设备名怎么获取的？

在openwrt的路由器上，如果telnet（或ssh）进去后，使用ifconfig会看到如下接口：

root@OpenWrt:/# ifconfig
br-lan Link encap:Ethernet  HWaddr 00:64:18:23:01:29
          inet addr:192.168.1.1  Bcast:192.168.1.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:29318 errors:0 dropped:980 overruns:0 frame:0
          TX packets:23960 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:3621134 (3.4 MiB) TX bytes:7020725 (6.6 MiB)

eth0 Link encap:Ethernet  HWaddr 00:64:18:23:01:29
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:29318 errors:0 dropped:0 overruns:0 frame:0
          TX packets:23960 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:4031586 (3.8 MiB) TX bytes:7020725 (6.6 MiB)
          Interrupt:4

使用brctl show br-lan还能看到如下结果：

root@OpenWrt:/# brctl show br-lan
bridge name    bridge id        STP enabled    interfaces
br-lan        7fff.006418230129    no        eth0

那么，这个eth0是保存在哪的呢？或者说是这么获取到的？怎么判断eth0就是lan口呢？