Re: [RFC bpf-next v3 5/5] selftests/bpf: Add test cases for sleepable BPF programs of the CGROUP_SOCKOPT type

Kui-Feng Lee
2023-08-15T23:37:51Z

On 8/15/23 13:57, Stanislav Fomichev wrote:
> On 08/15, thinker.li@gmail.com wrote:
>> From: Kui-Feng Lee <thinker.li@gmail.com>
>>
>> Do the same test as non-sleepable ones.
>>
>> Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
>> ---
>> .../testing/selftests/bpf/bpf_experimental.h | 36 +++
>> tools/testing/selftests/bpf/bpf_kfuncs.h | 41 +++
>> .../selftests/bpf/prog_tests/sockopt_sk.c | 112 +++++++-
>> .../testing/selftests/bpf/progs/sockopt_sk.c | 257 ++++++++++++++++++
>> .../selftests/bpf/verifier/sleepable.c | 2 +-
>> 5 files changed, 445 insertions(+), 3 deletions(-)
>>
>> diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
>> index 209811b1993a..9b5dfefe65dc 100644
>> --- a/tools/testing/selftests/bpf/bpf_experimental.h
>> +++ b/tools/testing/selftests/bpf/bpf_experimental.h
>> @@ -131,4 +131,40 @@ extern int bpf_rbtree_add_impl(struct bpf_rb_root *root, struct bpf_rb_node *nod
>> */
>> extern struct bpf_rb_node *bpf_rbtree_first(struct bpf_rb_root *root) __ksym;
>>
>> +/*
>> + * Description
>> + * Copy data from *ptr* to *sopt->optval*.
>> + * Return
>> + * >= 0 on success, or a negative error in case of failure.
>> + */
>> +extern int bpf_sockopt_dynptr_copy_to(struct bpf_sockopt *sopt,
>> + struct bpf_dynptr *ptr) __ksym;
>> +
>> +/* Description
>> + * Allocate a buffer of 'size' bytes for being installed as optval.
>> + * Returns
>> + * > 0 on success, the size of the allocated buffer
>> + * -ENOMEM or -EINVAL on failure
>> + */
>> +extern int bpf_sockopt_dynptr_alloc(struct bpf_sockopt *sopt, int size,
>> + struct bpf_dynptr *ptr__uninit) __ksym;
>> +
>> +/* Description
>> + * Install the buffer pointed to by 'ptr' as optval.
>> + * Returns
>> + * 0 on success
>> + * -EINVAL if the buffer is too small
>> + */
>> +extern int bpf_sockopt_dynptr_install(struct bpf_sockopt *sopt,
>> + struct bpf_dynptr *ptr) __ksym;
>> +
>> +/* Description
>> + * Release the buffer allocated by bpf_sockopt_dynptr_alloc.
>> + * Returns
>> + * 0 on success
>> + * -EINVAL if the buffer was not allocated by bpf_sockopt_dynptr_alloc
>> + */
>> +extern int bpf_sockopt_dynptr_release(struct bpf_sockopt *sopt,
>> + struct bpf_dynptr *ptr) __ksym;
>> +
>> #endif
>> diff --git a/tools/testing/selftests/bpf/bpf_kfuncs.h b/tools/testing/selftests/bpf/bpf_kfuncs.h
>> index 642dda0e758a..772040225257 100644
>> --- a/tools/testing/selftests/bpf/bpf_kfuncs.h
>> +++ b/tools/testing/selftests/bpf/bpf_kfuncs.h
>> @@ -41,4 +41,45 @@ extern bool bpf_dynptr_is_rdonly(const struct bpf_dynptr *ptr) __ksym;
>> extern __u32 bpf_dynptr_size(const struct bpf_dynptr *ptr) __ksym;
>> extern int bpf_dynptr_clone(const struct bpf_dynptr *ptr, struct bpf_dynptr *clone__init) __ksym;
>>
>> +extern int bpf_sockopt_dynptr_copy_to(struct bpf_sockopt *sopt,
>> + struct bpf_dynptr *ptr) __ksym;
>> +
>> +/* Description
>> + * Allocate a buffer of 'size' bytes for being installed as optval.
