Linux Ethernet Bridging - Aug 2020 - [Bridge] [RFC PATCH bpf-next 3/3] samples/bpf: Add a simple bridge example accelerated with XDP

This patch adds a simple example of XDP-based bridge with the new
bpf_fdb_lookup helper. This program simply forwards packets based
on the destination port given by FDB in the kernel. Note that both
vlan filtering and learning features are currently unsupported in
this example.

There is another plan to recreate a userspace application
(xdp_bridge_user.c) as a daemon process, which helps to automate
not only detection of status changes in bridge port but also
handling vlan protocol updates.

Note:?David?Ahern?suggested?a?new?bpf?helper?[1]?to?get?master
vlan/bonding?devices in?XDP?programs?attached?to?their?slaves
when?the?master?vlan/bonding?devices are?bridge?ports. If?this
idea?is?accepted?and?the?helper?is?introduced?in?the?future, we
can?handle?interfaces?slaved?to?vlan/bonding?devices in?this
sample?by?calling the?suggested?bpf?helper?(I?guess?it?can?get
vlan/bonding?ifindex?from?their?slave?ifindex). Notice?that?we
don't?need?to?change?bpf_fdb_lookup()?API?to?use?such?a?feature,
but?we?just?need?to?modify?bpf?programs?like?this?sample.

[1]: http://vger.kernel.org/lpc-networking2018.html#session-1

Signed-off-by: Yoshiki Komachi <komachi.yoshiki at gmail.com>
---
 samples/bpf/Makefile          |   3 +
 samples/bpf/xdp_bridge_kern.c | 129 ++++++++++++++++++
 samples/bpf/xdp_bridge_user.c | 239 ++++++++++++++++++++++++++++++++++
 3 files changed, 371 insertions(+)
 create mode 100644 samples/bpf/xdp_bridge_kern.c
 create mode 100644 samples/bpf/xdp_bridge_user.c

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index f87ee02073ba..d470368fe8de 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -53,6 +53,7 @@ tprogs-y += task_fd_query
 tprogs-y += xdp_sample_pkts
 tprogs-y += ibumad
 tprogs-y += hbm
+tprogs-y += xdp_bridge
 
 # Libbpf dependencies
 LIBBPF = $(TOOLS_PATH)/lib/bpf/libbpf.a
@@ -109,6 +110,7 @@ task_fd_query-objs := bpf_load.o task_fd_query_user.o
$(TRACE_HELPERS)
 xdp_sample_pkts-objs := xdp_sample_pkts_user.o $(TRACE_HELPERS)
 ibumad-objs := bpf_load.o ibumad_user.o $(TRACE_HELPERS)
 hbm-objs := bpf_load.o hbm.o $(CGROUP_HELPERS)
+xdp_bridge-objs := xdp_bridge_user.o
 
 # Tell kbuild to always build the programs
 always-y := $(tprogs-y)
@@ -170,6 +172,7 @@ always-y += ibumad_kern.o
 always-y += hbm_out_kern.o
 always-y += hbm_edt_kern.o
 always-y += xdpsock_kern.o
+always-y += xdp_bridge_kern.o
 
