SunOS man pages : resolver (3)
Resolver Library Functions resolver(3RESOLV)
NAME
resolver, res_ninit, fp_resstat, res_npquery, res_hostalias,
res_nquery, res_nsearch, res_nquerydomain, res_nmkquery,
res_nsend, res_nclose, res_nsendsigned, dn_comp, dn_expand,
hstrerror, res_init, res_query, res_search, res_mkquery,
res_send, herror, - resolver routines
SYNOPSIS
BIND 8.2.2 Interfaces
cc [ flag ... ] file ... -lresolv -lsocket -lnsl [ library ... ]
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <resolv.h>
#include <netdb.h>
int res_ninit(res_state statp);
void fp_resstat(const res_state statp, FILE *fp);
void res_npquery(const res_state statp, const u_char *msg,
int msglen, FILE *fp);
const char *res_hostalias(const res_state statp, const char
*name, char * name, char *buf, size_tbuflen);
int res_nquery(res_state statp, const char *dname, int
class, int type, u_char *answer, int datalen, int anslen);
int res_nsearch(res_state statp, const char *dname, int
class, int type, u_char *answer, int anslen);
int res_nquerydomain(res_state statp, const char *name,
const char *domain, int class, int type, u_char *answer, int
anslen);
int res_nmkquery(res_state statp, int op, const char *dname,
int class, int type, u_char *answer, int datalen, int
anslen);
int res_nsend(res_state statp, const u_char *msg, int
msglen, u_char *answer, int anslen);
void res_nclose(res_state statp);
int res_snendsigned(res_state statp, const u_char *msg, int
msglen, ns_tsig_key *key, u_char *answer, int anslen);
int dn_comp(const char *exp_dn, u_char *comp_dn, int length,
u_char **dnptrs, **lastdnptr);
SunOS 5.8 Last change: 28 Mar 2001 1
Resolver Library Functions resolver(3RESOLV)
int dn_expand(const u_char *msg, *eomorig, *comp_dn, char
*exp_dn, int length);
const char *hstrerror(int err);
Deprecated Interfaces
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <resolv.h>
#include <netdb.h>
int res_init(void);
int res_query(const char *dname, int class, int type, u_char
*answer, int anslen);
int res_search(const char *dname, int class, int type,
u_char *answer, int anslen);
int res_mkquery(int op, const char *dname, int class, int
type, const char *data, int datalen, struct rrec *newrr,
u_char *buf, int buflen);
int res_send(const u_char *msg, int msglen, u_char *answer,
int anslen);
void herror(const char *s);
DESCRIPTION
These routines are used for making, sending, and interpret-
ing query and reply messages with Internet domain name
servers.
State information is kept in statp and is used to control
the behavior of these functions. Set statp to all zeros
prior to making the first call to any of these functions.
The functions res_init(), res_query(), res_search(),
res_mkquery(), res_send(), and herror() are deprecated. They
are supplied for backwards compatability. They use global
configuration and state information that is kept in the
structure _res rather than state information referenced
through statp.
Most of the values in statp and _res are initialized to rea-
sonable defaults on the first call to res_ninit() or
res_init() and can be ignored. Options stored in statp-
>options or _res.options are defined in <resolv.h>. They
are stored as a simple bit mask containing the bitwise OR of
the options enabled.
SunOS 5.8 Last change: 28 Mar 2001 2
Resolver Library Functions resolver(3RESOLV)
RES_INIT
True if the initial name server address and default
domain name are initialized, that is, res_init() or
res_ninit() has been called.
RES_DEBUG
Print debugging messages.
RES_AAONLY
Accept authoritative answers only. With this option,
res_send() will continue until it finds an authorita-
tive answer or finds an error. Currently this option
is not implemented.
RES_USEVC
Use TCP connections for queries instead of UDP
datagrams.
RES_STAYOPEN
Use with RES_USEVC to keep the TCP connection open
between queries. This is a useful option for programs
that regularly do many queries. The normal mode used
should be UDP.
RES_IGNTC
Ignore truncation errors; that is, do not retry with
TCP.
RES_RECURSE
Set the recursion-desired bit in queries. This is the
default. res_send() and res_nsend() do not do itera-
tive queries and expect the name server to handle
recursion.
RES_DEFNAMES
If set, res_search() and res_nsearch() append the
default domain name to single-component names, that
is, names that do not contain a dot. This option is
enabled by default.
