[ovs-dev] [PATCH] Avoid crash in OvS while transmitting fragmented packets over tunnel.

Darrell Ball dball at vmware.com
Thu May 10 20:45:34 UTC 2018


Thanks Rohith
I see this patch was applied, but I have one question inline.


On 4/20/18, 1:48 AM, "ovs-dev-bounces at openvswitch.org on behalf of Rohith Basavaraja" <ovs-dev-bounces at openvswitch.org on behalf of rohith.basavaraja at ericsson.com> wrote:

    Currently when fragmented packets are to be transmitted in to tunnel,
    base_flow->nw_frag which was initially non-zero at reception is not
    reset to zero when the base_flow and flow are rewritten
    as part of the emulated tnl_push action in the ofproto-dpif-xlate
    module.
    
    Because of this when fragmented packets are transmitted out of tunnel,
    we hit crash caused by the following assert.
    
    lib/odp-util.c:5654: assertion flow->nw_proto == base_flow->nw_proto &&
    flow->nw_frag == base_flow->nw_frag failed in commit_set_ipv4_action()

Can you describe how you hit this assertion?
I have some testing in and around this code, but have not hit this yet, so I was curious?

    With the following change propagate_tunnel_data_to_flow__
    is modified to reset *nw_frag* to zero. 


    Also, that currently we don't
    fragment tunnelled packets, we should reset *nw_frag* to zero in
    propagate_tunnel_data_to_flow__.

    Signed-off-by: Jan Scheurich <jan.scheurich at ericsson.com>
    From: Rohith Basavaraja <rohith.basavaraja at ericsson.com>
    CC: Jan Scheurich <jan.scheurich at ericsson.com>
    
    ---
     ofproto/ofproto-dpif-xlate.c | 1 +
     1 file changed, 1 insertion(+)
    
    diff --git a/ofproto/ofproto-dpif-xlate.c b/ofproto/ofproto-dpif-xlate.c
    index 94e3ddb..e9ed037 100644
    --- a/ofproto/ofproto-dpif-xlate.c
    +++ b/ofproto/ofproto-dpif-xlate.c
    @@ -3310,6 +3310,7 @@ propagate_tunnel_data_to_flow__(struct flow *dst_flow,
         dst_flow->ipv6_dst = src_flow->tunnel.ipv6_dst;
         dst_flow->ipv6_src = src_flow->tunnel.ipv6_src;
     
    +    dst_flow->nw_frag = 0; /* Tunnel packets are unfragmented. */


         dst_flow->nw_tos = src_flow->tunnel.ip_tos;
         dst_flow->nw_ttl = src_flow->tunnel.ip_ttl;
         dst_flow->tp_dst = src_flow->tunnel.tp_dst;
    -- 
    1.9.1
    
    
    
    
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