 ifeq ($(ARCH), arm)
 # Strip all except -D__LINUX_ARM_ARCH__ option needed to handle linux
diff --git a/samples/bpf/xdp_bridge_kern.c b/samples/bpf/xdp_bridge_kern.c
new file mode 100644
index 000000000000..00f802503199
--- /dev/null
+++ b/samples/bpf/xdp_bridge_kern.c
@@ -0,0 +1,129 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 NTT Corp. All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ */
+#define KBUILD_MODNAME "foo"
+#include <uapi/linux/bpf.h>
+#include <linux/in.h>
+#include <linux/if_ether.h>
+#include <linux/if_packet.h>
+#include <linux/if_vlan.h>
+#include <linux/ip.h>
+#include <linux/ipv6.h>
+
+#include <bpf/bpf_helpers.h>
+
+struct {
+	__uint(type, BPF_MAP_TYPE_DEVMAP_HASH);
+	__uint(key_size, sizeof(int));
+	__uint(value_size, sizeof(int));
+	__uint(max_entries, 64);
+} xdp_tx_ports SEC(".maps");
+
+static __always_inline int xdp_bridge_proto(struct xdp_md *ctx, u16
br_vlan_proto)
+{
+	void *data_end = (void *)(long)ctx->data_end;
+	void *data = (void *)(long)ctx->data;
+	struct bpf_fdb_lookup fdb_lookup_params;
+	struct vlan_hdr *vlan_hdr = NULL;
+	struct ethhdr *eth = data;
+	u16 h_proto;
+	u64 nh_off;
+	int rc;
+
+	nh_off = sizeof(*eth);
+	if (data + nh_off > data_end)
+		return XDP_DROP;
+
+	__builtin_memset(&fdb_lookup_params, 0, sizeof(fdb_lookup_params));
+
+	h_proto = eth->h_proto;
+
+	if (unlikely(ntohs(h_proto) < ETH_P_802_3_MIN))
+		return XDP_PASS;
+
+	/* Handle VLAN tagged packet */
+	if (h_proto == br_vlan_proto) {
+		vlan_hdr = (void *)eth + nh_off;
+		nh_off += sizeof(*vlan_hdr);
+		if ((void *)eth + nh_off > data_end)
+			return XDP_PASS;
+
+		fdb_lookup_params.vlan_id = ntohs(vlan_hdr->h_vlan_TCI) &
+					VLAN_VID_MASK;
+	}
+
+	/* FIXME: Although Linux bridge provides us with vlan filtering (contains
+	 * PVID) at ingress, the feature is currently unsupported in this XDP program.
+	 *
+	 * Two ideas to realize the vlan filtering are below:
+	 *   1. usespace daemon monitors bridge vlan events and notifies XDP programs
+	 *      of them through BPF maps
+	 *   2. introduce another bpf helper to retrieve bridge vlan information
+	 *
+	 *
+	 * FIXME: After the vlan filtering, learning feature is required here, but
+	 * it is currently unsupported as well. If another bpf helper for learning
+	 * is accepted, the processing could be implemented in the future.
+	 */
+
+	memcpy(&fdb_lookup_params.addr, eth->h_dest, ETH_ALEN);
+
+	/* Note: This program definitely takes ifindex of ingress interface as
+	 * a bridge port. Linux networking devices can be stacked and physical
+	 * interfaces are not necessarily slaves of bridges (e.g., bonding or
+	 * vlan devices can be slaves of bridges), but stacked bridge ports are
+	 * currently unsupported in this program. In such cases, XDP programs
+	 * should be attached to a lower device in order to process packets with
+	 * higher speed. Then, a new bpf helper to find upper devices will be
+	 * required here in the future because they will be registered on FDB
+	 * in the kernel.
+	 */
+	fdb_lookup_params.ifindex = ctx->ingress_ifindex;
+
+	rc = bpf_fdb_lookup(ctx, &fdb_lookup_params, sizeof(fdb_lookup_params),
0);
+	if (rc != BPF_FDB_LKUP_RET_SUCCESS) {
+		/* In cases of flooding, XDP_PASS will be returned here */
+		return XDP_PASS;
+	}
+
+	/* FIXME: Although Linux bridge provides us with vlan filtering (contains
+	 * untagged policy) at egress as well, the feature is currently unsupported
+	 * in this XDP program.
+	 *
+	 * Two ideas to realize the vlan filtering are below:
+	 *   1. usespace daemon monitors bridge vlan events and notifies XDP programs
+	 *      of them through BPF maps
+	 *   2. introduce another bpf helper to retrieve bridge vlan information
+	 */
+
+	return bpf_redirect_map(&xdp_tx_ports, fdb_lookup_params.ifindex,
XDP_PASS);
+}
+
+SEC("xdp_bridge")
+int xdp_bridge_prog(struct xdp_md *ctx)
+{
+	return xdp_bridge_proto(ctx, 0);
+}
+
+SEC("xdp_8021q_bridge")
+int xdp_8021q_bridge_prog(struct xdp_md *ctx)
+{
+	return xdp_bridge_proto(ctx, htons(ETH_P_8021Q));
+}
+
+SEC("xdp_8021ad_bridge")
+int xdp_8021ad_bridge_prog(struct xdp_md *ctx)
+{
+	return xdp_bridge_proto(ctx, htons(ETH_P_8021AD));
+}
+
+char _license[] SEC("license") = "GPL";
diff --git a/samples/bpf/xdp_bridge_user.c b/samples/bpf/xdp_bridge_user.c
new file mode 100644
index 000000000000..6ed0a2ece6f4
--- /dev/null
+++ b/samples/bpf/xdp_bridge_user.c
@@ -0,0 +1,239 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 NTT Corp. All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ */
+
+#include <linux/bpf.h>
+#include <linux/if_link.h>
+#include <linux/limits.h>
+#include <net/if.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <libgen.h>
+
