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when the buffer is not long enough to hold the current host name. POSIX does not standardize error returns for gethostname(), so it doesn't matter which one we use, but ENAMETOOLONG is at least a little more intuitive, and mi suggests the existence of prior art. I've been running with this change for a while on my home machine with no effect. At the same time, I've updated the prototype for gethostname() to use the correct standard type (size_t) for the namelen argument. All of the in-tree callers fall into one of the following categories: 1) Call perror() or equivalent when gethostname() fails. 2) Ignore gethostname()'s return value entirely, potentially resulting in data corruption if the buffer is too small. 3) Fall back to a (possibly sensible) default value if gethostname() fails. Many of the callers I examined shows signs of confusion about the correct sizing of the host name buffer. gethostname(3) now has more information about this, as well as updated standards information. PR: 48114 Submitted by: mi (in part)
135 lines
3.8 KiB
Groff
135 lines
3.8 KiB
Groff
.\" Copyright (c) 1983, 1991, 1993
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.\" The Regents of the University of California. 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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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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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.\" @(#)gethostname.3 8.1 (Berkeley) 6/4/93
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.\" $FreeBSD$
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.\"
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.Dd August 18, 2003
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.Dt GETHOSTNAME 3
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.Os
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.Sh NAME
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.Nm gethostname ,
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.Nm sethostname
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.Nd get/set name of current host
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In unistd.h
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.Ft int
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.Fn gethostname "char *name" "size_t namelen"
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.Ft int
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.Fn sethostname "const char *name" "int namelen"
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.Sh DESCRIPTION
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The
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.Fn gethostname
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function
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returns the standard host name for the current processor, as
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previously set by
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.Fn sethostname .
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The
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.Fa namelen
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argument
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specifies the size of the
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.Fa name
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array.
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The returned name is null-terminated unless insufficient space is provided.
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.Pp
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The
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.Fn sethostname
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function
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sets the name of the host machine to be
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.Fa name ,
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which has length
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.Fa namelen .
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This call is restricted to the super-user and
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is normally used only when the system is bootstrapped.
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.Pp
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Host names are limited to
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.Brq Dv HOST_NAME_MAX
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characters, not including the trailing null, currently 255.
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.Sh RETURN VALUES
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.Rv -std
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.Sh ERRORS
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The following errors may be returned by these calls:
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.Bl -tag -width Er
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.It Bq Er EFAULT
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The
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.Fa name
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or
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.Fa namelen
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argument gave an
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invalid address.
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.It Bq Er ENAMETOOLONG
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The current host name is longer than
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.Fa namelen . (For
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.Fn gethostname
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only.)
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.It Bq Er EPERM
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The caller tried to set the host name and was not the super-user.
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.El
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.Sh SEE ALSO
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.Xr sysconf 3 ,
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.Xr sysctl 3
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.Sh STANDARDS
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The
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.Fn gethostname
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function conforms to
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.St -p1003.1-2001 .
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Callers should be aware that
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.Brq Dv HOST_NAME_MAX
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may be variable or infinite, but is guaranteed to be no less than
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.Brq Dv _POSIX_HOST_NAME_MAX .
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On older systems, this limit was defined in the non-standard header
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.Aq Pa sys/param.h
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as
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.Dv MAXHOSTNAMELEN ,
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and counted the terminating null.
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The
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.Fn sethostname
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function and the error returns for
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.Fn gethostname
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are not standardized.
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.Sh HISTORY
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The
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.Fn gethostname
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function appeared in
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.Bx 4.2 .
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The
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.Fa namelen
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argument to
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.Fn gethostname
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was changed to
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.Vt size_t
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in
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.Fx 5.2
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for alignment with
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.St -p1003.1-2001 .
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