Subject: Re: [PATCH v3 bpf-next 5/5] selftests/bpf: add selftest for bpf_xdp_ct_add and bpf_ct_refresh_timeout kfunc

From: Lorenzo Bianconi <[email-masked]>
Date: Wed, 18 May 2022 22:38:50 +0200

> 
> 
> On 5/18/22 3:43 AM, Lorenzo Bianconi wrote:
> > Introduce selftests for the following kfunc helpers:
> > - bpf_xdp_ct_add
> > - bpf_skb_ct_add
> > - bpf_ct_refresh_timeout
> > 
> > Signed-off-by: Lorenzo Bianconi <[email-masked]>
> > ---
> >   .../testing/selftests/bpf/prog_tests/bpf_nf.c |  4 ++
> >   .../testing/selftests/bpf/progs/test_bpf_nf.c | 72 +++++++++++++++----
> >   2 files changed, 64 insertions(+), 12 deletions(-)
> > 
> > diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_nf.c b/tools/testing/selftests/bpf/prog_tests/bpf_nf.c
> > index dd30b1e3a67c..be6c5650892f 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/bpf_nf.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/bpf_nf.c
> > @@ -39,6 +39,10 @@ void test_bpf_nf_ct(int mode)
> >   	ASSERT_EQ(skel->bss->test_enonet_netns_id, -ENONET, "Test ENONET for bad but valid netns_id");
> >   	ASSERT_EQ(skel->bss->test_enoent_lookup, -ENOENT, "Test ENOENT for failed lookup");
> >   	ASSERT_EQ(skel->bss->test_eafnosupport, -EAFNOSUPPORT, "Test EAFNOSUPPORT for invalid len__tuple");
> > +	ASSERT_EQ(skel->bss->test_add_entry, 0, "Test for adding new entry");
> > +	ASSERT_EQ(skel->bss->test_succ_lookup, 0, "Test for successful lookup");
> 
> The default value for test_add_entry/test_succ_lookup are 0. So even if the
> program didn't execute, the above still succeeds. So testing with
> a non-default value (0) might be a better choice.

ack, I will fix it in v4.

> 
> > +	ASSERT_TRUE(skel->bss->test_delta_timeout > 9 && skel->bss->test_delta_timeout <= 10,
> > +		    "Test for ct timeout update");
> 
> ASSERT_TRUE(skel->bss->test_delta_timeout == 10, ...)? Could you add some
> comments on why the value should be 10. It is not obvious by
> inspecting the code.

