3 files changed, 199 insertions, 7 deletions

diff --git a/drivers/net/netdevsim/bus.c b/drivers/net/netdevsim/bus.c
index bcbc1e19ed..64c0cdd31b 100644
--- a/drivers/net/netdevsim/bus.c
+++ b/drivers/net/netdevsim/bus.c
@@ -129,7 +129,7 @@ static void nsim_bus_dev_release(struct device *dev)
 		complete(&nsim_bus_devs_released);
 }
 
-static struct device_type nsim_bus_dev_type = {
+static const struct device_type nsim_bus_dev_type = {
 	.groups = nsim_bus_dev_attr_groups,
 	.release = nsim_bus_dev_release,
 };
@@ -232,9 +232,154 @@ del_device_store(const struct bus_type *bus, const char *buf, size_t count)
 }
 static BUS_ATTR_WO(del_device);
 
+static ssize_t link_device_store(const struct bus_type *bus, const char *buf, size_t count)
+{
+	struct netdevsim *nsim_a, *nsim_b, *peer;
+	struct net_device *dev_a, *dev_b;
+	unsigned int ifidx_a, ifidx_b;
+	int netnsfd_a, netnsfd_b, err;
+	struct net *ns_a, *ns_b;
+
+	err = sscanf(buf, "%d:%u %d:%u", &netnsfd_a, &ifidx_a, &netnsfd_b,
+		     &ifidx_b);
+	if (err != 4) {
+		pr_err("Format for linking two devices is \"netnsfd_a:ifidx_a netnsfd_b:ifidx_b\" (int uint int uint).\n");
+		return -EINVAL;
+	}
+
+	ns_a = get_net_ns_by_fd(netnsfd_a);
+	if (IS_ERR(ns_a)) {
+		pr_err("Could not find netns with fd: %d\n", netnsfd_a);
+		return -EINVAL;
+	}
+
+	ns_b = get_net_ns_by_fd(netnsfd_b);
+	if (IS_ERR(ns_b)) {
+		pr_err("Could not find netns with fd: %d\n", netnsfd_b);
+		put_net(ns_a);
+		return -EINVAL;
+	}
+
+	err = -EINVAL;
+	rtnl_lock();
+	dev_a = __dev_get_by_index(ns_a, ifidx_a);
+	if (!dev_a) {
+		pr_err("Could not find device with ifindex %u in netnsfd %d\n",
+		       ifidx_a, netnsfd_a);
+		goto out_err;
+	}
+
+	if (!netdev_is_nsim(dev_a)) {
+		pr_err("Device with ifindex %u in netnsfd %d is not a netdevsim\n",
+		       ifidx_a, netnsfd_a);
+		goto out_err;
+	}
+
+	dev_b = __dev_get_by_index(ns_b, ifidx_b);
+	if (!dev_b) {
+		pr_err("Could not find device with ifindex %u in netnsfd %d\n",
+		       ifidx_b, netnsfd_b);
+		goto out_err;
+	}
+
+	if (!netdev_is_nsim(dev_b)) {
+		pr_err("Device with ifindex %u in netnsfd %d is not a netdevsim\n",
+		       ifidx_b, netnsfd_b);
+		goto out_err;
+	}
+
+	if (dev_a == dev_b) {
+		pr_err("Cannot link a netdevsim to itself\n");
+		goto out_err;
+	}
+
+	err = -EBUSY;
+	nsim_a = netdev_priv(dev_a);
+	peer = rtnl_dereference(nsim_a->peer);
+	if (peer) {
+		pr_err("Netdevsim %d:%u is already linked\n", netnsfd_a,
+		       ifidx_a);
+		goto out_err;
+	}
+
+	nsim_b = netdev_priv(dev_b);
+	peer = rtnl_dereference(nsim_b->peer);
+	if (peer) {
+		pr_err("Netdevsim %d:%u is already linked\n", netnsfd_b,
+		       ifidx_b);
+		goto out_err;
+	}
+
+	err = 0;
+	rcu_assign_pointer(nsim_a->peer, nsim_b);
+	rcu_assign_pointer(nsim_b->peer, nsim_a);
+
+out_err:
+	put_net(ns_b);
+	put_net(ns_a);
+	rtnl_unlock();
+
+	return !err ? count : err;
+}
+static BUS_ATTR_WO(link_device);
+
+static ssize_t unlink_device_store(const struct bus_type *bus, const char *buf, size_t count)
+{
+	struct netdevsim *nsim, *peer;
+	struct net_device *dev;
+	unsigned int ifidx;
+	int netnsfd, err;
+	struct net *ns;
+
+	err = sscanf(buf, "%u:%u", &netnsfd, &ifidx);
+	if (err != 2) {
+		pr_err("Format for unlinking a device is \"netnsfd:ifidx\" (int uint).\n");
+		return -EINVAL;
+	}
+
+	ns = get_net_ns_by_fd(netnsfd);
+	if (IS_ERR(ns)) {
+		pr_err("Could not find netns with fd: %d\n", netnsfd);
+		return -EINVAL;
+	}
+
+	err = -EINVAL;
+	rtnl_lock();
+	dev = __dev_get_by_index(ns, ifidx);
+	if (!dev) {
+		pr_err("Could not find device with ifindex %u in netnsfd %d\n",
+		       ifidx, netnsfd);
+		goto out_put_netns;
+	}
+
+	if (!netdev_is_nsim(dev)) {
+		pr_err("Device with ifindex %u in netnsfd %d is not a netdevsim\n",
+		       ifidx, netnsfd);
+		goto out_put_netns;
+	}
+
+	nsim = netdev_priv(dev);
+	peer = rtnl_dereference(nsim->peer);
+	if (!peer)
+		goto out_put_netns;
+
+	err = 0;
+	RCU_INIT_POINTER(nsim->peer, NULL);
+	RCU_INIT_POINTER(peer->peer, NULL);
+
+out_put_netns:
+	put_net(ns);
+	rtnl_unlock();
+
+	return !err ? count : err;
+}
+static BUS_ATTR_WO(unlink_device);
+
 static struct attribute *nsim_bus_attrs[] = {
 	&bus_attr_new_device.attr,
 	&bus_attr_del_device.attr,
+	&bus_attr_link_device.attr,
+	&bus_attr_unlink_device.attr,
 	NULL
 };
 ATTRIBUTE_GROUPS(nsim_bus);
@@ -260,7 +405,7 @@ static int nsim_num_vf(struct device *dev)
 	return nsim_bus_dev->num_vfs;
 }
 