RES_DNSRCH
If this option is set, res_search() and res_nsearch()
search for host names in the current domain and in
parent domains. See hostname(1). This option is used
by the standard host lookup routine
gethostbyname(3NSL). This option is enabled by
default.
RES_NOALIASES
This option turns off the user level aliasing feature
controlled by the HOSTALIASES environment variable.
Network daemons should set this option.
SunOS 5.8 Last change: 28 Mar 2001 3
Resolver Library Functions resolver(3RESOLV)
RES_ROTATE
This option causes res_nsend() and res_send() to
rotate the list of nameservers in statp->nsaddr_list
or _res.nsaddr_list.
RES_KEEPTSIG
This option causes res_nsendsigned() to leave the mes-
sage unchanged after TSIG verification. Otherwise the
TSIG record would be removed and the
header would be updated.
res_ninit, res_init
The res_ninit() and res_init() routines read the configura-
tion file, if any is present, to get the default domain
name, search list and the Internet address of the local name
server(s). See resolv.conf(4). If no server is configured,
res_init() or res_ninit() will try to obtain name resolution
services from the host on which it is running. The current
domain name is defined by domainname(1M), or by the hostname
if it is not specified in the configuration file. Use the
environment variable LOCALDOMAIN to override the domain
name. This environment variable may contain several blank-
separated tokens if you wish to override the search list on
a per-process basis. This is similar to the search command
in the configuration file. You can set the RES_OPTIONS
environment variable to override certain internal resolver
options. You can otherwise set them by changing fields in
the statp /_res structure. Alternatively, they are inher-
ited from the configuration file's options command. See
resolv.conf(4) for information regarding the syntax of the
RES_OPTIONS environment variable. Initialization normally
occurs on the first call to one of the other resolver rou-
tines.
res_nquery, res_query
The res_nquery() and res_query() functions provides inter-
faces to the server query mechanism. They construct a
query, send it to the local server, await a response, and
make preliminary checks on the reply. The query requests
information of the specified type and class for the speci-
fied fully-qualified domain name dname. The reply message is
left in the answer buffer with length anslen supplied by the
caller. res_nquery() and res_query() return the length of
the answer, or -1 upon error.
The res_nquery() and res_query() routines return a length
that may be bigger than anslen. In that case, retry the
query with a larger buf. The answer to the second query may
be larger still], so it is recommended that you supply a buf
larger than the answer returned by the previous query.
answer must be large enough to receive a maximum UDP
response from the server or parts of the answer will be
SunOS 5.8 Last change: 28 Mar 2001 4
Resolver Library Functions resolver(3RESOLV)
silently discarded. The default maximum UDP response size
is 512 bytes.
res_nsearch, res_search
The res_nsearch() and res_search() routines make a query and
await a response, just like like res_nquery() and
res_query(). In addition, they implement the default and
search rules controlled by the RES_DEFNAMES and RES_DNSRCH
options. They return the length of the first successful
reply which is stored in answer. On error, they reurn -1.
The res_nsearch() and res_search() routines return a length
that may be bigger than anslen. In that case, retry the
query with a larger buf. The answer to the second query may
be larger still], so it is recommended that you supply a buf
larger than the answer returned by the previous query.
answer must be large enough to receive a maximum UDP
response from the server or parts of the answer will be
silently discarded. The default maximum UDP response size
is 512 bytes.
res_nmkquery, res_mkquery
These routines are used by res_nquery() and res_query(). The
res_nmkquery() and res_mkquery() functions construct a stan-
dard query message and place it in buf. The routine returns
the size of the query, or -1 if the query is larger than
buflen. The query type op is usually QUERY, but can be any
of the query types defined in <arpa/nameser.h>. The domain
name for the query is given by dname. newrr is currently
unused but is intended for making update messages.
res_nsend, res_send, res_nsendsigned
The res_nsend(), res_send(), and res_nsendsigned() routines
send a preformatted query that returns an answer. The rou-
tine calls res_ninit() or res_init(). If RES_INIT is not
set, the routine sends the query to the local name server
and handles timeouts and retries. Additionally, the
res_nsendsigned() uses TSIG signatures to add authentication
to the query and verify the response. In this case, only
one name server will be contacted. The routines return the
length of the reply message, or -1 if there are errors.
The res_nsend() and res_send() routines return a length that
may be bigger than anslen. In that case, retry the query
with a larger buf. The answer to the second query may be
larger still], so it is recommended that you supply a buf
larger than the answer returned by the previous query.
answer must be large enough to receive a maximum UDP
response from the server or parts of the answer will be
silently discarded. The default maximum UDP response size
is 512 bytes.