I added some tolerance to avoid races with jiffies update in test_bpf_nf.c

> 
> >   end:
> >   	test_bpf_nf__destroy(skel);
> >   }
> > diff --git a/tools/testing/selftests/bpf/progs/test_bpf_nf.c b/tools/testing/selftests/bpf/progs/test_bpf_nf.c
> > index f00a9731930e..361430dde3f7 100644
> > --- a/tools/testing/selftests/bpf/progs/test_bpf_nf.c
> > +++ b/tools/testing/selftests/bpf/progs/test_bpf_nf.c
> > @@ -1,6 +1,7 @@
> >   // SPDX-License-Identifier: GPL-2.0
> >   #include <vmlinux.h>
> >   #include <bpf/bpf_helpers.h>
> > +#include <bpf/bpf_endian.h>
> >   #define EAFNOSUPPORT 97
> >   #define EPROTO 71
> > @@ -8,6 +9,8 @@
> >   #define EINVAL 22
> >   #define ENOENT 2
> > +extern unsigned long CONFIG_HZ __kconfig;
> > +
> >   int test_einval_bpf_tuple = 0;
> >   int test_einval_reserved = 0;
> >   int test_einval_netns_id = 0;
> > @@ -16,6 +19,9 @@ int test_eproto_l4proto = 0;
> >   int test_enonet_netns_id = 0;
> >   int test_enoent_lookup = 0;
> >   int test_eafnosupport = 0;
> > +int test_add_entry = 0;
> > +int test_succ_lookup = 0;
> > +u32 test_delta_timeout = 0;
> >   struct nf_conn;
> > @@ -26,31 +32,40 @@ struct bpf_ct_opts___local {
> >   	u8 reserved[3];
> >   } __attribute__((preserve_access_index));
> > +struct nf_conn *bpf_xdp_ct_add(struct xdp_md *, struct bpf_sock_tuple *, u32,
> > +			       struct bpf_ct_opts___local *, u32) __ksym;
> >   struct nf_conn *bpf_xdp_ct_lookup(struct xdp_md *, struct bpf_sock_tuple *, u32,
> >   				  struct bpf_ct_opts___local *, u32) __ksym;
> > +struct nf_conn *bpf_skb_ct_add(struct __sk_buff *, struct bpf_sock_tuple *, u32,
> > +			       struct bpf_ct_opts___local *, u32) __ksym;
> >   struct nf_conn *bpf_skb_ct_lookup(struct __sk_buff *, struct bpf_sock_tuple *, u32,
> >   				  struct bpf_ct_opts___local *, u32) __ksym;
> >   void bpf_ct_release(struct nf_conn *) __ksym;
> > +void bpf_ct_refresh_timeout(struct nf_conn *, u32) __ksym;
> >   static __always_inline void
> > -nf_ct_test(struct nf_conn *(*func)(void *, struct bpf_sock_tuple *, u32,
> > -				   struct bpf_ct_opts___local *, u32),
> > +nf_ct_test(struct nf_conn *(*look_fn)(void *, struct bpf_sock_tuple *, u32,
> > +				      struct bpf_ct_opts___local *, u32),
> > +	   struct nf_conn *(*add_fn)(void *, struct bpf_sock_tuple *, u32,
> > +				     struct bpf_ct_opts___local *, u32),
> >   	   void *ctx)
> >   {
> >   	struct bpf_ct_opts___local opts_def = { .l4proto = IPPROTO_TCP, .netns_id = -1 };
> >   	struct bpf_sock_tuple bpf_tuple;
> >   	struct nf_conn *ct;
> > +	int err;
> >   	__builtin_memset(&bpf_tuple, 0, sizeof(bpf_tuple.ipv4));
> > -	ct = func(ctx, NULL, 0, &opts_def, sizeof(opts_def));
> > +	ct = look_fn(ctx, NULL, 0, &opts_def, sizeof(opts_def));
> >   	if (ct)
> >   		bpf_ct_release(ct);
> >   	else
> >   		test_einval_bpf_tuple = opts_def.error;
> >   	opts_def.reserved[0] = 1;
> > -	ct = func(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4), &opts_def, sizeof(opts_def));
> > +	ct = look_fn(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4), &opts_def,
> > +		     sizeof(opts_def));
> >   	opts_def.reserved[0] = 0;
> >   	opts_def.l4proto = IPPROTO_TCP;
> >   	if (ct)
> > @@ -59,21 +74,24 @@ nf_ct_test(struct nf_conn *(*func)(void *, struct bpf_sock_tuple *, u32,
> >   		test_einval_reserved = opts_def.error;
> >   	opts_def.netns_id = -2;
> > -	ct = func(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4), &opts_def, sizeof(opts_def));
> > +	ct = look_fn(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4), &opts_def,
> > +		     sizeof(opts_def));
> >   	opts_def.netns_id = -1;
> >   	if (ct)
> >   		bpf_ct_release(ct);
> >   	else
> >   		test_einval_netns_id = opts_def.error;
> > -	ct = func(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4), &opts_def, sizeof(opts_def) - 1);
> > +	ct = look_fn(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4), &opts_def,
> > +		     sizeof(opts_def) - 1);
> >   	if (ct)
> >   		bpf_ct_release(ct);
> >   	else
> >   		test_einval_len_opts = opts_def.error;
> >   	opts_def.l4proto = IPPROTO_ICMP;
> > -	ct = func(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4), &opts_def, sizeof(opts_def));
> > +	ct = look_fn(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4), &opts_def,
> > +		     sizeof(opts_def));
> >   	opts_def.l4proto = IPPROTO_TCP;
> >   	if (ct)
> >   		bpf_ct_release(ct);
> > @@ -81,37 +99,67 @@ nf_ct_test(struct nf_conn *(*func)(void *, struct bpf_sock_tuple *, u32,
> >   		test_eproto_l4proto = opts_def.error;
> >   	opts_def.netns_id = 0xf00f;
> > -	ct = func(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4), &opts_def, sizeof(opts_def));
> > +	ct = look_fn(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4), &opts_def,
> > +		     sizeof(opts_def));
> >   	opts_def.netns_id = -1;
> >   	if (ct)
> >   		bpf_ct_release(ct);
> >   	else
> >   		test_enonet_netns_id = opts_def.error;
> > -	ct = func(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4), &opts_def, sizeof(opts_def));
> > +	ct = look_fn(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4), &opts_def,
> > +		     sizeof(opts_def));
> >   	if (ct)
> >   		bpf_ct_release(ct);
> >   	else
> >   		test_enoent_lookup = opts_def.error;
> > -	ct = func(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4) - 1, &opts_def, sizeof(opts_def));
> > +	ct = look_fn(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4) - 1, &opts_def,
> > +		     sizeof(opts_def));
> >   	if (ct)
> >   		bpf_ct_release(ct);
> >   	else
> >   		test_eafnosupport = opts_def.error;
> > +
> > +	bpf_tuple.ipv4.saddr = bpf_get_prandom_u32(); /* src IP */
> > +	bpf_tuple.ipv4.daddr = bpf_get_prandom_u32(); /* dst IP */
> > +	bpf_tuple.ipv4.sport = bpf_htons(bpf_get_prandom_u32()); /* src port */
> > +	bpf_tuple.ipv4.dport = bpf_htons(bpf_get_prandom_u32()); /* dst port */
> 
> Since it is already random number, bpf_htons is not needed here.
> bpf_endian.h can also be removed.

ack, I will fix it in v4.

Regards,
Lorenzo

> 
> > +
> > +	ct = add_fn(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4), &opts_def,
> > +		    sizeof(opts_def));
> > +	if (ct) {
> > +		struct nf_conn *ct_lk;
> > +
> > +		ct_lk = look_fn(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4),
> > +				&opts_def, sizeof(opts_def));
> > +		if (ct_lk) {
> > +			/* update ct entry timeout */
> > +			bpf_ct_refresh_timeout(ct_lk, 10000);
> > +			test_delta_timeout = ct_lk->timeout - bpf_jiffies64();
> > +			test_delta_timeout /= CONFIG_HZ;
> > +			bpf_ct_release(ct_lk);
> > +		} else {
> > +			test_succ_lookup = opts_def.error;
> > +		}
> > +		bpf_ct_release(ct);
> > +	} else {
> > +		test_add_entry = opts_def.error;
> > +		test_succ_lookup = opts_def.error;
> > +	}
> >   }
> [...]
>