BpfCoordinator: publish upstream interface mtu to v4 offload rule
Respect the upstream interface mtu instead of always setting
mtu 1500.
Using upstream interface mtu is probably not the best solution
for tether offload pmtu but it at least respects the upstream
interface mtu which may be less than 1500.
Test: manual test
1. Connect to carrier Taiwan Star.
2. Enable tethering and check the mtu 1434 in dumpsys.
IPv4 Upstream: proto [inDstMac] iif(iface) src -> nat ->
dst [outDstMac] pmtu age
udp [02:10:45:32:ef:35] 54(54) 192.168.72.125:39034
-> 15(rmnet1) 100.83.189.11:39034
-> 142.251.43.14:443 [00:00:00:00:00:00] 1434 69657ms
IPv4 Downstream: proto [inDstMac] iif(iface) src -> nat
-> dst [outDstMac] pmtu age
udp [00:00:00:00:00:00] 15(rmnet1) 142.251.43.14:443
-> 54(54) 100.83.189.11:39034
-> 192.168.72.125:39034 [9a:8a:4d:ec:a4:7c] 1434 69633ms
Bug: 262860312
Test: atest BpfCoordinatorTest
Change-Id: Ic6dcb95ed76d5306053e4645b6baebc67ff082cf
2 files changed
