1 files changed, 323 insertions, 0 deletions
diff --git a/net/netfilter/nf_bpf_link.c b/net/netfilter/nf_bpf_link.c
new file mode 100644
index 000000000..0e4beae42
--- /dev/null
+++ b/net/netfilter/nf_bpf_link.c
@@ -0,0 +1,323 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <linux/filter.h>
+#include <linux/kmod.h>
+#include <linux/module.h>
+#include <linux/netfilter.h>
+
+#include <net/netfilter/nf_bpf_link.h>
+#include <uapi/linux/netfilter_ipv4.h>
+
+static unsigned int nf_hook_run_bpf(void *bpf_prog, struct sk_buff *skb,
+				    const struct nf_hook_state *s)
+{
+	const struct bpf_prog *prog = bpf_prog;
+	struct bpf_nf_ctx ctx = {
+		.state = s,
+		.skb = skb,
+	};
+
+	return bpf_prog_run(prog, &ctx);
+}
+
+struct bpf_nf_link {
+	struct bpf_link link;
+	struct nf_hook_ops hook_ops;
+	struct net *net;
+	u32 dead;
+	const struct nf_defrag_hook *defrag_hook;
+};
+
+#if IS_ENABLED(CONFIG_NF_DEFRAG_IPV4) || IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)
+static const struct nf_defrag_hook *
+get_proto_defrag_hook(struct bpf_nf_link *link,
+		      const struct nf_defrag_hook __rcu **ptr_global_hook,
+		      const char *mod)
+{
+	const struct nf_defrag_hook *hook;
+	int err;
+
+	/* RCU protects us from races against module unloading */
+	rcu_read_lock();
+	hook = rcu_dereference(*ptr_global_hook);
+	if (!hook) {
+		rcu_read_unlock();
+		err = request_module(mod);
+		if (err)
+			return ERR_PTR(err < 0 ? err : -EINVAL);
+
+		rcu_read_lock();
+		hook = rcu_dereference(*ptr_global_hook);
+	}
+
+	if (hook && try_module_get(hook->owner)) {
+		/* Once we have a refcnt on the module, we no longer need RCU */
+		hook = rcu_pointer_handoff(hook);
+	} else {
+		WARN_ONCE(!hook, "%s has bad registration", mod);
+		hook = ERR_PTR(-ENOENT);
+	}
+	rcu_read_unlock();
+
+	if (!IS_ERR(hook)) {
+		err = hook->enable(link->net);
+		if (err) {
+			module_put(hook->owner);
+			hook = ERR_PTR(err);
+		}
+	}
+
+	return hook;
+}
+#endif
+
+static int bpf_nf_enable_defrag(struct bpf_nf_link *link)
+{
+	const struct nf_defrag_hook __maybe_unused *hook;
+
+	switch (link->hook_ops.pf) {
+#if IS_ENABLED(CONFIG_NF_DEFRAG_IPV4)
+	case NFPROTO_IPV4:
+		hook = get_proto_defrag_hook(link, &nf_defrag_v4_hook, "nf_defrag_ipv4");
+		if (IS_ERR(hook))
+			return PTR_ERR(hook);
+
+		link->defrag_hook = hook;
+		return 0;
+#endif
+#if IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)
+	case NFPROTO_IPV6:
+		hook = get_proto_defrag_hook(link, &nf_defrag_v6_hook, "nf_defrag_ipv6");
+		if (IS_ERR(hook))
+			return PTR_ERR(hook);
+
+		link->defrag_hook = hook;
+		return 0;
+#endif
+	default:
+		return -EAFNOSUPPORT;
+	}
+}
+
+static void bpf_nf_disable_defrag(struct bpf_nf_link *link)
+{
+	const struct nf_defrag_hook *hook = link->defrag_hook;
+
+	if (!hook)
+		return;
+	hook->disable(link->net);
+	module_put(hook->owner);
+}
+
+static void bpf_nf_link_release(struct bpf_link *link)
+{
+	struct bpf_nf_link *nf_link = container_of(link, struct bpf_nf_link, link);
+
+	if (nf_link->dead)
+		return;
+
+	/* do not double release in case .detach was already called */
+	if (!cmpxchg(&nf_link->dead, 0, 1)) {
+		nf_unregister_net_hook(nf_link->net, &nf_link->hook_ops);
+		bpf_nf_disable_defrag(nf_link);
+	}
+}
+
+static void bpf_nf_link_dealloc(struct bpf_link *link)
+{
+	struct bpf_nf_link *nf_link = container_of(link, struct bpf_nf_link, link);
+
+	kfree(nf_link);
+}
+
+static int bpf_nf_link_detach(struct bpf_link *link)
+{
+	bpf_nf_link_release(link);
+	return 0;
+}
+
+static void bpf_nf_link_show_info(const struct bpf_link *link,
+				  struct seq_file *seq)
+{
+	struct bpf_nf_link *nf_link = container_of(link, struct bpf_nf_link, link);
+
+	seq_printf(seq, "pf:\t%u\thooknum:\t%u\tprio:\t%d\n",
+		   nf_link->hook_ops.pf, nf_link->hook_ops.hooknum,
+		   nf_link->hook_ops.priority);
+}
+
+static int bpf_nf_link_fill_link_info(const struct bpf_link *link,
+				      struct bpf_link_info *info)
+{
+	struct bpf_nf_link *nf_link = container_of(link, struct bpf_nf_link, link);
+
+	info->netfilter.pf = nf_link->hook_ops.pf;
+	info->netfilter.hooknum = nf_link->hook_ops.hooknum;
+	info->netfilter.priority = nf_link->hook_ops.priority;
