netfilter: revert introduction of egress hook

This reverts the following commits:

  8537f78647c0 ("netfilter: Introduce egress hook")
  5418d3881e1f ("netfilter: Generalize ingress hook")
  b030f194aed2 ("netfilter: Rename ingress hook include file")

>From the discussion in [0], the author's main motivation to add a hook
in fast path is for an out of tree kernel module, which is a red flag
to begin with. Other mentioned potential use cases like NAT{64,46}
is on future extensions w/o concrete code in the tree yet. Revert as
suggested [1] given the weak justification to add more hooks to critical
fast-path.

  [0] https://lore.kernel.org/netdev/cover.1583927267.git.lukas@wunner.de/
  [1] https://lore.kernel.org/netdev/20200318.011152.72770718915606186.davem@davemloft.net/

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Miller <davem@davemloft.net>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Nacked-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 58 insertions, 107 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 15f1e32b430c..654808bfad83 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1751,7 +1751,6 @@ enum netdev_priv_flags {
  *	@xps_maps:	XXX: need comments on this one
  *	@miniq_egress:		clsact qdisc specific data for
  *				egress processing
- *	@nf_hooks_egress:	netfilter hooks executed for egress packets
  *	@qdisc_hash:		qdisc hash table
  *	@watchdog_timeo:	Represents the timeout that is used by
  *				the watchdog (see dev_watchdog())
@@ -2027,9 +2026,6 @@ struct net_device {
 #ifdef CONFIG_NET_CLS_ACT
 	struct mini_Qdisc __rcu	*miniq_egress;
 #endif
-#ifdef CONFIG_NETFILTER_EGRESS
-	struct nf_hook_entries __rcu *nf_hooks_egress;
-#endif
 
 #ifdef CONFIG_NET_SCHED
 	DECLARE_HASHTABLE	(qdisc_hash, 4);
diff --git a/include/linux/netfilter_ingress.h b/include/linux/netfilter_ingress.h
new file mode 100644
index 000000000000..a13774be2eb5
--- /dev/null
+++ b/include/linux/netfilter_ingress.h
@@ -0,0 +1,58 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _NETFILTER_INGRESS_H_
+#define _NETFILTER_INGRESS_H_
+
+#include <linux/netfilter.h>
+#include <linux/netdevice.h>
+
+#ifdef CONFIG_NETFILTER_INGRESS
+static inline bool nf_hook_ingress_active(const struct sk_buff *skb)
+{
+#ifdef CONFIG_JUMP_LABEL
+	if (!static_key_false(&nf_hooks_needed[NFPROTO_NETDEV][NF_NETDEV_INGRESS]))
+		return false;
+#endif
+	return rcu_access_pointer(skb->dev->nf_hooks_ingress);
+}
+
+/* caller must hold rcu_read_lock */
+static inline int nf_hook_ingress(struct sk_buff *skb)
+{
+	struct nf_hook_entries *e = rcu_dereference(skb->dev->nf_hooks_ingress);
+	struct nf_hook_state state;
+	int ret;
+
+	/* Must recheck the ingress hook head, in the event it became NULL
+	 * after the check in nf_hook_ingress_active evaluated to true.
+	 */
+	if (unlikely(!e))
+		return 0;
+
+	nf_hook_state_init(&state, NF_NETDEV_INGRESS,
+			   NFPROTO_NETDEV, skb->dev, NULL, NULL,
+			   dev_net(skb->dev), NULL);
+	ret = nf_hook_slow(skb, &state, e, 0);
+	if (ret == 0)
+		return -1;
+
+	return ret;
+}
+
+static inline void nf_hook_ingress_init(struct net_device *dev)
+{
+	RCU_INIT_POINTER(dev->nf_hooks_ingress, NULL);
+}
+#else /* CONFIG_NETFILTER_INGRESS */
+static inline int nf_hook_ingress_active(struct sk_buff *skb)
+{
+	return 0;
+}
+
+static inline int nf_hook_ingress(struct sk_buff *skb)
+{
+	return 0;
+}
+
+static inline void nf_hook_ingress_init(struct net_device *dev) {}
+#endif /* CONFIG_NETFILTER_INGRESS */
+#endif /* _NETFILTER_INGRESS_H_ */
diff --git a/include/linux/netfilter_netdev.h b/include/linux/netfilter_netdev.h
deleted file mode 100644
index 92d3611a782e..000000000000
--- a/include/linux/netfilter_netdev.h
+++ /dev/null
@@ -1,102 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef _NETFILTER_NETDEV_H_
-#define _NETFILTER_NETDEV_H_
-
-#include <linux/netfilter.h>
-#include <linux/netdevice.h>
-
-#ifdef CONFIG_NETFILTER
-static __always_inline bool nf_hook_netdev_active(enum nf_dev_hooks hooknum,
-					  struct nf_hook_entries __rcu *hooks)
-{
-#ifdef CONFIG_JUMP_LABEL
-	if (!static_key_false(&nf_hooks_needed[NFPROTO_NETDEV][hooknum]))
-		return false;
-#endif
-	return rcu_access_pointer(hooks);
-}
-
-/* caller must hold rcu_read_lock */
-static __always_inline int nf_hook_netdev(struct sk_buff *skb,
-					  enum nf_dev_hooks hooknum,
-					  struct nf_hook_entries __rcu *hooks)
-{
-	struct nf_hook_entries *e = rcu_dereference(hooks);
-	struct nf_hook_state state;
-	int ret;
-
-	/* Must recheck the hook head, in the event it became NULL
-	 * after the check in nf_hook_netdev_active evaluated to true.
-	 */
-	if (unlikely(!e))
-		return 0;
-
-	nf_hook_state_init(&state, hooknum,
-			   NFPROTO_NETDEV, skb->dev, NULL, NULL,
-			   dev_net(skb->dev), NULL);
-	ret = nf_hook_slow(skb, &state, e, 0);
-	if (ret == 0)
-		return -1;
-
-	return ret;
-}
-#endif /* CONFIG_NETFILTER */
-
-static inline void nf_hook_netdev_init(struct net_device *dev)
-{
-#ifdef CONFIG_NETFILTER_INGRESS
-	RCU_INIT_POINTER(dev->nf_hooks_ingress, NULL);
-#endif
-#ifdef CONFIG_NETFILTER_EGRESS
-	RCU_INIT_POINTER(dev->nf_hooks_egress, NULL);
-#endif
-}
-
-#ifdef CONFIG_NETFILTER_INGRESS
-static inline bool nf_hook_ingress_active(const struct sk_buff *skb)
-{
-	return nf_hook_netdev_active(NF_NETDEV_INGRESS,
-				     skb->dev->nf_hooks_ingress);
-}
-
-static inline int nf_hook_ingress(struct sk_buff *skb)
-{
-	return nf_hook_netdev(skb, NF_NETDEV_INGRESS,
-			      skb->dev->nf_hooks_ingress);
-}
-#else /* CONFIG_NETFILTER_INGRESS */
-static inline int nf_hook_ingress_active(struct sk_buff *skb)
-{
-	return 0;
-}
-
-static inline int nf_hook_ingress(struct sk_buff *skb)
-{
-	return 0;
-}
-#endif /* CONFIG_NETFILTER_INGRESS */
-
-#ifdef CONFIG_NETFILTER_EGRESS
-static inline bool nf_hook_egress_active(const struct sk_buff *skb)
-{
-	return nf_hook_netdev_active(NF_NETDEV_EGRESS,
-				     skb->dev->nf_hooks_egress);
-}
-
-static inline int nf_hook_egress(struct sk_buff *skb)
-{
-	return nf_hook_netdev(skb, NF_NETDEV_EGRESS,
-			      skb->dev->nf_hooks_egress);
-}
-#else /* CONFIG_NETFILTER_EGRESS */
-static inline int nf_hook_egress_active(struct sk_buff *skb)
-{
-	return 0;
-}
-
-static inline int nf_hook_egress(struct sk_buff *skb)
-{
-	return 0;
-}
-#endif /* CONFIG_NETFILTER_EGRESS */
-#endif /* _NETFILTER_INGRESS_H_ */
diff --git a/include/uapi/linux/netfilter.h b/include/uapi/linux/netfilter.h
index d1616574c54f..ca9e63d6e0e4 100644
--- a/include/uapi/linux/netfilter.h
+++ b/include/uapi/linux/netfilter.h
@@ -50,7 +50,6 @@ enum nf_inet_hooks {
 
 enum nf_dev_hooks {
 	NF_NETDEV_INGRESS,
-	NF_NETDEV_EGRESS,
 	NF_NETDEV_NUMHOOKS
 };