ip addr flush hangs

ip addr flush hangs

[Olaf Kirch]

Hi,

I'm currently debugging the following problem: on a 2.6.3
kernel, when doing this

	ifconfig eth0 down
	ip addr flush dev eth0

The second command hangs indefinitely. The reason is that the kernel
reports ipv6-all-hosts (ff02::1) when dumping all addresses, but
RTM_DELADDR on ff02::1 doesn't do anything. As /sbin/ip will loop until
the kernel reports no more matching addresses, it will go on like that
forever.

I don't see an obvious fix to this issue. On one hand, calling ifconfig
down will result in a call to addrconf_ifdown(dev, 0).  This will clear
the list of unicast addresses assigned to this interface, but will not
clear the list of multicast addresses (it unloads them from the NIC,
and sends IGMP leave packets, but the list of addresses will remain
attached to the device). So it doesn't destroy the interface completely,
it zaps its state just partly, intentionally.

On the other hand, if you manually remove all addresses from the
interface, this will result in a call to addrconf_ifdown(dev, 1),
causing the mcast list to be zapped as well.

This is not entirely consistent. Should a NETDEV_DOWN zap the
ipv6 configuration completely?

Olaf
-- 
Olaf Kirch     |  Stop wasting entropy - start using predictable
okir@suse.de   |  tempfile names today!
---------------+ 

Re: ip addr flush hangs

[Olaf Kirch]

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On Tue, Mar 09, 2004 at 03:48:24PM +0100, Olaf Kirch wrote:
> This is not entirely consistent. Should a NETDEV_DOWN zap the
> ipv6 configuration completely?

Sorry to follow up on my own mail...

Cross-checking ipv4, I can see that it behaves the same way as IPv6
(i.e. NETDEV_DOWN partly leaves the interface configuration intact).
The difference though is that dump_ifaddr doesn't include multicast
addresses in its report.

The attached patch disables reporting of multicast and anycast
addresses in inet6_dump_ifaddr

Olaf
-- 
Olaf Kirch     |  Stop wasting entropy - start using predictable
okir@suse.de   |  tempfile names today!
---------------+ 

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--- linux-2.6.3/net/ipv6/addrconf.c.orig	2004-03-09 15:46:33.000000000 +0100
+++ linux-2.6.3/net/ipv6/addrconf.c	2004-03-09 16:04:54.000000000 +0100
@@ -2898,6 +2898,11 @@ static int inet6_dump_ifaddr(struct sk_b
 				goto done;
 		}
 #endif
+		/* You can't delete these via RTM_DELADDR, so we shouldn't
+		 * display them here. Otherwise "ip addr flush" will loop
+		 * forever trying to delete ff02::1 etc.
+		 * 				--okir */
+#if 0
 		/* multicast address */
 		for (ifmca = idev->mc_list; ifmca; 
 		     ifmca = ifmca->next, ip_idx++) {
@@ -2918,6 +2923,7 @@ static int inet6_dump_ifaddr(struct sk_b
 			    cb->nlh->nlmsg_seq, RTM_NEWADDR)) <= 0) 
 				goto done;
 		}
+#endif
 		read_unlock_bh(&idev->lock);
 		in6_dev_put(idev);
 	}

Re: ip addr flush hangs

[David S. Miller]

On Tue, 9 Mar 2004 16:07:30 +0100
Olaf Kirch <okir@suse.de> wrote:

> The attached patch disables reporting of multicast and anycast
> addresses in inet6_dump_ifaddr

Better to fix /sbin/ip, Andi Kleen posted a patch for that tool
in a thread on linux-kernel about this very issue.

Re: ip addr flush hangs

[Andi Kleen]

On Tue, Mar 09, 2004 at 11:25:29AM -0800, David S. Miller wrote:
> On Tue, 9 Mar 2004 16:07:30 +0100
> Olaf Kirch <okir@suse.de> wrote:
> 
> > The attached patch disables reporting of multicast and anycast
> > addresses in inet6_dump_ifaddr
> 
> Better to fix /sbin/ip, Andi Kleen posted a patch for that tool
> in a thread on linux-kernel about this very issue.

The patch was buggy unfortunately - it fixed one case, but broke another.
Fixing the root cause like Olaf proposes is better.

-Andi

Re: ip addr flush hangs

[David S. Miller]

On Tue, 9 Mar 2004 20:44:26 +0100
Andi Kleen <ak@suse.de> wrote:

> The patch was buggy unfortunately - it fixed one case, but broke another.
> Fixing the root cause like Olaf proposes is better.

Ok, I'll review Olaf's patch then.

Thanks.

Re: ip addr flush hangs

[Olaf Kirch]

On Tue, Mar 09, 2004 at 11:25:29AM -0800, David S. Miller wrote:
> > The attached patch disables reporting of multicast and anycast
> > addresses in inet6_dump_ifaddr
> 
> Better to fix /sbin/ip, Andi Kleen posted a patch for that tool
> in a thread on linux-kernel about this very issue.

