kern/58047: Bridging using rge* has issues

[john%ziaspace.com@localhost]

>Number:         58047
>Category:       kern
>Synopsis:       Bridging using rge* has issues
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Mar 17 22:35:00 +0000 2024
>Originator:     John Klos
>Release:        NetBSD 10.0_RC6
>Organization:
	
>Environment:
	
	
System: NetBSD r7900.zia.io 10.0_RC6 NetBSD 10.0_RC6 (R7900) #0: Wed Mar 13 03:45:16 UTC 2024  john%r7900.zia.io@localhost:/usr/obj-amd64/sys/arch/amd64/compile/R7900 amd64
Architecture: x86_64
Machine: amd64
>Description:
	
Trying to use a 2.5 Gbps Realtek rge interface has issues, as noted in 
PRs kern/57694 and kern/57972. The patch from kern/57694 helps a little.

Additionally, when one tries to use the rge interface in a bridge, odd 
behavior is observed. Connections through the bridge hang: some time out, 
others do not. NetBSD-current from today running as a guest in qemu-system-m68k
on a tap bridged with rge give lots of messages like these:

[ 224.9800030] vioif0: discarding oversize frame (len=1518)
[ 224.9800030] vioif0: discarding oversize frame (len=1518)
[ 227.9700030] vioif0: discarding oversize frame (len=1518)

Adding a Realtek re card and using that instead results in all the odd behavior 
going away.

This is a big problem, in my opinion, because many of the systems I've set up in 
the last year or so have all come with either rge or igc ethernet on board, and
people won't necessarily know they need a separate ethernet card for NetBSD to be
reliable.

>How-To-Repeat:
	
ifconfig bridge0 create
ifconfig bridge0 up
ifconfig tap0 create
ifconfig tap0 up
brconfig bridge0 add rge0 tap0

Then try to use tap0.
>Fix:
	

>Unformatted: