Test that the SO_INCOMING_NAPI_ID of a network file descriptor is
non-zero. This ensures that either the core networking stack or, in some
cases like netdevsim, the driver correctly sets the NAPI ID.

Signed-off-by: Joe Damato <jdamato@fastly.com>
---
 .../testing/selftests/drivers/net/.gitignore  |  1 +
 tools/testing/selftests/drivers/net/Makefile  |  6 +-
 .../testing/selftests/drivers/net/napi_id.py  | 24 ++++++
 .../selftests/drivers/net/napi_id_helper.c    | 83 +++++++++++++++++++
 4 files changed, 113 insertions(+), 1 deletion(-)
 create mode 100755 tools/testing/selftests/drivers/net/napi_id.py
 create mode 100644 tools/testing/selftests/drivers/net/napi_id_helper.c

diff --git a/tools/testing/selftests/drivers/net/.gitignore b/tools/testing/selftests/drivers/net/.gitignore
index ec746f374e85..72d2124fd513 100644
--- a/tools/testing/selftests/drivers/net/.gitignore
+++ b/tools/testing/selftests/drivers/net/.gitignore
@@ -1,2 +1,3 @@
 # SPDX-License-Identifier: GPL-2.0-only
+napi_id_helper
 xdp_helper
diff --git a/tools/testing/selftests/drivers/net/Makefile b/tools/testing/selftests/drivers/net/Makefile
index 0c95bd944d56..47247c2ef948 100644
--- a/tools/testing/selftests/drivers/net/Makefile
+++ b/tools/testing/selftests/drivers/net/Makefile
@@ -6,9 +6,13 @@ TEST_INCLUDES := $(wildcard lib/py/*.py) \
 		 ../../net/net_helper.sh \
 		 ../../net/lib.sh \
 
-TEST_GEN_FILES := xdp_helper
+TEST_GEN_FILES := \
+	napi_id_helper \
+	xdp_helper \
+# end of TEST_GEN_FILES
 
 TEST_PROGS := \
+	napi_id.py \
 	netcons_basic.sh \
 	netcons_fragmented_msg.sh \
 	netcons_overflow.sh \
diff --git a/tools/testing/selftests/drivers/net/napi_id.py b/tools/testing/selftests/drivers/net/napi_id.py
new file mode 100755
index 000000000000..54e51633a70a
--- /dev/null
+++ b/tools/testing/selftests/drivers/net/napi_id.py
@@ -0,0 +1,24 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+from lib.py import ksft_run, ksft_exit
+from lib.py import ksft_eq, NetDrvEpEnv
+from lib.py import bkg, cmd, rand_port, NetNSEnter
+
+def test_napi_id(cfg) -> None:
+    port = rand_port()
+    bin_remote = cfg.remote.deploy(cfg.test_dir / "napi_id_helper")
+    listen_cmd = f"{bin_remote} {cfg.addr_v['4']} {port}"
+
+    with bkg(listen_cmd, ksft_wait=3) as server:
+        cmd(f"echo a | socat - TCP:{cfg.addr_v['4']}:{port}", host=cfg.remote, shell=True)
+
+    ksft_eq(0, server.ret)
+
+def main() -> None:
+    with NetDrvEpEnv(__file__) as cfg:
+        ksft_run([test_napi_id], args=(cfg,))
+    ksft_exit()
+
+if __name__ == "__main__":
+    main()
diff --git a/tools/testing/selftests/drivers/net/napi_id_helper.c b/tools/testing/selftests/drivers/net/napi_id_helper.c
new file mode 100644
index 000000000000..7e8e7d373b61
--- /dev/null
+++ b/tools/testing/selftests/drivers/net/napi_id_helper.c
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <arpa/inet.h>
+#include <sys/socket.h>
+
+#include "ksft.h"
+
+int main(int argc, char *argv[])
+{
+	struct sockaddr_in address;
+	unsigned int napi_id;
+	unsigned int port;
+	socklen_t optlen;
+	char buf[1024];
+	int opt = 1;
+	int server;
+	int client;
+	int ret;
+
+	server = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
+	if (server < 0) {
+		perror("socket creation failed");
+		if (errno == EAFNOSUPPORT)
+			return -1;
+		return 1;
+	}
+
+	port = atoi(argv[2]);
+
+	if (setsockopt(server, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt))) {
+		perror("setsockopt");
+		return 1;
+	}
+
+	address.sin_family = AF_INET;
+	inet_pton(AF_INET, argv[1], &address.sin_addr);
+	address.sin_port = htons(port);
+
+	if (bind(server, (struct sockaddr *)&address, sizeof(address)) < 0) {
+		perror("bind failed");
+		return 1;
+	}
+
+	if (listen(server, 1) < 0) {
+		perror("listen");
+		return 1;
+	}
+
+	ksft_ready();
+
+	client = accept(server, NULL, 0);
+	if (client < 0) {
+		perror("accept");
+		return 1;
+	}
+
+	optlen = sizeof(napi_id);
+	ret = getsockopt(client, SOL_SOCKET, SO_INCOMING_NAPI_ID, &napi_id,
+			 &optlen);
+	if (ret != 0) {
+		perror("getsockopt");
+		return 1;
+	}
+
+	read(client, buf, 1024);
+
+	ksft_wait();
+
+	if (napi_id == 0) {
+		fprintf(stderr, "napi ID is 0\n");
+		return 1;
+	}
+
+	close(client);
+	close(server);
+
+	return 0;
+}
-- 
2.43.0

