[PATCH bpf-next v5 3/7] netfilter: nfnetlink hook: dump bpf prog id

Florian Westphal
2023-04-21T17:03:57Z

This allows userspace ("nft list hooks") to show which bpf program
is attached to which hook.

Without this, user only knows bpf prog is attached at prio
x, y, z at INPUT and FORWARD, but can't tell which program is where.

v4: kdoc fixups (Simon Horman)

Link: https://lore.kernel.org/bpf/ZEELzpNCnYJuZyod@corigine.com/
Signed-off-by: Florian Westphal <fw@strlen.de>
---
no changes since last version

include/uapi/linux/netfilter/nfnetlink_hook.h | 24 +++++-
net/netfilter/nfnetlink_hook.c | 81 ++++++++++++++++---
2 files changed, 89 insertions(+), 16 deletions(-)

diff --git a/include/uapi/linux/netfilter/nfnetlink_hook.h b/include/uapi/linux/netfilter/nfnetlink_hook.h
index bbcd285b22e1..84a561a74b98 100644
--- a/include/uapi/linux/netfilter/nfnetlink_hook.h
+++ b/include/uapi/linux/netfilter/nfnetlink_hook.h
@@ -32,8 +32,12 @@ enum nfnl_hook_attributes {
/**
* enum nfnl_hook_chain_info_attributes - chain description
*
- * NFNLA_HOOK_INFO_DESC: nft chain and table name (enum nft_table_attributes) (NLA_NESTED)
- * NFNLA_HOOK_INFO_TYPE: chain type (enum nfnl_hook_chaintype) (NLA_U32)
+ * @NFNLA_HOOK_INFO_DESC: nft chain and table name (NLA_NESTED)
+ * @NFNLA_HOOK_INFO_TYPE: chain type (enum nfnl_hook_chaintype) (NLA_U32)
+ *
+ * NFNLA_HOOK_INFO_DESC depends on NFNLA_HOOK_INFO_TYPE value:
+ * NFNL_HOOK_TYPE_NFTABLES: enum nft_table_attributes
+ * NFNL_HOOK_TYPE_BPF: enum nfnl_hook_bpf_attributes
*/
enum nfnl_hook_chain_info_attributes {
NFNLA_HOOK_INFO_UNSPEC,
@@ -55,10 +59,24 @@ enum nfnl_hook_chain_desc_attributes {
/**
* enum nfnl_hook_chaintype - chain type
*
- * @NFNL_HOOK_TYPE_NFTABLES nf_tables base chain
+ * @NFNL_HOOK_TYPE_NFTABLES: nf_tables base chain
+ * @NFNL_HOOK_TYPE_BPF: bpf program
*/
enum nfnl_hook_chaintype {
NFNL_HOOK_TYPE_NFTABLES = 0x1,
+ NFNL_HOOK_TYPE_BPF,
+};
+
+/**
+ * enum nfnl_hook_bpf_attributes - bpf prog description
+ *
+ * @NFNLA_HOOK_BPF_ID: bpf program id (NLA_U32)
+ */
+enum nfnl_hook_bpf_attributes {
+ NFNLA_HOOK_BPF_UNSPEC,
+ NFNLA_HOOK_BPF_ID,
+ __NFNLA_HOOK_BPF_MAX,
};
+#define NFNLA_HOOK_BPF_MAX (__NFNLA_HOOK_BPF_MAX - 1)

#endif /* _NFNL_HOOK_H */
diff --git a/net/netfilter/nfnetlink_hook.c b/net/netfilter/nfnetlink_hook.c
index 8120aadf6a0f..ade8ee1988b1 100644
--- a/net/netfilter/nfnetlink_hook.c
+++ b/net/netfilter/nfnetlink_hook.c
@@ -5,6 +5,7 @@
* Author: Florian Westphal <fw@strlen.de>
*/

+#include <linux/bpf.h>
#include <linux/module.h>
#include <linux/kallsyms.h>
#include <linux/kernel.h>
@@ -57,35 +58,76 @@ struct nfnl_dump_hook_data {
u8 hook;
};

