On Wed, 2024-06-12 at 09:59 +0200, Jesper Dangaard Brouer wrote:
>
> On 11/06/2024 22.11, Yan Zhai wrote:
> > skb does not include enough information to find out receiving
> > sockets/services and netns/containers on packet drops. In theory
> > skb->dev tells about netns, but it can get cleared/reused, e.g. by TCP
> > stack for OOO packet lookup. Similarly, skb->sk often identifies a local
> > sender, and tells nothing about a receiver.
> >
> > Allow passing an extra receiving socket to the tracepoint to improve
> > the visibility on receiving drops.
> >
> > Signed-off-by: Yan Zhai<y...@cloudflare.com>
> > ---
> > v3->v4: adjusted the TP_STRUCT field order to be consistent
> > v2->v3: fixed drop_monitor function prototype
> > ---
> > include/trace/events/skb.h | 11 +++++++----
> > net/core/dev.c | 2 +-
> > net/core/drop_monitor.c | 9 ++++++---
> > net/core/skbuff.c | 2 +-
> > 4 files changed, 15 insertions(+), 9 deletions(-)
> >
> > diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
> > index 07e0715628ec..3e9ea1cca6f2 100644
> > --- a/include/trace/events/skb.h
> > +++ b/include/trace/events/skb.h
> > @@ -24,13 +24,14 @@ DEFINE_DROP_REASON(FN, FN)
> > TRACE_EVENT(kfree_skb,
> >
> > TP_PROTO(struct sk_buff *skb, void *location,
> > - enum skb_drop_reason reason),
> > + enum skb_drop_reason reason, struct sock *rx_sk),
> >
> > - TP_ARGS(skb, location, reason),
> > + TP_ARGS(skb, location, reason, rx_sk),
> >
> > TP_STRUCT__entry(
> > __field(void *, skbaddr)
> > __field(void *, location)
> > + __field(void *, rx_skaddr)
>
> Is there any reason for appending the "addr" part to "rx_sk" ?
> It makes it harder to read this is the sk (socket).
>
> AFAICR the skbaddr naming is a legacy thing.
I'm double-minded about the above: I can see your point, but on the
flip side the 'addr' suffix is consistently used in net-related
tracepoints.
>
> > __field(unsigned short, protocol)
> > __field(enum skb_drop_reason, reason)
> > ),
> > @@ -38,12 +39,14 @@ TRACE_EVENT(kfree_skb,
> > TP_fast_assign(
> > __entry->skbaddr = skb;
> > __entry->location = location;
> > + __entry->rx_skaddr = rx_sk;
> > __entry->protocol = ntohs(skb->protocol);
> > __entry->reason = reason;
> > ),
> >
> > - TP_printk("skbaddr=%p protocol=%u location=%pS reason: %s",
> > - __entry->skbaddr, __entry->protocol, __entry->location,
> > + TP_printk("skbaddr=%p rx_skaddr=%p protocol=%u location=%pS reason: %s",
> ^^^^^^^^^
> I find it hard to visually tell skbaddr and rx_skaddr apart.
> And especially noticing the "skb" vs "sk" part of the string.
I agree 'rx_skaddr' is sub-optimal. Either be consistent with all the
other net tracepoints and use 'skaddr' (which will very likely will
increase Jesper concerns, but I personally have no problem with such
format) or prefer readability with something alike 'rx_sk' or (even
better) 'sk'.
Thanks,
Paolo
