[ovs-dev] [PATCH] datapath: Fix for force/commit action failures

[Greg Rose]

On 07/13/2017 10:08 AM, Darrell Ball wrote:
> 
> 
> On 7/13/17, 9:25 AM, "ovs-dev-bounces at openvswitch.org on behalf of Greg Rose" <ovs-dev-bounces at openvswitch.org on behalf of gvrose8192 at gmail.com> wrote:
> 
>      When there is an established connection in direction A->B, it is
>      possible to receive a packet on port B which then executes
>      ct(commit,force) without first performing ct() - ie, a lookup.
>      In this case, we would expect that this packet can delete the existing
>      entry so that we can commit a connection with direction B->A. However,
>      currently we only perform a check in skb_nfct_cached() for whether
>      OVS_CS_F_TRACKED is set and OVS_CS_F_INVALID is not set, ie that a
>      lookup previously occurred. In the above scenario, a lookup has not
>      occurred but we should still be able to statelessly look up the
>      existing entry and potentially delete the entry if it is in the
>      opposite direction.
>      
>      This patch extends the check to also hint that if the action has the
>      force flag set, then we will lookup the existing entry so that the
>      force check at the end of skb_nfct_cached has the ability to delete
>      the connection.
>      
>      CC: dev at openvswitch.org
>      CC: Pravin Shalar <pshelar at nicira.com>
>      Signed-off-by: Joe Stringer <joe at ovn.org>
>      Signed-off-by: Greg Rose <gvrose8192 at gmail.com>
>      ---
>       net/openvswitch/conntrack.c | 12 ++++++++----
>       1 file changed, 8 insertions(+), 4 deletions(-)
>      
>      diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
>      index 08679eb..9041cf8 100644
>      --- a/net/openvswitch/conntrack.c
>      +++ b/net/openvswitch/conntrack.c
>      @@ -641,17 +641,21 @@ static bool skb_nfct_cached(struct net *net,
>       	ct = nf_ct_get(skb, &ctinfo);
>       	/* If no ct, check if we have evidence that an existing conntrack entry
>       	 * might be found for this skb.  This happens when we lose a skb->_nfct
>      -	 * due to an upcall.  If the connection was not confirmed, it is not
>      -	 * cached and needs to be run through conntrack again.
>      +	 * due to an upcall, or if the direction is being forced.  If the
>      +	 * connection was not confirmed, it is not cached and needs to be run
>      +	 * through conntrack again.
>       	 */
>      -	if (!ct && key->ct_state & OVS_CS_F_TRACKED &&
>      +	if ((!ct && (key->ct_state & OVS_CS_F_TRACKED) &&
>       	    !(key->ct_state & OVS_CS_F_INVALID) &&
>      -	    key->ct_zone == info->zone.id) {
>      +	     key->ct_zone == info->zone.id) ||
>      +	     (!key->ct_state && info->force)) {
>       		ct = ovs_ct_find_existing(net, &info->zone, info->family, skb,
>       					  !!(key->ct_state
>       					     & OVS_CS_F_NAT_MASK));
>       		if (ct)
>       			nf_ct_get(skb, &ctinfo);
>      +		else
>      +			return false;
> 
> the above else case looks redundant since it maps to the following check
>       	if (!ct)
>       		return false;
> which services a superset of the code flow.

Sure, we can let it fall through... missed that.

After waiting for more review I'll send a V2 patch.

Thanks for the review Darrell

- Greg

> 
>       	}
>       	if (!ct)
>       		return false;
>      --
>      1.8.3.1
>      
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