Re: [PATCH bpf-next 1/2] bpf: allow __sk_buff tstamp in BPF_PROG_TEST_RUN

On Tue, Oct 15, 2019 at 4:15 PM Andrii Nakryiko
[off-list ref] wrote:

On Tue, Oct 15, 2019 at 2:26 PM Stanislav Fomichev [off-list ref] wrote:

quoted

It's useful for implementing EDT related tests (set tstamp, run the
test, see how the tstamp is changed or observe some other parameter).

Note that bpf_ktime_get_ns() helper is using monotonic clock, so for
the BPF programs that compare tstamp against it, tstamp should be
derived from clock_gettime(CLOCK_MONOTONIC, ...).

Signed-off-by: Stanislav Fomichev <redacted>
---
 net/bpf/test_run.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index 1153bbcdff72..0be4497cb832 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c

@@ -218,10 +218,18 @@ static int convert___skb_to_skb(struct sk_buff *skb, struct __sk_buff *__skb)

        if (!range_is_zero(__skb, offsetof(struct __sk_buff, cb) +
                           FIELD_SIZEOF(struct __sk_buff, cb),
+                          offsetof(struct __sk_buff, tstamp)))
+               return -EINVAL;
+
+       /* tstamp is allowed */
+
+       if (!range_is_zero(__skb, offsetof(struct __sk_buff, tstamp) +
+                          FIELD_SIZEOF(struct __sk_buff, tstamp),

with no context on this particular change whatsoever: isn't this the
same as offsetofend(struct __sk_buff, tstamp)? Same above for cb.

Overall, this seems like the 4th similar check, would it make sense to
add a static array of ranges we want to check for zeros and just loop
over it?..

I wouldn't bother, but offsetofend() is a good suggestion that
can be done in a followup.

Applied both patches. Thanks