ipv6 activity causing system hang in kernel 2.4.4

ipv6 activity causing system hang in kernel 2.4.4

[Tim Haynes]

    [I can't see evidence of this being reported before; apols if I'm
     wrong. Please also Cc: me as I only read l-k intermittently but would
     like to help out more.]

Hi,

I've been making very tentative forays into IPv6. However, in my simple
experiments thus far I appear to have located a bug:

1/ configure 2 machines with site-local IP#s - I'm using 
        ifconfig eth0 inet6 add fec0:1234:5:6::n 
2/ flood-ping from one to the other
3/ after about 15s, watch one box hang, needing magic-sysreq or hard reset

This is only with kernel 2.4.4; 2.4.2, 2.4.3 and NetBSD boxes are not
affected. It is independent of platform; I've reproduced it at will on a
lowly p75, an athlon, a p3-800 and on a powerbook/PPC.

All kernels are compiled to have ipv6 modular, netfilter modular...
everything with which I'm playing, modular.

Compiler versions:
| zsh, 12:06AM % gcc -v
| Reading specs from /usr/lib/gcc-lib/powerpc-linux/2.95.4/specs
| gcc version 2.95.4 20010319 (Debian prerelease)
| zsh, 12:06AM % gcc -v
| Reading specs from /usr/lib/gcc-lib/i386-linux/2.95.4/specs
| gcc version 2.95.4 20010319 (Debian prerelease)
(I'm tracking Debian/Unstable here.)

I have tcpdump logs (<http://spodzone.org.uk/~tim/ipv6/> - they're 570K
apiece); the `victim' machine receives nothing but ping-requests and sends
nothing but ping-replies until the file is truncated; the surviving box
sends nothing but requests and receives nothing but replies until it
becomes requests-only. (IOW there is no evidence of ARP, fragmentation
traffic, only the pings.)

The Changelog lists an `IPv6 packet re-assembly fix' in -pre2; my
suspicions lie in this area or with my compiler.

If there's anything else I can provide by way of diagnostics, please let me
know.

Cheers,

~Tim
-- 
<http://spodzone.org.uk/>

Re: ipv6 activity causing system hang in kernel 2.4.4

[David S. Miller]

Try this patch, posted the other day.  I bet if you inspected,
you'd find OOPSes in your logs:

--- ../vanilla/linux/net/ipv6/ndisc.c	Thu Apr 26 22:17:26 2001
+++ net/ipv6/ndisc.c	Fri May  4 18:44:54 2001
@@ -394,7 +382,7 @@
 	int send_llinfo;
 
 	len = sizeof(struct icmp6hdr) + sizeof(struct in6_addr);
-	send_llinfo = dev->addr_len && ipv6_addr_type(saddr) != IPV6_ADDR_ANY;
+	send_llinfo = dev->addr_len && saddr && ipv6_addr_type(saddr) != IPV6_ADDR_ANY;
 	if (send_llinfo)
 		len += NDISC_OPT_SPACE(dev->addr_len);
 

Re: ipv6 activity causing system hang in kernel 2.4.4

[Lukasz Trabinski]

In article <871yq3mllw.fsf@straw.pigsty.org.uk> you wrote:

> This is only with kernel 2.4.4; 2.4.2, 2.4.3 and NetBSD boxes are not
> affected. It is independent of platform; I've reproduced it at will on a
> lowly p75, an athlon, a p3-800 and on a powerbook/PPC.

I have just reproduced that on 2.4.5pre-1. It was only one ping (ping6)
(from the other side of ipv6 over ipv4 tunnel.


> All kernels are compiled to have ipv6 modular, netfilter modular...
> everything with which I'm playing, modular.

My configuration is without any ipv6/netfilter modules - all build in kernel.

portraits:~# gcc -v
Reading specs from /usr/lib/gcc-lib/i386-redhat-linux/2.96/specs
gcc version 2.96 20000731 (Red Hat Linux 7.1 2.96-81)

glibc-2.2.2-10 (i686) - RedHat 7.1, 1GB RAM, 2x Pentium III



-- 
*[ Łukasz Trąbiński ]*
SysAdmin @wsisiz.edu.pl