On 26/2/26 09:43, Jakub Kicinski wrote:

On Wed, 25 Feb 2026 15:46:33 +0800 Leon Hwang wrote:

quoted

Issue:
When a TCP socket in the CLOSE_WAIT state receives a RST packet, the
current implementation does not clear the socket's receive queue. This
causes SKBs in the queue to remain allocated until the socket is
explicitly closed by the application. As a consequence:

1. The page pool pages held by these SKBs are not released.

On what kernel version and driver are you observing this?

# uname -r
6.19.0-061900-generic

# ethtool -i eth0
driver: mlx5_core
version: 6.19.0-061900-generic
firmware-version: 26.43.2566 (MT_0000000531)

In addition, the Python scripts below reproduce that SKBs remain in the
receive queue.

Thanks,
Leon

---

server.py:

import socket
import time

HOST, PORT = "127.0.0.1", 9999

s = socket.socket()
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.setsockopt(socket.SOL_SOCKET, socket.SO_RCVBUF, 8 * 1024)

s.bind((HOST, PORT))
s.listen(1)

conn, addr = s.accept()
print("accepted", addr)

time.sleep(1)

print("Read 1st:", conn.recv(1))

try:
    conn.send(b"A")
    print("sent 1 byte to client")
except Exception as e:
    print("send failed:", e)

time.sleep(1)

conn.settimeout(0.2)
try:
    b = conn.recv(1)
    print("recv(1) after RST:", b, "len=", len(b))
except Exception as e:
    print("recv(1) after RST raised:", repr(e))

print("Conn remains opening..")

try:
    print("Press Ctrl+C to stop...")
    while True:
        time.sleep(1)
except KeyboardInterrupt:
    print("\nProgram interrupted by user. Exiting.")

conn.close()
s.close()


client.py:

import socket
import time

HOST, PORT = "127.0.0.1", 9999

c = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
c.connect((HOST, PORT))

payload = b"x" * (4 * 1024)  # 4KiB
c.sendall(payload)
time.sleep(0.1)
c.close()

time.sleep(3)