Index of Section 3 Manual Pages
| Interix / SUA | res_nmkupdate.3 | Interix / SUA |
res_nmkupdate(3) res_nmkupdate(3)
resolver
NAME
res_ninit, res_ourserver_p, fp_resstat, res_hostalias, res_pquery,
res_nquery, res_nsearch, res_nquerydomain, res_nmkquery, res_nsend,
res_nupdate, res_nmkupdate, res_nclose, res_nsendsigned, res_findzonecut,
res_getservers, res_setservers, dn_comp, dn_expand, hstrerror, res_init,
res_isourserver, fp_nquery, p_query, hostalias, res_query, res_search,
res_querydomain, res_mkquery, res_send, res_update, res_close, herror -
resolver routines
SYNOPSIS
#include
#include
#include
#include
#include
typedef struct __res_state *res_state;
int res_ninit(res_state statp);
int res_ourserver_p(const res_state statp, const struct sockaddr_in
*addr);
void fp_resstat(const res_state statp, FILE *fp);
const char * res_hostalias(const res_state statp, const char *name, char
*buf, size_t buflen);
int res_pquery(const res_state statp, const u_char *msg, int msglen, FILE
*fp);
int res_nquery(res_state statp, const char *dname, int class, int type,
u_char *answer, 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,
const u_char *data, int datalen, const u_char
*newrr,u_char *buf, int buflen);
int res_nsend(res_state statp, const u_char *msg, int msglen, u_char
*answer, int anslen);
int res_nupdate(res_state statp, ns_updrec *rrecp_in);
int res_nmkupdate(res_state statp, ns_updrec *rrecp_in, u_char *buf, int
buflen);
void res_nclose(res_state statp);
int res_nsendsigned(res_state statp, const u_char *msg, int msglen,
ns_tsig_key *key, u_char *answer, int anslen);
int res_findzonecut(res_state statp, const char *dname, ns_class class,
int options,
char *zname, size_t zsize, struct in_addr *addrs, int
naddrs);
int res_getservers(res_state statp, union res_sockaddr_union *set, int
cnt);
void res_setservers(res_state statp, const union res_sockaddr_union *set,
int cnt);
int dn_comp(const char *exp_dn, u_char *comp_dn, int length, u_char
*dnptrs,
u_char **lastdnptr);
int dn_expand(const u_char *msg, const u_char *eomorig, const u_char
*comp_dn,
char *exp_dn, int length);
const char *hstrerror(int err);
Deprecated
#include
#include
#include
#include
#include
int res_init(void);
int res_isourserver(const struct sockaddr_in *addr);
int fp_nquery(const u_char *msg, int msglen, FILE *fp);
void p_query(const u_char *msg, FILE *fp);
const char * hostalias(const char *name);
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_querydomain(const char *name, const char *domain, 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);
int res_update(ns_updrec *rrecp_in);
void res_close(void);
void herror(const char *s);
DESCRIPTION
These routines are used for making, sending and interpreting 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. statp should be set to all zeros prior to the first call
to any of these functions.
The functions res_init(), res_isourserver(), fp_nquery(), p_query(),
hostalias(), res_query(), res_search(), res_querydomain(), res_mkquery(),
res_send(), res_update(), res_close() and herror() are deprecated and are
supplied for compatability with old source code. They use global
configuration and state information that is kept in the structure _res
rather than that referenced through statp.
Most of the values in statp and _res are initialized on the first call to
res_ninit() / res_init() to reasonable defaults and can be ignored.
Options stored in statp->options / _res.options are defined in resolv.h
and are as follows. Options are stored as a simple bit mask containing the
bitwise ‘‘OR’’ of the options enabled.
RES_INIT
True if the initial name server address and default domain name are
initialized (i.e., res_ninit() / res_init() has been called).
RES_DEBUG
Print debugging messages.
RES_AAONLY
Accept authoritative answers only. Should continue until it finds an
authoritative answer or finds an error. Currently this is not
implemented.
RES_USEVC
Use TCP connections for queries instead of UDP datagrams.
RES_STAYOPEN
Used with RES_USEVC to keep the TCP connection open between queries.
This is useful only in programs that regularly do many queries. UDP
should be the normal mode used.
RES_IGNTC
Ignore truncation errors, i.e., don’t retry with TCP.
RES_RECURSE
Set the recursion-desired bit in queries. This is the default.
(res_nsend() / res_send() does not do iterative queries and expects
the name server to handle recursion.)
RES_DEFNAMES
If set, res_nsearch() / res_search() will append the default domain
name to single-component names (those that do not contain a dot). This
option is enabled by default.
RES_DNSRCH
If this option is set, res_nsearch() / res_search() will search for
host names in the current domain and in parent domains; see
hostname(@DESC_EXT@). This is used by the standard host lookup routine
gethostbyname(@LIB_NETWORK_EXT@). 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.
RES_USE_INET6
This option causes gethostbyname(@LIB_NETWORK_EXT@) to look for AAAA
records before looking for A records if none are found.
RES_ROTATE
This options causes the res_nsend() / res_send() to rotate the list of
nameservers in statp->nsaddr_list / _res.nsaddr_list.
RES_KEEPTSIG
This option causes res_nsendsigned() to leave the message unchanged
after TSIG verification; otherwise the TSIG record would be removed
and the header updated.
RES_NOTLDQUERY
This option causes res_nsearch() to not attempt to resolve a
unqualified name as if it were a top level domain (TLD). This option
can cause problems if the site has "localhost" as a TLD rather than
having localhost on one or more elements of the search list. This
option has no effect if neither RES_DEFNAMES or RES_DNSRCH is set.