His patch breaks ip addr flush completely, because it breaks the loop
before flushing the RTM_DELADDR packet to the netlink socket.

Even if you fix it to break out ofthe loop in the proper place, it is
still not entirely correct.  ip does addr list and addr flush in a loop,
because netlink can return only so many addresses in one packet. If you
break out of the loop unconditionally, as Andi does in his patch, you
break ip addr list/flush for systems with more than the normal number
of addresses per device.

I think IPv6 is really wrong in reporting multicast addresses via
RTM_GETADDR. IPv4 doesn't do this either.

Olaf
-- 
Olaf Kirch     |  Stop wasting entropy - start using predictable
okir@suse.de   |  tempfile names today!
---------------+ 

Re: ip addr flush hangs

[David S. Miller]

On Tue, 9 Mar 2004 16:07:30 +0100
Olaf Kirch <okir@suse.de> wrote:

> The attached patch disables reporting of multicast and anycast
> addresses in inet6_dump_ifaddr

Applied, except I changed it to just remove the code entirely instead
of commenting it out.

Re: ip addr flush hangs

[Shirley Ma]

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Hi, Dave,

This fix causes a problem for SNMP IPv6 MIBs. It requires to dump all
interface
address types unicast/mcast/anycast. I would like suggest to fix the ip
command to fix the problem.

Thanks
Shirley Ma
IBM Linux Technology Center
15300 SW Koll Parkway
Beaverton, OR 97006-6063
Phone: (503) 578-7638
FAX:      (503) 578-3228

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Re: ip addr flush hangs

[David S. Miller]

On Tue, 9 Mar 2004 15:56:00 -0800
Shirley Ma <xma@us.ibm.com> wrote:

> This fix causes a problem for SNMP IPv6 MIBs. It requires to dump all
> interface
> address types unicast/mcast/anycast. I would like suggest to fix the ip
> command to fix the problem.

We changed behavior which unexpectedly broke a pretty core tool
on everyone's system.  I'm not reverting this.

Create instead a new rtnetlink command which can ask for xxx_cast
type addresses on an interface.

Re: ip addr flush hangs

[YOSHIFUJI Hideaki / 吉藤英明]

In article <OF34091B26.07758A8E-ON87256E52.00833C04-88256E53.00004022@us.ibm.com> (at Tue, 9 Mar 2004 15:56:00 -0800), Shirley Ma <xma@us.ibm.com> says:

> This fix causes a problem for SNMP IPv6 MIBs. It requires to dump all
> interface
> address types unicast/mcast/anycast. I would like suggest to fix the ip
> command to fix the problem.

Grr... Putting anycast/multicast is not good idea.
(Sorry, I did not notice at that time...)

Anycast should use IFA_ANYCAST ifaddrmsg instead of IFA_ADDRESS.
Multicast should be provided in a different way (different rtmsg),
or use IFA_MULTICAST or something like that.

--yoshfuji

Re: ip addr flush hangs

[Shirley Ma]

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OK, I will submit a patch for anycast and multicast addresses throught
different rtmsg.

Thanks
Shirley Ma
IBM Linux Technology Center
15300 SW Koll Parkway
Beaverton, OR 97006-6063
Phone: (503) 578-7638
FAX:      (503) 578-3228




                                                                       
             YOSHIFUJI Hideaki                                         
             / 吉藤英明                                      
             <yoshfuji@linux-i                                          To
             pv6.org>                  davem@redhat.com,               
             Sent by: "Hideaki         netdev@oss.sgi.com, Shirley     
             YOSHIFUJI"                Ma/Beaverton/IBM@IBMUS          
             <yoshfuji@cerberu                                          cc
             s.hongo.wide.ad.j         okir@suse.de,                   
             p>                        yoshfuji@linux-ipv6.org         
                                                                   Subject
                                       Re: ip addr flush hangs         
             03/09/2004 07:32                                          
             PM                                                        
                                                                       
                                                                       
                                                                       
                                                                       




In article
<OF34091B26.07758A8E-ON87256E52.00833C04-88256E53.00004022@us.ibm.com> (at
Tue, 9 Mar 2004 15:56:00 -0800), Shirley Ma <xma@us.ibm.com> says:

> This fix causes a problem for SNMP IPv6 MIBs. It requires to dump all
> interface
> address types unicast/mcast/anycast. I would like suggest to fix the ip
> command to fix the problem.

Grr... Putting anycast/multicast is not good idea.
(Sorry, I did not notice at that time...)

Anycast should use IFA_ANYCAST ifaddrmsg instead of IFA_ADDRESS.
Multicast should be provided in a different way (different rtmsg),
or use IFA_MULTICAST or something like that.

--yoshfuji

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