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[v1,net-next,09/12] af_unix: Set drop reason in manage_oob().

Message ID 20250110092641.85905-10-kuniyu@amazon.com (mailing list archive)
State Changes Requested
Delegated to: Netdev Maintainers
Headers show
Series af_unix: Set skb drop reason in every kfree_skb() path. | expand

Commit Message

Kuniyuki Iwashima Jan. 10, 2025, 9:26 a.m. UTC 
AF_UNIX SOCK_STREAM socket supports MSG_OOB.

When OOB data is sent to a socket, recv() will break at that point.

If the next recv() does not have MSG_OOB, the normal data following
the OOB data is returned.

Then, the OOB skb is dropped.

Let's define a new drop reason for that case in manage_oob().

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

  # python3
  >>> from socket import *
  >>> s1, s2 = socketpair(AF_UNIX)
  >>> s1.send(b'a', MSG_OOB)
  >>> s1.send(b'b')
  >>> s2.recv(2)
  b'b'

  # cat /sys/kernel/tracing/trace_pipe
  ...
     python3-223 ... kfree_skb: ... location=unix_stream_read_generic+0x59e/0xc20 reason: UNIX_SKIP_OOB

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 include/net/dropreason-core.h | 6 ++++++
 net/unix/af_unix.c            | 2 +-
 2 files changed, 7 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h
index dea6bbe3ceaa..43e20acaa98a 100644
--- a/include/net/dropreason-core.h
+++ b/include/net/dropreason-core.h
@@ -12,6 +12,7 @@ 
 	FN(SOCKET_RCVBUFF)		\
 	FN(SOCKET_RCV_SHUTDOWN)		\
 	FN(UNIX_INFLIGHT_FD_LIMIT)	\
+	FN(UNIX_SKIP_OOB)		\
 	FN(PKT_TOO_SMALL)		\
 	FN(TCP_CSUM)			\
 	FN(UDP_CSUM)			\
@@ -156,6 +157,11 @@  enum skb_drop_reason {
 	 * are passed via SCM_RIGHTS but not yet received, reaching RLIMIT_NOFILE.
 	 */
 	SKB_DROP_REASON_UNIX_INFLIGHT_FD_LIMIT,
+	/**
+	 * @SKB_DROP_REASON_UNIX_SKIP_OOB: Out-Of-Band data is skipped by
+	 * recv() without MSG_OOB so dropped.
+	 */
+	SKB_DROP_REASON_UNIX_SKIP_OOB,
 	/** @SKB_DROP_REASON_PKT_TOO_SMALL: packet size is too small */
 	SKB_DROP_REASON_PKT_TOO_SMALL,
 	/** @SKB_DROP_REASON_TCP_CSUM: TCP checksum error */
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 1dfe791e8991..06d90767040e 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -2744,7 +2744,7 @@  static struct sk_buff *manage_oob(struct sk_buff *skb, struct sock *sk,
 	spin_unlock(&sk->sk_receive_queue.lock);
 
 	consume_skb(read_skb);
-	kfree_skb(unread_skb);
+	kfree_skb_reason(unread_skb, SKB_DROP_REASON_UNIX_SKIP_OOB);
 
 	return skb;
 }