add proper minimum bpfloader version annotations for block/clatd/dscp_policy/netd

In practice this doesn't actually really matter, since older versions
of the bpfloader won't even look in the relevant directories:

BpfLoader v0.9 is the first one that looks into
  '/apex/com.android.tethering/etc/bpf/net_shared',
but it is only v0.12 that pins the resulting programs and maps
correctly into
  /sys/fs/bpf/net_shared/
hence the annotations for block/clatd/dscp_policy.

BpfLoader v0.13 is the first one that looks into
  '/apex/com.android.tethering/etc/bpf/netd_shared'
subdirectory and pins into
  /sys/fs/bpf/netd_shared/
hence the annotation for netd.

But it's best to explicitly document the intent.

Note that in practice the mainline module will fail spectacularly
on a T OS if it can't find the programs and maps
(presumably due to the bpfloader being too old)
but will work on S even though the bpfloader there is much older,
because these programs/maps are not required on pre-T OS.

This change is thus really only documentation.

Bug: 218408035
Test: TreeHugger
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I5ffa2faf83ca337b84e34b01df84436629989c58
(cherry picked from commit acebffb966)
Merged-In: I5ffa2faf83ca337b84e34b01df84436629989c58

bpf_progs/block.c

@@ -19,6 +19,9 @@
 #include <netinet/in.h>
 #include <stdint.h>
 
+// The resulting .o needs to load on the Android T bpfloader v0.12+
+#define BPFLOADER_MIN_VER 12u
+
 #include "bpf_helpers.h"
 
 #define ALLOW 1

bpf_progs/clatd.c

@@ -30,6 +30,9 @@
 #define __kernel_udphdr udphdr
 #include <linux/udp.h>
 
+// The resulting .o needs to load on the Android T bpfloader v0.12+
+#define BPFLOADER_MIN_VER 12u
+
 #include "bpf_helpers.h"
 #include "bpf_net_helpers.h"
 #include "bpf_shared.h"

bpf_progs/dscp_policy.c

@@ -27,6 +27,9 @@
 #include <netinet/udp.h>
 #include <string.h>
 
+// The resulting .o needs to load on the Android T bpfloader v0.12+
+#define BPFLOADER_MIN_VER 12u
+
 #include "bpf_helpers.h"
 #include "dscp_policy.h"
 

bpf_progs/netd.c

@@ -14,6 +14,9 @@
  * limitations under the License.
  */
 
+// The resulting .o needs to load on the Android T Beta 3 bpfloader v0.13+
+#define BPFLOADER_MIN_VER 13u
+
 #include <bpf_helpers.h>
 #include <linux/bpf.h>
 #include <linux/if.h>