datapath: Avoid random tun_id in odp_packet_cmd_execute().

flow_extract() sets key->tun_id from OVS_CB(packet)->tun_id, which until
now has contained whatever Netlink put there in its NETLINK_CB structure.
Zero it earlier so that its value is at least predictable.

The resulting code is still not correct, because key->tun_id and
key->in_port are now set to arbitrary values.  I have known about this
since I wrote this function (and before, too, in its earlier incarnations),
but until now I did not think that it was a problem because I did not
think that there were any users along this code path.  But that is wrong:
sFlow sampling uses tun_id and in_port and ODP_ACTION_ATTR_CONTROLLER uses
in_port.  So we need a way to pass these back down from userspace.  An
upcoming commit will add a way.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Jesse Gross <jesse@nicira.com>

diff --git a/datapath/datapath.c b/datapath/datapath.c
index 5633dc9..b25b899 100644 (file)
--- a/datapath/datapath.c
+++ b/datapath/datapath.c
@@ -711,13 +711,13 @@ static int odp_packet_cmd_execute(struct sk_buff *skb, struct genl_info *info)
        else
                packet->protocol = htons(ETH_P_802_2);
 
+       /* Initialize OVS_CB (it came from Netlink so might not be zeroed). */
+       memset(OVS_CB(packet), 0, sizeof(struct ovs_skb_cb));
+
        err = flow_extract(packet, -1, &key, &is_frag);
        if (err)
                goto exit;
 
-       /* Initialize OVS_CB (it came from Netlink so might not be zeroed). */
-       memset(OVS_CB(packet), 0, sizeof(struct ovs_skb_cb));
-
        rcu_read_lock();
        dp = get_dp(odp_header->dp_ifindex);
        err = -ENODEV;