[RFC PATCH v2 bpf-next 06/15] xdp_flow: Prepare flow tables in bpf

[Toshiaki Makita <toshiaki.makita1@gmail.com>]

Add maps for flow tables in bpf. TC flower has hash tables for each flow
mask ordered by priority. To do the same thing, prepare a
hashmap-in-arraymap. As bpf does not provide ordered list, we emulate it
by an array. Each array entry has one-byte next index field to implement
a list. Also prepare a one-element array to point to the head index of
the list.

Because of the limitation of bpf maps, the outer array is implemented
using two array maps. "flow_masks" is the array to emulate the list and
its entries have the priority and mask of each flow table. For each
priority/mask, the same index entry of another map "flow_tables", which
is the hashmap-in-arraymap, points to the actual flow table.

The flow insertion logic in UMH and lookup logic in BPF will be
implemented in the following commits.

NOTE: This list emulation by array may be able to be realized by adding
ordered-list type map. In that case we also need map iteration API for
bpf progs.

Signed-off-by: Toshiaki Makita <toshiaki.makita1@gmail.com>
---
 net/xdp_flow/umh_bpf.h           | 18 +++++++++++
 net/xdp_flow/xdp_flow_kern_bpf.c | 22 +++++++++++++
 net/xdp_flow/xdp_flow_umh.c      | 70 ++++++++++++++++++++++++++++++++++++++--
 3 files changed, 108 insertions(+), 2 deletions(-)
 create mode 100644 net/xdp_flow/umh_bpf.h

diff --git a/net/xdp_flow/umh_bpf.h b/net/xdp_flow/umh_bpf.h
new file mode 100644
index 0000000..b4fe0c6
--- /dev/null
+++ b/net/xdp_flow/umh_bpf.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _NET_XDP_FLOW_UMH_BPF_H
+#define _NET_XDP_FLOW_UMH_BPF_H
+
+#include "msgfmt.h"
+
+#define MAX_FLOWS 1024
+#define MAX_FLOW_MASKS 255
+#define FLOW_MASKS_TAIL 255
+
+struct xdp_flow_mask_entry {
+	struct xdp_flow_key mask;
+	__u16 priority;
+	short count;
+	int next;
+};
+
+#endif
diff --git a/net/xdp_flow/xdp_flow_kern_bpf.c b/net/xdp_flow/xdp_flow_kern_bpf.c
index 74cdb1d..c101156 100644
--- a/net/xdp_flow/xdp_flow_kern_bpf.c
+++ b/net/xdp_flow/xdp_flow_kern_bpf.c
@@ -2,6 +2,28 @@
 #define KBUILD_MODNAME "foo"
 #include <uapi/linux/bpf.h>
 #include <bpf_helpers.h>
+#include "umh_bpf.h"
+
+struct bpf_map_def SEC("maps") flow_masks_head = {
+	.type = BPF_MAP_TYPE_ARRAY,
+	.key_size = sizeof(u32),
+	.value_size = sizeof(int),
+	.max_entries = 1,
+};
+
+struct bpf_map_def SEC("maps") flow_masks = {
+	.type = BPF_MAP_TYPE_ARRAY,
+	.key_size = sizeof(u32),
+	.value_size = sizeof(struct xdp_flow_mask_entry),
+	.max_entries = MAX_FLOW_MASKS,
+};
+
+struct bpf_map_def SEC("maps") flow_tables = {
+	.type = BPF_MAP_TYPE_ARRAY_OF_MAPS,
+	.key_size = sizeof(u32),
+	.value_size = sizeof(u32),
+	.max_entries = MAX_FLOW_MASKS,
+};
 
