Re: [PATCH bpf-next v5 9/9] bpf: xfrm: Add selftest for bpf_xdp_get_xfrm_state()
From: Eyal Birger
Date: Mon Dec 11 2023 - 19:26:12 EST
On Mon, Dec 11, 2023 at 3:49 PM Daniel Xu <dxu@xxxxxxxxx> wrote:
>
> On Mon, Dec 11, 2023 at 03:13:07PM -0800, Eyal Birger wrote:
> > On Mon, Dec 11, 2023 at 2:31 PM Daniel Xu <dxu@xxxxxxxxx> wrote:
> > >
> > > On Mon, Dec 11, 2023 at 01:39:25PM -0800, Eyal Birger wrote:
> > > > Hi Daniel,
> > > >
> > > > Tiny nits below in case you respin this for other reasons:
> > > >
> > > > On Mon, Dec 11, 2023 at 12:20 PM Daniel Xu <dxu@xxxxxxxxx> wrote:
> > > > >
> > > > > This commit extends test_tunnel selftest to test the new XDP xfrm state
> > > > > lookup kfunc.
> > > > >
> > > > > Co-developed-by: Antony Antony <antony.antony@xxxxxxxxxxx>
> > > > > Signed-off-by: Antony Antony <antony.antony@xxxxxxxxxxx>
> > > > > Signed-off-by: Daniel Xu <dxu@xxxxxxxxx>
> > > > > ---
> > > > > .../selftests/bpf/prog_tests/test_tunnel.c | 20 ++++++--
> > > > > .../selftests/bpf/progs/test_tunnel_kern.c | 51 +++++++++++++++++++
> > > > > 2 files changed, 67 insertions(+), 4 deletions(-)
> > > > >
> > > > > diff --git a/tools/testing/selftests/bpf/prog_tests/test_tunnel.c b/tools/testing/selftests/bpf/prog_tests/test_tunnel.c
> > > > > index 2d7f8fa82ebd..fc804095d578 100644
> > > > > --- a/tools/testing/selftests/bpf/prog_tests/test_tunnel.c
> > > > > +++ b/tools/testing/selftests/bpf/prog_tests/test_tunnel.c
> > > > > @@ -278,7 +278,7 @@ static int add_xfrm_tunnel(void)
> > > > > SYS(fail,
> > > > > "ip netns exec at_ns0 "
> > > > > "ip xfrm state add src %s dst %s proto esp "
> > > > > - "spi %d reqid 1 mode tunnel "
> > > > > + "spi %d reqid 1 mode tunnel replay-window 42 "
> > > > > "auth-trunc 'hmac(sha1)' %s 96 enc 'cbc(aes)' %s",
> > > > > IP4_ADDR_VETH0, IP4_ADDR1_VETH1, XFRM_SPI_IN_TO_OUT, XFRM_AUTH, XFRM_ENC);
> > > > > SYS(fail,
> > > > > @@ -292,7 +292,7 @@ static int add_xfrm_tunnel(void)
> > > > > SYS(fail,
> > > > > "ip netns exec at_ns0 "
> > > > > "ip xfrm state add src %s dst %s proto esp "
> > > > > - "spi %d reqid 2 mode tunnel "
> > > > > + "spi %d reqid 2 mode tunnel replay-window 42 "
> > > >
> > > > nit: why do you need to set the replay-window in both directions?
> > >
> > > No reason - probably just careless here.