+#include <bpf/libbpf.h>
+#include <bpf/bpf.h>
+
+#define STRERR_BUFSIZE  128
+
+static __u32 xdp_flags = XDP_FLAGS_UPDATE_IF_NOEXIST;
+
+static int do_attach(int idx, int prog_fd, int map_fd, const char *name)
+{
+	int err;
+
+	err = bpf_set_link_xdp_fd(idx, prog_fd, xdp_flags);
+	if (err < 0) {
+		printf("ERROR: failed to attach program to %s\n", name);
+		return err;
+	}
+
+	/* Adding ifindex as a possible egress TX port */
+	err = bpf_map_update_elem(map_fd, &idx, &idx, 0);
+	if (err)
+		printf("ERROR: failed using device %s as TX-port\n", name);
+
+	return err;
+}
+
+static int do_detach(int idx, const char *name)
+{
+	int err;
+
+	err = bpf_set_link_xdp_fd(idx, -1, xdp_flags);
+	if (err < 0)
+		printf("ERROR: failed to detach program from %s\n", name);
+
+	/* FIXME: Need to delete the corresponding entry in shared devmap
+	 * with bpf_map_delete_elem((map_fd, &idx);
+	 */
+	return err;
+}
+
+static int do_reuse_map(struct bpf_map *map, char *pin_path, bool *pinned)
+{
+	const char *path = "/sys/fs/bpf/xdp_bridge";
+	char errmsg[STRERR_BUFSIZE];
+	int err, len, pin_fd;
+
+	len = snprintf(pin_path, PATH_MAX, "%s/%s", path,
bpf_map__name(map));
+	if (len < 0)
+		return -EINVAL;
+	else if (len >= PATH_MAX)
+		return -ENAMETOOLONG;
+
+	pin_fd = bpf_obj_get(pin_path);
+	if (pin_fd < 0) {
+		err = -errno;
+		if (err == -ENOENT) {
+			*pinned = false;
+			return 0;
+		}
+
+		libbpf_strerror(-err, errmsg, sizeof(errmsg));
+		printf("couldn't retrieve pinned map: %s\n", errmsg);
+		return err;
+	}
+
+	err = bpf_map__reuse_fd(map, pin_fd);
+	if (err) {
+		printf("failed to reuse map: %s\n", strerror(errno));
+		close(pin_fd);
+	}
+
+	return err;
+}
+
+static void usage(const char *prog)
+{
+	fprintf(stderr,
+		"usage: %s [OPTS] interface-list\n"
+		"\nOPTS:\n"
+		"    -Q    enable vlan filtering (802.1Q)\n"
+		"    -A    enable vlan filtering (802.1ad)\n"
+		"    -d    detach program\n",
+		prog);
+}
+
+int main(int argc, char **argv)
+{
+	struct bpf_object_open_attr attr = {
+		.prog_type = BPF_PROG_TYPE_XDP,
+	};
+	char filename[PATH_MAX], pin_path[PATH_MAX];
+	const char *prog_name = "xdp_bridge";
+	int prog_fd = -1, map_fd = -1;
+	struct bpf_program *prog;
+	struct bpf_object *obj;
+	int opt, i, idx, err;
+	struct bpf_map *map;
+	bool pinned = true;
+	int attach = 1;
+	int ret = 0;
+
+	while ((opt = getopt(argc, argv, ":dQASF")) != -1) {
+		switch (opt) {
+		case 'd':
+			attach = 0;
+			break;
+		case 'S':
+			xdp_flags |= XDP_FLAGS_SKB_MODE;
+			break;
+		case 'F':
+			xdp_flags &= ~XDP_FLAGS_UPDATE_IF_NOEXIST;
+			break;
+		case 'Q':
+			prog_name = "xdp_8021q_bridge";
+			break;
+		case 'A':
+			prog_name = "xdp_8021ad_bridge";
+			break;
+		default:
+			usage(basename(argv[0]));
+			return 1;
+		}
+	}
+
+	if (!(xdp_flags & XDP_FLAGS_SKB_MODE))
+		xdp_flags |= XDP_FLAGS_DRV_MODE;
+
+	if (optind == argc) {
+		usage(basename(argv[0]));
+		return 1;
+	}
+
+	if (attach) {
+		snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
+		attr.file = filename;
+
+		if (access(filename, O_RDONLY) < 0) {
+			printf("error accessing file %s: %s\n",
+				filename, strerror(errno));
+			return 1;
+		}
+
+		obj = bpf_object__open_xattr(&attr);
+		if (libbpf_get_error(obj)) {
+			printf("cannot open xdp program: %s\n", strerror(errno));
+			return 1;
+		}
+
+		map = bpf_object__find_map_by_name(obj, "xdp_tx_ports");
+		if (libbpf_get_error(map)) {
+			printf("map not found: %s\n", strerror(errno));
+			goto err;
+		}
+
+		err = do_reuse_map(map, pin_path, &pinned);
+		if (err) {
+			printf("error reusing map %s: %s\n",
+				bpf_map__name(map), strerror(errno));
+			goto err;
+		}
+
+		err = bpf_object__load(obj);
+		if (err) {
+			printf("cannot load xdp program: %s\n", strerror(errno));
+			goto err;
+		}
+
+		prog = bpf_object__find_program_by_title(obj, prog_name);
+		prog_fd = bpf_program__fd(prog);
+		if (prog_fd < 0) {
+			printf("program not found: %s\n", strerror(prog_fd));
+			goto err;
+		}
+
+		map_fd = bpf_map__fd(map);
+		if (map_fd < 0) {
+			printf("map not found: %s\n", strerror(map_fd));
+			goto err;
+		}
+
+		if (!pinned) {
+			err = bpf_map__pin(map, pin_path);
+			if (err) {
+				printf("failed to pin map: %s\n", strerror(errno));
+				goto err;
+			}
+		}
+	}
+
+	for (i = optind; i < argc; ++i) {
+		idx = if_nametoindex(argv[i]);
+		if (!idx)
+			idx = strtoul(argv[i], NULL, 0);
+
+		if (!idx) {
+			fprintf(stderr, "Invalid arg\n");
+			return 1;
+		}
+		if (attach) {
+			err = do_attach(idx, prog_fd, map_fd, argv[i]);
+			if (err)
+				ret = err;
+		} else {
+			err = do_detach(idx, argv[i]);
+			if (err)
+				ret = err;
+		}
+	}
+
+	return ret;
+err:
+    bpf_object__close(obj);
+    return 1;
+}
-- 
2.20.1 (Apple Git-117)