>> + * Returns
>> + * > 0 on success, the size of the allocated buffer
>> + * -ENOMEM or -EINVAL on failure
>> + */
>> +extern int bpf_sockopt_dynptr_alloc(struct bpf_sockopt *sopt, int size,
>> + struct bpf_dynptr *ptr__uninit) __ksym;
>> +
>> +/* Description
>> + * Install the buffer pointed to by 'ptr' as optval.
>> + * Returns
>> + * 0 on success
>> + * -EINVAL if the buffer is too small
>> + */
>> +extern int bpf_sockopt_dynptr_install(struct bpf_sockopt *sopt,
>> + struct bpf_dynptr *ptr) __ksym;
>> +
>> +/* Description
>> + * Release the buffer allocated by bpf_sockopt_dynptr_alloc.
>> + * Returns
>> + * 0 on success
>> + * -EINVAL if the buffer was not allocated by bpf_sockopt_dynptr_alloc
>> + */
>> +extern int bpf_sockopt_dynptr_release(struct bpf_sockopt *sopt,
>> + struct bpf_dynptr *ptr) __ksym;
>> +
>> +/* Description
>> + * Initialize a dynptr to access the content of optval passing
>> + * to {get,set}sockopt()s.
>> + * Returns
>> + * > 0 on success, the size of the allocated buffer
>> + * -ENOMEM or -EINVAL on failure
>> + */
>> +extern int bpf_sockopt_dynptr_from(struct bpf_sockopt *sopt,
>> + struct bpf_dynptr *ptr__uninit,
>> + unsigned int size) __ksym;
>> +
>> #endif
>> diff --git a/tools/testing/selftests/bpf/prog_tests/sockopt_sk.c b/tools/testing/selftests/bpf/prog_tests/sockopt_sk.c
>> index 05d0e07da394..85255648747f 100644
>> --- a/tools/testing/selftests/bpf/prog_tests/sockopt_sk.c
>> +++ b/tools/testing/selftests/bpf/prog_tests/sockopt_sk.c
>> @@ -92,6 +92,7 @@ static int getsetsockopt(void)
>> }
>> if (buf.u8[0] != 0x01) {
>> log_err("Unexpected buf[0] 0x%02x != 0x01", buf.u8[0]);
>> + log_err("optlen %d", optlen);
>> goto err;
>> }
>>
>> @@ -220,7 +221,7 @@ static int getsetsockopt(void)
>> return -1;
>> }
>>
>> -static void run_test(int cgroup_fd)
>> +static void run_test_nonsleepable(int cgroup_fd)
>> {
>> struct sockopt_sk *skel;
>>
>> @@ -246,6 +247,106 @@ static void run_test(int cgroup_fd)
>> sockopt_sk__destroy(skel);
>> }
>>
>> +static void run_test_nonsleepable_mixed(int cgroup_fd)
>> +{
>> + struct sockopt_sk *skel;
>> +
>> + skel = sockopt_sk__open_and_load();
>> + if (!ASSERT_OK_PTR(skel, "skel_load"))
>> + goto cleanup;
>> +
>> + skel->bss->page_size = getpagesize();
>> + skel->bss->skip_sleepable = 1;
>> +
>> + skel->links._setsockopt_s =
>> + bpf_program__attach_cgroup(skel->progs._setsockopt_s, cgroup_fd);
>> + if (!ASSERT_OK_PTR(skel->links._setsockopt_s, "setsockopt_link (sleepable)"))
>> + goto cleanup;
>> +
>> + skel->links._getsockopt_s =
>> + bpf_program__attach_cgroup(skel->progs._getsockopt_s, cgroup_fd);
>> + if (!ASSERT_OK_PTR(skel->links._getsockopt_s, "getsockopt_link (sleepable)"))