 SEC("xdp_flow")
 int xdp_flow_prog(struct xdp_md *ctx)
diff --git a/net/xdp_flow/xdp_flow_umh.c b/net/xdp_flow/xdp_flow_umh.c
index 85c5c7b..515c2fd 100644
--- a/net/xdp_flow/xdp_flow_umh.c
+++ b/net/xdp_flow/xdp_flow_umh.c
@@ -13,7 +13,7 @@
 #include <sys/resource.h>
 #include <linux/hashtable.h>
 #include <linux/err.h>
-#include "msgfmt.h"
+#include "umh_bpf.h"
 
 extern char xdp_flow_bpf_start;
 extern char xdp_flow_bpf_end;
@@ -99,11 +99,13 @@ static int setup(void)
 
 static int load_bpf(int ifindex, struct bpf_object **objp)
 {
+	int prog_fd, flow_tables_fd, flow_meta_fd, flow_masks_head_fd, err;
+	struct bpf_map *flow_tables, *flow_masks_head;
+	int zero = 0, flow_masks_tail = FLOW_MASKS_TAIL;
 	struct bpf_object_open_attr attr = {};
 	char path[256], errbuf[ERRBUF_SIZE];
 	struct bpf_program *prog;
 	struct bpf_object *obj;
-	int prog_fd, err;
 	ssize_t len;
 
 	len = snprintf(path, 256, "/proc/self/fd/%d", progfile_fd);
@@ -131,6 +133,48 @@ static int load_bpf(int ifindex, struct bpf_object **objp)
 	bpf_object__for_each_program(prog, obj)
 		bpf_program__set_type(prog, attr.prog_type);
 
+	flow_meta_fd = bpf_create_map(BPF_MAP_TYPE_HASH,
+				      sizeof(struct xdp_flow_key),
+				      sizeof(struct xdp_flow_actions),
+				      MAX_FLOWS, 0);
+	if (flow_meta_fd < 0) {
+		err = -errno;
+		pr_err("map creation for flow_tables meta failed: %s\n",
+		       strerror(errno));
+		goto err;
+	}
+
+	flow_tables_fd = bpf_create_map_in_map(BPF_MAP_TYPE_ARRAY_OF_MAPS,
+					       "flow_tables", sizeof(__u32),
+					       flow_meta_fd, MAX_FLOW_MASKS, 0);
+	if (flow_tables_fd < 0) {
+		err = -errno;
+		pr_err("map creation for flow_tables failed: %s\n",
+		       strerror(errno));
+		close(flow_meta_fd);
+		goto err;
+	}
+
+	close(flow_meta_fd);
+
+	flow_tables = bpf_object__find_map_by_name(obj, "flow_tables");
+	if (!flow_tables) {
+		pr_err("Cannot find flow_tables\n");
+		err = -ENOENT;
+		close(flow_tables_fd);
+		goto err;
+	}
+
+	err = bpf_map__reuse_fd(flow_tables, flow_tables_fd);
+	if (err) {
+		err = libbpf_err(err, errbuf);
+		pr_err("Failed to reuse flow_tables fd: %s\n", errbuf);
+		close(flow_tables_fd);
+		goto err;
+	}
+
+	close(flow_tables_fd);
+
 	err = bpf_object__load(obj);
 	if (err) {
 		err = libbpf_err(err, errbuf);
@@ -138,6 +182,28 @@ static int load_bpf(int ifindex, struct bpf_object **objp)
 		goto err;
 	}
 
+	flow_masks_head = bpf_object__find_map_by_name(obj, "flow_masks_head");
+	if (!flow_masks_head) {
+		pr_err("Cannot find flow_masks_head map\n");
+		err = -ENOENT;
+		goto err;
+	}
+
+	flow_masks_head_fd = bpf_map__fd(flow_masks_head);
+	if (flow_masks_head_fd < 0) {
+		err = libbpf_err(flow_masks_head_fd, errbuf);
+		pr_err("Invalid flow_masks_head fd: %s\n", errbuf);
+		goto err;
+	}
+
+	if (bpf_map_update_elem(flow_masks_head_fd, &zero, &flow_masks_tail,
+				0)) {
+		err = -errno;
+		pr_err("Failed to initialize flow_masks_head: %s\n",
+		       strerror(errno));
+		goto err;
+	}
+
 	prog = bpf_object__find_program_by_title(obj, "xdp_flow");
 	if (!prog) {
 		pr_err("Cannot find xdp_flow program\n");
-- 
1.8.3.1