NetBSD/etc/autofs/include_nis_nullfs

#!/usr/bin/awk -f
#-
# Copyright (c) 2017 G. Paul Ziemba
# All rights reserved.
#
#  Redistribution and use in source and binary forms, with or without
#  modification, are permitted provided that the following conditions
#  are met:
#  1. Redistributions of source code must retain the above copyright
#     notice, this list of conditions and the following disclaimer.
#  2. Redistributions in binary form must reproduce the above copyright
#     notice, this list of conditions and the following disclaimer in the
#     documentation and/or other materials provided with the distribution.
#
#  THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
#  ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
#  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
#  ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
#  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
#  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
#  OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
#  HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
#  LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
#  OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
#  SUCH DAMAGE.
#
# $NetBSD: include_nis_nullfs,v 1.1 2018/01/09 03:31:14 christos Exp $
#

#
# /etc/autofs/include_nis_nullfs
#
# automountd Directory Services script for NIS
#
# SYNOPSIS
#       include_nis_nullfs <mapname>
#
#       include_nis_nullfs <mapname> <key>
#
# DESCRIPTION
#
#       This script provides a Directory Services map for automountd
#       based on NIS. Please see auto_master(5) for general information.
#
#       The first form, with one argument, emits the entire named NIS map.
#       The second form, with two arguments, emits the map entry for the
#       key given in the second argument.
#
#       This script attempts to determine the names and IP addresses
#       of the local host. Map entries matching the local host are
#       rewritten to specify nullfs mounts (instead of the default
#       NFS) to reduce access overhead in the kernel.
#
#	If a map entry contains multiple location fields, it is not changed.
#


# Populate list of names and IP addrs thet mean "this host"
# into myhostnames array
BEGIN {
    #
    # Set self hostnames
    #

    "hostname -s" | getline;
    myhostnames[$0] = 1;

    "hostname -f" | getline;
    myhostnames[$0] = 1;

    myhostnames["localhost"] = 1

    "hostname -f" | getline;
    localdomain=$0
    myhostnames["localhost."localdomain] = 1

    while ("ifconfig" | getline) {
	if ($1 == "inet") {
	    myhostnames[$2] = 1;
	}
    }

    # debug
#            print "--- hostname list start ----"
#            for (i in myhostnames) {
#                print i
#            }
#            print "--- hostname list end ----"

    if (ARGC == 2) {
	# mapname only
	while ("ypcat -k " ARGV[1] | getline) {
	    proc_mapline(1)
	}
    }
    if (ARGC == 3) {
	# mapname and keyname
	while ("ypmatch " ARGV[2] " " ARGV[1] | getline) {
	    proc_mapline(0)
	}
    }
    exit 0
}

function is_self(hostname)
{
    if (myhostnames[hostname]) {
	return 1
    }
    return 0
}

#
# Lines are of the form [key] [-opts] location1 [... locationN]
#
# indicate index of key field with first positional parameter
# 1 means keyfield is the first field
# 0 means keyfield is not present
#
function proc_mapline(keyfield)
{
    optionsfield = 0
    locationfield = 0
    locationcount = 0

    for (i=keyfield+1; i <= NF; ++i) {
	if (!optionsfield) {
	    if ($i ~ /^-/) {
		# the first options field found on the line
		optionsfield = i;
		continue
	    }
	}
	# Assumption: location contains colon (":")
	if (optionsfield && ($i ~ /:/) && ($i !~ /^-/)) {
	    ++locationcount
	    if (!locationfield) {
		# the first location field found on the line
		locationfield = i
	    }
	}
    }

    #
    # If location not found, do not modify.
    #
    # If there is more than one location, do not modify. Rationale:
    # Options are applied to all locations. We ca not have "nullfs"
    # for only some locations and "nfs" for others for a given
    # map key (i.e., a line). The usual reason for multiple
    # locations is for redundancy using replicated volumes on
    # multiple hosts, so multiple hosts imply fstype=nfs (the
    # FreeBSD default for automounter maps).
    #
    # Hypothetically there could be a map entry with multiple
    # locations all with host parts matching "me". In that case,
    # it would be safe to rewrite the locations and specify
    # nullfs, but the code does not handle this case.
    #
    if (locationcount == 1) {
	#
	# We have a line with exactly one location field
	#
	# Assumption: location has no more than one colon (":")
	#
	n=split($locationfield,location,":")
	if (is_self(location[1])) {
	    $locationfield = ":" location[2]
	    if (optionsfield) {
		# append to existing options
		$optionsfield = $optionsfield ",fstype=nullfs"
	    } else {
		# sneak in ahead of location
		$locationfield = "-fstype=nullfs " $locationfield
	    }
	}
    }

    print
}