netfilter: nfnetlink hook: dump bpf prog id

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>
Link: https://lore.kernel.org/r/20230421170300.24115-4-fw@strlen.de
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 68 insertions, 13 deletions

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;