> > >
> > > >
> > > > > "auth-trunc 'hmac(sha1)' %s 96 enc 'cbc(aes)' %s",
> > > > > IP4_ADDR1_VETH1, IP4_ADDR_VETH0, XFRM_SPI_OUT_TO_IN, XFRM_AUTH, XFRM_ENC);
> > > > > SYS(fail,
> > > > > @@ -313,7 +313,7 @@ static int add_xfrm_tunnel(void)
> > > > > */
> > > > > SYS(fail,
> > > > > "ip xfrm state add src %s dst %s proto esp "
> > > > > - "spi %d reqid 1 mode tunnel "
> > > > > + "spi %d reqid 1 mode tunnel replay-window 42 "
> > > > > "auth-trunc 'hmac(sha1)' %s 96 enc 'cbc(aes)' %s",
> > > > > IP4_ADDR_VETH0, IP4_ADDR1_VETH1, XFRM_SPI_IN_TO_OUT, XFRM_AUTH, XFRM_ENC);
> > > > > SYS(fail,
> > > > > @@ -325,7 +325,7 @@ static int add_xfrm_tunnel(void)
> > > > > /* root -> at_ns0 */
> > > > > SYS(fail,
> > > > > "ip xfrm state add src %s dst %s proto esp "
> > > > > - "spi %d reqid 2 mode tunnel "
> > > > > + "spi %d reqid 2 mode tunnel replay-window 42 "
> > > > > "auth-trunc 'hmac(sha1)' %s 96 enc 'cbc(aes)' %s",
> > > > > IP4_ADDR1_VETH1, IP4_ADDR_VETH0, XFRM_SPI_OUT_TO_IN, XFRM_AUTH, XFRM_ENC);
> > > > > SYS(fail,
> > > > > @@ -628,8 +628,10 @@ static void test_xfrm_tunnel(void)
> > > > > {
> > > > > DECLARE_LIBBPF_OPTS(bpf_tc_hook, tc_hook,
> > > > > .attach_point = BPF_TC_INGRESS);
> > > > > + LIBBPF_OPTS(bpf_xdp_attach_opts, opts);
> > > > > struct test_tunnel_kern *skel = NULL;
> > > > > struct nstoken *nstoken;
> > > > > + int xdp_prog_fd;
> > > > > int tc_prog_fd;
> > > > > int ifindex;
> > > > > int err;
> > > > > @@ -654,6 +656,14 @@ static void test_xfrm_tunnel(void)
> > > > > if (attach_tc_prog(&tc_hook, tc_prog_fd, -1))
> > > > > goto done;
> > > > >
> > > > > + /* attach xdp prog to tunnel dev */
> > > > > + xdp_prog_fd = bpf_program__fd(skel->progs.xfrm_get_state_xdp);
> > > > > + if (!ASSERT_GE(xdp_prog_fd, 0, "bpf_program__fd"))
> > > > > + goto done;
> > > > > + err = bpf_xdp_attach(ifindex, xdp_prog_fd, XDP_FLAGS_REPLACE, &opts);
> > > > > + if (!ASSERT_OK(err, "bpf_xdp_attach"))
> > > > > + goto done;
> > > > > +
> > > > > /* ping from at_ns0 namespace test */
> > > > > nstoken = open_netns("at_ns0");
> > > > > err = test_ping(AF_INET, IP4_ADDR_TUNL_DEV1);
> > > > > @@ -667,6 +677,8 @@ static void test_xfrm_tunnel(void)
> > > > > goto done;
> > > > > if (!ASSERT_EQ(skel->bss->xfrm_remote_ip, 0xac100164, "remote_ip"))
> > > > > goto done;
> > > > > + if (!ASSERT_EQ(skel->bss->xfrm_replay_window, 42, "replay_window"))
> > > > > + goto done;
> > > > >
> > > > > done:
> > > > > delete_xfrm_tunnel();
> > > > > diff --git a/tools/testing/selftests/bpf/progs/test_tunnel_kern.c b/tools/testing/selftests/bpf/progs/test_tunnel_kern.c
> > > > > index 3a59eb9c34de..c0dd38616562 100644
> > > > > --- a/tools/testing/selftests/bpf/progs/test_tunnel_kern.c
> > > > > +++ b/tools/testing/selftests/bpf/progs/test_tunnel_kern.c
> > > > > @@ -30,6 +30,10 @@ int bpf_skb_set_fou_encap(struct __sk_buff *skb_ctx,
> > > > > struct bpf_fou_encap *encap, int type) __ksym;
