I noticed that Linux has been updated on later versions to always consume the skb in calls to dev_queue_xmit, and may even drop the skb after returning a return code of NETDEV_TX_OK which seems kind of broken. I have an application which requires guaranteed skb transmission and the following code seems to work well for me if I call the netdev->netdev_ops->ndo_start_xmit function directly instead of using dev_queue_xmit.
Is there a method of calling dev_queue_xmit which guarantees packet transmission? The current implementation of dev_queue_xmit used to return error codes without consuming the skb, which allowed programs which call it to simply resend the failing skb by calling dev_queue_xmit again without having to recreate and repopulate the skb. There also appears to be no reliable way to know for certain if dev_queue_xmit even sent a packet since it can at times return NETDEV_TX_OK then turn around and drop the packet later on. I have it working calling the ndo_start_xmit driver function directly which does seem to guarantee transmission, but would like to know if there is a way to get guaranteed TX of skb's with dev_queue_xmit. Jeff