+	info->netfilter.flags = 0;
+
+	return 0;
+}
+
+static int bpf_nf_link_update(struct bpf_link *link, struct bpf_prog *new_prog,
+			      struct bpf_prog *old_prog)
+{
+	return -EOPNOTSUPP;
+}
+
+static const struct bpf_link_ops bpf_nf_link_lops = {
+	.release = bpf_nf_link_release,
+	.dealloc = bpf_nf_link_dealloc,
+	.detach = bpf_nf_link_detach,
+	.show_fdinfo = bpf_nf_link_show_info,
+	.fill_link_info = bpf_nf_link_fill_link_info,
+	.update_prog = bpf_nf_link_update,
+};
+
+static int bpf_nf_check_pf_and_hooks(const union bpf_attr *attr)
+{
+	int prio;
+
+	switch (attr->link_create.netfilter.pf) {
+	case NFPROTO_IPV4:
+	case NFPROTO_IPV6:
+		if (attr->link_create.netfilter.hooknum >= NF_INET_NUMHOOKS)
+			return -EPROTO;
+		break;
+	default:
+		return -EAFNOSUPPORT;
+	}
+
+	if (attr->link_create.netfilter.flags & ~BPF_F_NETFILTER_IP_DEFRAG)
+		return -EOPNOTSUPP;
+
+	/* make sure conntrack confirm is always last */
+	prio = attr->link_create.netfilter.priority;
+	if (prio == NF_IP_PRI_FIRST)
+		return -ERANGE;  /* sabotage_in and other warts */
+	else if (prio == NF_IP_PRI_LAST)
+		return -ERANGE;  /* e.g. conntrack confirm */
+	else if ((attr->link_create.netfilter.flags & BPF_F_NETFILTER_IP_DEFRAG) &&
+		 prio <= NF_IP_PRI_CONNTRACK_DEFRAG)
+		return -ERANGE;  /* cannot use defrag if prog runs before nf_defrag */
+
+	return 0;
+}
+
+int bpf_nf_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
+{
+	struct net *net = current->nsproxy->net_ns;
+	struct bpf_link_primer link_primer;
+	struct bpf_nf_link *link;
+	int err;
+
+	if (attr->link_create.flags)
+		return -EINVAL;
+
+	err = bpf_nf_check_pf_and_hooks(attr);
+	if (err)
+		return err;
+
+	link = kzalloc(sizeof(*link), GFP_USER);
+	if (!link)
+		return -ENOMEM;
+
+	bpf_link_init(&link->link, BPF_LINK_TYPE_NETFILTER, &bpf_nf_link_lops, prog);
+
+	link->hook_ops.hook = nf_hook_run_bpf;
+	link->hook_ops.hook_ops_type = NF_HOOK_OP_BPF;
+	link->hook_ops.priv = prog;
+
+	link->hook_ops.pf = attr->link_create.netfilter.pf;
+	link->hook_ops.priority = attr->link_create.netfilter.priority;
+	link->hook_ops.hooknum = attr->link_create.netfilter.hooknum;
+
+	link->net = net;
+	link->dead = false;
+	link->defrag_hook = NULL;
+
+	err = bpf_link_prime(&link->link, &link_primer);
+	if (err) {
+		kfree(link);
+		return err;
+	}
+
+	if (attr->link_create.netfilter.flags & BPF_F_NETFILTER_IP_DEFRAG) {
+		err = bpf_nf_enable_defrag(link);
+		if (err) {
+			bpf_link_cleanup(&link_primer);
+			return err;
+		}
+	}
+
+	err = nf_register_net_hook(net, &link->hook_ops);
+	if (err) {
+		bpf_nf_disable_defrag(link);
+		bpf_link_cleanup(&link_primer);
+		return err;
+	}
+
+	return bpf_link_settle(&link_primer);
+}
+
+const struct bpf_prog_ops netfilter_prog_ops = {
+	.test_run = bpf_prog_test_run_nf,
+};
+
+static bool nf_ptr_to_btf_id(struct bpf_insn_access_aux *info, const char *name)
+{
+	struct btf *btf;
+	s32 type_id;
+
+	btf = bpf_get_btf_vmlinux();
+	if (IS_ERR_OR_NULL(btf))
+		return false;
+
+	type_id = btf_find_by_name_kind(btf, name, BTF_KIND_STRUCT);
+	if (WARN_ON_ONCE(type_id < 0))
+		return false;
+
+	info->btf = btf;
+	info->btf_id = type_id;
+	info->reg_type = PTR_TO_BTF_ID | PTR_TRUSTED;
+	return true;
+}
+
+static bool nf_is_valid_access(int off, int size, enum bpf_access_type type,
+			       const struct bpf_prog *prog,
+			       struct bpf_insn_access_aux *info)
+{
+	if (off < 0 || off >= sizeof(struct bpf_nf_ctx))
+		return false;
+
+	if (type == BPF_WRITE)
+		return false;
+
+	switch (off) {
+	case bpf_ctx_range(struct bpf_nf_ctx, skb):
+		if (size != sizeof_field(struct bpf_nf_ctx, skb))
+			return false;
+
+		return nf_ptr_to_btf_id(info, "sk_buff");
+	case bpf_ctx_range(struct bpf_nf_ctx, state):
+		if (size != sizeof_field(struct bpf_nf_ctx, state))
+			return false;
+
+		return nf_ptr_to_btf_id(info, "nf_hook_state");
+	default:
+		return false;
+	}
+
+	return false;
+}
+
+static const struct bpf_func_proto *
+bpf_nf_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
+{
+	return bpf_base_func_proto(func_id);
+}
+
+const struct bpf_verifier_ops netfilter_verifier_ops = {
+	.is_valid_access	= nf_is_valid_access,
+	.get_func_proto		= bpf_nf_func_proto,
+};