From: "D. Wythe" <[email protected]>
This patches attempt to implements updating of progs within
bpf netfilter link, allowing user update their ebpf netfilter
prog in hot update manner.
Besides, a corresponding test case has been added to verify
whether the update works.
--
v1:
1. remove unnecessary context, access the prog directly via rcu.
2. remove synchronize_rcu(), dealloc the nf_link via kfree_rcu.
3. check the dead flag during the update.
D. Wythe (2):
netfilter: bpf: support prog update
selftests/bpf: Add netfilter link prog update test
net/netfilter/nf_bpf_link.c | 68 ++++++++++++++----
.../bpf/prog_tests/netfilter_link_update_prog.c | 83 ++++++++++++++++++++++
.../bpf/progs/test_netfilter_link_update_prog.c | 24 +++++++
3 files changed, 160 insertions(+), 15 deletions(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/netfilter_link_update_prog.c
create mode 100644 tools/testing/selftests/bpf/progs/test_netfilter_link_update_prog.c
--
1.8.3.1
From: "D. Wythe" <[email protected]>
Update prog for active links and verify whether
the prog has been successfully replaced.
Expected output:
./test_progs -t netfilter_link_update_prog
Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED
Signed-off-by: D. Wythe <[email protected]>
---
.../bpf/prog_tests/netfilter_link_update_prog.c | 83 ++++++++++++++++++++++
.../bpf/progs/test_netfilter_link_update_prog.c | 24 +++++++
2 files changed, 107 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/netfilter_link_update_prog.c
create mode 100644 tools/testing/selftests/bpf/progs/test_netfilter_link_update_prog.c
diff --git a/tools/testing/selftests/bpf/prog_tests/netfilter_link_update_prog.c b/tools/testing/selftests/bpf/prog_tests/netfilter_link_update_prog.c
new file mode 100644
index 00000000..d23b544
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/netfilter_link_update_prog.c
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <test_progs.h>
+#include <linux/netfilter.h>
+#include <network_helpers.h>
+#include "test_netfilter_link_update_prog.skel.h"
+
+#define SERVER_ADDR "127.0.0.1"
+#define SERVER_PORT 12345
+
+static const char dummy_message[] = "A dummy message";
+
+static int send_dummy(int client_fd)
+{
+ struct sockaddr_storage saddr;
+ struct sockaddr *saddr_p;
+ socklen_t saddr_len;
+ int err;
+
+ saddr_p = (struct sockaddr *)&saddr;
+ err = make_sockaddr(AF_INET, SERVER_ADDR, SERVER_PORT, &saddr, &saddr_len);
+ if (!ASSERT_OK(err, "make_sockaddr"))
+ return -1;
+
+ err = sendto(client_fd, dummy_message, sizeof(dummy_message) - 1, 0, saddr_p, saddr_len);
+ if (!ASSERT_GE(err, 0, "sendto"))
+ return -1;
+
+ return 0;
+}
+
+void test_netfilter_link_update_prog(void)
+{
+ LIBBPF_OPTS(bpf_netfilter_opts, opts,
+ .pf = NFPROTO_IPV4,
+ .hooknum = NF_INET_LOCAL_OUT,
+ .priority = 100);
+ struct test_netfilter_link_update_prog *skel;
+ struct bpf_program *prog;
+ int server_fd, client_fd;
+ int err;
+
+ skel = test_netfilter_link_update_prog__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "test_netfilter_link_update_prog__open_and_load"))
+ goto out;
+
+ prog = skel->progs.nf_link_prog;
+
+ if (!ASSERT_OK_PTR(prog, "load program"))
+ goto out;
+
+ skel->links.nf_link_prog = bpf_program__attach_netfilter(prog, &opts);
+ if (!ASSERT_OK_PTR(skel->links.nf_link_prog, "attach netfilter program"))
+ goto out;
+
+ server_fd = start_server(AF_INET, SOCK_DGRAM, SERVER_ADDR, SERVER_PORT, 0);
+ if (!ASSERT_GE(server_fd, 0, "start_server"))
+ goto out;
+
+ client_fd = connect_to_fd(server_fd, 0);
+ if (!ASSERT_GE(client_fd, 0, "connect_to_fd"))
+ goto out;
+
+ send_dummy(client_fd);
+
+ ASSERT_EQ(skel->bss->counter, 0, "counter should be zero");
+
+ err = bpf_link__update_program(skel->links.nf_link_prog, skel->progs.nf_link_prog_new);
+ if (!ASSERT_OK(err, "bpf_link__update_program"))
+ goto out;
+
+ send_dummy(client_fd);
+ ASSERT_GE(skel->bss->counter, 0, "counter should be greater than zero");
+out:
+ if (client_fd > 0)
+ close(client_fd);
+ if (server_fd > 0)
+ close(server_fd);
+
+ test_netfilter_link_update_prog__destroy(skel);
+}
+
+
diff --git a/tools/testing/selftests/bpf/progs/test_netfilter_link_update_prog.c b/tools/testing/selftests/bpf/progs/test_netfilter_link_update_prog.c
new file mode 100644
index 00000000..42ae332
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_netfilter_link_update_prog.c
@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+
+#define NF_ACCEPT 1
+
+SEC("netfilter")
+int nf_link_prog(struct bpf_nf_ctx *ctx)
+{
+ return NF_ACCEPT;
+}
+
+u64 counter = 0;
+
+SEC("netfilter")
+int nf_link_prog_new(struct bpf_nf_ctx *ctx)
+{
+ counter++;
+ return NF_ACCEPT;
+}
+
+char _license[] SEC("license") = "GPL";
+
--
1.8.3.1
From: "D. Wythe" <[email protected]>
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 <[email protected]>
---
net/netfilter/nf_bpf_link.c | 68 +++++++++++++++++++++++++++++++++++----------
1 file changed, 53 insertions(+), 15 deletions(-)
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;
--
1.8.3.1
D. Wythe <[email protected]> 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.
On 12/15/23 10:17 PM, Florian Westphal wrote:
> D. Wythe <[email protected]> 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.