Bug 214631

Summary:	Creating a macvlan with as bridge as parent -> NO-CARRIER on both
Product:	Networking	Reporter:	jan (jan)
Component:	Other	Assignee:	Stephen Hemminger (stephen)
Status:	NEW ---
Severity:	blocking	CC:	jan
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:	5.7+	Subsystem:
Regression:	Yes	Bisected commit-id:

Description jan@delandtsheer.eu 2021-10-06 15:09:30 UTC

When creating a macvlan with a bridge as parent, interfaces brought up, have NO-CARRIER.
Only when connecting another type of interface to the bridge (like a dummy) and bring it up, the bridge and macvlan start forwarding


ip netns add tns
ip link add tbr type bridge
ip link add tmv link tbr type macvlan mode bridge
ip link set tmv netns tns
ip link set tbr up
ip -n tns link set lo up
ip -n tns link set tmv up


behaviour :
  kernel 5.4 -> that always works
  kernel 5.10 -> mostly works, __sometimes__ not
  kernel 5.14 -> never works

verifyable with `ip link show dev tbr` having NO-CARRIER

When it doesn't work:
ip link add tdum type dummy
ip link set tdum master tbr
ip link set tdum up

and then the bridge and macvlans start forwarding

Comment 1 jan@delandtsheer.eu 2021-10-07 19:19:41 UTC

Apparently the same behavior exists for ipvlan.

We upgraded our kernel from 5.4 to 5.10, as more and more need arose for supporting newer hardware, but this different behavior breaks our whole network stack, and is of major concern :-(

Can someone please have a look ?

Thanks
Jan