[PATCH v5 bpf-next 1/3] netfilter: nf_tables: add flowtable map for xdp offload

Lorenzo Bianconi
2024-06-14T15:41:18Z

From: Florian Westphal <fw@strlen.de>

This adds a small internal mapping table so that a new bpf (xdp) kfunc
can perform lookups in a flowtable.

As-is, xdp program has access to the device pointer, but no way to do a
lookup in a flowtable -- there is no way to obtain the needed struct
without questionable stunts.

This allows to obtain an nf_flowtable pointer given a net_device
structure.

In order to keep backward compatibility, the infrastructure allows the
user to add a given device to multiple flowtables, but it will always
return the first added mapping performing the lookup since it assumes
the right configuration is 1:1 mapping between flowtables and net_devices.

Signed-off-by: Florian Westphal <fw@strlen.de>
Co-developed-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
---
include/net/netfilter/nf_flow_table.h | 8 ++
net/netfilter/Makefile | 2 +-
net/netfilter/nf_flow_table_offload.c | 6 +-
net/netfilter/nf_flow_table_xdp.c | 163 ++++++++++++++++++++++++++
4 files changed, 176 insertions(+), 3 deletions(-)
create mode 100644 net/netfilter/nf_flow_table_xdp.c

diff --git a/include/net/netfilter/nf_flow_table.h b/include/net/netfilter/nf_flow_table.h
index 9abb7ee40d72f..688e02b287cc4 100644
--- a/include/net/netfilter/nf_flow_table.h
+++ b/include/net/netfilter/nf_flow_table.h
@@ -305,6 +305,14 @@ struct flow_ports {
__be16 source, dest;
};

+struct nf_flowtable *nf_flowtable_by_dev(const struct net_device *dev);
+int nf_flow_offload_xdp_setup(struct nf_flowtable *flowtable,
+ struct net_device *dev,
+ enum flow_block_command cmd);
+void nf_flow_offload_xdp_cancel(struct nf_flowtable *flowtable,
+ struct net_device *dev,
+ enum flow_block_command cmd);
+
unsigned int nf_flow_offload_ip_hook(void *priv, struct sk_buff *skb,
const struct nf_hook_state *state);
unsigned int nf_flow_offload_ipv6_hook(void *priv, struct sk_buff *skb,
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index 614815a3ed738..18046872a38aa 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -142,7 +142,7 @@ obj-$(CONFIG_NFT_FWD_NETDEV) += nft_fwd_netdev.o
# flow table infrastructure
obj-$(CONFIG_NF_FLOW_TABLE) += nf_flow_table.o
nf_flow_table-objs := nf_flow_table_core.o nf_flow_table_ip.o \
- nf_flow_table_offload.o
+ nf_flow_table_offload.o nf_flow_table_xdp.o
nf_flow_table-$(CONFIG_NF_FLOW_TABLE_PROCFS) += nf_flow_table_procfs.o

obj-$(CONFIG_NF_FLOW_TABLE_INET) += nf_flow_table_inet.o
diff --git a/net/netfilter/nf_flow_table_offload.c b/net/netfilter/nf_flow_table_offload.c
index a010b25076ca0..d9b019c98694b 100644
--- a/net/netfilter/nf_flow_table_offload.c
+++ b/net/netfilter/nf_flow_table_offload.c
@@ -1192,7 +1192,7 @@ int nf_flow_table_offload_setup(struct nf_flowtable *flowtable,
int err;

if (!nf_flowtable_hw_offload(flowtable))
- return 0;
+ return nf_flow_offload_xdp_setup(flowtable, dev, cmd);

if (dev->netdev_ops->ndo_setup_tc)
err = nf_flow_table_offload_cmd(&bo, flowtable, dev, cmd,
@@ -1200,8 +1200,10 @@ int nf_flow_table_offload_setup(struct nf_flowtable *flowtable,
else
err = nf_flow_table_indr_offload_cmd(&bo, flowtable, dev, cmd,
&extack);
- if (err < 0)
+ if (err < 0) {
+ nf_flow_offload_xdp_cancel(flowtable, dev, cmd);
return err;
+ }