+static struct nlattr *nfnl_start_info_type(struct sk_buff *nlskb, enum nfnl_hook_chaintype t)
+{
+ struct nlattr *nest = nla_nest_start(nlskb, NFNLA_HOOK_CHAIN_INFO);
+ int ret;
+
+ if (!nest)
+ return NULL;
+
+ ret = nla_put_be32(nlskb, NFNLA_HOOK_INFO_TYPE, htonl(t));
+ if (ret == 0)
+ return nest;
+
+ nla_nest_cancel(nlskb, nest);
+ return NULL;
+}
+
+static int nfnl_hook_put_bpf_prog_info(struct sk_buff *nlskb,
+ const struct nfnl_dump_hook_data *ctx,
+ unsigned int seq,
+ const struct bpf_prog *prog)
+{
+ struct nlattr *nest, *nest2;
+ int ret;
+
+ if (!IS_ENABLED(CONFIG_NETFILTER_BPF_LINK))
+ return 0;
+
+ if (WARN_ON_ONCE(!prog))
+ return 0;
+
+ nest = nfnl_start_info_type(nlskb, NFNL_HOOK_TYPE_BPF);
+ if (!nest)
+ return -EMSGSIZE;
+
+ nest2 = nla_nest_start(nlskb, NFNLA_HOOK_INFO_DESC);
+ if (!nest2)
+ goto cancel_nest;
+
+ ret = nla_put_be32(nlskb, NFNLA_HOOK_BPF_ID, htonl(prog->aux->id));
+ if (ret)
+ goto cancel_nest;
+
+ nla_nest_end(nlskb, nest2);
+ nla_nest_end(nlskb, nest);
+ return 0;
+
+cancel_nest:
+ nla_nest_cancel(nlskb, nest);
+ return -EMSGSIZE;
+}
+
static int nfnl_hook_put_nft_chain_info(struct sk_buff *nlskb,
const struct nfnl_dump_hook_data *ctx,
unsigned int seq,
- const struct nf_hook_ops *ops)
+ struct nft_chain *chain)
{
struct net *net = sock_net(nlskb->sk);
struct nlattr *nest, *nest2;
- struct nft_chain *chain;
int ret = 0;

- if (ops->hook_ops_type != NF_HOOK_OP_NF_TABLES)
- return 0;
-
- chain = ops->priv;
if (WARN_ON_ONCE(!chain))
return 0;

if (!nft_is_active(net, chain))
return 0;

- nest = nla_nest_start(nlskb, NFNLA_HOOK_CHAIN_INFO);
+ nest = nfnl_start_info_type(nlskb, NFNL_HOOK_TYPE_NFTABLES);
if (!nest)
return -EMSGSIZE;

- ret = nla_put_be32(nlskb, NFNLA_HOOK_INFO_TYPE,
- htonl(NFNL_HOOK_TYPE_NFTABLES));
- if (ret)
- goto cancel_nest;
-
nest2 = nla_nest_start(nlskb, NFNLA_HOOK_INFO_DESC);
if (!nest2)
goto cancel_nest;
@@ -171,7 +213,20 @@ static int nfnl_hook_dump_one(struct sk_buff *nlskb,
if (ret)
goto nla_put_failure;

- ret = nfnl_hook_put_nft_chain_info(nlskb, ctx, seq, ops);
+ switch (ops->hook_ops_type) {
+ case NF_HOOK_OP_NF_TABLES:
+ ret = nfnl_hook_put_nft_chain_info(nlskb, ctx, seq, ops->priv);
+ break;
+ case NF_HOOK_OP_BPF:
+ ret = nfnl_hook_put_bpf_prog_info(nlskb, ctx, seq, ops->priv);
+ break;
+ case NF_HOOK_OP_UNDEFINED:
+ break;
+ default:
+ WARN_ON_ONCE(1);
+ break;
+ }
+
if (ret)
goto nla_put_failure;

--
2.39.2