> > > > > int bpf_skb_get_fou_encap(struct __sk_buff *skb_ctx,
> > > > > struct bpf_fou_encap *encap) __ksym;
> > > > > +struct xfrm_state *
> > > > > +bpf_xdp_get_xfrm_state(struct xdp_md *ctx, struct bpf_xfrm_state_opts *opts,
> > > > > + u32 opts__sz) __ksym;
> > > > > +void bpf_xdp_xfrm_state_release(struct xfrm_state *x) __ksym;
> > > > >
> > > > > struct {
> > > > > __uint(type, BPF_MAP_TYPE_ARRAY);
> > > > > @@ -950,4 +954,51 @@ int xfrm_get_state(struct __sk_buff *skb)
> > > > > return TC_ACT_OK;
> > > > > }
> > > > >
> > > > > +volatile int xfrm_replay_window = 0;
> > > > > +
> > > > > +SEC("xdp")
> > > > > +int xfrm_get_state_xdp(struct xdp_md *xdp)
> > > > > +{
> > > > > + struct bpf_xfrm_state_opts opts = {};
> > > > > + struct xfrm_state *x = NULL;
> > > > > + struct ip_esp_hdr *esph;
> > > > > + struct bpf_dynptr ptr;
> > > > > + u8 esph_buf[8] = {};
> > > > > + u8 iph_buf[20] = {};
> > > > > + struct iphdr *iph;
> > > > > + u32 off;
> > > > > +
> > > > > + if (bpf_dynptr_from_xdp(xdp, 0, &ptr))
> > > > > + goto out;
> > > > > +
> > > > > + off = sizeof(struct ethhdr);
> > > > > + iph = bpf_dynptr_slice(&ptr, off, iph_buf, sizeof(iph_buf));
> > > > > + if (!iph || iph->protocol != IPPROTO_ESP)
> > > > > + goto out;
> > > > > +
> > > > > + off += sizeof(struct iphdr);
> > > > > + esph = bpf_dynptr_slice(&ptr, off, esph_buf, sizeof(esph_buf));
> > > > > + if (!esph)
> > > > > + goto out;
> > > > > +
> > > > > + opts.netns_id = BPF_F_CURRENT_NETNS;
> > > > > + opts.daddr.a4 = iph->daddr;
> > > > > + opts.spi = esph->spi;
> > > > > + opts.proto = IPPROTO_ESP;
> > > > > + opts.family = AF_INET;
> > > > > +
> > > > > + x = bpf_xdp_get_xfrm_state(xdp, &opts, sizeof(opts));
> > > > > + if (!x || opts.error)
> > > >
> > > > nit: how can opts.error be non zero if x == NULL?
> > >
> > > Ignoring the new -ENOENT case, it can't. Which is why I'm testing that
> > > behavior here.
> >
> > I'm sorry, I don't understand.
> >
> > AFAICT, regardless of the -ENOENT change, I don't see
> > how (!x) is false and (opt.error) is true, and so
> > "if (!x || opts.error)" is always equivalent to "if (!x)".
> >
> > What am I missing?
> > Eyal.
>
> The selftests are tests so my intention was to check edge cases here.
> In normal operation it shouldn't be possible that
> bpf_xdp_get_xfrm_state() returns non-NULL and also an error. Maybe
> another way of writing this would be:
>
> if (!x)
> goto out;
> assert(opts.error == 0);
I think this would convey the "edge case testing" notion better.
>
> If I'm trying to be too clever (or maybe just wrong) or it's pointless,
> I can remove the `opts.error` condition.
At least for me the tests also serve as references as to how the
API is expected to be used, so I think it'd be clearer without
signaling that opts.error could potentially be nonzero on success.
An assertion would indeed make that clear.
Thanks for the explanation,
Eyal.