-static struct bus_type nsim_bus = {
+static const struct bus_type nsim_bus = {
 	.name		= DRV_NAME,
 	.dev_name	= DRV_NAME,
 	.bus_groups	= nsim_bus_groups,
diff --git a/drivers/net/netdevsim/netdev.c b/drivers/net/netdevsim/netdev.c
index 77e8250282..d405809030 100644
--- a/drivers/net/netdevsim/netdev.c
+++ b/drivers/net/netdevsim/netdev.c
@@ -29,18 +29,35 @@
 static netdev_tx_t nsim_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct netdevsim *ns = netdev_priv(dev);
+	unsigned int len = skb->len;
+	struct netdevsim *peer_ns;
 
+	rcu_read_lock();
 	if (!nsim_ipsec_tx(ns, skb))
-		goto out;
+		goto out_drop_free;
 
+	peer_ns = rcu_dereference(ns->peer);
+	if (!peer_ns)
+		goto out_drop_free;
+
+	skb_tx_timestamp(skb);
+	if (unlikely(dev_forward_skb(peer_ns->netdev, skb) == NET_RX_DROP))
+		goto out_drop_cnt;
+
+	rcu_read_unlock();
 	u64_stats_update_begin(&ns->syncp);
 	ns->tx_packets++;
-	ns->tx_bytes += skb->len;
+	ns->tx_bytes += len;
 	u64_stats_update_end(&ns->syncp);
+	return NETDEV_TX_OK;
 
-out:
+out_drop_free:
 	dev_kfree_skb(skb);
-
+out_drop_cnt:
+	rcu_read_unlock();
+	u64_stats_update_begin(&ns->syncp);
+	ns->tx_dropped++;
+	u64_stats_update_end(&ns->syncp);
 	return NETDEV_TX_OK;
 }
 