The res_ninit() / res_init() routine reads the configuration file (if any;
see resolver(@FORMAT_EXT@)) to get the default domain name, search list
and the Internet address of the local name server(s). If no server is
configured, the host running the resolver is tried. The current domain
name is defined by the hostname if not specified in the configuration
file; it can be overridden by the environment variable LOCALDOMAIN. 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. Another environment variable
(‘‘RES_OPTIONS’’) can be set to override certain
internal resolver options which are otherwise set by changing fields in
the statp / _res structure or are inherited from the configuration
file’s options command. The syntax of the
‘‘RES_OPTIONS’’ environment variable is explained
in resolver(@FORMAT_EXT@). Initialization normally occurs on the first
call to one of the other resolver routines.
The res_nquery() / res_query() functions provides interfaces to the server
query mechanism. They constructs a query, sends it to the local server,
awaits a response, and makes preliminary checks on the reply. The query
requests information of the specified type and class for the specified
fully-qualified domain name dname. The reply message is left in the answer
buffer with length anslen supplied by the caller. res_nquery() /
res_query() return -1 on error or the length of the answer.
The res_nsearch() / res_search() routines make a query and awaits a
response like res_nquery() / res_query(), but in addition, it implements
the default and search rules controlled by the RES_DEFNAMES and RES_DNSRCH
options. It returns the length of the first successful reply which is
stored in answer or -1 on error.
The remaining routines are lower-level routines used by res_nquery() /
res_query(). The res_nmkquery() / res_mkquery() functions constructs a
standard query message and places it in buf. It 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 . The domain name for the query is given by dname. Newrr is
currently unused but is intended for making update messages.
The res_nsend() / res_send() / res_nsendsigned() routines sends a pre-
formatted query and returns an answer. It will call res_ninit() /
res_init() if RES_INIT is not set, send the query to the local name
server, and handle timeouts and retries. Additionally, res_nsendsigned()
will use TSIG signatures to add authentication to the query and verify the
response. In this case, only one nameserver will be contacted. The length
of the reply message is returned, or -1 if there were errors.
res_nquery() / res_query(), res_nsearch() / res_search() and res_nsend() /
res_send() return a length that may be bigger than anslen. In that case
the query should be retried with a bigger buffer. NOTE the answer to the
second query may be larger still so supplying a buffer that bigger that
the answer returned by the previous query is recommended.
answer MUST be big 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.
The function res_ourserver_p() returns true when inp is one of the servers
in statp->nsaddr_list / _res.nsaddr_list.
The functions fp_nquery() / p_query() print out the query and any answer
in msg on fp. p_query() is equivalent to fp_nquery() with msglen set to
512.
The function fp_resstat() prints out the active flag bits in statp-
>options preceeded by the text ";; res options:" on file.
The functions res_hostalias() / hostalias() lookup up name in the file
referred to by the HOSTALIASES files return a fully qualified hostname if
found or NULL if not found or an error occurred. res_hostalias() uses buf
to store the result in, hostalias() uses a static buffer.
The functions res_getservers() and res_setservers() are used to get and
set the list of server to be queried.
The functions res_nupdate() / res_update() take a list of ns_updrec
rrecp_in. Identifies the containing zone for each record and groups the
records according to containing zone maintaining in zone order then sends
and update request to the servers for these zones. The number of zones
updated is returned or -1 on error. Note that res_nupdate() will perform
TSIG authenticated dynamic update operations if the key is not NULL.
The function res_findzonecut() discovers the closest enclosing zone cut
for a specified domain name, and finds the IP addresses of the
zone’s master servers.
The functions res_nmkupdate() / res_mkupdate() take a linked list of
ns_updrec rrecp_in and construct a UPDATE message in buf. res_nmkupdate()
/ res_mkupdate() return the length of the constructed message on no error
or one of the following error values.
-1
An error occurred parsing rrecp_in.
-2
The buffer buf was too small.
-3
The first record was not a zone section or there was a section order
problem. The section order is S_ZONE, S_PREREQ and S_UPDATE.
-4
A number overflow occurred.
-5
Unknown operation or no records.
The functions res_nclose() / res_close() close any open files referenced
through statp / _res.
The dn_comp() function compresses the domain name exp_dn and stores it in
comp_dn. The size of the compressed name is returned or -1 if there were
errors. The size of the array pointed to by comp_dn is given by length.
The compression uses an array of pointers dnptrs to previously-compressed
names in the current message. The first pointer points to to the beginning
of the message and the list ends with NULL. The limit to the array is
specified by lastdnptr. A side effect of dn_comp() is to update the list
of pointers for labels inserted into the message as the name is
compressed. If dnptr is NULL, names are not compressed. If lastdnptr is
NULL, the list of labels is not updated.
The dn_expand() entry 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 the message. eomorig is a pointer to
the first location after the message. The uncompressed name is placed in
the buffer indicated by exp_dn which is of size length. The size of
compressed name is returned or -1 if there was an error.
The variables statp->res_h_errno / _res.res_h_errno and external variable
h_errno is set whenever an error occurs during resolver operation. The
following definitions are given in :
#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 parameter s, the constant string ": ", and a message
corresponding to the value of h_errno.
The hstrerror() function returns a string which is the message text
corresponding to the value of the err parameter.
FILE
/etc/resolv.conf
SEE ALSO
gethostbyname(3)
RFC1032, RFC1033, RFC1034, RFC1035, RFC974; SMM:11, "Name Server
Operations Guide for BIND"
4th Berkeley Distribution July 4, 2000 4th Berkeley Distribution
USAGE NOTES
None of these functions are thread safe.
None of these functions are async-signal safe.