>> + goto cleanup;
>> +
>> + skel->links._setsockopt =
>> + bpf_program__attach_cgroup(skel->progs._setsockopt, cgroup_fd);
>> + if (!ASSERT_OK_PTR(skel->links._setsockopt, "setsockopt_link"))
>> + goto cleanup;
>> +
>> + skel->links._getsockopt =
>> + bpf_program__attach_cgroup(skel->progs._getsockopt, cgroup_fd);
>> + if (!ASSERT_OK_PTR(skel->links._getsockopt, "getsockopt_link"))
>> + goto cleanup;
>> +
>> + ASSERT_OK(getsetsockopt(), "getsetsockopt");
>> +
>> +cleanup:
>> + sockopt_sk__destroy(skel);
>> +}
>> +
>> +static void run_test_sleepable(int cgroup_fd)
>> +{
>> + struct sockopt_sk *skel;
>> +
>> + skel = sockopt_sk__open_and_load();
>> + if (!ASSERT_OK_PTR(skel, "skel_load"))
>> + goto cleanup;
>> +
>> + skel->bss->page_size = getpagesize();
>> +
>> + skel->links._setsockopt_s =
>> + bpf_program__attach_cgroup(skel->progs._setsockopt_s, cgroup_fd);
>> + if (!ASSERT_OK_PTR(skel->links._setsockopt_s, "setsockopt_link"))
>> + goto cleanup;
>> +
>> + skel->links._getsockopt_s =
>> + bpf_program__attach_cgroup(skel->progs._getsockopt_s, cgroup_fd);
>> + if (!ASSERT_OK_PTR(skel->links._getsockopt_s, "getsockopt_link"))
>> + goto cleanup;
>> +
>> + ASSERT_OK(getsetsockopt(), "getsetsockopt");
>> +
>> +cleanup:
>> + sockopt_sk__destroy(skel);
>> +}
>> +
>> +static void run_test_sleepable_mixed(int cgroup_fd)
>> +{
>> + struct sockopt_sk *skel;
>> +
>> + skel = sockopt_sk__open_and_load();
>> + if (!ASSERT_OK_PTR(skel, "skel_load"))
>> + goto cleanup;
>> +
>> + skel->bss->page_size = getpagesize();
>> + skel->bss->skip_nonsleepable = 1;
>> +
>> + skel->links._setsockopt =
>> + bpf_program__attach_cgroup(skel->progs._setsockopt, cgroup_fd);
>> + if (!ASSERT_OK_PTR(skel->links._setsockopt, "setsockopt_link (nonsleepable)"))
>> + goto cleanup;
>> +
>> + skel->links._getsockopt =
>> + bpf_program__attach_cgroup(skel->progs._getsockopt, cgroup_fd);
>> + if (!ASSERT_OK_PTR(skel->links._getsockopt, "getsockopt_link (nonsleepable)"))
>> + goto cleanup;
>> +
>> + skel->links._setsockopt_s =
>> + bpf_program__attach_cgroup(skel->progs._setsockopt_s, cgroup_fd);
>> + if (!ASSERT_OK_PTR(skel->links._setsockopt_s, "setsockopt_link"))
>> + goto cleanup;
>> +
>> + skel->links._getsockopt_s =
>> + bpf_program__attach_cgroup(skel->progs._getsockopt_s, cgroup_fd);
>> + if (!ASSERT_OK_PTR(skel->links._getsockopt_s, "getsockopt_link"))
>> + goto cleanup;
>> +
>> + ASSERT_OK(getsetsockopt(), "getsetsockopt");
>> +
>> +cleanup:
>> + sockopt_sk__destroy(skel);
>> +}
>> +
>> void test_sockopt_sk(void)
>> {
>> int cgroup_fd;
>> @@ -254,6 +355,13 @@ void test_sockopt_sk(void)
>> if (!ASSERT_GE(cgroup_fd, 0, "join_cgroup /sockopt_sk"))
>> return;
>>
>> - run_test(cgroup_fd);
