net: mctp: test: move TX packetqueue from dst to dev

To capture TX packets during a test, we are currently intercepting the
dst->output with an implementation that adds the transmitted packet to
a skb queue attached to the test-specific mock dst. The netdev itself is
not involved in the test TX path.

Instead, we can just use our test device to stash TXed packets for later
inspection by the test. This means we can include the actual
mctp_dst_output() implementation in the test (by setting dst.output in
the test case), and don't need to be creating fake dst objects, or their
corresponding skb queues.

We need to ensure that the netdev is up to allow delivery to
ndo_start_xmit, but the tests assume active devices at present anyway.

Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Link: https://patch.msgid.link/20251126-dev-mctp-test-tx-queue-v2-1-4e5bbd1d6c57@codeconstruct.com.au
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 16 insertions, 29 deletions

diff --git a/net/mctp/test/utils.c b/net/mctp/test/utils.c
index 35f6be814567..37f1ba62a2ab 100644
--- a/net/mctp/test/utils.c
+++ b/net/mctp/test/utils.c
@@ -13,7 +13,10 @@
 static netdev_tx_t mctp_test_dev_tx(struct sk_buff *skb,
 				    struct net_device *ndev)
 {
-	kfree_skb(skb);
+	struct mctp_test_dev *dev = netdev_priv(ndev);
+
+	skb_queue_tail(&dev->pkts, skb);
+
 	return NETDEV_TX_OK;
 }
 
@@ -26,7 +29,7 @@ static void mctp_test_dev_setup(struct net_device *ndev)
 	ndev->type = ARPHRD_MCTP;
 	ndev->mtu = MCTP_DEV_TEST_MTU;
 	ndev->hard_header_len = 0;
-	ndev->tx_queue_len = DEFAULT_TX_QUEUE_LEN;
+	ndev->tx_queue_len = 0;
 	ndev->flags = IFF_NOARP;
 	ndev->netdev_ops = &mctp_test_netdev_ops;
 	ndev->needs_free_netdev = true;
@@ -51,6 +54,7 @@ static struct mctp_test_dev *__mctp_test_create_dev(unsigned short lladdr_len,
 	dev->ndev = ndev;
 	ndev->addr_len = lladdr_len;
 	dev_addr_set(ndev, lladdr);
+	skb_queue_head_init(&dev->pkts);
 
 	rc = register_netdev(ndev);
 	if (rc) {
@@ -63,6 +67,11 @@ static struct mctp_test_dev *__mctp_test_create_dev(unsigned short lladdr_len,
 	dev->mdev->net = mctp_default_net(dev_net(ndev));
 	rcu_read_unlock();
 
+	/* bring the device up; we want to be able to TX immediately */
+	rtnl_lock();
+	dev_open(ndev, NULL);
+	rtnl_unlock();
+
 	return dev;
 }
 
@@ -79,26 +88,15 @@ struct mctp_test_dev *mctp_test_create_dev_lladdr(unsigned short lladdr_len,
 
 void mctp_test_destroy_dev(struct mctp_test_dev *dev)
 {
+	skb_queue_purge(&dev->pkts);
 	mctp_dev_put(dev->mdev);
 	unregister_netdev(dev->ndev);
 }
 
-static const unsigned int test_pktqueue_magic = 0x5f713aef;
-
-void mctp_test_pktqueue_init(struct mctp_test_pktqueue *tpq)
-{
-	tpq->magic = test_pktqueue_magic;
-	skb_queue_head_init(&tpq->pkts);
-}
-
 static int mctp_test_dst_output(struct mctp_dst *dst, struct sk_buff *skb)
 {
-	struct kunit *test = current->kunit_test;
-	struct mctp_test_pktqueue *tpq = test->priv;
-
-	KUNIT_ASSERT_EQ(test, tpq->magic, test_pktqueue_magic);
-
-	skb_queue_tail(&tpq->pkts, skb);
+	skb->dev = dst->dev->dev;
+	dev_queue_xmit(skb);
 
 	return 0;
 }
@@ -169,11 +167,9 @@ struct mctp_test_route *mctp_test_create_route_gw(struct net *net,
 	return rt;
 }
 
-/* Convenience function for our test dst; release with mctp_test_dst_release()
- */
+/* Convenience function for our test dst; release with mctp_dst_release() */
 void mctp_test_dst_setup(struct kunit *test, struct mctp_dst *dst,
-			 struct mctp_test_dev *dev,
-			 struct mctp_test_pktqueue *tpq, unsigned int mtu)
+			 struct mctp_test_dev *dev, unsigned int mtu)
 {
 	KUNIT_EXPECT_NOT_ERR_OR_NULL(test, dev);
 
@@ -183,15 +179,6 @@ void mctp_test_dst_setup(struct kunit *test, struct mctp_dst *dst,
 	__mctp_dev_get(dst->dev->dev);
 	dst->mtu = mtu;
 	dst->output = mctp_test_dst_output;
-	mctp_test_pktqueue_init(tpq);
-	test->priv = tpq;
-}
-
-void mctp_test_dst_release(struct mctp_dst *dst,
-			   struct mctp_test_pktqueue *tpq)
-{
-	mctp_dst_release(dst);
-	skb_queue_purge(&tpq->pkts);
 }
 
 void mctp_test_route_destroy(struct kunit *test, struct mctp_test_route *rt)