tree 3f114768a6b05160e7d136779882aa965eafca49
parent 73b42b0f955c23975e1b290facb87561882b93f4
author Maciej Żenczykowski <maze@google.com> 1637677423 -0800
committer Maciej Żenczykowski <maze@google.com> 1637838238 +0000

better compatibility for unusual Qualcomm/Mediatek cellular ARPHRD_* values

see kernel/private/wembley/+/refs/heads/tm-4.19/include/uapi/linux/if_arp.h
which has #define ARPHRD_PUREIP 520 (and is a Mediatek based device)

or Qualcomm based Pixel 3 and older kernels (<=4.9) which #define ARPHRD_RAWIP 530
(unlike Pixel 4/5 which are 4.14/4.19 and use the upstream ARPHRD_RAWIP of 519)

We stop supporting 520/530 starting with 5.11+ since those as GKI 2.0 only kernels
cannot be using non-upstream-ed constants (btw. this is probably true for 5.10-S
as well, but let's play it safe).  For pre-5.11 we're lucky because even now
(with 5.15 released) upstream has yet to define an ARPHRD_* for either one of
520 or 530, so there's no harm in 'squatting' on this unused space.

This approach also means there's absolutely no change in behaviour on
pre-launch-T devices, since they all are at most running 5.10 kernels.

We'll be able to get rid of this code in the far future once we stop shipping
mainline tethering updates to pre-5.10 Mediatek or pre-4.14 Qualcomm devices.
This will likely be many years.

Test: TreeHugger
Bug: 207057951
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I767b5fc56bc826e088507aea8ae7a30aa8aa424a