Re: [PATCH bpf-next] selftests/xsk: add xdp populate metadata test

[Maciej Fijalkowski <maciej.fijalkowski@intel.com>]

On Mon, Mar 20, 2023 at 03:57:05PM +0530, Tushar Vyavahare wrote:
> Add a new test in copy-mode for testing the copying of metadata from the
> buffer in kernel-space to user-space. This is accomplished by adding a
> new XDP program and using the bss map to store a counter that is written
> to the metadata field. This counter is incremented for every packet so
> that the number becomes unique and should be the same as the payload. It
> is store in the bss so the value can be reset between runs.
> 
> The XDP program populates the metadata and the userspace program checks
> the value stored in the metadata field against the payload using the new
> is_metadata_correct() function. To turn this verification on or off, add
> a new parameter (use_metadata) to the ifobject structure.
> 

Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>

> Signed-off-by: Tushar Vyavahare <tushar.vyavahare@intel.com>
> ---
>  .../selftests/bpf/progs/xsk_xdp_progs.c       | 25 ++++++++++
>  .../testing/selftests/bpf/xsk_xdp_metadata.h  |  5 ++
>  tools/testing/selftests/bpf/xskxceiver.c      | 46 ++++++++++++++++++-
>  tools/testing/selftests/bpf/xskxceiver.h      |  2 +
>  4 files changed, 77 insertions(+), 1 deletion(-)
>  create mode 100644 tools/testing/selftests/bpf/xsk_xdp_metadata.h
> 
> diff --git a/tools/testing/selftests/bpf/progs/xsk_xdp_progs.c b/tools/testing/selftests/bpf/progs/xsk_xdp_progs.c
> index 744a01d0e57d..a630c95c7471 100644
> --- a/tools/testing/selftests/bpf/progs/xsk_xdp_progs.c
> +++ b/tools/testing/selftests/bpf/progs/xsk_xdp_progs.c
> @@ -3,6 +3,7 @@
>  
>  #include <linux/bpf.h>
>  #include <bpf/bpf_helpers.h>
> +#include "xsk_xdp_metadata.h"
>  
>  struct {
>  	__uint(type, BPF_MAP_TYPE_XSKMAP);
> @@ -12,6 +13,7 @@ struct {
>  } xsk SEC(".maps");
>  
>  static unsigned int idx;
> +int count = 0;
>  
>  SEC("xdp") int xsk_def_prog(struct xdp_md *xdp)
>  {
> @@ -27,4 +29,27 @@ SEC("xdp") int xsk_xdp_drop(struct xdp_md *xdp)
>  	return bpf_redirect_map(&xsk, 0, XDP_DROP);
>  }
>  
> +SEC("xdp") int xsk_xdp_populate_metadata(struct xdp_md *xdp)
> +{
> +	void *data, *data_meta;
> +	struct xdp_info *meta;
> +	int err;
> +
> +	/* Reserve enough for all custom metadata. */
> +	err = bpf_xdp_adjust_meta(xdp, -(int)sizeof(struct xdp_info));
> +	if (err)
> +		return XDP_DROP;
> +
> +	data = (void *)(long)xdp->data;
> +	data_meta = (void *)(long)xdp->data_meta;
> +
> +	if (data_meta + sizeof(struct xdp_info) > data)
> +		return XDP_DROP;
> +
> +	meta = data_meta;
> +	meta->count = count++;
> +
> +	return bpf_redirect_map(&xsk, 0, XDP_DROP);
> +}
> +
>  char _license[] SEC("license") = "GPL";
> diff --git a/tools/testing/selftests/bpf/xsk_xdp_metadata.h b/tools/testing/selftests/bpf/xsk_xdp_metadata.h
> new file mode 100644
> index 000000000000..943133da378a
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/xsk_xdp_metadata.h
> @@ -0,0 +1,5 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +struct xdp_info {
> +	__u64 count;
> +} __attribute__((aligned(32)));
> diff --git a/tools/testing/selftests/bpf/xskxceiver.c b/tools/testing/selftests/bpf/xskxceiver.c
> index a17655107a94..b65e0645b0cd 100644
> --- a/tools/testing/selftests/bpf/xskxceiver.c
> +++ b/tools/testing/selftests/bpf/xskxceiver.c
> @@ -103,6 +103,7 @@
>  #include <bpf/bpf.h>
>  #include <linux/filter.h>
>  #include "../kselftest.h"
> +#include "xsk_xdp_metadata.h"
>  
>  static const char *MAC1 = "\x00\x0A\x56\x9E\xEE\x62";
>  static const char *MAC2 = "\x00\x0A\x56\x9E\xEE\x61";
> @@ -464,6 +465,7 @@ static void __test_spec_init(struct test_spec *test, struct ifobject *ifobj_tx,
>  		ifobj->use_fill_ring = true;
>  		ifobj->release_rx = true;
>  		ifobj->validation_func = NULL;
> +		ifobj->use_metadata = false;
>  
>  		if (i == 0) {
>  			ifobj->rx_on = false;
> @@ -798,6 +800,20 @@ static bool is_offset_correct(struct xsk_umem_info *umem, struct pkt_stream *pkt
>  	return false;
>  }
>  
> +static bool is_metadata_correct(struct pkt *pkt, void *buffer, u64 addr)
> +{
> +	void *data = xsk_umem__get_data(buffer, addr);
> +	struct xdp_info *meta = data - sizeof(struct xdp_info);
> +
> +	if (meta->count != pkt->payload) {
> +		ksft_print_msg("[%s] expected meta_count [%d], got meta_count [%d]\n",
> +			       __func__, pkt->payload, meta->count);
> +		return false;
> +	}
> +
> +	return true;
> +}
> +
>  static bool is_pkt_valid(struct pkt *pkt, void *buffer, u64 addr, u32 len)
>  {
>  	void *data = xsk_umem__get_data(buffer, addr);
> @@ -959,7 +975,8 @@ static int receive_pkts(struct test_spec *test, struct pollfd *fds)
>  			addr = xsk_umem__add_offset_to_addr(addr);
>  
>  			if (!is_pkt_valid(pkt, umem->buffer, addr, desc->len) ||
> -			    !is_offset_correct(umem, pkt_stream, addr, pkt->addr))
> +			    !is_offset_correct(umem, pkt_stream, addr, pkt->addr) ||
> +			    (ifobj->use_metadata && !is_metadata_correct(pkt, umem->buffer, addr)))
>  				return TEST_FAILURE;
>  
>  			if (ifobj->use_fill_ring)
> @@ -1686,6 +1703,30 @@ static void testapp_xdp_drop(struct test_spec *test)
>  	testapp_validate_traffic(test);
>  }
>  
> +static void testapp_xdp_metadata_count(struct test_spec *test)
> +{
> +	struct xsk_xdp_progs *skel_rx = test->ifobj_rx->xdp_progs;
> +	struct xsk_xdp_progs *skel_tx = test->ifobj_tx->xdp_progs;
> +	struct bpf_map *data_map;
> +	int count = 0;
> +	int key = 0;
> +
> +	test_spec_set_name(test, "XDP_METADATA_COUNT");
> +	test_spec_set_xdp_prog(test, skel_rx->progs.xsk_xdp_populate_metadata,
> +			       skel_tx->progs.xsk_xdp_populate_metadata,
> +			       skel_rx->maps.xsk, skel_tx->maps.xsk);
> +	test->ifobj_rx->use_metadata = true;
> +
> +	data_map = bpf_object__find_map_by_name(skel_rx->obj, "xsk_xdp_.bss");
> +	if (!data_map || !bpf_map__is_internal(data_map))
> +		exit_with_error(ENOMEM);
> +
> +	if (bpf_map_update_elem(bpf_map__fd(data_map), &key, &count, BPF_ANY))
> +		exit_with_error(errno);
> +
> +	testapp_validate_traffic(test);
> +}
> +
>  static void testapp_poll_txq_tmout(struct test_spec *test)
>  {
>  	test_spec_set_name(test, "POLL_TXQ_FULL");
> @@ -1835,6 +1876,9 @@ static void run_pkt_test(struct test_spec *test, enum test_mode mode, enum test_
>  	case TEST_TYPE_XDP_DROP_HALF:
>  		testapp_xdp_drop(test);
>  		break;
> +	case TEST_TYPE_XDP_METADATA_COUNT:
> +		testapp_xdp_metadata_count(test);
> +		break;
>  	default:
>  		break;
>  	}
> diff --git a/tools/testing/selftests/bpf/xskxceiver.h b/tools/testing/selftests/bpf/xskxceiver.h
> index 3e8ec7d8ec32..bdb4efedf3a9 100644
> --- a/tools/testing/selftests/bpf/xskxceiver.h
> +++ b/tools/testing/selftests/bpf/xskxceiver.h
> @@ -88,6 +88,7 @@ enum test_type {
>  	TEST_TYPE_STATS_FILL_EMPTY,
>  	TEST_TYPE_BPF_RES,
>  	TEST_TYPE_XDP_DROP_HALF,
> +	TEST_TYPE_XDP_METADATA_COUNT,
>  	TEST_TYPE_MAX
>  };
>  
> @@ -158,6 +159,7 @@ struct ifobject {
>  	bool use_fill_ring;
>  	bool release_rx;
>  	bool shared_umem;
> +	bool use_metadata;
>  	u8 dst_mac[ETH_ALEN];
>  	u8 src_mac[ETH_ALEN];
>  };
> -- 
> 2.25.1
>