fix(usb): stable gadget MAC so the host NIC keeps one MAC across reboots#828
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fix(usb): stable gadget MAC so the host NIC keeps one MAC across reboots#828BeaconCat wants to merge 1 commit into
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The USB network gadget (rndis.usb0 / ncm.usb0) is created without dev_addr or host_addr, so the kernel picks a random MAC for both the device side and the host side on every bind. S10uuid later pins the device-side usb0 via 'ip link set', but the host_addr -- the MAC the attached PC's RNDIS/NCM adapter uses -- stays random and changes on every re-enumeration/reboot. The host then registers a brand-new network adapter each time, piling up stale adapters/MACs (e.g. ~10 after a few reboots) and breaking anything that keys off the MAC. Derive both MACs from the chip UID (same scheme S10uuid already uses for eth0 and usb0), before binding the gadget: dev_addr = 48:da:35:6e:<uid> host_addr = 48:da:35:6d:<uid> Verified on a NanoKVM Cube: host_addr went from random a6:3f:5d:8a:7d:52 to a stable 48:da:35:6d:26:62, identical across two reboots. Fixes sipeed#740
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Problem
Plugging one NanoKVM (Cube) into a PC over USB ends up creating many network adapters / MAC addresses on the host — ~10 after a few reboots.
Root cause: the USB network gadget
rndis.usb0/ncm.usb0is created inS03usbdevwithout settingdev_addrorhost_addr, so the kernel assigns a random MAC to both the device side and the host side on every bind.S10uuidlater pins the device-sideusb0withip link set, but thehost_addr— the MAC the attached PC's RNDIS/NCM adapter uses — stays random and changes on every re-enumeration/reboot. Windows then registers a brand-new adapter each time, piling up stale adapters/MACs and breaking anything that keys off the MAC (DHCP reservations, WoL, firewall rules…).Fix
Derive both MACs deterministically from the chip UID (the same
sha512sum /sys/class/cvi-base/base_uidschemeS10uuidalready uses foreth0/usb0), set before binding the gadget:Guarded on a non-empty UID; falls back to the old random behaviour if
base_uidis unavailable. Applies to both thencmandrndispaths.Verified on hardware (NanoKVM Cube)
a6:3f:5d:8a:7d:52(random, changes every boot)48:da:35:6d:26:6248:da:35:6d:26:62(stable)Fixes #740