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

On Thu, Dec 30, 2021 at 4:18 AM David Ahern [off-list ref] wrote:

On 12/29/21 7:32 AM, menglong8.dong@gmail.com wrote:

quoted

From: Menglong Dong <redacted>

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 <redacted>
---
 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.

quoted

 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

quoted

+     SKB_DROP_REASON_BAD_PACKET,

SKB_DROP_REASON_PKT_TOO_SMALL

User oriented messages, not code based.

Ok, get it!

Thanks!
Menglong Dong

quoted

+     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;