[RFC,bpf-next,v1,2/4] netfilter: add bpf_xdp_flow_offload_lookup kfunc

Commit Message

Lorenzo Bianconi May 10, 2024, 2:01 p.m. UTC

Introduce bpf_xdp_flow_offload_lookup kfunc in order to perform the
lookup of a given flowtable entry based on a fib tuple of incoming
traffic.
bpf_xdp_flow_offload_lookup can be used as building block to offload
in xdp the processing of sw flowtable when hw flowtable is not
available.

Signed-off-by: Lorenzo Bianconi <[e-mail]>
---
 include/net/netfilter/nf_flow_table.h |  9 +++
 net/netfilter/Makefile                |  5 ++
 net/netfilter/nf_flow_table_bpf.c     | 95 +++++++++++++++++++++++++++
 net/netfilter/nf_flow_table_inet.c    |  2 +
 4 files changed, 111 insertions(+)
 create mode 100644 net/netfilter/nf_flow_table_bpf.c

Patch

diff --git a/include/net/netfilter/nf_flow_table.h b/include/net/netfilter/nf_flow_table.h
index 0bbe6ea8e0651..2f78bacb45d6a 100644
--- a/include/net/netfilter/nf_flow_table.h
+++ b/include/net/netfilter/nf_flow_table.h
@@ -312,6 +312,15 @@  unsigned int nf_flow_offload_ip_hook(void *priv, struct sk_buff *skb,
 unsigned int nf_flow_offload_ipv6_hook(void *priv, struct sk_buff *skb,
 				       const struct nf_hook_state *state);
 
+#if IS_ENABLED(CONFIG_DEBUG_INFO_BTF) || IS_ENABLED(CONFIG_DEBUG_INFO_BTF_MODULES)
+extern int nf_flow_offload_register_bpf(void);
+#else
+static inline int nf_flow_offload_register_bpf(void)
+{
+	return 0;
+}
+#endif
+
 #define MODULE_ALIAS_NF_FLOWTABLE(family)	\
 	MODULE_ALIAS("nf-flowtable-" __stringify(family))
 
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index 614815a3ed738..eb91a54b9fa9a 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -143,6 +143,11 @@  obj-$(CONFIG_NFT_FWD_NETDEV)	+= nft_fwd_netdev.o
 obj-$(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
+ifeq ($(CONFIG_NF_FLOW_TABLE),m)
+nf_flow_table-objs += nf_flow_table_bpf.o
+else ifeq ($(CONFIG_NF_FLOW_TABLE),y)
+nf_flow_table-objs += nf_flow_table_bpf.o
+endif
 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_bpf.c b/net/netfilter/nf_flow_table_bpf.c
new file mode 100644
index 0000000000000..836a1127e4052
--- /dev/null
+++ b/net/netfilter/nf_flow_table_bpf.c
@@ -0,0 +1,95 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/* Unstable Flow Table Helpers for XDP hook
+ *
+ * These are called from the XDP programs.
+ * Note that it is allowed to break compatibility for these functions since
+ * the interface they are exposed through to BPF programs is explicitly
+ * unstable.
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <net/netfilter/nf_flow_table.h>
+#include <linux/bpf.h>
+#include <linux/btf.h>
+#include <net/xdp.h>
+
+__diag_push();
+__diag_ignore_all("-Wmissing-prototypes",
+		  "Global functions as their definitions will be in nf_flow_table BTF");
+
+static struct flow_offload_tuple_rhash *
+bpf_xdp_flow_offload_tuple_lookup(struct net_device *dev,
+				  struct flow_offload_tuple *tuple,
+				  __be16 proto)
+{
+	struct flow_offload_tuple_rhash *tuplehash;
+	struct nf_flowtable *flow_table;
+	struct flow_offload *flow;
+
+	flow_table = nf_flowtable_by_dev(dev);
+	if (!flow_table)
+		return ERR_PTR(-ENOENT);
+
+	tuplehash = flow_offload_lookup(flow_table, tuple);
+	if (!tuplehash)
+		return ERR_PTR(-ENOENT);
+
+	flow = container_of(tuplehash, struct flow_offload,
+			    tuplehash[tuplehash->tuple.dir]);
+	flow_offload_refresh(flow_table, flow, false);
+
+	return tuplehash;
+}
+
+__bpf_kfunc struct flow_offload_tuple_rhash *
+bpf_xdp_flow_offload_lookup(struct xdp_md *ctx,
+			    struct bpf_fib_lookup *fib_tuple,
+			    u32 fib_tuple__sz)
+{
+	struct xdp_buff *xdp = (struct xdp_buff *)ctx;
+	struct flow_offload_tuple tuple = {
+		.iifidx = fib_tuple->ifindex,
+		.l3proto = fib_tuple->family,
+		.l4proto = fib_tuple->l4_protocol,
+		.src_port = fib_tuple->sport,
+		.dst_port = fib_tuple->dport,
+	};
+	__be16 proto;
+
+	switch (fib_tuple->family) {
+	case AF_INET:
+		tuple.src_v4.s_addr = fib_tuple->ipv4_src;
+		tuple.dst_v4.s_addr = fib_tuple->ipv4_dst;
+		proto = htons(ETH_P_IP);
+		break;
+	case AF_INET6:
+		tuple.src_v6 = *(struct in6_addr *)&fib_tuple->ipv6_src;
+		tuple.dst_v6 = *(struct in6_addr *)&fib_tuple->ipv6_dst;
+		proto = htons(ETH_P_IPV6);
+		break;
+	default:
+		return ERR_PTR(-EINVAL);
+	}
+
+	return bpf_xdp_flow_offload_tuple_lookup(xdp->rxq->dev, &tuple, proto);
+}
+
+__diag_pop()
+
+BTF_KFUNCS_START(nf_ft_kfunc_set)
+BTF_ID_FLAGS(func, bpf_xdp_flow_offload_lookup)
+BTF_KFUNCS_END(nf_ft_kfunc_set)
+
+static const struct btf_kfunc_id_set nf_flow_offload_kfunc_set = {
+	.owner = THIS_MODULE,
+	.set   = &nf_ft_kfunc_set,
+};
+
+int nf_flow_offload_register_bpf(void)
+{
+	return register_btf_kfunc_id_set(BPF_PROG_TYPE_XDP,
+					 &nf_flow_offload_kfunc_set);
+}
+EXPORT_SYMBOL_GPL(nf_flow_offload_register_bpf);
diff --git a/net/netfilter/nf_flow_table_inet.c b/net/netfilter/nf_flow_table_inet.c
index 6eef15648b7b0..b13587238eceb 100644
--- a/net/netfilter/nf_flow_table_inet.c
+++ b/net/netfilter/nf_flow_table_inet.c
@@ -98,6 +98,8 @@  static int __init nf_flow_inet_module_init(void)
 	nft_register_flowtable_type(&flowtable_ipv6);
 	nft_register_flowtable_type(&flowtable_inet);
 
+	nf_flow_offload_register_bpf();
+
 	return 0;
 }