On Tue, 4 Jun 2024 14:47:38 -0700 Yan Zhai <[email protected]> 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 <[email protected]> > --- > 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..aa6b46b6172c 100644 > --- a/include/trace/events/skb.h > +++ b/include/trace/events/skb.h > @@ -24,15 +24,16 @@ 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(unsigned short, protocol) > __field(enum skb_drop_reason, reason) > + __field(void *, rx_skaddr) Please add the pointer after the other pointers: __field(void *, skbaddr) __field(void *, location) + __field(void *, rx_skaddr) __field(unsigned short, protocol) __field(enum skb_drop_reason, reason) otherwise you are adding holes in the ring buffer event. The TP_STRUCT__entry() is a structure that is saved in the ring buffer. We want to avoid alignment holes. I also question having a short before the enum, if the emum is 4 bytes. The short should be at the end. In fact, looking at the format file, there is a 2 byte hole: # cat /sys/kernel/tracing/events/skb/kfree_skb/format name: kfree_skb ID: 1799 format: field:unsigned short common_type; offset:0; size:2; signed:0; field:unsigned char common_flags; offset:2; size:1; signed:0; field:unsigned char common_preempt_count; offset:3; size:1; signed:0; field:int common_pid; offset:4; size:4; signed:1; field:void * skbaddr; offset:8; size:8; signed:0; field:void * location; offset:16; size:8; signed:0; field:unsigned short protocol; offset:24; size:2; signed:0; field:enum skb_drop_reason reason; offset:28; size:4; signed:0; Notice that "protocol" is 2 bytes in size at offset 24, but "reason" starts at offset 28. This means at offset 26, there's a 2 byte hole. -- Steve > ), > > TP_fast_assign( > @@ -40,12 +41,14 @@ TRACE_EVENT(kfree_skb, > __entry->location = location; > __entry->protocol = ntohs(skb->protocol); > __entry->reason = reason; > + __entry->rx_skaddr = rx_sk; > ), >
