[PATCH bpf-next v5 6/7] bpf: add test_run support for netfilter program type

Florian Westphal
2023-04-21T17:04:17Z

add glue code so a bpf program can be run using userspace-provided
netfilter state and packet/skb.

Default is to use ipv4:output hook point, but this can be overridden by
userspace. Userspace provided netfilter state is restricted, only hook and
protocol families can be overridden and only to ipv4/ipv6.

Signed-off-by: Florian Westphal <fw@strlen.de>
---
no changes since last version

include/linux/bpf.h | 3 +
net/bpf/test_run.c | 158 ++++++++++++++++++++++++++++++++++++
net/netfilter/nf_bpf_link.c | 1 +
3 files changed, 162 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 18b592fde896..e53ceee1df37 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2264,6 +2264,9 @@ int bpf_prog_test_run_raw_tp(struct bpf_prog *prog,
int bpf_prog_test_run_sk_lookup(struct bpf_prog *prog,
const union bpf_attr *kattr,
union bpf_attr __user *uattr);
+int bpf_prog_test_run_nf(struct bpf_prog *prog,
+ const union bpf_attr *kattr,
+ union bpf_attr __user *uattr);
bool btf_ctx_access(int off, int size, enum bpf_access_type type,
const struct bpf_prog *prog,
struct bpf_insn_access_aux *info);
diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index f170e8a17974..e79e3a415ca9 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -19,7 +19,9 @@
#include <linux/error-injection.h>
#include <linux/smp.h>
#include <linux/sock_diag.h>
+#include <linux/netfilter.h>
#include <net/xdp.h>
+#include <net/netfilter/nf_bpf_link.h>

#define CREATE_TRACE_POINTS
#include <trace/events/bpf_test_run.h>
@@ -1691,6 +1693,162 @@ int bpf_prog_test_run_syscall(struct bpf_prog *prog,
return err;
}

+static int verify_and_copy_hook_state(struct nf_hook_state *state,
+ const struct nf_hook_state *user,
+ struct net_device *dev)
+{
+ if (user->in || user->out)
+ return -EINVAL;
+
+ if (user->net || user->sk || user->okfn)
+ return -EINVAL;
+
+ switch (user->pf) {
+ case NFPROTO_IPV4:
+ case NFPROTO_IPV6:
+ switch (state->hook) {
+ case NF_INET_PRE_ROUTING:
+ state->in = dev;
+ break;
+ case NF_INET_LOCAL_IN:
+ state->in = dev;
+ break;
+ case NF_INET_FORWARD:
+ state->in = dev;
+ state->out = dev;
+ break;
+ case NF_INET_LOCAL_OUT:
+ state->out = dev;
+ break;
+ case NF_INET_POST_ROUTING:
+ state->out = dev;
+ break;
+ }
+
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ state->pf = user->pf;
+ state->hook = user->hook;
+
+ return 0;
+}
+
+static __be16 nfproto_eth(int nfproto)
+{
+ switch (nfproto) {
+ case NFPROTO_IPV4:
+ return htons(ETH_P_IP);
+ case NFPROTO_IPV6:
+ break;
+ }
+
+ return htons(ETH_P_IPV6);
+}
+
+int bpf_prog_test_run_nf(struct bpf_prog *prog,
+ const union bpf_attr *kattr,
+ union bpf_attr __user *uattr)
+{
+ struct net *net = current->nsproxy->net_ns;
+ struct net_device *dev = net->loopback_dev;
+ struct nf_hook_state *user_ctx, hook_state = {
+ .pf = NFPROTO_IPV4,
+ .hook = NF_INET_LOCAL_OUT,
+ };
+ u32 size = kattr->test.data_size_in;
+ u32 repeat = kattr->test.repeat;
+ struct bpf_nf_ctx ctx = {
+ .state = &hook_state,
+ };
+ struct sk_buff *skb = NULL;
+ u32 retval, duration;
+ void *data;
+ int ret;
+
+ if (kattr->test.flags || kattr->test.cpu || kattr->test.batch_size)
+ return -EINVAL;
+
+ if (size < sizeof(struct iphdr))
+ return -EINVAL;
+
+ data = bpf_test_init(kattr, kattr->test.data_size_in, size,
+ NET_SKB_PAD + NET_IP_ALIGN,
+ SKB_DATA_ALIGN(sizeof(struct skb_shared_info)));
+ if (IS_ERR(data))
+ return PTR_ERR(data);
+
+ if (!repeat)
+ repeat = 1;
+
+ user_ctx = bpf_ctx_init(kattr, sizeof(struct nf_hook_state));
+ if (IS_ERR(user_ctx)) {
+ kfree(data);
+ return PTR_ERR(user_ctx);
+ }
+
+ if (user_ctx) {
+ ret = verify_and_copy_hook_state(&hook_state, user_ctx, dev);
+ if (ret)
+ goto out;
+ }
+
+ skb = slab_build_skb(data);
+ if (!skb) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ data = NULL; /* data released via kfree_skb */
+
+ skb_reserve(skb, NET_SKB_PAD + NET_IP_ALIGN);
+ __skb_put(skb, size);
+
+ ret = -EINVAL;
+
+ if (hook_state.hook != NF_INET_LOCAL_OUT) {
+ if (size < ETH_HLEN + sizeof(struct iphdr))
+ goto out;
+
+ skb->protocol = eth_type_trans(skb, dev);
+ switch (skb->protocol) {
+ case htons(ETH_P_IP):
+ if (hook_state.pf == NFPROTO_IPV4)
+ break;
+ goto out;
+ case htons(ETH_P_IPV6):
+ if (size < ETH_HLEN + sizeof(struct ipv6hdr))
+ goto out;
+ if (hook_state.pf == NFPROTO_IPV6)
+ break;
+ goto out;
+ default:
+ ret = -EPROTO;
+ goto out;
+ }
+
+ skb_reset_network_header(skb);
+ } else {
+ skb->protocol = nfproto_eth(hook_state.pf);
+ }
+
+ ctx.skb = skb;
+
+ ret = bpf_test_run(prog, &ctx, repeat, &retval, &duration, false);
+ if (ret)
+ goto out;
+
+ ret = bpf_test_finish(kattr, uattr, NULL, NULL, 0, retval, duration);
+
+out:
+ kfree(user_ctx);
+ kfree_skb(skb);
+ kfree(data);
+ return ret;
+}
+
static const struct btf_kfunc_id_set bpf_prog_test_kfunc_set = {
.owner = THIS_MODULE,
.set = &test_sk_check_kfunc_ids,
diff --git a/net/netfilter/nf_bpf_link.c b/net/netfilter/nf_bpf_link.c
index 49cfc5215386..c36da56d756f 100644
--- a/net/netfilter/nf_bpf_link.c
+++ b/net/netfilter/nf_bpf_link.c
@@ -166,6 +166,7 @@ int bpf_nf_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
}

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)
--
2.39.2