netdev - Re: BUG: IPv6 stops working after a while, needs ip ne del command to reset

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Date:	Tue, 17 Aug 2010 15:15:20 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Thomas Habets <thomas@...ets.pp.se>
Cc:	linux-kernel@...r.kernel.org, netdev <netdev@...r.kernel.org>
Subject: Re: BUG: IPv6 stops working after a while, needs ip ne del command
 to reset

Le mardi 17 août 2010 à 13:08 +0200, Thomas Habets a écrit :
> Aha! New development:
> 
> The Cisco router can't discover the address of the Linux box because Linux 
> doesn't seem to be listening to ff02::1 (all-nodes).
> 
> -----------
> cisco#ping ff02::1
> Output Interface: GigabitEthernet1/2
> Type escape sequence to abort.
> Sending 5, 100-byte ICMP Echos to FF02::1, timeout is 2 seconds:
> Packet sent with a source address of 
> FE80::222:55FF:FE17:4B80%GigabitEthernet1/2
> 
> Request 0 timed out
> Request 1 timed out
> Request 2 timed out
> Request 3 timed out
> Request 4 timed out
> Success rate is 0 percent (0/5)
> 0 multicast replies and 0 errors.
> ------------
> 
> If i set promisc mode on the interface (tcpdump without -p or "ip link set 
> promisc on eth0") it starts working (both normal ping and the above ping 
> from the Cisco to ff02::1). It continues working until I guess the 
> neighbor table on the cisco times out (leaving it overnight seems to 
> be enough idle time) or I manually do a "clear ipv6 neig".
> 
> So great news! I can reproduce it at will with no waiting time! Right 
> after rebooting the Linux box I run "clear ipv6 neighbors" and Linux can 
> no longer ping the router. Tested reproducing it immediately after reboot.
> 
> The Linux box itself can ping ff02::1%eth0 with no problem, and gets 
> replies from the fe80:: link-local of itself and the Cisco router.
> 
> So could this be that for some reason the NIC isn't listening 
> multicast MAC address 33:33:ff:5c:00:02 ?
> 

That would be very surprising, but who knows...

Can you try : "ifconfig eth0 allmulti"

Maybe tg3 driver has a problem building the mulicast table for this 5715


> Is there a way to see the list of addresses that get past the NIC? Or can 
> this perhaps be filtered after the NIC, but before tcpdump -p?
> 
> Since this now looks like a NIC thing, here's some info about eth0:
> 
> $ dmesg | grep eth0
> [...]
> tg3 0000:03:04.0: eth0: Tigon3 [partno(N/A) rev 9003] (PCIX:133MHz:64-bit) 
> MAC address 00:24:81:a3:44:24
> tg3 0000:03:04.0: eth0: attached PHY is 5714 (10/100/1000Base-T Ethernet) 
> (WireSpeed[1])
> tg3 0000:03:04.0: eth0: RXcsums[1] LinkChgREG[0] MIirq[0] ASF[1] TSOcap[1]
> tg3 0000:03:04.0: eth0: dma_rwctrl[76148000] dma_mask[40-bit]
> [...]
> 
> $ sudo lspci -v -s 03:04.0
> 03:04.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5715 
> Gigabit Ethernet (rev a3)
> Subsystem: Hewlett-Packard Company NC326i PCIe Dual Port Gigabit Server 
> Adapter
> Flags: bus master, 66MHz, medium devsel, latency 64, IRQ 47
> Memory at fdff0000 (64-bit, non-prefetchable) [size=64K]
> Memory at fdfe0000 (64-bit, non-prefetchable) [size=64K]
> Expansion ROM at <ignored> [disabled]
> Capabilities: [40] PCI-X non-bridge device
> Capabilities: [48] Power Management version 2
> Capabilities: [50] Vital Product Data <?>
> Capabilities: [58] Message Signalled Interrupts: Mask- 64bit+ Queue=0/3 
> Enable+
> Kernel driver in use: tg3
> Kernel modules: tg3
> 
> $ sudo ifconfig eth0
> eth0      Link encap:Ethernet  HWaddr 00:24:81:a3:44:24
>            inet addr:x.x.x.x  Bcast:x.x.x.x 
> Mask:255.255.255.252
>            inet6 addr: 2a00:800:752:1::5c:2/112 Scope:Global
>            inet6 addr: fe80::224:81ff:fea3:4424/64 Scope:Link
>            UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>            RX packets:928 errors:0 dropped:0 overruns:0 frame:0
>            TX packets:834 errors:0 dropped:0 overruns:0 carrier:0
>            collisions:0 txqueuelen:1000
>            RX bytes:142281 (138.9 KiB)  TX bytes:154616 (150.9 KiB)
>            Interrupt:16
> 
> I have doublechecked iptables, ip6tables and arptables, and they are 
> either not compiled in the kernel or they are empty ACCEPT lists.


If you let a "tcpdump" running with -p option, do you receive the packet
sent to ethernet dest 33:33:ff:5c:00:02 ?

If you can see it with tcpdump, then NIC gave the frame to us.



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