Re: How to setup Jumbo Frames? NetBSD Dom0 and FreeBSD XENHVM

[John Nemeth <jnemeth%cue.bc.ca@localhost>]

On Jun 27,  3:21pm, "Mike C." wrote:
} On 06/27/13 07:43, Manuel Bouyer wrote:
} > On Thu, Jun 27, 2013 at 04:47:10AM +0000, Mike C. wrote:
} >>
} >> First, sorry if I'm asking something basic.
} >>
} >> I have a re1 interface that supports jumbo frames (MTU up to 7422), the
} >> card is set up correct, however I need a bridge for xen!
} >>
} >> When I try to change the bridge mtu settings:
} >> # ifconfig bridge0 mtu 7422
} >> ifconfig: SIOCSIFMTU: Network dropped connection on reset
} >>
} >> However ifconfig shows the mtu at 7422:
} >> # ifconfig bridge0                                                        
} >> bridge0: flags=0 mtu 7422
} >>
} >> And the biggest problem comes when I try t start a domu... if the
} >> bridge0 interface has a mtu different than 1500 I can't start the domu,
} >> because the virtual interface creation fails with:
} >>
} >> brconfig: add xvif5i0: Invalid argument
} > I guess you could change the /usr/pkg/etc/xen/scripts/vif-bridge
} > script to set the mtu of the xvif before adding it to the bridge.
} >
} > But I'm not sure that the netfront/netback (at last as implemented
} > on NetBSD) supports MTU larger than 4k.
} 
} Forgot to mention I tried that...
} 
} While staring the domU I see
} ifconfig xvif5i0 up
} ifconfig: SIOCSIFMTU: Invalid argument
} ifconfig: SIOCSIFMTU: Network dropped connection on reset (this is for
} the bridge)
} 
} If I set the script to set the MTU to any value other than 1500 thats
} what I get!
} 
} I tried 9000 last night and today with 4000, has you can see the bridge
} mtu changes even though I see the "Network dropped connection on reset
} message"
} 
} ---> bridge0: flags=41<UP,RUNNING> mtu 4000
} 
} I was under the impression that since Xen 4.1+ mtu of 9000 are
} supported, at least I according to the change log it should:
} "Fixes to properly support jumbo frames (mtu 9000) with vif-bridge script."
} 
} But perhaps NetBSD needs some specific patch for this...
} 
} NOTE: I'm running 4.2.2 compile from source following the instructions
} at: http://wiki.xen.org/wiki/Compiling_Xen_From_Source_on_NetBSD.

     Xen 4.2 is in pkgsrc and you would probably be better off with
it.  It fixes a whole lot of problems and adds functionality.

     However, your problem sounds like it could possibly be with
the backend driver in the kernel.  Certainly, it is something that
is going to need significant investigation.

}-- End of excerpt from "Mike C."