On Mon, Sep 09, 2019 at 05:01:46PM +0200, Eric Dumazet wrote:
> On Mon, Sep 9, 2019 at 4:30 PM Thomas Higdon <t...@fb.com> wrote:
> > diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
> > index b3564f85a762..20237987ccc8 100644
> > --- a/include/uapi/linux/tcp.h
> > +++ b/include/uapi/linux/tcp.h
> > @@ -270,6 +270,8 @@ struct tcp_info {
> > __u64 tcpi_bytes_retrans; /* RFC4898 tcpEStatsPerfOctetsRetrans
> > */
> > __u32 tcpi_dsack_dups; /* RFC4898 tcpEStatsStackDSACKDups */
> > __u32 tcpi_reord_seen; /* reordering events seen */
> > +
> > + __u32 tcpi_rcv_ooopack; /* Out-of-order packets received */
>
> This is problematic : you create a 32bit hole in this structure that
> we will never be able to fill.
>
> We need to add another metric here so that the whole 64bit space is used.
I don't have another metric to add currently. Perhaps I could first place
a '__u32 _reserved' member so that someone else may replace it with
a 32-bit member in the future. Unless there is a canonical way to do
this? I couldn't find any prior examples.
> > diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
> > index 706cbb3b2986..2774680c5d05 100644
> > --- a/net/ipv4/tcp_input.c
> > +++ b/net/ipv4/tcp_input.c
> > @@ -4555,6 +4555,7 @@ static void tcp_data_queue_ofo(struct sock *sk,
> > struct sk_buff *skb)
> > tp->pred_flags = 0;
> > inet_csk_schedule_ack(sk);
> >
> > + tp->rcv_ooopack++;
>
> We count skbs or we count segments ?
>
> (GRO might have aggregated multiple segments)
Let's count segments -- I will copy the technique of tcp_segs_in(), which
checks the maximum of 1 and gso_segs from the lower layer. Interestingly,
on my development machine, which uses the virtio-net driver, when LRO is
enabled, gso_segs is always zero, even when an aggregated segment is
passed up the stack. I guess this may be a problem with virtio-net? It
still seems that using gso_segs here is the correct solution.
