From: Johnson, D. <dj...@ap...> - 2005-06-08 02:45:42
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Blaisorblade, The host kernel is 2.4.28+skas. The UML kernel is 2.4.26. Fragmented = packets work most of the time. Only when there is a burst of UDP going = into the UML host, fragmented or non-fragmented, are packets lost. Thanks, Don > -----Original Message----- > From: Blaisorblade [mailto:bla...@ya...] > Sent: Tuesday, June 07, 2005 5:29 PM > To: use...@li... > Cc: Johnson, Don > Subject: Re: [uml-user] Losing packets between eth0 and uml-bridge >=20 >=20 > On Wednesday 08 June 2005 02:20, Johnson, Don wrote: > > Configuration: > > > > 20 UML instances on a P4 2.8 Ghz w/ .75 GB memory > How old are they? On <=3D 2.6.9 there was a UDP checksum=20 > problem with fragmented=20 > packets... (guess on 2.4 this hasn't happened but I'm not too sure). > > a bridge (uml-bridge) set up with 20 interfaces, one for=20 > each of the UML > > instances uml-bridge has ip address of 10.3.82.4 > > UML instances have addresses 10.3.82.5-24 > > UML instances have a default route of 10.3.82.4 > > eth0 has address of 10.3.0.82 > > zebra+rip advertise the 10.3.82.x route as 10.3.0.82 > > ip_forwarding is enabled > > > > Problem: > > > > When a burst of UDP packets is sent to a number of UML=20 > hosts (i.e. several > > packets to each host), packets are lost between eth0 and uml-bridge. > > tcpdump on eth0 shows all incoming packets. tcpdump on=20 > uml-bridge shows > > missing packets. Running ifconfig for uml-bridge shows lost=20 > TX packets at > > about the same rate as is shown between the two tcpdump sessions. > > > > This computer is one of 30-50 units (some with up to 250=20 > UML instances) > > that we use to simulate thousands of computers. Originally=20 > I used bridging > > to connect uml-bridge to eth0 but with hundreds of ip=20 > addresses bridging > > onto a single network segment (with proxy arp enabled), arp=20 > caching became > > a problem. My solution was to route between the uml-bridge and eth0 > > (instead of adding eth0 to the bridge) and use zebra+rip=20 > for the route > > advertising. Functionally it works really well but inbound=20 > UDP packets in > > bursts are lost. TCP works just fine. Anyone have any ideas=20 > about those > > lost packets? > > > > > > ------------------------------------------------------- > > This SF.Net email is sponsored by: NEC IT Guy Games. How=20 > far can you > > shotput a projector? How fast can you ride your desk chair=20 > down the office > > luge track? If you want to score the big prize, get to know=20 > the little guy. > > Play to win an NEC 61" plasma display: http://www.necitguy.com/?r > > _______________________________________________ > > User-mode-linux-user mailing list > > Use...@li... > > https://lists.sourceforge.net/lists/listinfo/user-mode-linux-user >=20 > --=20 > Inform me of my mistakes, so I can keep imitating Homer=20 > Simpson's "Doh!". > Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso",=20 > ICQ 215621894) > http://www.user-mode-linux.org/~blaisorblade >=20 > =09 > ___________________________________=20 > Yahoo! Messenger: chiamate gratuite in tutto il mondo=20 > http://it.beta.messenger.yahoo.com >=20 >=20 |
From: Johnson, D. <dj...@ap...> - 2005-06-09 01:49:43
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I seemed to have solved the problem, mostly. If a really long burst = (200+) of UDP packets hits a UML host with 200 UML instances, there are = still a few packets lost. My comp has only .75 GB of memory so maybe = it's a buffer issue. I will try it on a 4GB machine to see how that = goes. The problem: When adding interfaces (created with 'tunctl -u user -t umlif..') to the = bridge, the bridge takes the mac address of the 1st interface added. In = my configuration the 1st interface, and mac address, will be assigned to = the first uml instance created. I think there is a conflict for inbound = packets routed from eth0 to the bridge when two interfaces (bridge and = 1st uml interface) have the same mac address. I created an unused = interface that I added to the bridge at start up (so the bridge has it's = own unshared mac address) and also set the bridge to promiscuous. This = seemed to do the trick. > -----Original Message----- > From: Blaisorblade [mailto:bla...@ya...] > Sent: Tuesday, June 07, 2005 5:29 PM > To: use...@li... > Cc: Johnson, Don > Subject: Re: [uml-user] Losing packets between eth0 and uml-bridge >=20 >=20 > On Wednesday 08 June 2005 02:20, Johnson, Don wrote: > > Configuration: > > > > 20 UML instances on a P4 2.8 Ghz w/ .75 GB memory > How old are they? On <=3D 2.6.9 there was a UDP checksum=20 > problem with fragmented=20 > packets... (guess on 2.4 this hasn't happened but I'm not too sure). > > a bridge (uml-bridge) set up with 20 interfaces, one for=20 > each of the UML > > instances uml-bridge has ip address of 10.3.82.4 > > UML instances have addresses 10.3.82.5-24 > > UML instances have a default route of 10.3.82.4 > > eth0 has address of 10.3.0.82 > > zebra+rip advertise the 10.3.82.x route as 10.3.0.82 > > ip_forwarding is enabled > > > > Problem: > > > > When a burst of UDP packets is sent to a number of UML=20 > hosts (i.e. several > > packets to each host), packets are lost between eth0 and uml-bridge. > > tcpdump on eth0 shows all incoming packets. tcpdump on=20 > uml-bridge shows > > missing packets. Running ifconfig for uml-bridge shows lost=20 > TX packets at > > about the same rate as is shown between the two tcpdump sessions. > > > > This computer is one of 30-50 units (some with up to 250=20 > UML instances) > > that we use to simulate thousands of computers. Originally=20 > I used bridging > > to connect uml-bridge to eth0 but with hundreds of ip=20 > addresses bridging > > onto a single network segment (with proxy arp enabled), arp=20 > caching became > > a problem. My solution was to route between the uml-bridge and eth0 > > (instead of adding eth0 to the bridge) and use zebra+rip=20 > for the route > > advertising. Functionally it works really well but inbound=20 > UDP packets in > > bursts are lost. TCP works just fine. Anyone have any ideas=20 > about those > > lost packets? > > > > > > ------------------------------------------------------- > > This SF.Net email is sponsored by: NEC IT Guy Games. How=20 > far can you > > shotput a projector? How fast can you ride your desk chair=20 > down the office > > luge track? If you want to score the big prize, get to know=20 > the little guy. > > Play to win an NEC 61" plasma display: http://www.necitguy.com/?r > > _______________________________________________ > > User-mode-linux-user mailing list > > Use...@li... > > https://lists.sourceforge.net/lists/listinfo/user-mode-linux-user >=20 > --=20 > Inform me of my mistakes, so I can keep imitating Homer=20 > Simpson's "Doh!". > Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso",=20 > ICQ 215621894) > http://www.user-mode-linux.org/~blaisorblade >=20 > =09 > ___________________________________=20 > Yahoo! Messenger: chiamate gratuite in tutto il mondo=20 > http://it.beta.messenger.yahoo.com >=20 >=20 |