>> + if (test__start_subtest("nonsleepable"))
>> + run_test_nonsleepable(cgroup_fd);
>> + if (test__start_subtest("sleepable"))
>> + run_test_sleepable(cgroup_fd);
>> + if (test__start_subtest("nonsleepable_mixed"))
>> + run_test_nonsleepable_mixed(cgroup_fd);
>> + if (test__start_subtest("sleepable_mixed"))
>> + run_test_sleepable_mixed(cgroup_fd);
>> close(cgroup_fd);
>> }
>> diff --git a/tools/testing/selftests/bpf/progs/sockopt_sk.c b/tools/testing/selftests/bpf/progs/sockopt_sk.c
>> index cb990a7d3d45..efacd3b88c40 100644
>> --- a/tools/testing/selftests/bpf/progs/sockopt_sk.c
>> +++ b/tools/testing/selftests/bpf/progs/sockopt_sk.c
>> @@ -5,10 +5,16 @@
>> #include <netinet/in.h>
>> #include <bpf/bpf_helpers.h>
>>
>> +typedef int bool;
>> +#include "bpf_kfuncs.h"
>> +
>> char _license[] SEC("license") = "GPL";
>>
>> int page_size = 0; /* userspace should set it */
>>
>> +int skip_sleepable = 0;
>> +int skip_nonsleepable = 0;
>> +
>> #ifndef SOL_TCP
>> #define SOL_TCP IPPROTO_TCP
>> #endif
>> @@ -34,6 +40,9 @@ int _getsockopt(struct bpf_sockopt *ctx)
>> struct sockopt_sk *storage;
>> struct bpf_sock *sk;
>>
>> + if (skip_nonsleepable)
>> + return 1;
>> +
>> /* Bypass AF_NETLINK. */
>> sk = ctx->sk;
>> if (sk && sk->family == AF_NETLINK)
>> @@ -136,6 +145,134 @@ int _getsockopt(struct bpf_sockopt *ctx)
>> return 1;
>> }
>>
>> +SEC("cgroup/getsockopt.s")
>> +int _getsockopt_s(struct bpf_sockopt *ctx)
>> +{
>> + struct tcp_zerocopy_receive *zcvr;
>> + struct bpf_dynptr optval_dynptr;
>> + struct sockopt_sk *storage;
>> + __u8 *optval, *optval_end;
>> + struct bpf_sock *sk;
>> + char buf[1];
>> + __u64 addr;
>> + int ret;
>> +
>> + if (skip_sleepable)
>> + return 1;
>> +
>> + /* Bypass AF_NETLINK. */
>> + sk = ctx->sk;
>> + if (sk && sk->family == AF_NETLINK)
>> + return 1;
>> +
>> + optval = ctx->optval;
>> + optval_end = ctx->optval_end;
>> +
>> + /* Make sure bpf_get_netns_cookie is callable.
>> + */
>> + if (bpf_get_netns_cookie(NULL) == 0)
>> + return 0;
>> +
>> + if (bpf_get_netns_cookie(ctx) == 0)
>> + return 0;
>> +
>> + if (ctx->level == SOL_IP && ctx->optname == IP_TOS) {
>> + /* Not interested in SOL_IP:IP_TOS;
>> + * let next BPF program in the cgroup chain or kernel
>> + * handle it.
>> + */
>> + return 1;
>> + }
>> +
>> + if (ctx->level == SOL_SOCKET && ctx->optname == SO_SNDBUF) {
>> + /* Not interested in SOL_SOCKET:SO_SNDBUF;
>> + * let next BPF program in the cgroup chain or kernel
>> + * handle it.
>> + */
>> + return 1;
>> + }
>> +
>> + if (ctx->level == SOL_TCP && ctx->optname == TCP_CONGESTION) {
>> + /* Not interested in SOL_TCP:TCP_CONGESTION;
>> + * let next BPF program in the cgroup chain or kernel
>> + * handle it.
