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brctl addbr br0
ifconfig br0
br0 MAC is 00:00:00:00:00:00
brctl addif br0 eth1  (eth1 is xx:xx:xx:xx:xx:33)
ifconfig br0
br0 MAC is xx:xx:xx:xx:xx:33  same as eth1, auto change
brctl addif br0 eth2  (eth2 is xx:xx:xx:xx:xx:30)
ifconfig br0
br0 MAC is xx:xx:xx:xx:xx:30  same as eth2, For eth2 less than eth1, auto change
ifconfig eth2 hw ether xx:xx:xx:xx:xx:50
ifconfig br0
br0 MAC is xx:xx:xx:xx:xx:33  same as eth1, auto change
ifconfig br0 hw ether xx:xx:xx:xx:xx:99
ifconfig br0
br0 MAC is xx:xx:xx:xx:xx:33  same as eth1, NOT change
ifconfig br0 hw ether xx:xx:xx:xx:xx:33  ;same as eth1
ifconfig eth2 hw ether xx:xx:xx:xx:xx:20  ;less than eth1
ifconfig br0
br0 MAC is xx:xx:xx:xx:xx:33  same as eth1, `ifconfig br0 hw` NOT effective
ifconfig eth1 hw ether xx:xx:xx:xx:xx:50  ;upper op,we set br0 = eth1's MAC,now we change eth1 MAC
ifconfig br0
br0 MAC is xx:xx:xx:xx:xx:20  same as eth2, auto change
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  source code dir is: linux-2.4.x/net/bridge
 
  - br_device.c
      br_dev_setup() ×¢²áÁËһЩº¯Êý£¬ÆäÖР dev->set_mac_address = br_set_mac_address;  //Õâ¸ö¾ÍÊÇifconfig br0 hw etherµ÷Óõĺ¯ÊýÁË
     
      static int  br_set_mac_address(struct net_device *dev, void *addr)
          {
            struct net_bridge *br = dev->priv;
            struct sockaddr *sa = (struct sockaddr *) addr;
           
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