On Thu, Jul 30, 2020 at 9:45 PM Yoshiki Komachi
<komachi.yoshiki at gmail.com> wrote:
>
> This patch adds a simple example of XDP-based bridge with the new
> bpf_fdb_lookup helper. This program simply forwards packets based
> on the destination port given by FDB in the kernel. Note that both
> vlan filtering and learning features are currently unsupported in
> this example.
>
> There is another plan to recreate a userspace application
> (xdp_bridge_user.c) as a daemon process, which helps to automate
> not only detection of status changes in bridge port but also
> handling vlan protocol updates.
>
> Note: David Ahern suggested a new bpf helper [1] to get master
> vlan/bonding devices in XDP programs attached to their slaves
> when the master vlan/bonding devices are bridge ports. If this
> idea is accepted and the helper is introduced in the future, we
> can handle interfaces slaved to vlan/bonding devices in this
> sample by calling the suggested bpf helper (I guess it can get
> vlan/bonding ifindex from their slave ifindex). Notice that we
> don't need to change bpf_fdb_lookup() API to use such a feature,
> but we just need to modify bpf programs like this sample.
>
> [1]: http://vger.kernel.org/lpc-networking2018.html#session-1
>
> Signed-off-by: Yoshiki Komachi <komachi.yoshiki at gmail.com>
> ---
Have you tried using a BPF skeleton for this? It could have saved a
bunch of mechanical code for your example. Also libbpf supports map
pinning out of the box now, I wonder if it would just work in your
case. Also it would be nice if you tried using BPF link-based approach
for this example, to show how it can be used. Thanks!