@@ -70,6 +87,7 @@ nsim_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats)
 		start = u64_stats_fetch_begin(&ns->syncp);
 		stats->tx_bytes = ns->tx_bytes;
 		stats->tx_packets = ns->tx_packets;
+		stats->tx_dropped = ns->tx_dropped;
 	} while (u64_stats_fetch_retry(&ns->syncp, start));
 }
 
@@ -265,6 +283,22 @@ nsim_set_features(struct net_device *dev, netdev_features_t features)
 	return 0;
 }
 
+static int nsim_get_iflink(const struct net_device *dev)
+{
+	struct netdevsim *nsim, *peer;
+	int iflink;
+
+	nsim = netdev_priv(dev);
+
+	rcu_read_lock();
+	peer = rcu_dereference(nsim->peer);
+	iflink = peer ? READ_ONCE(peer->netdev->ifindex) :
+			READ_ONCE(dev->ifindex);
+	rcu_read_unlock();
+
+	return iflink;
+}
+
 static const struct net_device_ops nsim_netdev_ops = {
 	.ndo_start_xmit		= nsim_start_xmit,
 	.ndo_set_rx_mode	= nsim_set_rx_mode,
@@ -282,6 +316,7 @@ static const struct net_device_ops nsim_netdev_ops = {
 	.ndo_set_vf_rss_query_en = nsim_set_vf_rss_query_en,
 	.ndo_setup_tc		= nsim_setup_tc,
 	.ndo_set_features	= nsim_set_features,
+	.ndo_get_iflink		= nsim_get_iflink,
 	.ndo_bpf		= nsim_bpf,
 };
 
@@ -302,7 +337,6 @@ static void nsim_setup(struct net_device *dev)
 	eth_hw_addr_random(dev);
 
 	dev->tx_queue_len = 0;
-	dev->flags |= IFF_NOARP;
 	dev->flags &= ~IFF_MULTICAST;
 	dev->priv_flags |= IFF_LIVE_ADDR_CHANGE |
 			   IFF_NO_QUEUE;
@@ -413,8 +447,13 @@ err_free_netdev:
 void nsim_destroy(struct netdevsim *ns)
 {
 	struct net_device *dev = ns->netdev;
+	struct netdevsim *peer;
 
 	rtnl_lock();
+	peer = rtnl_dereference(ns->peer);
+	if (peer)
+		RCU_INIT_POINTER(peer->peer, NULL);
+	RCU_INIT_POINTER(ns->peer, NULL);
 	unregister_netdevice(dev);
 	if (nsim_dev_port_is_pf(ns->nsim_dev_port)) {
 		nsim_macsec_teardown(ns);
@@ -427,6 +466,11 @@ void nsim_destroy(struct netdevsim *ns)
 	free_netdev(dev);
 }
 
+bool netdev_is_nsim(struct net_device *dev)
+{
+	return dev->netdev_ops == &nsim_netdev_ops;
+}
+
 static int nsim_validate(struct nlattr *tb[], struct nlattr *data[],
 			 struct netlink_ext_ack *extack)
 {
diff --git a/drivers/net/netdevsim/netdevsim.h b/drivers/net/netdevsim/netdevsim.h
index 028c825b86..553c4b9b4f 100644
--- a/drivers/net/netdevsim/netdevsim.h
+++ b/drivers/net/netdevsim/netdevsim.h
@@ -98,6 +98,7 @@ struct netdevsim {
 
 	u64 tx_packets;
 	u64 tx_bytes;
+	u64 tx_dropped;
 	struct u64_stats_sync syncp;
 
 	struct nsim_bus_dev *nsim_bus_dev;
@@ -125,11 +126,13 @@ struct netdevsim {
 	} udp_ports;
 
 	struct nsim_ethtool ethtool;
+	struct netdevsim __rcu *peer;
 };
 
 struct netdevsim *
 nsim_create(struct nsim_dev *nsim_dev, struct nsim_dev_port *nsim_dev_port);
 void nsim_destroy(struct netdevsim *ns);
+bool netdev_is_nsim(struct net_device *dev);
 
 void nsim_ethtool_init(struct netdevsim *ns);