netdev - Re: [PATCH bpf-next v3 4/6] selftests/bpf: refactor xdp_context

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Message-ID: <Z7yof3pafRsMwBrf@mini-arch>
Date: Mon, 24 Feb 2025 09:12:31 -0800
From: Stanislav Fomichev <stfomichev@...il.com>
To: Marcus Wichelmann <marcus.wichelmann@...zner-cloud.de>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	bpf@...r.kernel.org, linux-kselftest@...r.kernel.org,
	willemdebruijn.kernel@...il.com, jasowang@...hat.com,
	andrew+netdev@...n.ch, davem@...emloft.net, edumazet@...gle.com,
	kuba@...nel.org, pabeni@...hat.com, andrii@...nel.org,
	eddyz87@...il.com, mykolal@...com, ast@...nel.org,
	daniel@...earbox.net, martin.lau@...ux.dev, song@...nel.org,
	yonghong.song@...ux.dev, john.fastabend@...il.com,
	kpsingh@...nel.org, sdf@...ichev.me, haoluo@...gle.com,
	jolsa@...nel.org, shuah@...nel.org, hawk@...nel.org
Subject: Re: [PATCH bpf-next v3 4/6] selftests/bpf: refactor
 xdp_context_functional test and bpf program

On 02/24, Marcus Wichelmann wrote:
> The existing XDP metadata test works by creating a veth pair and
> attaching XDP & TC programs that drop the packet when the condition of
> the test isn't fulfilled. The test then pings through the veth pair and
> succeeds when the ping comes through.
> 
> While this test works great for a veth pair, it is hard to replicate for
> tap devices to test the XDP metadata support of them. A similar test for
> the tun driver would either involve logic to reply to the ping request,
> or would have to capture the packet to check if it was dropped or not.
> 
> To make the testing of other drivers easier while still maximizing code
> reuse, this commit refactors the existing xdp_context_functional test to
> use a test_result map. Instead of conditionally passing or dropping the
> packet, the TC program is changed to copy the received metadata into the
> value of that single-entry array map. Tests can then verify that the map
> value matches the expectation.
> 
> This testing logic is easy to adapt to other network drivers as the only
> remaining requirement is that there is some way to send a custom
> Ethernet packet through it that triggers the XDP & TC programs.
> 
> The payload of the Ethernet packet is used as the test data that is
> expected to be passed as metadata from the XDP to the TC program and
> written to the map. It has a fixed size of 32 bytes which is a
> reasonalbe size that should be supported by both drivers. Additional
> packet headers are not necessary for the test and were therefore skipped
> to keep the testing code short.
> 
> Signed-off-by: Marcus Wichelmann <marcus.wichelmann@...zner-cloud.de>
> ---
>  .../bpf/prog_tests/xdp_context_test_run.c     | 99 +++++++++++++++----
>  .../selftests/bpf/progs/test_xdp_meta.c       | 56 ++++++-----
>  2 files changed, 112 insertions(+), 43 deletions(-)
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c b/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c
> index 937da9b7532a..4043f220d7c0 100644
> --- a/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c
> +++ b/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c
> @@ -4,13 +4,19 @@
>  #include "test_xdp_context_test_run.skel.h"
>  #include "test_xdp_meta.skel.h"
>  
> -#define TX_ADDR "10.0.0.1"
> -#define RX_ADDR "10.0.0.2"
>  #define RX_NAME "veth0"
>  #define TX_NAME "veth1"
>  #define TX_NETNS "xdp_context_tx"
>  #define RX_NETNS "xdp_context_rx"
>  
> +#define TEST_PAYLOAD_LEN 32
> +static const __u8 test_payload[TEST_PAYLOAD_LEN] = {
> +	0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
> +	0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18,
> +	0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28,
> +	0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38,
> +};
> +
>  void test_xdp_context_error(int prog_fd, struct bpf_test_run_opts opts,
>  			    __u32 data_meta, __u32 data, __u32 data_end,
>  			    __u32 ingress_ifindex, __u32 rx_queue_index,
> @@ -112,15 +118,66 @@ void test_xdp_context_test_run(void)
>  	test_xdp_context_test_run__destroy(skel);
>  }
>  
> -void test_xdp_context_functional(void)

[..]

> +int send_test_packet(int ifindex)

nit: static? same for assert_test_result below