Re: [PATCH net-next 2/2] net: skb: use kfree_skb_with_reason() in tcp_v4_rcv()

[Menglong Dong]

On Thu, Dec 30, 2021 at 4:18 AM David Ahern <dsahern@xxxxxxxxx> wrote:
>
> On 12/29/21 7:32 AM, menglong8.dong@xxxxxxxxx wrote:
> > From: Menglong Dong <imagedong@xxxxxxxxxxx>
> >
> > Replace kfree_skb() with kfree_skb_with_reason() in tcp_v4_rcv().
> > Following drop reason are added:
> >
> > SKB_DROP_REASON_NO_SOCK
> > SKB_DROP_REASON_BAD_PACKET
> > SKB_DROP_REASON_TCP_CSUM
> >
> > After this patch, 'kfree_skb' event will print message like this:
> >
> > $           TASK-PID     CPU#  |||||  TIMESTAMP  FUNCTION
> > $              | |         |   |||||     |         |
> >           <idle>-0       [000] ..s1.    36.113438: kfree_skb: skbaddr=(____ptrval____) protocol=2048 location=(____ptrval____) reason: NO_SOCK
> >
> > The reason of skb drop is printed too.
> >
> > Signed-off-by: Menglong Dong <imagedong@xxxxxxxxxxx>
> > ---
> >  include/linux/skbuff.h     |  3 +++
> >  include/trace/events/skb.h |  3 +++
> >  net/ipv4/tcp_ipv4.c        | 10 ++++++++--
>
> your first patch set was targeting UDP and now you are starting with tcp?

Yeah, I think TCP is used more, which can be a good starting point. After
all, general protocols are all my target.

>
>
> >  3 files changed, 14 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> > index 3620b3ff2154..f85db6c035d1 100644
> > --- a/include/linux/skbuff.h
> > +++ b/include/linux/skbuff.h
> > @@ -313,6 +313,9 @@ struct sk_buff;
> >   */
> >  enum skb_drop_reason {
> >       SKB_DROP_REASON_NOT_SPECIFIED,
> > +     SKB_DROP_REASON_NO_SOCK,
>
> SKB_DROP_REASON_NO_SOCKET
>
> > +     SKB_DROP_REASON_BAD_PACKET,
>
> SKB_DROP_REASON_PKT_TOO_SMALL
>
> User oriented messages, not code based.
>

Ok, get it!

Thanks!
Menglong Dong

>
> > +     SKB_DROP_REASON_TCP_CSUM,
> >       SKB_DROP_REASON_MAX,
> >  };
> >
> > diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
> > index cab1c08a30cd..b9ea6b4ed7ec 100644
> > --- a/include/trace/events/skb.h
> > +++ b/include/trace/events/skb.h
> > @@ -11,6 +11,9 @@
> >
> >  #define TRACE_SKB_DROP_REASON                                        \
> >       EM(SKB_DROP_REASON_NOT_SPECIFIED, NOT_SPECIFIED)        \
> > +     EM(SKB_DROP_REASON_NO_SOCK, NO_SOCK)                    \
> > +     EM(SKB_DROP_REASON_BAD_PACKET, BAD_PACKET)              \
> > +     EM(SKB_DROP_REASON_TCP_CSUM, TCP_CSUM)                  \
> >       EMe(SKB_DROP_REASON_MAX, HAHA_MAX)
> >
> >  #undef EM
> > diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> > index ac10e4cdd8d0..03dc4c79b84b 100644
> > --- a/net/ipv4/tcp_ipv4.c
> > +++ b/net/ipv4/tcp_ipv4.c
> > @@ -1971,8 +1971,10 @@ int tcp_v4_rcv(struct sk_buff *skb)
> >       const struct tcphdr *th;
> >       bool refcounted;
> >       struct sock *sk;
> > +     int drop_reason;
> >       int ret;
> >
> > +     drop_reason = 0;
>
>         drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
>