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
Change-Id: If30536c444d9a661a162b935b1dd28df2d88f9b7
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Merged-In: I82771644045e0e37f73725730bd0bd2265ac5b77
2 files changed