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[RFC,nf-next,v1,1/2] netfilter: bpf: support prog update

Message ID 1702609653-45835-2-git-send-email-alibuda@linux.alibaba.com (mailing list archive)
State Superseded
Delegated to: Netdev Maintainers
Headers show
Series netfilter: bpf: support prog update | expand

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bpf/vmtest-bpf-next-VM_Test-7 success Logs for aarch64-gcc / test (test_progs, false, 360) / test_progs on aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-16 success Logs for x86_64-gcc / test (test_maps, false, 360) / test_maps on x86_64 with gcc
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bpf/vmtest-bpf-next-VM_Test-22 success Logs for x86_64-gcc / test (test_progs, false, 360) / test_progs on x86_64 with gcc
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bpf/vmtest-bpf-next-VM_Test-34 success Logs for x86_64-llvm-18 / test
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bpf/vmtest-bpf-next-VM_Test-27 success Logs for x86_64-gcc / veristat / veristat on x86_64 with gcc
bpf/vmtest-bpf-next-VM_Test-24 success Logs for x86_64-gcc / test (test_progs_no_alu32_parallel, true, 30) / test_progs_no_alu32_parallel on x86_64 with gcc
bpf/vmtest-bpf-next-VM_Test-30 success Logs for x86_64-llvm-17 / test
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Guessed tree name to be net-next
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 1117 this patch: 1117
netdev/cc_maintainers success CCed 10 of 10 maintainers
netdev/build_clang success Errors and warnings before: 1143 this patch: 1143
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 1144 this patch: 1144
netdev/checkpatch warning WARNING: line length of 83 exceeds 80 columns WARNING: line length of 84 exceeds 80 columns
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

D. Wythe Dec. 15, 2023, 3:07 a.m. UTC
From: "D. Wythe" <alibuda@linux.alibaba.com>

To support the prog update, we need to ensure that the prog seen
within the hook is always valid. Considering that hooks are always
protected by rcu_read_lock(), which provide us the ability to
access the prog under rcu.

Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>
---
 net/netfilter/nf_bpf_link.c | 68 +++++++++++++++++++++++++++++++++++----------
 1 file changed, 53 insertions(+), 15 deletions(-)

Comments

Florian Westphal Dec. 15, 2023, 2:17 p.m. UTC | #1
D. Wythe <alibuda@linux.alibaba.com> wrote:
>  	const struct nf_defrag_hook *defrag_hook;
> +	const struct bpf_prog __rcu *nf_prog;

Hmm, why do we need this pointer?
Can't you just re-use bpf_nf_link->link.prog?

> +	rcu_assign_pointer(nf_link->nf_prog, new_prog);
> +	old_prog = xchg(&link->prog, new_prog);

This looks redundant, I think you can remove the nf_prog
pointer again.

Rest LGTM.
D. Wythe Dec. 18, 2023, 3:06 a.m. UTC | #2
On 12/15/23 10:17 PM, Florian Westphal wrote:
> D. Wythe <alibuda@linux.alibaba.com> wrote:
>>   	const struct nf_defrag_hook *defrag_hook;
>> +	const struct bpf_prog __rcu *nf_prog;
> Hmm, why do we need this pointer?
> Can't you just re-use bpf_nf_link->link.prog?
Accessing nf_link->link.prog directly is a bit strange because it is not 
marked as __rcu, which will generate a compilation warning,
thus we need to perform a type conversion.

But I do not intend to insist on it. I will remove it in the next version.

Best wishes,
D. Wythe
>
>> +	rcu_assign_pointer(nf_link->nf_prog, new_prog);
>> +	old_prog = xchg(&link->prog, new_prog);
> This looks redundant, I think you can remove the nf_prog
> pointer again.
>
> Rest LGTM.
diff mbox series

Patch

diff --git a/net/netfilter/nf_bpf_link.c b/net/netfilter/nf_bpf_link.c
index e502ec0..e17f256 100644
--- a/net/netfilter/nf_bpf_link.c
+++ b/net/netfilter/nf_bpf_link.c
@@ -8,17 +8,8 @@ 
 #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);
-}
+/* protect link update in parallel */
+static DEFINE_MUTEX(bpf_nf_mutex);
 
 struct bpf_nf_link {
 	struct bpf_link link;
@@ -26,8 +17,22 @@  struct bpf_nf_link {
 	struct net *net;
 	u32 dead;
 	const struct nf_defrag_hook *defrag_hook;
+	const struct bpf_prog __rcu *nf_prog;
+	struct rcu_head head;
 };
 
+static unsigned int nf_hook_run_bpf(void *bpf_link, struct sk_buff *skb,
+				    const struct nf_hook_state *s)
+{
+	const struct bpf_nf_link *link = bpf_link;
+	struct bpf_nf_ctx ctx = {
+		.state = s,
+		.skb = skb,
+	};
+
+	return bpf_prog_run(rcu_dereference(link->nf_prog), &ctx);
+}
+
 #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,
@@ -126,8 +131,7 @@  static void bpf_nf_link_release(struct bpf_link *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);
+	kfree_rcu(nf_link, head);
 }
 
 static int bpf_nf_link_detach(struct bpf_link *link)
@@ -162,7 +166,35 @@  static int bpf_nf_link_fill_link_info(const struct bpf_link *link,
 static int bpf_nf_link_update(struct bpf_link *link, struct bpf_prog *new_prog,
 			      struct bpf_prog *old_prog)
 {
-	return -EOPNOTSUPP;
+	struct bpf_nf_link *nf_link = container_of(link, struct bpf_nf_link, link);
+	int err = 0;
+
+	mutex_lock(&bpf_nf_mutex);
+
+	if (nf_link->dead) {
+		err = -EPERM;
+		goto out;
+	}
+
+	/* target old_prog mismatch */
+	if (old_prog && link->prog != old_prog) {
+		err = -EPERM;
+		goto out;
+	}
+
+	old_prog = link->prog;
+	if (old_prog == new_prog) {
+		/* don't need update */
+		bpf_prog_put(new_prog);
+		goto out;
+	}
+
+	rcu_assign_pointer(nf_link->nf_prog, new_prog);
+	old_prog = xchg(&link->prog, new_prog);
+	bpf_prog_put(old_prog);
+out:
+	mutex_unlock(&bpf_nf_mutex);
+	return err;
 }
 
 static const struct bpf_link_ops bpf_nf_link_lops = {
@@ -226,7 +258,13 @@  int bpf_nf_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
 
 	link->hook_ops.hook = nf_hook_run_bpf;
 	link->hook_ops.hook_ops_type = NF_HOOK_OP_BPF;
-	link->hook_ops.priv = prog;
+
+	rcu_assign_pointer(link->nf_prog, prog);
+
+	/* bpf_nf_link_release & bpf_nf_link_dealloc() can ensures that link remains
+	 * valid at all times within nf_hook_run_bpf().
+	 */
+	link->hook_ops.priv = link;
 
 	link->hook_ops.pf = attr->link_create.netfilter.pf;
 	link->hook_ops.priority = attr->link_create.netfilter.priority;