From 37decdb0ccbbe21c811faa659d41733d7c766761 Mon Sep 17 00:00:00 2001
From: Alex Becker <alex@beckerlab.net>
Date: Thu, 17 Sep 2026 07:33:52 -0500
Subject: [PATCH] fix: add .netns_ok flag + regression test for Linux < 5.14

---
 homa_plumbing.c           |  1 +
 test/mock.c               |  8 ++++++++
 test/mock.h               |  3 +++
 test/unit_homa_plumbing.c | 34 ++++++++++++++++++++++++++++++++++
 4 files changed, 46 insertions(+)

diff --git a/homa_plumbing.c b/homa_plumbing.c
index cd5ef1eb..5c60cc89 100644
--- a/homa_plumbing.c
+++ b/homa_plumbing.c
@@ -144,6 +144,7 @@ static struct net_protocol homa_protocol = {
 	.handler =	homa_softirq,
 	.err_handler =	homa_err_handler_v4,
 	.no_policy =     1,
+	.netns_ok =      1,
 };
 
 static struct inet6_protocol homav6_protocol = {
diff --git a/test/mock.c b/test/mock.c
index cc9e00a3..c17ba30f 100644
--- a/test/mock.c
+++ b/test/mock.c
@@ -147,6 +147,10 @@ static int registered_qdiscs;
 /* Registered by most recent call to register_qdisc. */
 static struct Qdisc_ops *qdisc_ops;
 
+/* Arguments from the most recent inet_add_protocol call. Reset for each test. */
+const struct net_protocol *mock_inet_protocol;
+unsigned char mock_inet_protocol_num;
+
 /* Keeps track of all the results returned by ip_route_output_flow that
  * have not yet been freed. Reset for each test.
  */
@@ -703,6 +707,8 @@ int inet_add_offload(const struct net_offload *prot, unsigned char protocol)
 
 int inet_add_protocol(const struct net_protocol *prot, unsigned char num)
 {
+	mock_inet_protocol = prot;
+	mock_inet_protocol_num = num;
 	return 0;
 }
 
@@ -2599,6 +2605,8 @@ void mock_teardown(void)
 	mock_dst_check_errors = 0;
 	mock_import_ubuf_errors = 0;
 	mock_import_iovec_errors = 0;
+	mock_inet_protocol = NULL;
+	mock_inet_protocol_num = 0;
 	mock_ip6_xmit_errors = 0;
 	mock_ip_queue_xmit_errors = 0;
 	mock_kmalloc_errors = 0;
diff --git a/test/mock.h b/test/mock.h
index c7506817..2952bf76 100644
--- a/test/mock.h
+++ b/test/mock.h
@@ -182,6 +182,9 @@ extern int         mock_ethtool_ksettings_errors;
 extern bool        mock_exit_thread;
 extern int         mock_import_iovec_errors;
 extern int         mock_import_ubuf_errors;
+extern const struct net_protocol
+		  *mock_inet_protocol;
+extern unsigned char mock_inet_protocol_num;
 extern int         mock_ip6_xmit_errors;
 extern int         mock_ip_queue_xmit_errors;
 extern bool        mock_ipv6;
diff --git a/test/unit_homa_plumbing.c b/test/unit_homa_plumbing.c
index fda82062..6dbc5fc7 100644
--- a/test/unit_homa_plumbing.c
+++ b/test/unit_homa_plumbing.c
@@ -8,6 +8,7 @@
 #include "ccutils.h"
 #include "mock.h"
 #include "utils.h"
+#include <linux/version.h>
 
 FIXTURE(homa_plumbing) {
 	struct in6_addr client_ip[1];
@@ -1692,3 +1693,36 @@ TEST_F(homa_plumbing, homa_poll__socket_readable)
 	EXPECT_EQ(POLLIN | POLLRDNORM | POLLOUT | POLLWRNORM,
 		  homa_poll(NULL, &sock, NULL));
 }
+
+/* Older kernels require netns_ok to be registered on kernel modules
+ * Regression check that .netns_ok does not get accidentally removed
+ * from homa_plumbing.c
+ * Linux 5.14 removed this field entirely
+ */
+#if LINUX_VERSION_CODE < KERNEL_VERSION(5, 14, 0)
+TEST_F(homa_plumbing, homa_load__ipv4_netns_enabled)
+{
+	int result;
+
+	/* Release the fixture's Homa instance before loading the global one. */
+	homa_destroy(&self->homa);
+
+	/* Require this load to supply the captured registration. */
+	mock_inet_protocol = NULL;
+	mock_inet_protocol_num = 0;
+
+	result = homa_load();
+	ASSERT_EQ(0, result);
+
+	/* Inspect the protocol handed to inet_add_protocol. Use nonfatal
+	 * expectations and a null check -> run homa_unload on failure.
+	 */
+	EXPECT_NE(NULL, mock_inet_protocol);
+	EXPECT_EQ(IPPROTO_HOMA, mock_inet_protocol_num);
+	/* Cast the bit-field for the assertion macro's type inference. */
+	if (mock_inet_protocol)
+		EXPECT_EQ(1, (int)mock_inet_protocol->netns_ok);
+
+	homa_unload();
+}
+#endif