Subject: Re: [PATCH net v2 2/2] bpf: selftests: send packet to devmap redirect XDP

From: Stanislav Fomichev <[email-masked]>
Date: Fri, 6 Sep 2024 13:24:30 -0700

On 09/06, Florian Kauer wrote:
> The current xdp_devmap_attach test attaches a program
> that redirects to another program via devmap.
> 
> It is, however, never executed, so do that to catch
> any bugs that might occur during execution.
> 
> Also, execute the same for a veth pair so that we
> also cover the non-generic path.
> 
> Warning: Running this without the bugfix in this series
> will likely crash your system.
> 
> Signed-off-by: Florian Kauer <[email-masked]>
> ---
>  .../selftests/bpf/prog_tests/xdp_devmap_attach.c   | 114 +++++++++++++++++++--
>  1 file changed, 108 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_devmap_attach.c b/tools/testing/selftests/bpf/prog_tests/xdp_devmap_attach.c
> index ce6812558287..c9034f8ae63b 100644
> --- a/tools/testing/selftests/bpf/prog_tests/xdp_devmap_attach.c
> +++ b/tools/testing/selftests/bpf/prog_tests/xdp_devmap_attach.c
> @@ -1,6 +1,9 @@
>  // SPDX-License-Identifier: GPL-2.0
> +#include <arpa/inet.h>
>  #include <uapi/linux/bpf.h>
>  #include <linux/if_link.h>
> +#include <network_helpers.h>
> +#include <net/if.h>
>  #include <test_progs.h>
>  
>  #include "test_xdp_devmap_helpers.skel.h"
> @@ -17,7 +20,7 @@ static void test_xdp_with_devmap_helpers(void)
>  		.ifindex = IFINDEX_LO,
>  	};
>  	__u32 len = sizeof(info);
> -	int err, dm_fd, map_fd;
> +	int err, dm_fd, dm_fd_redir, map_fd;
>  	__u32 idx = 0;
>  
>  
> @@ -25,14 +28,11 @@ static void test_xdp_with_devmap_helpers(void)
>  	if (!ASSERT_OK_PTR(skel, "test_xdp_with_devmap_helpers__open_and_load"))
>  		return;
>  
> -	dm_fd = bpf_program__fd(skel->progs.xdp_redir_prog);
> -	err = bpf_xdp_attach(IFINDEX_LO, dm_fd, XDP_FLAGS_SKB_MODE, NULL);
> +	dm_fd_redir = bpf_program__fd(skel->progs.xdp_redir_prog);
> +	err = bpf_xdp_attach(IFINDEX_LO, dm_fd_redir, XDP_FLAGS_SKB_MODE, NULL);
>  	if (!ASSERT_OK(err, "Generic attach of program with 8-byte devmap"))
>  		goto out_close;
>  
> -	err = bpf_xdp_detach(IFINDEX_LO, XDP_FLAGS_SKB_MODE, NULL);
> -	ASSERT_OK(err, "XDP program detach");
> -
>  	dm_fd = bpf_program__fd(skel->progs.xdp_dummy_dm);
>  	map_fd = bpf_map__fd(skel->maps.dm_ports);
>  	err = bpf_prog_get_info_by_fd(dm_fd, &info, &len);
> @@ -47,6 +47,23 @@ static void test_xdp_with_devmap_helpers(void)
>  	ASSERT_OK(err, "Read devmap entry");
>  	ASSERT_EQ(info.id, val.bpf_prog.id, "Match program id to devmap entry prog_id");
>  
> +	/* send a packet to trigger any potential bugs in there */
> +	char data[10] = {};
> +	DECLARE_LIBBPF_OPTS(bpf_test_run_opts, opts,
> +			    .data_in = &data,
> +			    .data_size_in = 10,
> +			    .flags = BPF_F_TEST_XDP_LIVE_FRAMES,
> +			    .repeat = 1,
> +		);
> +	err = bpf_prog_test_run_opts(dm_fd_redir, &opts);
> +	ASSERT_OK(err, "XDP test run");
> +
> +	/* wait for the packets to be flushed */
> +	kern_sync_rcu();
> +
> +	err = bpf_xdp_detach(IFINDEX_LO, XDP_FLAGS_SKB_MODE, NULL);
> +	ASSERT_OK(err, "XDP program detach");
> +
>  	/* can not attach BPF_XDP_DEVMAP program to a device */
>  	err = bpf_xdp_attach(IFINDEX_LO, dm_fd, XDP_FLAGS_SKB_MODE, NULL);
>  	if (!ASSERT_NEQ(err, 0, "Attach of BPF_XDP_DEVMAP program"))
> @@ -124,6 +141,88 @@ static void test_xdp_with_devmap_frags_helpers(void)
>  	test_xdp_with_devmap_frags_helpers__destroy(skel);
>  }
>  
> +static void test_xdp_with_devmap_helpers_veth(void)
> +{
> +	struct test_xdp_with_devmap_helpers *skel;

skel needs to be initialized to NULL ....

> +	struct bpf_prog_info info = {};
> +	struct bpf_devmap_val val = {};
> +	struct nstoken *nstoken = NULL;
> +	__u32 len = sizeof(info);
> +	int err, dm_fd, dm_fd_redir, map_fd, ifindex_dst;
> +	__u32 idx = 0;
> +
> +	SYS(out_close, "ip netns add testns");
> +	nstoken = open_netns("testns");
> +	if (!ASSERT_OK_PTR(nstoken, "setns"))
> +		goto out_close;

... for this goto to not do test_xdp_with_devmap_helpers__destroy(garbage)

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