[U-Boot-Users] "undefined reference"error in net.c

[wang cheng <wangcheng@rails.com.cn>]

dear all,
    When I follow the steps to port u-boot to my board according to 
README  ,error appeared in "make".

   I didn't change anything about net ,but there are many "undefined 
reference"error in net.c ,displayed as below: why??

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..................
tart-group board/windriver/libwindriver.a cpu/mpc8xx/libmpc8xx.a 
lib_ppc/libppc.a fs/jffs2/libjffs2.a fs/fdos/libfdos.a fs/fat/libfat.a 
net/libnet.a disk/libdisk.a rtc/librtc.a dtt/libdtt.a 
drivers/libdrivers.a drivers/sk98lin/libsk98lin.a post/libpost.a 
post/cpu/libcpu.a common/libcommon.a lib_generic/libgeneric.a  --end-
group \
                -Map u-boot.map -o u-boot
net/libnet.a(net.o): In function `ArpRequest':
/home/wang/u-boot-0.4.8/net/net.c:185: undefined reference to `eth_send'
net/libnet.a(net.o): In function `NetLoop':
/home/wang/u-boot-0.4.8/net/net.c:257: undefined reference to `eth_halt'
/home/wang/u-boot-0.4.8/net/net.c:258: undefined reference to `eth_init'
/home/wang/u-boot-0.4.8/net/net.c:381: undefined reference to `eth_rx'
/home/wang/u-boot-0.4.8/net/net.c:387: undefined reference to `eth_halt'
/home/wang/u-boot-0.4.8/net/net.c:424: undefined reference to `eth_halt'
net/libnet.a(net.o): In function `NetSendPacket':
/home/wang/u-boot-0.4.8/net/net.c:507: undefined reference to `eth_send'
net/libnet.a(net.o): In function `NetSendUDPPacket':
/home/wang/u-boot-0.4.8/net/net.c:552: undefined reference to `eth_send'
net/libnet.a(net.o): In function `NetReceive':
/home/wang/u-boot-0.4.8/net/net.c:726: undefined reference to `eth_send'
/home/wang/u-boot-0.4.8/net/net.c:752: undefined reference to `eth_send'
make: *** [u-boot] Error 1
    
thanks !