>  samples/bpf/Makefile          |   3 +
>  samples/bpf/xdp_bridge_kern.c | 129 ++++++++++++++++++
>  samples/bpf/xdp_bridge_user.c | 239 ++++++++++++++++++++++++++++++++++
>  3 files changed, 371 insertions(+)
>  create mode 100644 samples/bpf/xdp_bridge_kern.c
>  create mode 100644 samples/bpf/xdp_bridge_user.c
>
[...]

> 2020/08/01 2:48?Andrii Nakryiko <andrii.nakryiko at gmail.com>????:
> 
> On Thu, Jul 30, 2020 at 9:45 PM Yoshiki Komachi
> <komachi.yoshiki at gmail.com> wrote:
>> 
>> This patch adds a simple example of XDP-based bridge with the new
>> bpf_fdb_lookup helper. This program simply forwards packets based
>> on the destination port given by FDB in the kernel. Note that both
>> vlan filtering and learning features are currently unsupported in
>> this example.
>> 
>> There is another plan to recreate a userspace application
>> (xdp_bridge_user.c) as a daemon process, which helps to automate
>> not only detection of status changes in bridge port but also
>> handling vlan protocol updates.
>> 
>> Note: David Ahern suggested a new bpf helper [1] to get master
>> vlan/bonding devices in XDP programs attached to their slaves
>> when the master vlan/bonding devices are bridge ports. If this
>> idea is accepted and the helper is introduced in the future, we
>> can handle interfaces slaved to vlan/bonding devices in this
>> sample by calling the suggested bpf helper (I guess it can get
>> vlan/bonding ifindex from their slave ifindex). Notice that we
>> don't need to change bpf_fdb_lookup() API to use such a feature,
>> but we just need to modify bpf programs like this sample.
>> 
>> [1]: http://vger.kernel.org/lpc-networking2018.html#session-1
>> 
>> Signed-off-by: Yoshiki Komachi <komachi.yoshiki at gmail.com>
>> ---
> 
> Have you tried using a BPF skeleton for this? It could have saved a
> bunch of mechanical code for your example. Also libbpf supports map
> pinning out of the box now, I wonder if it would just work in your
> case. Also it would be nice if you tried using BPF link-based approach
> for this example, to show how it can be used. Thanks!
> 
It is still under consideration, but these features seems to be useful for
this example.

I would try to apply them in the next version.

Thank you for giving me good advice.

Best regards,
> 
>> samples/bpf/Makefile          |   3 +
>> samples/bpf/xdp_bridge_kern.c | 129 ++++++++++++++++++
>> samples/bpf/xdp_bridge_user.c | 239 ++++++++++++++++++++++++++++++++++
>> 3 files changed, 371 insertions(+)
>> create mode 100644 samples/bpf/xdp_bridge_kern.c
>> create mode 100644 samples/bpf/xdp_bridge_user.c
>> 
> 
> [...]
?
Yoshiki Komachi
komachi.yoshiki at gmail.com