Add realhostname() - a function to correctly lookup
a name by address and ensure that the name resolves back to the original address.
This commit is contained in:
parent
2075407db2
commit
595f220e04
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=45392
@ -7,10 +7,10 @@ CFLAGS+=-Wall -DLIBC_SCCS -I${.CURDIR} -I${.CURDIR}/../../sys
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#CFLAGS+=LOGIN_CAP_AUTH
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SRCS= login.c login_tty.c logout.c logwtmp.c pty.c setproctitle.c \
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login_cap.c login_class.c login_auth.c login_times.c login_ok.c \
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_secure_path.c uucplock.c property.c auth.c
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_secure_path.c uucplock.c property.c auth.c realhostname.c
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MAN3+= login.3 login_auth.3 login_tty.3 logout.3 logwtmp.3 pty.3 \
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setproctitle.3 login_cap.3 login_class.3 login_times.3 login_ok.3 \
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_secure_path.3 uucplock.3 property.3 auth.3
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_secure_path.3 uucplock.3 property.3 auth.3 realhostname.3
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MAN5+= login.conf.5 auth.conf.5
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MLINKS+= property.3 properties_read.3 property.3 properties_free.3
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MLINKS+= property.3 property_find.3
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@ -18,7 +18,7 @@
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* 5. Modifications may be freely made to this file providing the above
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* conditions are met.
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*
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* $Id: libutil.h,v 1.20 1998/10/09 07:32:38 jkh Exp $
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* $Id: libutil.h,v 1.21 1998/12/16 17:52:15 bde Exp $
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*/
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#ifndef _LIBUTIL_H_
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@ -37,6 +37,7 @@ typedef struct _property {
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struct termios;
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struct winsize;
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struct utmp;
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struct in_addr;
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__BEGIN_DECLS
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void setproctitle __P((const char *_fmt, ...)) __printf0like(1, 2);
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@ -58,6 +59,7 @@ properties properties_read __P((int fd));
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void properties_free __P((properties list));
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char *property_find __P((properties list, const char *name));
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char *auth_getval __P((const char *name));
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int realhostname __P((char *host, size_t hsize, const struct in_addr *ip));
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__END_DECLS
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#define UU_LOCK_INUSE (1)
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@ -70,4 +72,10 @@ __END_DECLS
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#define UU_LOCK_TRY_ERR (-6)
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#define UU_LOCK_OWNER_ERR (-7)
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/* return values from realhostname() */
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#define HOSTNAME_FOUND (0)
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#define HOSTNAME_INCORRECTNAME (1)
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#define HOSTNAME_INVALIDADDR (2)
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#define HOSTNAME_INVALIDNAME (3)
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#endif /* !_LIBUTIL_H_ */
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106
lib/libutil/realhostname.3
Normal file
106
lib/libutil/realhostname.3
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@ -0,0 +1,106 @@
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.\" Copyright (c) 1999 Brian Somers <brian@Awfulhak.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $Id:$
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.\"
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.Dd April 6, 1999
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.Os
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.Dt REALHOSTNAME 3
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.Sh NAME
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.Nm realhostname
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.Nd "convert an IP number to the real host name"
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.Sh SYNOPSIS
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.Fd #include <sys/types.h>
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.Fd #include <netinet/in.h>
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.Fd #include <libutil.h>
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.Ft int
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.Fn realhostname "char *host" "size_t hsize" "const struct in_addr *ip"
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.Pp
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Link with
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.Va -lutil
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on the
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.Xr cc 1
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command line.
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.Sh DESCRIPTION
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The function
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.Fn realhostname
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converts
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.Ar ip
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to the corresponding host name. This is done by resolving
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.Ar ip
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to a host name and then ensuring that the host name resolves
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back to
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.Ar ip .
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.Pp
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.Ar host
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must point to a buffer of at least
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.Ar hsize
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bytes, and will always be written to by this function.
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.Pp
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If the name resolution doesn't work both ways or if the host name is longer
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than
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.Ar hsize
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bytes,
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.Xr inet_ntoa 3
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is used to convert
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.Ar ip
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to an ascii form.
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.Pp
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If the string written to
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.Ar host
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is
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.Ar hsize
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bytes long,
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.Ar host
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will not be NUL terminated.
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.Sh RETURN VALUES
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.Fn realhostname
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will return one of the following constants which are defined in
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.Pa libutil.h :
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.Pp
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.Bl -tag -width XXX -offset XXX
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.It Li HOSTNAME_FOUND
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A valid host name was found.
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.It Li HOSTNAME_INCORRECTNAME
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A host name was found, but it did not resolve back to the passed
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.Ar ip .
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.Ar host
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now contains the numeric value of
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.Ar ip .
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.It Li HOSTNAME_INVALIDADDR
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.Ar ip
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could not be resolved.
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.Ar host
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now contains the numeric value of
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.Ar ip .
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.It Li HOSTNAME_INVALIDNAME
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A host name was found, but it could not be resolved back to any ip number.
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.Ar host
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now contains the numeric value of
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.Ar ip .
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.El
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.Sh SEE ALSO
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.Xr gethostbyaddr 3 ,
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.Xr gethostbyname 3 ,
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.Xr inet_ntoa 3
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73
lib/libutil/realhostname.c
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73
lib/libutil/realhostname.c
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@ -0,0 +1,73 @@
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/*-
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* Copyright (c) 1999 Brian Somers <brian@Awfulhak.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $Id:$
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*/
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#include <sys/param.h>
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#include <sys/socket.h>
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#include <netdb.h>
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#include <netinet/in.h>
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#include <arpa/inet.h>
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#include <stdio.h>
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#include <string.h>
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#include "libutil.h"
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int
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realhostname(char *host, size_t hsize, const struct in_addr *ip)
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{
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int result;
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struct hostent *hp;
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result = HOSTNAME_INVALIDADDR;
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hp = gethostbyaddr((char *)ip, sizeof *ip, AF_INET);
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if (hp != NULL && strlen(hp->h_name) <= hsize) {
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char lookup[MAXHOSTNAMELEN + 1];
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strncpy(lookup, hp->h_name, sizeof lookup - 1);
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lookup[sizeof lookup - 1] = '\0';
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hp = gethostbyname(lookup);
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if (hp == NULL)
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result = HOSTNAME_INVALIDNAME;
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else for (; ; hp->h_addr_list++) {
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if (hp->h_addr_list[0] == NULL) {
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result = HOSTNAME_INCORRECTNAME;
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break;
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}
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if (!memcmp(*hp->h_addr_list, ip, sizeof *ip)) {
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strncpy(host, lookup, hsize);
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return HOSTNAME_FOUND;
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}
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}
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}
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strncpy(host, inet_ntoa(*ip), hsize);
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return result;
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}
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