SunOS 5.8 Last change: 28 Mar 2001 5
Resolver Library Functions resolver(3RESOLV)
res_npquery
The function res_npquery() prints out the query and any
answer in msg on fp.
fp_resstat
The function fp_resstat() prints out the active flag bits in
statp->options preceded by the text ";; res options:" on
file.
res_hostalias
The function res_hostalias() looks up name in the file
referred to by the HOSTALIASES environment variable and
returns the fully qualified host name. If name is not found
or an error occurs, NULL is returned. res_hostalias() stores
the result in buf.
res_nclose
The res_nclose() function closes any open files referenced
through statp.
dn_comp
dn_comp() compresses the domain name exp_dn and stores it in
comp_dn. dn_comp() returns the size of the compressed name,
or -1 if there were errors. length is the size of the array
pointed to by comp_dn.
dnptrs is a pointer to the head of the list of pointers to
previously compressed names in the current message. The
first pointer must point to the beginning of the message.
The list ends with NULL. The limit to the array is specified
by lastdnptr.
A side effect of calling dn_comp() is to update the list of
pointers for labels inserted into the message by dn_comp()
as the name is compressed. If dnptrs is NULL, names are not
compressed. If lastdnptr is NULL, dn_comp() does not update
the list of labels.
dn_expand
dn_expand() expands the compressed domain name comp_dn to a
full domain name. The compressed name is contained in a
query or reply message. msg is a pointer to the beginning of
that message. The uncompressed name is placed in the buffer
indicated by exp_dn, which is of size length.dn_expand()
returns the size of the compressed name, or -1 if there was
an error.
hstrerror, herror
The variables statp->res_h_errno and _res.res_h_errno and
external variable h_errno are set whenever an error
occurs during a resolver operation. The following defini-
tions are given in <netdb.h>:
SunOS 5.8 Last change: 28 Mar 2001 6
Resolver Library Functions resolver(3RESOLV)
#define NETDB_INTERNAL -1 /* see errno */
#define NETDB_SUCCESS 0 /* no problem */
#define HOST_NOT_FOUND 1 /* Authoritative Answer Host not found */
#define TRY_AGAIN 2 /* Non-Authoritative not found, or SERVFAIL */
#define NO_RECOVERY 3 /* Non-Recoverable: FORMERR, REFUSED, NOTIMP*/
#define NO_DATA 4 /* Valid name, no data for requested type */
The herror() function writes a message to the diagnostic
output consisting of the string parameters, the constant
string ": ", and a message corresponding to the value of
h_errno.
The hstrerror() function returns a string, which is the mes-
sage text that corresponds to the value of the err parame-
ter.
FILES
/etc/resolv.conf
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| ____________________________|_____________________________|_
| Availability | SUNWcsl (32-bit) |
| ____________________________|_____________________________|_
| | SUNWcslx (64-bit) |
| ____________________________|_____________________________|_
| Interface Stability | Standard BIND 8.2.2 |
| ____________________________|_____________________________|_
| MT-Level | Unsafe for Deprecated|
| | Interfaces; MT-Safe for all|
| | others. |
|_____________________________|_____________________________|
SEE ALSO
domainname(1M), in.named(1M), gethostbyname(3NSL),
libresolv(3LIB), resolv.conf(4), attributes(5)
Lottor, M. RFC 1033, Domain Administrators Operations Guide.
Network Working Group. November 1987.
Mockapetris, Paul. RFC 1034, Domain Names - Concepts and
Facilities. Network Working Group. November 1987.
Mockapetris, Paul. RFC 1035, Domain Names - Implementation
and Specification. Network Working Group. November 1987.
SunOS 5.8 Last change: 28 Mar 2001 7
Resolver Library Functions resolver(3RESOLV)
Partridge, Craig. RFC 974, Mail Routing and the Domain Sys-
tem. Network Working Group. January 1986.
Stahl, M. RFC 1032, Domain Administrators Guide. Network
Working Group. November 1987.
Vixie, Paul, Dunlap, Kevin J., Karels, Michael J. Name
Server Operations Guide for BIND. Internet Software Consor-
tium, 1996.
NOTES
When the caller supplies a work buffer, for example the
answer buffer argument to res_nsend() or res_send(), the
buffer should be aligned on an eight byte boundary. Other-
wise, an error such as a SIGBUS may result.
SunOS 5.8 Last change: 28 Mar 2001 8
|
 |
|
|
