Commit c32f0bd7 authored by Kuniyuki Iwashima's avatar Kuniyuki Iwashima Committed by Jakub Kicinski
Browse files

af_unix: Set drop reason in unix_release_sock(). 



unix_release_sock() is called when the last refcnt of struct file
is released.

Let's define a new drop reason SKB_DROP_REASON_SOCKET_CLOSE and
set it for kfree_skb() in unix_release_sock().

  # echo 1 > /sys/kernel/tracing/events/skb/kfree_skb/enable

  # python3
  >>> from socket import *
  >>> s1, s2 = socketpair(AF_UNIX)
  >>> s1.send(b'hello world')
  >>> s2.close()

  # cat /sys/kernel/tracing/trace_pipe
  ...
     python3-280 ... kfree_skb: ... protocol=0 location=unix_release_sock+0x260/0x420 reason: SOCKET_CLOSE

To be precise, unix_release_sock() is also called for a new child
socket in unix_stream_connect() when something fails, but the new
sk does not have skb in the recv queue then and no event is logged.

Note that only tcp_inbound_ao_hash() uses a similar drop reason,
SKB_DROP_REASON_TCP_CLOSE, and this can be generalised later.

Signed-off-by: default avatarKuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250116053441.5758-3-kuniyu@amazon.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 454d4024

include/net/dropreason-core.h

+3 −0
Original line number Diff line number Diff line
@@ -6,6 +6,7 @@ 
#define DEFINE_DROP_REASON(FN, FNe)	\

	FN(NOT_SPECIFIED)		\

	FN(NO_SOCKET)			\

	FN(SOCKET_CLOSE)		\

	FN(SOCKET_FILTER)		\

	FN(SOCKET_RCVBUFF)		\

	FN(PKT_TOO_SMALL)		\
@@ -138,6 +139,8 @@ enum skb_drop_reason { 
	 * 3) no valid child socket during 3WHS process

	 */

	SKB_DROP_REASON_NO_SOCKET,

	/** @SKB_DROP_REASON_SOCKET_CLOSE: socket is close()d */

	SKB_DROP_REASON_SOCKET_CLOSE,

	/** @SKB_DROP_REASON_SOCKET_FILTER: dropped by socket filter */

	SKB_DROP_REASON_SOCKET_FILTER,

	/** @SKB_DROP_REASON_SOCKET_RCVBUFF: socket receive buff is full */

net/unix/af_unix.c

+2 −2
Original line number Diff line number Diff line
@@ -716,7 +716,7 @@ static void unix_release_sock(struct sock *sk, int embrion) 
			unix_release_sock(skb->sk, 1);



		/* passed fds are erased in the kfree_skb hook */

		kfree_skb(skb);

		kfree_skb_reason(skb, SKB_DROP_REASON_SOCKET_CLOSE);

	}



	if (path.dentry)