netd bpf - implement ingress discard based on {dstip,ifindex}

Cherry-pick of aosp/2731354 to backport VPN security fix to non-mainline
U devices.
This CL removes bpf_existence_test.cpp change in aosp/2731354 since u
branches use module prebuilt as default.

Test: TreeHugger
Bug: 193031925
Signed-off-by: Maciej Żenczykowski <maze@google.com>
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:e1a82cc1cc04ed49f022825010316cde7758c2fb)
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:807a915d2113781a9a42f47c6244729c91aa0d4b)
Merged-In: If30536c444d9a661a162b935b1dd28df2d88f9b7
Change-Id: If30536c444d9a661a162b935b1dd28df2d88f9b7
2 files changed