bridge-stp.in

#!/bin/sh
#
# Configuration is in @bridgestpconffile@
#
# `/sbin/bridge-stp <bridge> <start|stop>` is called by the kernel when STP is
# enabled/disabled on a bridge (via `brctl stp <bridge> <on|off>`).  The kernel
# enables user_stp mode if that command returns 0, or enables kernel_stp mode if
# that command returns any other value.
#
# If called with the above arguments, this script determines whether MSTP should
# be used for the specified bridge (based on the "MSTP_BRIDGES" configuration
# value), starts/stops mstpd if necessary, and calls
# `mstpctl <addbridge|delbridge> <bridge>` to add/remove the bridge from mstpd
# (possibly in a background job after a delay; see the comments in the code
# below).  No further configuration is performed automatically by this script at
# that time.  Additional configuration is usually performed by
# @ifupdownfile@ (which calls `brctl stp <bridge> on`
# to trigger this script to start mstpd if necessary).
#
# This script is not intended to be called with the above arguments directly
# (not via the kernel).  However, this script may be called directly as
# `mstpctl_restart_config` or `/sbin/bridge-stp restart_config` to reconfigure
# (using `@configbridgefile@ <bridge>` or an alternative command specified using
# a "config_cmd" configuration value) all existing bridges that are using mstpd,
# or called as `mstp_restart` or `/sbin/bridge-stp restart` to restart mstpd and
# then reconfigure all bridges that are using it.
#
# To avoid kernel deadlocks, this script (and any foreground processes it runs)
# must not make any changes (using brctl, ifconfig, ip, /sys/..., etc) to the
# bridge or any associated kernel network interfaces in any code paths that are
# used when this script is called by the kernel.

# Parse arguments.
CalledAs="$(basename "$0")"
if [ "$CalledAs" = 'mstpctl_restart_config' ]; then
    action='restart_config'
elif [ $# -eq 1 ] && [ "$1" = 'restart_config' ]; then
    action='restart_config'
elif [ "$CalledAs" = 'mstp_restart' ]; then
    action='restart'
elif [ $# -eq 1 ] && [ "$1" = 'restart' ]; then
    action='restart'
elif [ $# -eq 2 ] && [ "$2" = 'start' ]; then
    action='start'
    bridge="$1"
elif [ $# -eq 2 ] && [ "$2" = 'stop' ]; then
    action='stop'
    bridge="$1"
else
    echo "Usage: $0 <bridge> {start|stop}" >&2
    echo "   or: $0 {restart|restart_config}" >&2
    exit 1
fi

# Make sure this script is being run as root.
if [ "$(id -u)" != '0' ]; then
    echo 'This script must be run as root' >&2
    exit 1
fi

# Ensure that we have a sane umask.
umask 022

# Ensure that we have a sane PATH.
PATH='/sbin:/usr/sbin:/bin:/usr/bin'
export PATH

# Define some relevant paths.
mstpctl='@mstpctlfile@'
mstpd='@mstpdfile@'
config_cmd='@configbridgefile@'
pid_file='@mstpdpidfile@'
net_dir='/sys/class/net'

# Set default config values.
# If 'y', mstpd will be automatically started/stopped as needed.
MANAGE_MSTPD='y'
# Arguments to pass to mstpd when it is started.
MSTPD_ARGS=''
# A space-separated list of bridges for which MSTP should be used in place of
# the kernel's STP implementation.  If empty, MSTP will be used for all bridges.
MSTP_BRIDGES=''

# Read the config.
if [ -e '@bridgestpconffile@' ]; then
    . '@bridgestpconffile@'
fi

# Ensure that mstpctl and mstpd exist and are executable.
if [ -z "$mstpctl" ] || [ ! -x "$mstpctl" ]; then
    echo "mstpctl binary does not exist or is not executable" >&2
    exit 2
fi
if [ "$MANAGE_MSTPD" = 'y' ]; then
    if [ -z "$mstpd" ] || [ ! -x "$mstpd" ]; then
        echo "mstpd binary does not exist or is not executable" >&2
        exit 2
    fi
fi

# Determine whether mstpd should manage STP for the specified bridge.
# Returns 0 if mstpd should manage STP for the specified bridge, or 1 if mstpd
# should not manage STP for the specified bridge.
is_mstp_bridge()
{
    if [ -z "$MSTP_BRIDGES" ]; then
        return 0
    fi
    for b in $MSTP_BRIDGES; do
        if [ "$1" = "$b" ]; then
            return 0
        fi
    done
    return 1
}

case "$action" in
    start)
        # Make sure the specified bridge is valid.
        if [ ! -d "$net_dir/$bridge/bridge" ]; then
            echo "'$bridge' is not a bridge" >&2
            exit 1
        fi

