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SubjectRe: kernel >= 4.0: crashes when using traceroute6 with isatap
Date
Am Dienstag, 12. Mai 2015, 16:18:54 schrieb Vlad Yasevich:
> On 05/06/2015 06:11 PM, Wolfgang Walter wrote:
> > Am Mittwoch, 6. Mai 2015, 11:15:18 schrieben Sie:
> >> (Cc'ing netdev.)
> >>
> >> On Sat, May 2, 2015 at 5:29 AM, Wolfgang Walter <linux@stwm.de> wrote:
> >>> Am Samstag, 2. Mai 2015, 02:16:36 schrieb Wolfgang Walter:
> >>>> Hello,
> >>>>
> >>>> kernel 4.0 (and 4.0.1) crashes immediately when I use traceroute6 with
> >>>> an
> >>>> isatap-tunnel.
> >>>
> >>> I did some further tests. To trigger the crash you need
> >>>
> >>> * isatap-tunnel (probably any sit-tunnel will do it)
> >>> * raw-socket
> >>> * udp
> >>>
> >>> Using icmpv6 or tcp i.e. does not trigger it.
> >>
> >> Do you have a script to reproduce it?
> >>
> >>
> >> Thanks for the bug report!
> >
> > You need a isatap-server with say ipv4-address $X
> >
> > Then, on host with 4.0, start isatapd: isatapd --mtu 1280 $X
> >
> > then do
> >
> > traceroute6 www.google.de
> >
> > Regards,
>
> Hi Walter
>
> Could you try this patch. Looks like raw passes transhdrlen
> of 0 on the first packet and that makes IPv4 behave correctly,
> but not IPv6.
>
>
> diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
> index 7fde1f2..fd9c079 100644
> --- a/net/ipv6/ip6_output.c
> +++ b/net/ipv6/ip6_output.c
> @@ -1278,7 +1278,7 @@ emsgsize:
> /* If this is the first and only packet and device
> * supports checksum offloading, let's use it.
> */
> - if (!skb && sk->sk_protocol == IPPROTO_UDP &&
> + if (transhdrlen && sk->sk_protocol == IPPROTO_UDP &&
> length + fragheaderlen < mtu &&
> rt->dst.dev->features & NETIF_F_V6_CSUM &&
> !exthdrlen)

Ok, that works as fix. No crash and checksums are ok.

Regards,
--
Wolfgang Walter
Studentenwerk München
Anstalt des öffentlichen Rechts


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