Provided by: libunbound-dev_1.9.0-2_amd64 bug

NAME

       libunbound,  unbound.h, ub_ctx, ub_result, ub_callback_type, ub_ctx_create, ub_ctx_delete,
       ub_ctx_set_option,  ub_ctx_get_option,  ub_ctx_config,  ub_ctx_set_fwd,   ub_ctx_set_stub,
       ub_ctx_set_tls,   ub_ctx_resolvconf,   ub_ctx_hosts,   ub_ctx_add_ta,  ub_ctx_add_ta_autr,
       ub_ctx_add_ta_file, ub_ctx_trustedkeys, ub_ctx_debugout, ub_ctx_debuglevel,  ub_ctx_async,
       ub_poll,    ub_wait,   ub_fd,   ub_process,   ub_resolve,   ub_resolve_async,   ub_cancel,
       ub_resolve_free,       ub_strerror,       ub_ctx_print_local_zones,       ub_ctx_zone_add,
       ub_ctx_zone_remove,  ub_ctx_data_add, ub_ctx_data_remove - Unbound DNS validating resolver
       1.9.0 functions.

SYNOPSIS

       #include <unbound.h>

       struct ub_ctx * ub_ctx_create(void);

       void ub_ctx_delete(struct ub_ctx* ctx);

       int ub_ctx_set_option(struct ub_ctx* ctx, char* opt, char* val);

       int ub_ctx_get_option(struct ub_ctx* ctx, char* opt, char** val);

       int ub_ctx_config(struct ub_ctx* ctx, char* fname);

       int ub_ctx_set_fwd(struct ub_ctx* ctx, char* addr);

       int ub_ctx_set_stub(struct ub_ctx* ctx, char* zone, char* addr,
                 int isprime);

       int ub_ctx_set_tls(struct ub_ctx* ctx, int tls);

       int ub_ctx_resolvconf(struct ub_ctx* ctx, char* fname);

       int ub_ctx_hosts(struct ub_ctx* ctx, char* fname);

       int ub_ctx_add_ta(struct ub_ctx* ctx, char* ta);

       int ub_ctx_add_ta_autr(struct ub_ctx* ctx, char* fname);

       int ub_ctx_add_ta_file(struct ub_ctx* ctx, char* fname);

       int ub_ctx_trustedkeys(struct ub_ctx* ctx, char* fname);

       int ub_ctx_debugout(struct ub_ctx* ctx, FILE* out);

       int ub_ctx_debuglevel(struct ub_ctx* ctx, int d);

       int ub_ctx_async(struct ub_ctx* ctx, int dothread);

       int ub_poll(struct ub_ctx* ctx);

       int ub_wait(struct ub_ctx* ctx);

       int ub_fd(struct ub_ctx* ctx);

       int ub_process(struct ub_ctx* ctx);

       int ub_resolve(struct ub_ctx* ctx, char* name,
                  int rrtype, int rrclass, struct ub_result** result);

       int ub_resolve_async(struct ub_ctx* ctx, char* name,
                        int rrtype, int rrclass, void* mydata,
                        ub_callback_type callback, int* async_id);

       int ub_cancel(struct ub_ctx* ctx, int async_id);

       void ub_resolve_free(struct ub_result* result);

       const char * ub_strerror(int err);

       int ub_ctx_print_local_zones(struct ub_ctx* ctx);

       int ub_ctx_zone_add(struct ub_ctx* ctx, char* zone_name, char* zone_type);

       int ub_ctx_zone_remove(struct ub_ctx* ctx, char* zone_name);

       int ub_ctx_data_add(struct ub_ctx* ctx, char* data);

       int ub_ctx_data_remove(struct ub_ctx* ctx, char* data);

DESCRIPTION

       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 unbound(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.

       The library uses a variable of type struct ub_ctx to keep context between calls. The  user
       must  maintain  it, creating it with ub_ctx_create and deleting it with ub_ctx_delete.  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.

       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.

       The functions are discussed in turn below.

FUNCTIONS

       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 ub_ctx_resolvconf
              and 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.

       ub_ctx_delete
              Delete validation context and free associated resources.  Outstanding async queries
              are killed and callbacks are not called for them.

       ub_ctx_set_option
              A  power-user  interface  that  lets you specify one of the options from the config
              file format, see unbound.conf(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 ':'.

       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.

       ub_ctx_config
              A  power-user  interface  that  lets  you  specify  an  unbound  config  file,  see
              unbound.conf(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.

       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.

       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.

       ub_ctx_set_tls
              Enable DNS over TLS (DoT) for machines set with ub_ctx_set_fwd.  At this time it is
              only possible to set configuration before the first resolve is done.

       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 resolv.conf(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.

       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.

       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.

       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
              unbound-anchor(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.

       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.

       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.

       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.

       ub_ctx_debuglevel
              Set  debug  verbosity  for the context. Output is directed to stderr.  Higher debug
              level gives more output.

       ub_ctx_async
              Set a context behaviour for asynchronous action.  if set to true, enables threading
              and  a  call to 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  ub_resolve_async  calls  have  been made have no effect (delete and
              re-create the context to change).

       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 ub_process to do callbacks.

       ub_wait
              Wait for a context to finish with results. Calls ub_process after the wait for you.
              After the wait, there are no more outstanding asynchronous queries.

       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 ub_process to
              continue processing.

       ub_process
              Call this routine to continue processing results from the validating resolver (when
              the fd becomes readable).  Will perform necessary callbacks.

       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.

       ub_resolve_async
              Perform  asynchronous resolution and validation of the target name.  Arguments mean
              the same as for ub_resolve 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

              void my_callback_function(void* my_arg, int err,
                                struct ub_result* result);

              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.

       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.

       ub_resolve_free
              Free struct ub_result contents after use.

       ub_strerror
              Convert error value from one of the unbound library functions to a  human  readable
              string.

       ub_ctx_print_local_zones
              Debug printout the local authority information to debug output.

       ub_ctx_zone_add
              Add new zone to local authority info, like local-zone unbound.conf(5) statement.

       ub_ctx_zone_remove
              Delete zone from local authority info.

       ub_ctx_data_add
              Add  resource  record data to local authority info, like local-data unbound.conf(5)
              statement.

       ub_ctx_data_remove
              Delete local authority data from the name given.

RESULT DATA STRUCTURE

       The result of the DNS resolution and validation  is  returned  as  struct  ub_result.  The
       result structure contains the following entries.

            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 */
            };

       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.

RETURN VALUES

       Many routines return an error code. The value 0 (zero) denotes no  error  happened.  Other
       values  can  be  passed  to  ub_strerror  to  obtain a readable error string.  ub_strerror
       returns a zero terminated string.  ub_ctx_create  returns  NULL  on  an  error  (a  malloc
       failure).   ub_poll  returns  true  if some information may be available, false otherwise.
       ub_fd returns a file descriptor or  -1  on  error.   ub_ctx_config  and  ub_ctx_resolvconf
       attempt to leave errno informative on a function return with file read failure.

SEE ALSO

       unbound.conf(5), unbound(8).

AUTHORS

       Unbound developers are mentioned in the CREDITS file in the distribution.