FREEBSD 使用 ng_eiface 和 ng_bridge 创建虚拟以太网接口

使用通用以太网接口 netgraph 节点，可以创建可通过 ifconfig(8) 访问的新接口，使用以太网桥接 netgraph 节点类型可以在不同的以太网节点类型之间进行桥接。通过组合这两种类型，可以在同一物理接口上创建具有不同以太网 (MAC) 地址的多个接口。这是从标准 FreeBSD 发行版附带的 netgraph ether.bridge 示例脚本修改而来的示例脚本：

#!/bin/sh
#
# Author: Jan Melen-jan(at)melen.org
#
# This script sets up an Ethernet bridging network across multiple
# ng_eiface(4) using the ng_bridge(4) and ng_ether(4) netgraph
# node types.
#

BRIDGE_NAME="bnet0"

VIRTUAL_IFACES="ngeth0 ngeth1 ngeth2"
LOCAL_IFACE="bge0"

# Routine to verify node's existence.
vether_verify() {
    ngctl info ${BRIDGE_NAME}: >/dev/null 2>&1
    if [ $? -ne 0 ]; then
        echo "${BRIDGE_NAME}: bridge network not found"
        exit 1
    fi
}

# Start/restart routine.
vether_start() {

    # Load netgraph KLD's as necessary.
    for KLD in ng_ether ng_bridge; do
        if ! kldstat -v | grep -qw ${KLD}; then
            echo -n "Loading ${KLD}.ko... "
            kldload ${KLD} || exit 1
            echo "done"
        fi
    done

    # Reset all interfaces.
    vether_stop

    # Verify all interfaces exist.
    LINKNUM=2
   ETHERADDR=`ifconfig ${LOCAL_IFACE} ether | grep "ether" | cut -b 8-22`
    for ETHER in ${VIRTUAL_IFACES}; do
        if ! ngctl info ${ETHER}: >/dev/null 2>&1; then
           ngctl mkpeer . eiface hook ether
        fi
       ifconfig ${ETHER} ether ${ETHERADDR}${LINKNUM}
        ifconfig ${ETHER} up || exit 1
        LINKNUM=`expr ${LINKNUM} + 1`
    done

    # Create new ng_bridge(4) node, attached to the first interface.
    ngctl mkpeer ${LOCAL_IFACE}: bridge lower link0 || exit 1
    ngctl name ${LOCAL_IFACE}:lower ${BRIDGE_NAME} || exit 1
   ngctl connect ${LOCAL_IFACE}: ${BRIDGE_NAME}: upper link1 || exit 1

    LINKNUM=2
    # Attach other interfaces as well.
    for ETHER in ${VIRTUAL_IFACES}; do
        if [ ${LINKNUM} != 0 ]; then
            ngctl connect ${ETHER}: ${BRIDGE_NAME}: 
                ether link${LINKNUM} || exit 1
        fi
        LINKNUM=`expr ${LINKNUM} + 1`
    done

    # Set all interfaces in promiscuous mode and don't overwrite src addr.
    for ETHER in ${LOCAL_IFACE}; do
        ngctl msg ${ETHER}: setpromisc 1
        ngctl msg ${ETHER}: setautosrc 0
    done
}

# Stop routine.
vether_stop() {
    ngctl kill ${BRIDGE_NAME}: >/dev/null 2>&1
    for ETHER in ${VIRTUAL_IFACES} ${LOCAL_IFACE}; do
        ngctl kill ${ETHER}: >/dev/null 2>&1
    done
}

# Main entry point.
case $1 in
    start)
        vether_start
        ;;
    stop)
        vether_verify
        vether_stop
        ;;
    *)
        echo "usage: $0 [ start | stop ]"
        exit 1
esac