Dear xiwang, I know that this problem is cause by switch, but what I cann do is to let linux box accommodate this situation. I have captured the packets, it shows that netgear switch just forward the same arp request without modifying anything, so the packet is totally the SAME. Best regards, Watson 2008-12-15 --------------------------------- Email: watsonlll@xxxxxxxxx ======= 2008-12-15 16:35:18 You wrote：======= >why the packet return from switch? usually, the switch don't return back the >orig-packet. > >refering to your description, i think the packet return back to linux box, >the packet already changed. so you can sniffer the packet from switch and >from linux box, compare the packet, if is there a different on SMAC field. > > > > >-----邮件原件----- >发件人: linux-net-owner@xxxxxxxxxxxxxxx [mailto:linux-net-owner@xxxxxxxxxxxx >org] 代表 watson >发送时间: 2008年12月15日 16:06 >收件人: netdev@xxxxxxxxxxxxxxx; linux-net@xxxxxxxxxxxxxxx >主题: [problem] Duplicate IP and MAC address ARP issue > >Dear guys, > >I am building a linux box base on linux kernel 2.4.31 and I can modify the >source code but can not change to other version. >eveything is ok until I connect my box to Netgear POE switch, this switch >will send ARP request packet back to box, >then box's network will "down", and can not send out any IP packet except >ARP. > >test environment: >---------------------------------------------- >| 10Mbps HUB | >| | >---------------------------------------------- > | | | > | | | >--------------------- | ---------------------- >| Linux 2.4.31 | | | Netgear POE switch | >| 192.168.0.155 | | | FS108P | >| 00:0e:e9:80:22:60 | | | | >--------------------- | ---------------------- > | >--------------------- | >| my laptop | | >| 192.168.0.8 |--| >| 00:15:58:7c:b9:1d | >--------------------- > >I found that linux box works fine before I connect netgear POE switch to the >same HUB. >I discovered netgear switch will forward ARP request which receive from HUB >back to HUB, linux box will be sick after he receive this same package. > >What I have tried: (arp.c, route.c, ip_input.c locate in >\linux-2.4.31\net\ipv4\) >1. add some code in front of arp_rcv()/arp.c to detect/drop the ARP request >packet which send back by switch, but not work. >since arp_rcv() is called by device layer and it will drop the wrong ARP >packet, I thought this packet should not affect the box, but the fact is >there. >2. discovered skb->dst will be NULL in ip_rcv_finish()/ip_input.c when box >didn't receive wrong packet, but after box receive wrong packet, skb->dst >will hold something, >so ip_rcv_finish() will not call ip_route_input(), even I get rid of the >judgement of "if (skb->dst == NULL)", ip_route_input() will return failed. > >static inline int ip_rcv_finish(struct sk_buff *skb) >{ >struct net_device *dev = skb->dev; >struct iphdr *iph = skb->nh.iph; >/* > * Initialise the virtual path cache for the packet. It describes > * how the packet travels inside Linux networking. > */ >if (skb->dst == NULL) { >if (ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, dev)) >goto drop; >} >... > >some other informaion: ># ifconfig >eth0 Link encap:Ethernet HWaddr 00:0E:E9:80:22:60 > inet addr:192.168.0.155 Bcast:192.168.0.255 Mask:255.255.255.0 > UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 > RX packets:7 errors:0 dropped:0 overruns:0 frame:0 > TX packets:216 errors:0 dropped:0 overruns:0 carrier:0 > collisions:0 txqueuelen:1000 > RX bytes:676 (676.0 B) TX bytes:9072 (8.8 KiB) > Interrupt:39 >lo Link encap:Local Loopback > inet addr:127.0.0.1 Mask:255.0.0.0 > UP LOOPBACK RUNNING MTU:16436 Metric:1 > RX packets:78 errors:0 dropped:0 overruns:0 frame:0 > TX packets:78 errors:0 dropped:0 overruns:0 carrier:0 > collisions:0 txqueuelen:0 > RX bytes:6708 (6.5 KiB) TX bytes:6708 (6.5 KiB) ># route -n >Kernel IP routing table >Destination Gateway Genmask Flags Metric Ref Use >Iface >192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 >127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 >eth0 >0.0.0.0 192.168.0.2 0.0.0.0 UG 0 0 0 >eth0 >(note: when I connect switch to HUB, route -n will output the same message) > >Another clue which I found is when box occur this problem, several "ifconfig >eth0 up" can make the network of box work again, but it will still fail >after receive wrong ARP packet. > >I have no idea how to fix this problem, it has spent me more than two weeks >and beyond my ability, so it is very appreciated if anyone can help me, >thank you! > >Best regards, >Watson > >2008-12-15 >--------------------------------- >Email: watsonlll@xxxxxxxxx > > > >-- >To unsubscribe from this list: send the line "unsubscribe linux-net" in >the body of a message to majordomo@xxxxxxxxxxxxxxx >More majordomo info at http://vger.kernel.org/majordomo-info.html > >--------------------------------------------------------------------------------------------------- >Confidentiality Notice: The information contained in this e-mail and any accompanying attachment(s) >is intended only for the use of the intended recipient and may be confidential and/or privileged of >Neusoft Corporation, its subsidiaries and/or its affiliates. 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