Bug 157737

Summary: System doesn't accept MTU setting with NM
Product: [openSUSE] SUSE Linux 10.1 Reporter: Juergen Orschiedt <jorschiedt>
Component: NetworkAssignee: Robert Love <rml>
Status: RESOLVED DUPLICATE QA Contact: E-mail List <qa-bugs>
Severity: Normal    
Priority: P5 - None CC: suse-beta
Version: Beta 7   
Target Milestone: RC 1   
Hardware: Other   
OS: Other   
Whiteboard:
Found By: Other Services Priority:
Business Priority: Blocker: ---
Marketing QA Status: --- IT Deployment: ---
Attachments: ifconfig eth
ifconfig wlan
YaST2: setting mtu to <empty> for eth1, eth2
YaST2: setting mtu to 1488 for eth1, eth2
Screenshot of Network throughput via VPN with 1500MTU
VPN connection 1500MTU
NM mtu hook

Description Juergen Orschiedt 2006-03-13 20:27:02 UTC
Because of DSL (arcor) I want to set MTU <1492 to avoid fragmentation.
Configured MTU 1488 for both NICS (eth, wlan) with YaST.
Nevertheless, ipstack uses MTU of 1500bytes.

eth1      Link encap:Ethernet  HWaddr 00:14:22:C3:ED:80
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
          Interrupt:169

eth2      Link encap:Ethernet  HWaddr 00:13:CE:CE:53:D1
          inet addr:192.168.200.103  Bcast:192.168.200.255  Mask:255.255.255.0
          inet6 addr: fe80::213:ceff:fece:53d1/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:571 errors:0 dropped:25 overruns:0 frame:0
          TX packets:477 errors:0 dropped:4 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:285338765 (272.1 Mb)  TX bytes:19174345 (18.2 Mb)
          Interrupt:209 Base address:0xa000 Memory:dfbff000-dfbfffff
Comment 1 Juergen Orschiedt 2006-03-13 20:27:57 UTC
Created attachment 72657 [details]
ifconfig eth
Comment 2 Juergen Orschiedt 2006-03-13 20:29:29 UTC
Created attachment 72658 [details]
ifconfig wlan
Comment 3 Michael Gross 2006-03-14 12:58:28 UTC
Please attach the yast logfiles.
Comment 4 Juergen Orschiedt 2006-03-14 13:14:34 UTC
Where do I find them?
Comment 5 Juergen Orschiedt 2006-03-14 13:18:37 UTC
sorry, I'm a bit stupid today...
first set:
changing mtu from 1488 to <empty> for eth1, eth2
Comment 6 Juergen Orschiedt 2006-03-14 13:22:00 UTC
Created attachment 72768 [details]
YaST2: setting mtu to <empty> for eth1, eth2
Comment 7 Juergen Orschiedt 2006-03-14 13:25:03 UTC
Created attachment 72770 [details]
YaST2: setting mtu to 1488 for eth1, eth2
Comment 8 Juergen Orschiedt 2006-03-14 13:26:55 UTC
ifconfig after #7 (had to reconnect WLAN manually after YaST)

eth1      Link encap:Ethernet  HWaddr 00:14:22:C3:ED:80
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
          Interrupt:169

eth2      Link encap:Ethernet  HWaddr 00:13:CE:CE:53:D1
          inet addr:192.168.200.102  Bcast:192.168.200.255  Mask:255.255.255.0
          inet6 addr: fe80::213:ceff:fece:53d1/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:365 errors:0 dropped:12 overruns:0 frame:0
          TX packets:242 errors:0 dropped:4 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:2350988 (2.2 Mb)  TX bytes:694108 (677.8 Kb)
          Interrupt:209 Base address:0x6000 Memory:dfbff000-dfbfffff
Comment 9 Michael Gross 2006-03-15 13:23:26 UTC
Ressigning to Martin.
Comment 10 Martin Vidner 2006-03-15 13:41:10 UTC
NetworkManager -> Robert
Comment 11 Robert Love 2006-03-15 14:20:28 UTC
We won't support user-specified MTU settings for Code10.

In the meantime, you can place a script in /etc/NetworkManager/dispatcher.d that sets the MTU for you.  $1 is the interface name and $2 is "up" or "down" depending on whether the interface is now up or down.
Comment 12 Juergen Orschiedt 2006-03-15 20:52:36 UTC
Ok, just for completeness...
Because of the MTU problem we will see a lot of problems with Turnpike VPN.
Turnpike tries to set the route mtu to 1350, which doesn't work.
Because the stack signals 1500, we get, if we have a "MTU Black Hole" between Server and Client, stucking connections because of truncated packages.

Even if the connection doesn't stuck we have horrible throughputs (see attached pic) which was created with a single file download via VPN over a 6MBit DSL. Timeouts up to 15sec are quite normal in this case.
Manual setting the MTU to 1350 increased the average throughput to approx. 350kB/sec, without outages.

Comment 13 Juergen Orschiedt 2006-03-15 20:54:00 UTC
Created attachment 73098 [details]
Screenshot of Network throughput via VPN with 1500MTU
Comment 14 Juergen Orschiedt 2006-03-15 20:55:40 UTC
Created attachment 73099 [details]
VPN connection 1500MTU
Comment 15 Robert Love 2006-03-15 20:56:24 UTC
Shouldn't Turnpike be fixed/modified?
Comment 17 Robert Love 2006-03-21 17:57:41 UTC
I'll read the values from sysconfig, if any, and set them on interface up in NM.
Comment 18 Robert Love 2006-03-21 17:58:24 UTC
See bug #159354

*** This bug has been marked as a duplicate of 159354 ***
Comment 19 Juergen Orschiedt 2006-03-21 18:13:26 UTC
Got a code snipet from zoz which solved my problem.
See attached /etc/sysconfig/network/ip-up.d/ifcfg-mtu-hook
Comment 20 Juergen Orschiedt 2006-03-21 18:16:31 UTC
Created attachment 74277 [details]
NM mtu hook
Comment 21 Robert Love 2006-03-21 18:17:27 UTC
Yes, this was the dispatcher script I was speaking of.

The next build of NM will respect the MTU value, anyhow.