On Fri, 18 Apr 2025 01:37:05 +0000 Joe Damato wrote:
> +    bin_remote = cfg.remote.deploy(cfg.test_dir / "napi_id_helper")
> +    listen_cmd = f"{bin_remote} {cfg.addr_v['4']} {port}"
> +
> +    with bkg(listen_cmd, ksft_wait=3) as server:

Sorry, not sure how I misread v2 but you are running the helper locally.
So you don't have to deploy it to the remote machine :(

BTW does removing the ksft_wait() from the binary work? Or does it
cause trouble? Don't think we need to wait for anything in this case.
With the XSK test we had to wait for the test to do the inspection
before we unbound. Here once we get the connection we can just exit, no?

On Wed, Apr 23, 2025 at 04:16:12PM -0700, Jakub Kicinski wrote:
> On Fri, 18 Apr 2025 01:37:05 +0000 Joe Damato wrote:
> > +    bin_remote = cfg.remote.deploy(cfg.test_dir / "napi_id_helper")
> > +    listen_cmd = f"{bin_remote} {cfg.addr_v['4']} {port}"
> > +
> > +    with bkg(listen_cmd, ksft_wait=3) as server:
> 
> Sorry, not sure how I misread v2 but you are running the helper locally.
> So you don't have to deploy it to the remote machine :(

OK I can remove that and fix the macro guard for the v4.

> BTW does removing the ksft_wait() from the binary work? Or does it
> cause trouble? Don't think we need to wait for anything in this case.
> With the XSK test we had to wait for the test to do the inspection
> before we unbound. Here once we get the connection we can just exit, no?

I agree that we can just exit, but removing the wait breaks ksft
utils:

# Exception| Traceback (most recent call last):
# Exception|   File "/home/jdamato/code/net-next/tools/testing/selftests/net/lib/py/ksft.py", line 223, in ksft_run
# Exception|     case(*args)
# Exception|   File "/home/jdamato/code/net-next/./tools/testing/selftests/drivers/net/napi_id.py", line 13, in test_napi_id
# Exception|     with bkg(listen_cmd, ksft_wait=3) as server:
# Exception|   File "/home/jdamato/code/net-next/tools/testing/selftests/net/lib/py/utils.py", line 130, in __exit__
# Exception|     return self.process(terminate=self.terminate, fail=self.check_fail)
# Exception|            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
# Exception|   File "/home/jdamato/code/net-next/tools/testing/selftests/net/lib/py/utils.py", line 78, in process
# Exception|     os.write(self.ksft_term_fd, b"1")
# Exception| BrokenPipeError: [Errno 32] Broken pipe

LMK how you'd like me to proceed ?

I'm thinking:
  - Leave ksft_wait()
  - macro guard
  - don't deploy helper to remote machine

On Wed, 23 Apr 2025 17:06:05 -0700 Joe Damato wrote:
> # Exception| Traceback (most recent call last):
> # Exception|   File "/home/jdamato/code/net-next/tools/testing/selftests/net/lib/py/ksft.py", line 223, in ksft_run
> # Exception|     case(*args)
> # Exception|   File "/home/jdamato/code/net-next/./tools/testing/selftests/drivers/net/napi_id.py", line 13, in test_napi_id
> # Exception|     with bkg(listen_cmd, ksft_wait=3) as server:
> # Exception|   File "/home/jdamato/code/net-next/tools/testing/selftests/net/lib/py/utils.py", line 130, in __exit__
> # Exception|     return self.process(terminate=self.terminate, fail=self.check_fail)
> # Exception|            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> # Exception|   File "/home/jdamato/code/net-next/tools/testing/selftests/net/lib/py/utils.py", line 78, in process
> # Exception|     os.write(self.ksft_term_fd, b"1")
> # Exception| BrokenPipeError: [Errno 32] Broken pipe

Thanks for testing! Makes sense, I don't think it's worth complicating
the Python side to handle the "ready but no wait" case if it doesnt
work as is.

> LMK how you'd like me to proceed ?
> 
> I'm thinking:
>   - Leave ksft_wait()
>   - macro guard
>   - don't deploy helper to remote machine

SG!