Add BPF_F_TEST_SKB_CHECKSUM_COMPLETE tests for tc programs that move the skb out of CHECKSUM_COMPLETE with bpf_skb_change_tail():
- change_tail_trim trims the last 4 bytes of pkt_v4. They hold the non-zero tcp.urg_ptr, so the stale skb->csum no longer matches the packet. - change_tail_grow_write appends 4 zero bytes, which on their own do not change the sum, and then writes a byte with BPF_F_RECOMPUTE_CSUM. That write can no longer update skb->csum. Both return -EBADMSG without the preceding test_run fix and pass with it. Also add store_no_recompute as a negative test. It writes a byte without BPF_F_RECOMPUTE_CSUM, so the skb stays CHECKSUM_COMPLETE with a stale skb->csum, and test_run must keep returning -EBADMSG. This checks that the validation still runs for CHECKSUM_COMPLETE skbs. The passing case, a CHECKSUM_COMPLETE skb whose checksum is updated correctly, is already covered by test_skb_pkt_end. Assisted-by: LLM Signed-off-by: Maxim Skokov <[email protected]> --- .../bpf/prog_tests/skb_csum_complete.c | 39 ++++++++++++++++ .../selftests/bpf/progs/skb_csum_complete.c | 46 +++++++++++++++++++ 2 files changed, 85 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/skb_csum_complete.c create mode 100644 tools/testing/selftests/bpf/progs/skb_csum_complete.c diff --git a/tools/testing/selftests/bpf/prog_tests/skb_csum_complete.c b/tools/testing/selftests/bpf/prog_tests/skb_csum_complete.c new file mode 100644 index 0000000000000..919f24dbacd3d --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/skb_csum_complete.c @@ -0,0 +1,39 @@ +// SPDX-License-Identifier: GPL-2.0 +#include <test_progs.h> +#include <network_helpers.h> +#include "skb_csum_complete.skel.h" + +static void run(struct bpf_program *prog, int expected_err) +{ + LIBBPF_OPTS(bpf_test_run_opts, topts, + .data_in = &pkt_v4, + .data_size_in = sizeof(pkt_v4), + .repeat = 1, + .flags = BPF_F_TEST_SKB_CHECKSUM_COMPLETE, + ); + int err; + + err = bpf_prog_test_run_opts(bpf_program__fd(prog), &topts); + if (!ASSERT_EQ(err, expected_err, "test_run")) + return; + if (!expected_err) + ASSERT_EQ(topts.retval, 0, "retval"); +} + +void test_skb_csum_complete(void) +{ + struct skb_csum_complete *skel; + + skel = skb_csum_complete__open_and_load(); + if (!ASSERT_OK_PTR(skel, "skel_open_and_load")) + return; + + if (test__start_subtest("change_tail_trim")) + run(skel->progs.change_tail_trim, 0); + if (test__start_subtest("change_tail_grow_write")) + run(skel->progs.change_tail_grow_write, 0); + if (test__start_subtest("store_no_recompute")) + run(skel->progs.store_no_recompute, -EBADMSG); + + skb_csum_complete__destroy(skel); +} diff --git a/tools/testing/selftests/bpf/progs/skb_csum_complete.c b/tools/testing/selftests/bpf/progs/skb_csum_complete.c new file mode 100644 index 0000000000000..644731a12dc87 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/skb_csum_complete.c @@ -0,0 +1,46 @@ +// SPDX-License-Identifier: GPL-2.0 +#include <vmlinux.h> +#include <bpf/bpf_helpers.h> + +SEC("tc") +int change_tail_trim(struct __sk_buff *skb) +{ + /* + * Drops CHECKSUM_COMPLETE. skb->csum still covers the trimmed bytes, + * which hold the non-zero tcp.urg_ptr of pkt_v4, so it no longer + * matches the packet. + */ + if (bpf_skb_change_tail(skb, skb->len - 4, 0)) + return 1; + return 0; +} + +SEC("tc") +int change_tail_grow_write(struct __sk_buff *skb) +{ + __u8 val = 0xab; + + /* + * Drops CHECKSUM_COMPLETE. The new bytes are zero and do not change + * the sum, but the write below can no longer update skb->csum. + */ + if (bpf_skb_change_tail(skb, skb->len + 4, 0)) + return 1; + if (bpf_skb_store_bytes(skb, skb->len - 1, &val, sizeof(val), + BPF_F_RECOMPUTE_CSUM)) + return 2; + return 0; +} + +SEC("tc") +int store_no_recompute(struct __sk_buff *skb) +{ + __u8 val = 0xab; + + /* skb stays CHECKSUM_COMPLETE, but skb->csum is not updated. */ + if (bpf_skb_store_bytes(skb, skb->len - 1, &val, sizeof(val), 0)) + return 1; + return 0; +} + +char _license[] SEC("license") = "GPL"; -- 2.47.3