>> + */
>> + return 1;
>> + }
>> +
>> + if (ctx->level == SOL_TCP && ctx->optname == TCP_ZEROCOPY_RECEIVE) {
>> + /* Verify that TCP_ZEROCOPY_RECEIVE triggers.
>> + * It has a custom implementation for performance
>> + * reasons.
>> + */
>> +
>> + bpf_sockopt_dynptr_from(ctx, &optval_dynptr, sizeof(*zcvr));
>> + zcvr = bpf_dynptr_data(&optval_dynptr, 0, sizeof(*zcvr));
>> + addr = zcvr ? zcvr->address : 0;
>> + bpf_sockopt_dynptr_release(ctx, &optval_dynptr);
>
> This starts to look more usable, thank you for the changes!
> Let me poke the api a bit more, I'm not super familiar with the dynptrs.
>
> here: bpf_sockopt_dynptr_from should probably be called
> bpf_dynptr_from_sockopt to match bpf_dynptr_from_mem?

agree!

>
>> +
>> + return addr != 0 ? 0 : 1;
>> + }
>> +
>> + if (ctx->level == SOL_IP && ctx->optname == IP_FREEBIND) {
>> + if (optval + 1 > optval_end)
>> + return 0; /* bounds check */
>> +
>> + ctx->retval = 0; /* Reset system call return value to zero */
>> +
>> + /* Always export 0x55 */
>> + buf[0] = 0x55;
>> + ret = bpf_sockopt_dynptr_alloc(ctx, 1, &optval_dynptr);
>> + if (ret >= 0) {
>> + bpf_dynptr_write(&optval_dynptr, 0, buf, 1, 0);
>> + ret = bpf_sockopt_dynptr_copy_to(ctx, &optval_dynptr);
>> + }
>> + bpf_sockopt_dynptr_release(ctx, &optval_dynptr);
>
> Does bpf_sockopt_dynptr_alloc and bpf_sockopt_dynptr_release need to be
> sockopt specific? Seems like we should provide, instead, some generic
> bpf_dynptr_alloc/bpf_dynptr_release and make
> bpf_sockopt_dynptr_copy_to/install work with them? WDYT?

I found that kmalloc can not be called in the context of nmi, slab or
page alloc path. It is why we don't have functions like
bpf_dynptr_alloc/bpf_dynptr_release yet. That means we need someone
to implement an allocator for BPF programs. And, then, we can have
bpf_dynptr_alloc unpon it. (There is an implementation of
bpf_dynptr_alloc() in the early versions of the patchset of dynptr.
But, be removed before landing.)

>
>> + if (ret < 0)
>> + return 0;
>> + ctx->optlen = 1;
>> +
>> + /* Userspace buffer is PAGE_SIZE * 2, but BPF
>> + * program can only see the first PAGE_SIZE
>> + * bytes of data.
>> + */
>> + if (optval_end - optval != page_size && 0)
>> + return 0; /* unexpected data size */
>> +
>> + return 1;
>> + }
>> +
>> + if (ctx->level != SOL_CUSTOM)
>> + return 0; /* deny everything except custom level */
>> +
>> + if (optval + 1 > optval_end)
>> + return 0; /* bounds check */
>> +
>> + storage = bpf_sk_storage_get(&socket_storage_map, ctx->sk, 0,
>> + BPF_SK_STORAGE_GET_F_CREATE);
>> + if (!storage)
>> + return 0; /* couldn't get sk storage */
>> +
>> + if (!ctx->retval)
>> + return 0; /* kernel should not have handled
>> + * SOL_CUSTOM, something is wrong!
