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188 lines
4.7 KiB
Groff
188 lines
4.7 KiB
Groff
.\"
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.\" Copyright (C) 2000, 2001 Internet Software Consortium.
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.\"
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.\" Permission to use, copy, modify, and distribute this software for any
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.\" purpose with or without fee is hereby granted, provided that the above
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.\" copyright notice and this permission notice appear in all copies.
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.\"
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.\" THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM
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.\" DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
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.\" INTERNET SOFTWARE CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT,
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.\" INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
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.\" FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
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.\" NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
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.\" WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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.\"
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.TH "LWRES_GETIPNODE" "3" "Jun 30, 2000" "BIND9" ""
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.SH NAME
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lwres_getipnodebyname, lwres_getipnodebyaddr, lwres_freehostent \- lightweight resolver nodename / address translation API
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.SH SYNOPSIS
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\fB#include <lwres/netdb.h>
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.sp
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.na
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struct hostent *
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lwres_getipnodebyname(const char *name, int af, int flags, int *error_num);
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.ad
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.sp
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.na
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struct hostent *
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lwres_getipnodebyaddr(const void *src, size_t len, int af, int *error_num);
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.ad
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.sp
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.na
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void
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lwres_freehostent(struct hostent *he);
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.ad
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\fR
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.SH "DESCRIPTION"
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.PP
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These functions perform thread safe, protocol independent
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nodename-to-address and address-to-nodename
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translation as defined in RFC2553.
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.PP
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They use a
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\fBstruct hostent\fR
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which is defined in
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\fInamedb.h\fR:
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.sp
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.nf
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struct hostent {
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char *h_name; /* official name of host */
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char **h_aliases; /* alias list */
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int h_addrtype; /* host address type */
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int h_length; /* length of address */
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char **h_addr_list; /* list of addresses from name server */
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};
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#define h_addr h_addr_list[0] /* address, for backward compatibility */
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.sp
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.fi
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.PP
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The members of this structure are:
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.TP
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\fBh_name\fR
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The official (canonical) name of the host.
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.TP
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\fBh_aliases\fR
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A NULL-terminated array of alternate names (nicknames) for the host.
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.TP
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\fBh_addrtype\fR
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The type of address being returned - usually
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\fBPF_INET\fR
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or
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\fBPF_INET6\fR.
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.TP
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\fBh_length\fR
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The length of the address in bytes.
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.TP
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\fBh_addr_list\fR
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A
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\fBNULL\fR
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terminated array of network addresses for the host.
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Host addresses are returned in network byte order.
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.PP
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\fBlwres_getipnodebyname()\fR
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looks up addresses of protocol family
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\fIaf\fR
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for the hostname
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\fIname\fR.
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The
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\fIflags\fR
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parameter contains ORed flag bits to
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specify the types of addresses that are searched
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for, and the types of addresses that are returned.
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The flag bits are:
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.TP
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\fBAI_V4MAPPED\fR
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This is used with an
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\fIaf\fR
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of AF_INET6, and causes IPv4 addresses to be returned as IPv4-mapped
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IPv6 addresses.
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.TP
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\fBAI_ALL\fR
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This is used with an
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\fIaf\fR
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of AF_INET6, and causes all known addresses (IPv6 and IPv4) to be returned.
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If AI_V4MAPPED is also set, the IPv4 addresses are return as mapped
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IPv6 addresses.
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.TP
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\fBAI_ADDRCONFIG\fR
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Only return an IPv6 or IPv4 address if here is an active network
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interface of that type. This is not currently implemented
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in the BIND 9 lightweight resolver, and the flag is ignored.
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.TP
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\fBAI_DEFAULT\fR
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This default sets the
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AI_V4MAPPED
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and
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AI_ADDRCONFIG
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flag bits.
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.PP
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\fBlwres_getipnodebyaddr()\fR
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performs a reverse lookup
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of address
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\fIsrc\fR
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which is
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\fIlen\fR
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bytes long.
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\fIaf\fR
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denotes the protocol family, typically
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\fBPF_INET\fR
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or
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\fBPF_INET6\fR.
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.PP
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\fBlwres_freehostent()\fR
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releases all the memory associated with
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the
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\fBstruct hostent\fR
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pointer
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\fIhe\fR.
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Any memory allocated for the
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h_name,
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h_addr_list
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and
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h_aliases
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is freed, as is the memory for the
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\fBhostent\fR
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structure itself.
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.SH "RETURN VALUES"
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.PP
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If an error occurs,
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\fBlwres_getipnodebyname()\fR
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and
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\fBlwres_getipnodebyaddr()\fR
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set
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\fI*error_num\fR
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to an appropriate error code and the function returns a
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\fBNULL\fR
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pointer.
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The error codes and their meanings are defined in
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\fI<lwres/netdb.h>\fR:
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.TP
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\fBHOST_NOT_FOUND\fR
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No such host is known.
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.TP
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\fBNO_ADDRESS\fR
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The server recognised the request and the name but no address is
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available. Another type of request to the name server for the
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domain might return an answer.
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.TP
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\fBTRY_AGAIN\fR
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A temporary and possibly transient error occurred, such as a
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failure of a server to respond. The request may succeed if
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retried.
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.TP
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\fBNO_RECOVERY\fR
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An unexpected failure occurred, and retrying the request
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is pointless.
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.PP
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\fBlwres_hstrerror\fR(3)
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translates these error codes to suitable error messages.
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.SH "SEE ALSO"
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.PP
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\fBRFC2553\fR,
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\fBlwres\fR(3),
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\fBlwres_gethostent\fR(3),
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\fBlwres_getaddrinfo\fR(3),
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\fBlwres_getnameinfo\fR(3),
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\fBlwres_hstrerror\fR(3).
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