HP-UX Reference (11i v2 03/08) - 3 Library Functions N-Z (vol 7)

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resolver(3N) resolver(3N)

dn_comp() 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. length is the size of the

array pointed to by comp_dn. 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.

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 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 −1if

there was an error.

Obsolescent Routine

herror() herror() supports existing applications to print an error message describing

a failure. ANSI applications must specify the following deﬁnition for

her-

ror():

void herror(const char *);

The argument string s is printed ﬁrst, followed by a colon, a blank, the mes-

sage, and a new-line. herror() may be removed in future releases.

RETURN VALUE

Error return status from

res_search() is indicated by a return value of −1. The external integer

h_errno can then be checked to see whether this is a temporary failure or an invalid or unknown host.

In a multithreaded application using kernel thread, a thread speciﬁc

h_errno is allocated for each

thread.

ERRORS

h_errno can have the following values:

HOST_NOT_FOUND No such host is known.

TRY_AGAIN This is usually a temporary error and means that the local server did not

receive a response from an authoritative server. A retry at some later time

may succeed.

NO_RECOVERY Some unexpected server failure was encountered. This is a non-recoverable

error.

NO_DATA The name is known to the name server, but there is no data of the requested

type associated with this name; this is not a temporary error. Another type of

request to the name server using this domain name will result in an answer.

WARNINGS

The

_res.options ﬁeld should be modiﬁed only by using set_resfield() call, and should not be

manipulated directly. h_errno is referenced as an extern int for non-threaded applications and is

deﬁned as function call macro for multithreaded applications in ﬁle /usr/include/netdb.h

. Appli-

cations which reference

h_errno should include /usr/include/netdb.h.

_res is referenced as an extern struct _res_state for non-threaded applications and is deﬁned

as function call macro for multithreaded application in ﬁle /usr/include/resolv.h

. Applications

which reference

_res should include /usr/include/resolv.h.

AUTHOR

These resolver routines were developed by the University of California, Berkeley.

FILES

/etc/resolv.conf Resolver conﬁguration ﬁle.