>> + */
>> + ctx->retval = 0; /* Reset system call return value to zero */
>> +
>> + buf[0] = storage->val;
>> + ret = bpf_sockopt_dynptr_alloc(ctx, 1, &optval_dynptr);
>> + if (ret >= 0) {
>> + bpf_dynptr_write(&optval_dynptr, 0, buf, 1, 0);
>> + ret = bpf_sockopt_dynptr_copy_to(ctx, &optval_dynptr);
>> + }
>> + bpf_sockopt_dynptr_release(ctx, &optval_dynptr);
>> + if (ret < 0)
>> + return 0;
>> + ctx->optlen = 1;
>> +
>> + return 1;
>> +}
>> +
>> SEC("cgroup/setsockopt")
>> int _setsockopt(struct bpf_sockopt *ctx)
>> {
>> @@ -144,6 +281,9 @@ int _setsockopt(struct bpf_sockopt *ctx)
>> struct sockopt_sk *storage;
>> struct bpf_sock *sk;
>>
>> + if (skip_nonsleepable)
>> + return 1;
>> +
>> /* Bypass AF_NETLINK. */
>> sk = ctx->sk;
>> if (sk && sk->family == AF_NETLINK)
>> @@ -236,3 +376,120 @@ int _setsockopt(struct bpf_sockopt *ctx)
>> ctx->optlen = 0;
>> return 1;
>> }
>> +
>> +SEC("cgroup/setsockopt.s")
>> +int _setsockopt_s(struct bpf_sockopt *ctx)
>> +{
>> + struct bpf_dynptr optval_buf;
>> + struct sockopt_sk *storage;
>> + __u8 *optval, *optval_end;
>> + struct bpf_sock *sk;
>> + __u8 tmp_u8;
>> + __u32 tmp;
>> + int ret;
>> +
>> + if (skip_sleepable)
>> + return 1;
>> +
>> + optval = ctx->optval;
>> + optval_end = ctx->optval_end;
>> +
>> + /* Bypass AF_NETLINK. */
>> + sk = ctx->sk;
>> + if (sk && sk->family == AF_NETLINK)
>> + return -1;
>> +
>> + /* Make sure bpf_get_netns_cookie is callable.
>> + */
>> + if (bpf_get_netns_cookie(NULL) == 0)
>> + return 0;
>> +
>> + if (bpf_get_netns_cookie(ctx) == 0)
>> + return 0;
>> +
>> + if (ctx->level == SOL_IP && ctx->optname == IP_TOS) {
>> + /* Not interested in SOL_IP:IP_TOS;
>> + * let next BPF program in the cgroup chain or kernel
>> + * handle it.
>> + */
>> + ctx->optlen = 0; /* bypass optval>PAGE_SIZE */
>> + return 1;
>> + }
>> +
>> + if (ctx->level == SOL_SOCKET && ctx->optname == SO_SNDBUF) {
>> + /* Overwrite SO_SNDBUF value */
>> +
>> + ret = bpf_sockopt_dynptr_alloc(ctx, sizeof(__u32),
>> + &optval_buf);
>> + if (ret < 0)
>> + bpf_sockopt_dynptr_release(ctx, &optval_buf);
>> + else {
>> + tmp = 0x55AA;
>> + bpf_dynptr_write(&optval_buf, 0, &tmp, sizeof(tmp), 0);
>> + ret = bpf_sockopt_dynptr_install(ctx, &optval_buf);
>
> One thing I'm still slightly confused about is
> bpf_sockopt_dynptr_install vs bpf_sockopt_dynptr_copy_to. I do
> understand that it comes from getsockopt vs setsockopt (and the ability,
> in setsockopt, to allocate larger buffers), but I wonder whether
> we can hide everything under single bpf_sockopt_dynptr_copy_to call?
>
> For getsockopt, it stays as is. For setsockopt, it would work like
> _install currently does. Would that work? From user perspective,
> if we provide a simple call that does the right thing, seems a bit
> more usable? The only problem is probably the fact that _install
> explicitly moves the ownership, but I don't see why copy_to can't
> have the same "consume" semantics?