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// SPDX-License-Identifier: GPL-2.0
#include <linux/bpf.h>
#include <linux/filter.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;
};
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;
/* prevent hook-not-found warning splat from netfilter core when
* .detach was already called
*/
if (!cmpxchg(&nf_link->dead, 0, 1))
nf_unregister_net_hook(nf_link->net, &nf_link->hook_ops);
}
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)
{
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)
return -EOPNOTSUPP;
/* make sure conntrack confirm is always last.
*
* In the future, if userspace can e.g. request defrag, then
* "defrag_requested && prio before NF_IP_PRI_CONNTRACK_DEFRAG"
* should fail.
*/
switch (attr->link_create.netfilter.priority) {
case NF_IP_PRI_FIRST: return -ERANGE; /* sabotage_in and other warts */
case NF_IP_PRI_LAST: return -ERANGE; /* e.g. conntrack confirm */
}
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;
err = bpf_link_prime(&link->link, &link_primer);
if (err) {
kfree(link);
return err;
}
err = nf_register_net_hook(net, &link->hook_ops);
if (err) {
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,
};
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