resolver.3

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 3 代码 · 共 225 行

.\" Copyright (c) 1985 Regents of the University of California.
.\" All rights reserved.  The Berkeley software License Agreement
.\" specifies the terms and conditions for redistribution.
.\"
.\"	@(#)resolver.3	1.7 (Berkeley) 5/27/86
.\"
.TH resolver 3
.SH Name
res_mkquery, res_send, res_init, dn_comp, dn_expand \- resolver routines
.SH Syntax
.nf
.B #include <sys/types.h>
.br
.B #include <netinet/in.h>
.br
.B #include <arpa/nameser.h>
.br
.B #include <resolv.h>
.PP
.B "res_mkquery(\fIop, dname, class, type, data, datalen, newrr, buf, buflen\fP)"
.br
.B int \fIop\fP;
.br
.B char *\fIdname\fP;
.br
.B int \fIclass, type\fP;
.br
.B char *\fIdata\fP;
.br
.B int \fIdatalen\fP;
.br
.B struct rrec *\fInewrr\fP;
.br
.B char *\fIbuf\fP;
.br
.B int \fIbuflen\fP;
.PP
.B res_send(\fImsg, msglen, answer, anslen\fP)
.br
.B char *\fImsg\fP;
.br
.B int \fImsglen\fP;
.br
.B char *\fIanswer\fP;
.br
.B int \fIanslen\fP;
.PP
.B res_init()
.PP
.B dn_comp(\fIexp_dn, comp_dn, length, dnptrs, lastdnptr\fP)
.br
.B char *\fIexp_dn, *comp_dn\fP;
.br
.B int \fIlength\fP;
.br
.B char **\fIdnptrs, **lastdnptr\fP;
.PP
.B dn_expand(\fImsg, eomorig, comp_dn, exp_dn, length\fP)
.br
.B char *\fImsg, *eomorig, *comp_dn, exp_dn\fP;
.br
.B int \fIlength\fP;
.SH Description
The resolver routines are used for making,
sending,
.NXR "resolver routines"
.NXR "resolver routines" "and BIND servers"
and interpreting packets to BIND servers.
Global information that is used by the
resolver routines is kept in the variable
.PN _res .
Most of the values have reasonable defaults and you need not be
concerned with them.
The options are a simple bit mask and are or'ed in to enable.
The options stored in
.PN _res.options
are defined in
.PN /usr/include/resolv.h
and are as follows:
.IP RES_INIT 19
True if the initial name server address and default domain name are
initialized,
for example if
.PN res_init
has been called.
.IP RES_DEBUG
Print debugging messages.
.IP RES_AAONLY
Accept authoritative answers only.
.\" The
.\" .B res_send
.\" routine continues until it finds an authoritative answer
.\" or finds an error.
.\" Currently this is not implemented.
.IP RES_USEVC
Use TCP connections for queries instead of UDP.
.IP RES_STAYOPEN
This is used with
.PN RES_USEVC
to keep the TCP connection open between queries.
This is useful only in programs that regularly do many queries.
You should normally use UDP.
.\" .IP RES_IGNTC
.\" Unused currently (ignore truncation errors, for example,
.\"  do not retry with TCP).
.IP RES_RECURSE
Set the recursion desired bit in queries.
This is the default.
The
.PN res_send
routine does not do iterative queries and expects the BIND server
to handle recursion.
.IP RES_DEFNAMES
Append the default domain name to single label queries.
This is the default.
.PP
The following lists the routines found in
.PN /usr/lib/libc.a
.IP res_init 16
This routine reads the initialization file to get the default
domain name and the Internet address of the initial hosts
running the name server.
If this line does not exist,
the host running the resolver is tried.
.IP res_mkquery
This routine makes a standard query message and places it in
.IR buf .
The
.I res_mkquery
routine returns the size of the query or \-1 if the query is
larger than
.IR buflen .
.RS
.IP op
The opcode is usually
.PN QUERY ,
but can be any of the query types defined in
.IR nameser.h .
.IP Dname
This variable is the domain name.
If
.I dname
consists of a single label and the
.PN RES_DEFNAMES
flag is enabled,
which is the default,
.I dname
is appended with the current domain name.
The current domain name is defined in a system file,
but you can override it by using the environment variable
.PN LOCALDOMAIN .
.RE
.\" .IP newrr
.\" This routine is currently unused,
.\" but is intended for making update messages.
.sp
.IP res_send
This routine sends a query to the BIND servers and returns an answer.
It calls the
.PN res_init
routine.
If
.PN RES_INIT
is not set, 
.PN res_send
sends the query to the local name server,
and handle timeouts and retries.
The length of the message is returned or
\-1 if there were errors.
.IP dn_comp
This routine compresses the domain name
.I exp_dn
and stores it in
.IR comp_dn .
The size of the compressed name is returned or \-1 if there were errors.
The
.I length
is the size of the array pointed to by
.IR comp_dn .
.RS
.IP dnptrs
This variable is a list of pointers to previously compressed names
in the current message.
The first pointer points to
the beginning of the message and the list ends with
.PN NULL .
.IP lastdnptr
This is a pointer to the end of the array pointed to by
.IR dnptrs .
A side effect is to update the list of pointers for
labels inserted into the message by
.I dn_comp
as the name is compressed.
If
.I dnptr
is NULL, the names are not compressed.
If
.I lastdnptr
is NULL, the list is not updated.
.RE
.IP dn_expand
This routine expands the compressed domain name
.PN comp_dn
to a full BIND domain name.
Expanded names are converted to upper case.
.RS
.IP msg
This variable is a pointer to the beginning of the message.
.IP exp_dn
This variable is a pointer to a buffer of size
.I length
for the result.
The size of the compressed name is returned or \-1 if there was an error.
.RE
.SH Files
.PN /etc/resolv.conf
.br
.PN /usr/include/resolv.h
.br
.PN /usr/include/arpa/nameser.h
.SH See Also
named(8), resolv.conf(5)
.br
.I Guide to the BIND/Hesiod Service