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loopback: create blackhole net device similar to loopack.
jira LE-3201 Rebuild_History Non-Buildable kernel-rt-4.18.0-553.27.1.rt7.368.el8_10 commit-author Mahesh Bandewar <maheshb@google.com> commit 4de83b8 Empty-Commit: Cherry-Pick Conflicts during history rebuild. Will be included in final tarball splat. Ref for failed cherry-pick at: ciq/ciq_backports/kernel-rt-4.18.0-553.27.1.rt7.368.el8_10/4de83b88.failed Create a blackhole net device that can be used for "dead" dst entries instead of loopback device. This blackhole device differs from loopback in few aspects: (a) It's not per-ns. (b) MTU on this device is ETH_MIN_MTU (c) The xmit function is essentially kfree_skb(). and (d) since it's not registered it won't have ifindex. Lower MTU effectively make the device not pass the MTU check during the route check when a dst associated with the skb is dead. Signed-off-by: Mahesh Bandewar <maheshb@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> (cherry picked from commit 4de83b8) Signed-off-by: Jonathan Maple <jmaple@ciq.com> # Conflicts: # include/linux/netdevice.h
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‎ciq/ciq_backports/kernel-rt-4.18.0-553.27.1.rt7.368.el8_10/4de83b88.failed‎

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loopback: create blackhole net device similar to loopack.
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jira LE-3201
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Rebuild_History Non-Buildable kernel-rt-4.18.0-553.27.1.rt7.368.el8_10
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commit-author Mahesh Bandewar <maheshb@google.com>
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commit 4de83b88c66a1e4dba426b29766fb68e61d93792
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Empty-Commit: Cherry-Pick Conflicts during history rebuild.
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Will be included in final tarball splat. Ref for failed cherry-pick at:
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ciq/ciq_backports/kernel-rt-4.18.0-553.27.1.rt7.368.el8_10/4de83b88.failed
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Create a blackhole net device that can be used for "dead"
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dst entries instead of loopback device. This blackhole device differs
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from loopback in few aspects: (a) It's not per-ns. (b) MTU on this
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device is ETH_MIN_MTU (c) The xmit function is essentially kfree_skb().
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and (d) since it's not registered it won't have ifindex.
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Lower MTU effectively make the device not pass the MTU check during
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the route check when a dst associated with the skb is dead.
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Signed-off-by: Mahesh Bandewar <maheshb@google.com>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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(cherry picked from commit 4de83b88c66a1e4dba426b29766fb68e61d93792)
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Signed-off-by: Jonathan Maple <jmaple@ciq.com>
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# Conflicts:
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# include/linux/netdevice.h
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diff --cc include/linux/netdevice.h
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index 41a5e560a32a,88292953aa6f..000000000000
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--- a/include/linux/netdevice.h
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+++ b/include/linux/netdevice.h
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@@@ -5414,9 -4870,6 +5414,13 @@@ do {
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#define PTYPE_HASH_SIZE (16)
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#define PTYPE_HASH_MASK (PTYPE_HASH_SIZE - 1)
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++<<<<<<< HEAD
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+/* Note: Avoid these macros in fast path, prefer per-cpu or per-queue counters. */
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+#define DEV_STATS_INC(DEV, FIELD) atomic_long_inc(&(DEV)->stats.__##FIELD)
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+#define DEV_STATS_ADD(DEV, FIELD, VAL) \
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+ atomic_long_add((VAL), &(DEV)->stats.__##FIELD)
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++=======
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+ extern struct net_device *blackhole_netdev;
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++>>>>>>> 4de83b88c66a (loopback: create blackhole net device similar to loopack.)
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#endif /* _LINUX_NETDEVICE_H */
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diff --git a/drivers/net/loopback.c b/drivers/net/loopback.c
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index 2df7f60fe052..48d7842d5f9c 100644
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--- a/drivers/net/loopback.c
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+++ b/drivers/net/loopback.c
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@@ -59,6 +59,13 @@
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#include <net/net_namespace.h>
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#include <linux/u64_stats_sync.h>
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+/* blackhole_netdev - a device used for dsts that are marked expired!