return nf_flow_table_block_setup(flowtable, &bo, cmd);
}
diff --git a/net/netfilter/nf_flow_table_xdp.c b/net/netfilter/nf_flow_table_xdp.c
new file mode 100644
index 0000000000000..b9bdf27ba9bd3
--- /dev/null
+++ b/net/netfilter/nf_flow_table_xdp.c
@@ -0,0 +1,163 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/netfilter.h>
+#include <linux/rhashtable.h>
+#include <linux/netdevice.h>
+#include <net/flow_offload.h>
+#include <net/netfilter/nf_flow_table.h>
+
+struct flow_offload_xdp_ft {
+ struct list_head head;
+ struct nf_flowtable *ft;
+ struct rcu_head rcuhead;
+};
+
+struct flow_offload_xdp {
+ struct hlist_node hnode;
+ unsigned long net_device_addr;
+ struct list_head head;
+};
+
+#define NF_XDP_HT_BITS 4
+static DEFINE_HASHTABLE(nf_xdp_hashtable, NF_XDP_HT_BITS);
+static DEFINE_MUTEX(nf_xdp_hashtable_lock);
+
+/* caller must hold rcu read lock */
+struct nf_flowtable *nf_flowtable_by_dev(const struct net_device *dev)
+{
+ unsigned long key = (unsigned long)dev;
+ struct flow_offload_xdp *iter;
+
+ hash_for_each_possible_rcu(nf_xdp_hashtable, iter, hnode, key) {
+ if (key == iter->net_device_addr) {
+ struct flow_offload_xdp_ft *ft_elem;
+
+ /* The user is supposed to insert a given net_device
+ * just into a single nf_flowtable so we always return
+ * the first element here.
+ */
+ ft_elem = list_first_or_null_rcu(&iter->head,
+ struct flow_offload_xdp_ft,
+ head);
+ return ft_elem ? ft_elem->ft : NULL;
+ }
+ }
+
+ return NULL;
+}
+
+static int nf_flowtable_by_dev_insert(struct nf_flowtable *ft,
+ const struct net_device *dev)
+{
+ struct flow_offload_xdp *iter, *elem = NULL;
+ unsigned long key = (unsigned long)dev;
+ struct flow_offload_xdp_ft *ft_elem;
+
+ ft_elem = kzalloc(sizeof(*ft_elem), GFP_KERNEL_ACCOUNT);
+ if (!ft_elem)
+ return -ENOMEM;
+
+ ft_elem->ft = ft;
+
+ mutex_lock(&nf_xdp_hashtable_lock);
+
+ hash_for_each_possible(nf_xdp_hashtable, iter, hnode, key) {
+ if (key == iter->net_device_addr) {
+ elem = iter;
+ break;
+ }
+ }
+
+ if (!elem) {
+ elem = kzalloc(sizeof(*elem), GFP_KERNEL_ACCOUNT);
+ if (!elem)
+ goto err_unlock;
+
+ elem->net_device_addr = key;
+ INIT_LIST_HEAD(&elem->head);
+ hash_add_rcu(nf_xdp_hashtable, &elem->hnode, key);
+ }
+ list_add_tail_rcu(&ft_elem->head, &elem->head);
+
+ mutex_unlock(&nf_xdp_hashtable_lock);
+
+ return 0;
+
+err_unlock:
+ mutex_unlock(&nf_xdp_hashtable_lock);
+ kfree(ft_elem);
+
+ return -ENOMEM;
+}
+
+static void nf_flowtable_by_dev_remove(struct nf_flowtable *ft,
+ const struct net_device *dev)
+{
+ struct flow_offload_xdp *iter, *elem = NULL;
+ unsigned long key = (unsigned long)dev;
+
+ mutex_lock(&nf_xdp_hashtable_lock);
+
+ hash_for_each_possible(nf_xdp_hashtable, iter, hnode, key) {
+ if (key == iter->net_device_addr) {
+ elem = iter;
+ break;
+ }
+ }
+
+ if (elem) {
+ struct flow_offload_xdp_ft *ft_elem, *ft_next;
+
+ list_for_each_entry_safe(ft_elem, ft_next, &elem->head, head) {
+ if (ft_elem->ft == ft) {
+ list_del_rcu(&ft_elem->head);
+ kfree_rcu(ft_elem, rcuhead);
+ }
+ }
+
+ if (list_empty(&elem->head))
+ hash_del_rcu(&elem->hnode);
+ else
+ elem = NULL;
+ }
+
+ mutex_unlock(&nf_xdp_hashtable_lock);
+
+ if (elem) {
+ synchronize_rcu();
+ kfree(elem);
+ }
+}
+
+int nf_flow_offload_xdp_setup(struct nf_flowtable *flowtable,
+ struct net_device *dev,
+ enum flow_block_command cmd)
+{
+ switch (cmd) {
+ case FLOW_BLOCK_BIND:
+ return nf_flowtable_by_dev_insert(flowtable, dev);
+ case FLOW_BLOCK_UNBIND:
+ nf_flowtable_by_dev_remove(flowtable, dev);
+ return 0;
+ }
+
+ WARN_ON_ONCE(1);
+ return 0;
+}
+
+void nf_flow_offload_xdp_cancel(struct nf_flowtable *flowtable,
+ struct net_device *dev,
+ enum flow_block_command cmd)
+{
+ switch (cmd) {
+ case FLOW_BLOCK_BIND:
+ nf_flowtable_by_dev_remove(flowtable, dev);
+ return;
+ case FLOW_BLOCK_UNBIND:
+ /* We do not re-bind in case hw offload would report error
+ * on *unregister*.
+ */
+ break;
+ }
+}
--
2.45.1