On Tue, May 18, 2021 at 12:56 PM John Fastabend <john.fastabend@xxxxxxxxx> wrote: > > Cong Wang wrote: > > On Mon, May 17, 2021 at 10:36 PM John Fastabend > > <john.fastabend@xxxxxxxxx> wrote: > > > > > > Cong Wang wrote: > > > > From: Cong Wang <cong.wang@xxxxxxxxxxxxx> > > > > > > > > sk_psock_verdict_recv() clones the skb and uses the clone > > > > afterward, so udp_read_sock() should free the original skb after > > > > done using it. > > > > > > The clone only happens if sk_psock_verdict_recv() returns >0. > > > > Sure, in case of error, no one uses the original skb either, > > so still need to free it. > > But the data is going to be dropped then. I'm questioning if this > is the best we can do or not. Its simplest sure, but could we > do a bit more work and peek those skbs or requeue them? Otherwise > if you cross memory limits for a bit your likely to drop these > unnecessarily. What are the benefits of not dropping it? When sockmap takes over sk->sk_data_ready() it should have total control over the skb's in the receive queue. Otherwise user-space recvmsg() would race with sockmap when they try to read the first skb at the same time, therefore potentially user-space could get duplicated data (one via recvmsg(), one via sockmap). I don't see any benefits but races here. Thanks.