        # Determine whether the specified bridge should use MSTP.
        if ! is_mstp_bridge "$bridge"; then
            echo "Ignoring bridge '$bridge' that is not listed in \$MSTP_BRIDGES"
            exit 10
        fi

        # Start mstpd if necessary.
        if ! pidof -c -s mstpd >/dev/null; then
            if [ "$MANAGE_MSTPD" != 'y' ]; then
                echo 'mstpd is not running' >&2
                exit 3
            fi
            echo 'mstpd is not running'
            echo 'Starting mstpd ...'
            "$mstpd" $MSTPD_ARGS || exit 3

            # Due to kernel locks, mstpd will not respond to mstpctl until after
            # this script exits, so `mstpctl addbridge <bridge>` must be run as
            # an asynchronous background process.
            # On some systems (eg. OpenWrt), mstpctl will fail if it is called
            # too soon after mstpd is started, so the call must also be delayed.
            #
            # To avoid race conditions, any scripts that configure the bridge
            # immediately after calling `brctl stp <bridge> on` should
            # explicitly call `mstpctl addbridge <bridge>` themselves before
            # configuring the bridge.  (It should not hurt to call
            # `mstpctl addbridge <bridge>` multiple times.)
            #
            # If `mstpctl addbridge` fails, we could turn STP off and back on
            # again to fall back to kernel STP mode.  However, that could cause
            # an infinite loop if mstpd is being started successfully but is
            # then dying before or when mstpctl connects to it.  To avoid that
            # possibility, we instead simply turn STP off if `mstpctl addbridge`
            # fails.
            ( sleep 1 ; "$mstpctl" addbridge "$bridge" || brctl stp "$bridge" off ) &
            exit 0
        fi

        # Add bridge to mstpd.
        "$mstpctl" addbridge "$bridge" || exit 3
        ;;
    stop)
        # Remove bridge from mstpd.
        "$mstpctl" delbridge "$bridge" || exit 3

        # Exit if mstpd should not be stopped when it is no longer used.
        if [ "$MANAGE_MSTPD" != 'y' ]; then
            exit 0
        fi

        # Exit if any other bridges are using mstpd.
        for bridge in $(ls "$net_dir"); do
            # Ignore interfaces that are not bridges.
            if [ ! -e "$net_dir/$bridge/bridge/stp_state" ]; then
                continue
            fi

            # Ignore bridges that should not use MSTP.
            if ! is_mstp_bridge "$bridge"; then
                continue
            fi

            # If bridge is in user_stp mode, then it is probably using MSTP.
            read State < "$net_dir/$bridge/bridge/stp_state"
            if [ "$State" = '2' ]; then
                exit 0
            fi
        done

        # Kill mstpd, since no bridges are currently using it.
        kill $(pidof -c mstpd)
        ;;
    restart|restart_config)
        if [ "$action" = 'restart' ]; then
            # Kill mstpd.
            pids="$(pidof -c mstpd)" ; Err=$?
            if [ $Err -eq 0 ]; then
                echo 'Stopping mstpd ...'
                kill $pids
            fi

            # Start mstpd.
            echo 'Starting mstpd ...'
            "$mstpd" $MSTPD_ARGS || exit 3
        fi

        # Reconfigure bridges.
        for bridge in $(ls "$net_dir"); do
            # Ignore interfaces that are not bridges.
            if [ ! -e "$net_dir/$bridge/bridge/stp_state" ]; then
                continue
            fi

            # Ignore bridges that should not use MSTP.
            if ! is_mstp_bridge "$bridge"; then
                continue
            fi

            # Skip bridges that have STP disabled.
            read State < "$net_dir/$bridge/bridge/stp_state"
            if [ "$State" = '0' ]; then
                echo
                echo "Skipping bridge '$bridge' that has STP disabled."
                echo "To configure this bridge to use MSTP, run:"
                echo "brctl stp '$bridge' on"
                continue
            fi

            # Skip bridges that are not in user_stp mode.
            if [ "$State" != '2' ]; then
                echo
                echo "Skipping bridge '$bridge' that is not in user_stp mode."
                echo "To reconfigure this bridge to use MSTP, run:"
                echo "brctl stp '$bridge' off ; brctl stp '$bridge' on"
                continue
            fi

            # Add bridge to mstpd and configure.
            echo "Adding/configuring bridge '$bridge' ..."
            "$mstpctl" addbridge "$bridge" || continue
            if [ -x "$config_cmd" ] || type "$config_cmd" 2>/dev/null >/dev/null ; then
                "$config_cmd" "$bridge"
            fi
        done
        echo
        echo 'Done'
        ;;
esac