DS record.
|
|
If the file is writable, it is updated when the trust anchor changes.
|
|
At this time it is only possible to add trusted keys before the
|
|
first resolve is done.
|
|
.TP
|
|
.B ub_ctx_add_ta_file
|
|
Add trust anchors to the given context.
|
|
Pass name of a file with DS and DNSKEY records in zone file format.
|
|
At this time it is only possible to add trusted keys before the
|
|
first resolve is done.
|
|
.TP
|
|
.B ub_ctx_trustedkeys
|
|
Add trust anchors to the given context.
|
|
Pass the name of a bind\-style config file with trusted\-keys{}.
|
|
At this time it is only possible to add trusted keys before the
|
|
first resolve is done.
|
|
.TP
|
|
.B ub_ctx_debugout
|
|
Set debug and error log output to the given stream. Pass NULL to disable
|
|
output. Default is stderr. File\-names or using syslog can be enabled
|
|
using config options, this routine is for using your own stream.
|
|
.TP
|
|
.B ub_ctx_debuglevel
|
|
Set debug verbosity for the context. Output is directed to stderr.
|
|
Higher debug level gives more output.
|
|
.TP
|
|
.B ub_ctx_async
|
|
Set a context behaviour for asynchronous action.
|
|
if set to true, enables threading and a call to
|
|
.B ub_resolve_async
|
|
creates a thread to handle work in the background.
|
|
If false, a process is forked to handle work in the background.
|
|
Changes to this setting after
|
|
.B ub_resolve_async
|
|
calls have been made have no effect (delete and re\-create the context
|
|
to change).
|
|
.TP
|
|
.B ub_poll
|
|
Poll a context to see if it has any new results.
|
|
Do not poll in a loop, instead extract the fd below to poll for readiness,
|
|
and then check, or wait using the wait routine.
|
|
Returns 0 if nothing to read, or nonzero if a result is available.
|
|
If nonzero, call
|
|
.B ub_process
|
|
to do callbacks.
|
|
.TP
|
|
.B ub_wait
|
|
Wait for a context to finish with results. Calls
|
|
.B ub_process
|
|
after the wait for you. After the wait, there are no more outstanding
|
|
asynchronous queries.
|
|
.TP
|
|
.B ub_fd
|
|
Get file descriptor. Wait for it to become readable, at this point
|
|
answers are returned from the asynchronous validating resolver.
|
|
Then call the \fBub_process\fR to continue processing.
|
|
.TP
|
|
.B ub_process
|
|
Call this routine to continue processing results from the validating
|
|
resolver (when the fd becomes readable).
|
|
Will perform necessary callbacks.
|
|
.TP
|
|
.B ub_resolve
|
|
Perform resolution and validation of the target name.
|
|
The name is a domain name in a zero terminated text string.
|
|
The rrtype and rrclass are DNS type and class codes.
|
|
The result structure is newly allocated with the resulting data.
|
|
.TP
|
|
.B ub_resolve_async
|
|
Perform asynchronous resolution and validation of the target name.
|
|
Arguments mean the same as for \fBub_resolve\fR except no
|
|
data is returned immediately, instead a callback is called later.
|
|
The callback receives a copy of the mydata pointer, that you can use to pass
|
|
information to the callback. The callback type is a function pointer to
|
|
a function declared as
|
|
.IP
|
|
void my_callback_function(void* my_arg, int err,
|
|
.br
|
|
struct ub_result* result);
|
|
.IP
|
|
The async_id is returned so you can (at your option) decide to track it
|
|
and cancel the request if needed. If you pass a NULL pointer the async_id
|
|
is not returned.
|
|
.TP
|
|
.B ub_cancel
|
|
Cancel an async query in progress. This may return an error if the query
|
|
does not exist, or the query is already being delivered, in that case you
|
|
may still get a callback for the query.
|
|
.TP
|
|
.B ub_resolve_free
|
|
Free struct ub_result contents after use.
|
|
.TP
|
|
.B ub_strerror
|
|
Convert error value from one of the unbound library functions
|
|
to a human readable string.
|
|
.TP
|
|
.B ub_ctx_print_local_zones
|
|
Debug printout the local authority information to debug output.
|
|
.TP
|
|
.B ub_ctx_zone_add
|
|
Add new zone to local authority info, like local\-zone \fIunbound.conf\fR(5)
|
|
statement.
|
|
.TP
|
|
.B ub_ctx_zone_remove
|
|
Delete zone from local authority info.
|
|
.TP
|
|
.B ub_ctx_data_add
|
|
Add resource record data to local authority info, like local\-data
|
|
\fIunbound.conf\fR(5) statement.
|
|
.TP
|
|
.B ub_ctx_data_remove
|
|
Delete local authority data from the name given.
|
|
.SH "RESULT DATA STRUCTURE"
|
|
The result of the DNS resolution and validation is returned as
|
|
\fIstruct ub_result\fR. The result structure contains the following entries.
|
|
.P
|
|
.nf
|
|
struct ub_result {
|
|
char* qname; /* text string, original question */
|
|
int qtype; /* type code asked for */
|
|
int qclass; /* class code asked for */
|
|
char** data; /* array of rdata items, NULL terminated*/
|
|
int* len; /* array with lengths of rdata items */
|
|
char* canonname; /* canonical name of result */
|
|
int rcode; /* additional error code in case of no data */
|
|
void* answer_packet; /* full network format answer packet */
|
|
int answer_len; /* length of packet in octets */
|
|
int havedata; /* true if there is data */
|
|
int nxdomain; /* true if nodata because name does not exist */
|
|
int secure; /* true if result is secure */
|
|
int bogus; /* true if a security failure happened */
|
|
char* why_bogus; /* string with error if bogus */
|
|
int ttl; /* number of seconds the result is valid */
|
|
};
|
|
.fi
|
|
.P
|
|
If both secure and bogus are false, security was not enabled for the
|
|
domain of the query. Else, they are not both true, one of them is true.
|
|
.SH "RETURN VALUES"
|
|
Many routines return an error code. The value 0 (zero) denotes no error
|
|
happened. Other values can be passed to
|
|
.B ub_strerror
|
|
to obtain a readable error string.
|
|
.B ub_strerror
|
|
returns a zero terminated string.
|
|
.B ub_ctx_create
|
|
returns NULL on an error (a malloc failure).
|
|
.B ub_poll
|
|
returns true if some information may be available, false otherwise.
|
|
.B ub_fd
|
|
returns a file descriptor or \-1 on error.
|
|
.B ub_ctx_config
|
|
and
|
|
.B ub_ctx_resolvconf
|
|
attempt to leave errno informative on a function return with file read failure.
|
|
.SH "SEE ALSO"
|
|
\fIunbound.conf\fR(5),
|
|
\fIunbound\fR(8).
|
|
.SH "AUTHORS"
|
|
.B Unbound
|
|
developers are mentioned in the CREDITS file in the distribution.
|