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+ * This is global device (instead of per-net-ns) since it's not needed
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+ * to be per-ns and gets initialized at boot time.
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+ */
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+struct net_device *blackhole_netdev;
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+EXPORT_SYMBOL(blackhole_netdev);
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+
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/* The higher levels take care of making this non-reentrant (it's
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* called with bh's disabled).
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*/
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@@ -166,12 +173,14 @@ static const struct net_device_ops loopback_ops = {
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.ndo_set_mac_address = eth_mac_addr,
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};
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-/* The loopback device is special. There is only one instance
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- * per network namespace.
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- */
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-static void loopback_setup(struct net_device *dev)
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+static void gen_lo_setup(struct net_device *dev,
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+ unsigned int mtu,
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+ const struct ethtool_ops *eth_ops,
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+ const struct header_ops *hdr_ops,
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+ const struct net_device_ops *dev_ops,
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+ void (*dev_destructor)(struct net_device *dev))
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{
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- dev->mtu = 64 * 1024;
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+ dev->mtu = mtu;
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dev->hard_header_len = ETH_HLEN; /* 14 */
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dev->min_header_len = ETH_HLEN; /* 14 */
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dev->addr_len = ETH_ALEN; /* 6 */
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@@ -190,11 +199,20 @@ static void loopback_setup(struct net_device *dev)
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| NETIF_F_NETNS_LOCAL
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| NETIF_F_VLAN_CHALLENGED
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| NETIF_F_LOOPBACK;
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- dev->ethtool_ops = &loopback_ethtool_ops;
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- dev->header_ops = &eth_header_ops;
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- dev->netdev_ops = &loopback_ops;
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+ dev->ethtool_ops = eth_ops;
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+ dev->header_ops = hdr_ops;
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+ dev->netdev_ops = dev_ops;
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dev->needs_free_netdev = true;
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- dev->priv_destructor = loopback_dev_free;
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+ dev->priv_destructor = dev_destructor;
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+}
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+
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+/* The loopback device is special. There is only one instance
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+ * per network namespace.
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+ */
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+static void loopback_setup(struct net_device *dev)
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+{
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+ gen_lo_setup(dev, (64 * 1024), &loopback_ethtool_ops, &eth_header_ops,
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+ &loopback_ops, loopback_dev_free);
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}
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/* Setup and register the loopback device. */
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@@ -229,3 +247,43 @@ static __net_init int loopback_net_init(struct net *net)
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struct pernet_operations __net_initdata loopback_net_ops = {
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.init = loopback_net_init,
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};
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+
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+/* blackhole netdevice */
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+static netdev_tx_t blackhole_netdev_xmit(struct sk_buff *skb,
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+ struct net_device *dev)
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+{
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+ kfree_skb(skb);
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+ net_warn_ratelimited("%s(): Dropping skb.\n", __func__);
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+ return NETDEV_TX_OK;
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+}
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+
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+static const struct net_device_ops blackhole_netdev_ops = {
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+ .ndo_start_xmit = blackhole_netdev_xmit,
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+};
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+
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+/* This is a dst-dummy device used specifically for invalidated
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+ * DSTs and unlike loopback, this is not per-ns.
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+ */
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+static void blackhole_netdev_setup(struct net_device *dev)
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+{
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+ gen_lo_setup(dev, ETH_MIN_MTU, NULL, NULL, &blackhole_netdev_ops, NULL);
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+}
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+
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+/* Setup and register the blackhole_netdev. */
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+static int __init blackhole_netdev_init(void)
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+{
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+ blackhole_netdev = alloc_netdev(0, "blackhole_dev", NET_NAME_UNKNOWN,
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+ blackhole_netdev_setup);
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+ if (!blackhole_netdev)
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+ return -ENOMEM;
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+
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+ dev_init_scheduler(blackhole_netdev);
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+ dev_activate(blackhole_netdev);
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+
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+ blackhole_netdev->flags |= IFF_UP | IFF_RUNNING;
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+ dev_net_set(blackhole_netdev, &init_net);
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+
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+ return 0;
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+}
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+
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+device_initcall(blackhole_netdev_init);
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* Unmerged path include/linux/netdevice.h

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