source: udev-lfs/write_net_rules@ b2b1e1a

#!/bin/sh -e

# This script is run to create persistent network device naming rules
# based on properties of the device.
# If the interface needs to be renamed, INTERFACE_NEW=<name> will be printed
# on stdout to allow udev to IMPORT it.

# variables used to communicate:
#   MATCHADDR             MAC address used for the match
#   MATCHID               bus_id used for the match
#   MATCHDEVID            dev_id used for the match
#   MATCHDRV              driver name used for the match
#   MATCHIFTYPE           interface type match
#   COMMENT               comment to add to the generated rule
#   INTERFACE_NAME        requested name supplied by external tool
#   INTERFACE_NEW         new interface name returned by rule writer

# Copyright (C) 2006 Marco d'Itri <md@Linux.IT>
# Copyright (C) 2007 Kay Sievers <kay.sievers@vrfy.org>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

# debug, if UDEV_LOG=<debug>
if [ -n "$UDEV_LOG" ]; then
        if [ "$UDEV_LOG" -ge 7 ]; then
                set -x
        fi
fi

RULES_FILE='/etc/udev/rules.d/70-persistent-net.rules'

. /lib/udev/rule_generator.functions

interface_name_taken() {
        local value="$(find_all_rules 'NAME=' $INTERFACE)"
        if [ "$value" ]; then
                return 0
        else
                return 1
        fi
}

find_next_available() {
        raw_find_next_available "$(find_all_rules 'NAME=' "$1")"
}

write_rule() {
        local match="$1"
        local name="$2"
        local comment="$3"

        {
        if [ "$PRINT_HEADER" ]; then
                PRINT_HEADER=
                echo "# This file was automatically generated by the $0"
                echo "# program, run by the persistent-net-generator.rules rules file."
                echo "#"
                echo "# You can modify it, as long as you keep each rule on a single"
                echo "# line, and change only the value of the NAME= key."
        fi

        echo ""
        [ "$comment" ] && echo "# $comment"
        echo "SUBSYSTEM==\"net\", ACTION==\"add\"$match, NAME=\"$name\""
        } >> $RULES_FILE
}

if [ -z "$INTERFACE" ]; then
        echo "missing \$INTERFACE" >&2
        exit 1
fi

# Prevent concurrent processes from modifying the file at the same time.
lock_rules_file

# Check if the rules file is writeable.
choose_rules_file

# the DRIVERS key is needed to not match bridges and VLAN sub-interfaces
if [ "$MATCHADDR" ]; then
        match="$match, DRIVERS==\"?*\", ATTR{address}==\"$MATCHADDR\""
fi

if [ "$MATCHDRV" ]; then
        match="$match, DRIVERS==\"$MATCHDRV\""
fi

if [ "$MATCHDEVID" ]; then
        match="$match, ATTR{dev_id}==\"$MATCHDEVID\""
fi

if [ "$MATCHID" ]; then
        match="$match, KERNELS==\"$MATCHID\""
fi

if [ "$MATCHIFTYPE" ]; then
        match="$match, ATTR{type}==\"$MATCHIFTYPE\""
fi

if [ -z "$match" ]; then
        echo "missing valid match" >&2
        unlock_rules_file
        exit 1
fi

basename=${INTERFACE%%[0-9]*}
match="$match, KERNEL==\"$basename*\""

if [ "$INTERFACE_NAME" ]; then
        # external tools may request a custom name
        COMMENT="$COMMENT (custom name provided by external tool)"
        if [ "$INTERFACE_NAME" != "$INTERFACE" ]; then
                INTERFACE=$INTERFACE_NAME;
                echo "INTERFACE_NEW=$INTERFACE"
        fi
else
        # if a rule using the current name already exists, find a new name
        if interface_name_taken; then
                INTERFACE="$basename$(find_next_available "$basename[0-9]*")"
                # prevent INTERFACE from being "eth" instead of "eth0"
                [ "$INTERFACE" = "${INTERFACE%%[ \[\]0-9]*}" ] && INTERFACE=${INTERFACE}0
                echo "INTERFACE_NEW=$INTERFACE"
        fi
fi

write_rule "$match" "$INTERFACE" "$COMMENT"

unlock_rules_file

exit 0