Steps to reproduce: ifconfing eth0 mtu 1500 ifconfing eth0.100 mtu 1500 ping www.ru -s 2000 -- BAD -- ---------------- ifconfing eth0 mtu 1500 ifconfing eth0.100 mtu 1496 ping www.ru -s 2000 --NORMAL--
Begin forwarded message: Date: Thu, 4 May 2006 23:15:56 -0700 From: bugme-daemon@bugzilla.kernel.org To: bugme-new@lists.osdl.org Subject: [Bugme-new] [Bug 6495] New: Vlan MTU Fragmentation http://bugzilla.kernel.org/show_bug.cgi?id=6495 Summary: Vlan MTU Fragmentation Kernel Version: 2.6.16.12 Status: NEW Severity: normal Owner: shemminger@osdl.org Submitter: slavon@bigtelecom.ru Steps to reproduce: ifconfing eth0 mtu 1500 ifconfing eth0.100 mtu 1500 ping www.ru -s 2000 -- BAD -- ---------------- ifconfing eth0 mtu 1500 ifconfing eth0.100 mtu 1496 ping www.ru -s 2000 --NORMAL-- ------- You are receiving this mail because: ------- You are on the CC list for the bug, or are watching someone who is.
Andrew Morton wrote: > > Begin forwarded message: > > Date: Thu, 4 May 2006 23:15:56 -0700 > From: bugme-daemon@bugzilla.kernel.org > To: bugme-new@lists.osdl.org > Subject: [Bugme-new] [Bug 6495] New: Vlan MTU Fragmentation > > > http://bugzilla.kernel.org/show_bug.cgi?id=6495 > > Summary: Vlan MTU Fragmentation > Kernel Version: 2.6.16.12 > Status: NEW > Severity: normal > Owner: shemminger@osdl.org > Submitter: slavon@bigtelecom.ru > > > Steps to reproduce: > > ifconfing eth0 mtu 1500 > ifconfing eth0.100 mtu 1500 > > ping www.ru -s 2000 > -- BAD -- > > ---------------- > > ifconfing eth0 mtu 1500 > ifconfing eth0.100 mtu 1496 > > ping www.ru -s 2000 > --NORMAL-- This is almost definately a bug in the ethernet driver. The driver needs to be modified so that it can send/receive pkts that are MTU + 4 bytes for the VLAN header. We need to know what NIC/driver this user is using... Ben > > ------- You are receiving this mail because: ------- > You are on the CC list for the bug, or are watching someone who is. > - > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >
05:0a.0 Ethernet controller: 3Com Corporation 3c905C-TX/TX-M [Tornado] (rev 78) Subsystem: 3Com Corporation 3C905C-TX Fast Etherlink for PC Management NIC Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- Latency: 32 (2500ns min, 2500ns max), Cache Line Size 08 Interrupt: pin A routed to IRQ 7 Region 0: I/O ports at 9c00 [size=128] Region 1: Memory at feafe000 (32-bit, non-prefetchable) [size=128] [virtual] Expansion ROM at fe900000 [disabled] [size=128K] Capabilities: <access denied> Also try Realtek network adapter (if need - i say chipset tomorow) slavon@dmitry ~ $ /sbin/lsmod 8021q 14856 0 ... 3c59x 36200 0 mii 4160 1 3c59x
On Fri, 05 May 2006 08:57:06 -0700 Ben Greear <greearb@candelatech.com> wrote: > Andrew Morton wrote: > > > > Begin forwarded message: > > > > Date: Thu, 4 May 2006 23:15:56 -0700 > > From: bugme-daemon@bugzilla.kernel.org > > To: bugme-new@lists.osdl.org > > Subject: [Bugme-new] [Bug 6495] New: Vlan MTU Fragmentation > > > > > > http://bugzilla.kernel.org/show_bug.cgi?id=6495 > > > > Summary: Vlan MTU Fragmentation > > Kernel Version: 2.6.16.12 > > Status: NEW > > Severity: normal > > Owner: shemminger@osdl.org > > Submitter: slavon@bigtelecom.ru > > > > > > Steps to reproduce: > > > > ifconfing eth0 mtu 1500 > > ifconfing eth0.100 mtu 1500 > > > > ping www.ru -s 2000 > > -- BAD -- > > > > ---------------- > > > > ifconfing eth0 mtu 1500 > > ifconfing eth0.100 mtu 1496 > > > > ping www.ru -s 2000 > > --NORMAL-- > > This is almost definately a bug in the ethernet driver. The driver needs > to be modified so that it can send/receive pkts that are MTU + 4 bytes for the > VLAN header. > > We need to know what NIC/driver this user is using... > > Ben > Sorry, I should have added Badalian to Cc:. He's using 3c905C (3c59x.c, allegedly maintained by myself). (Badalian, please use emailed reply-to-all rather than the bugzilla interface for the remainder of this discussion, thanks).
Andrew Morton wrote: > Sorry, I should have added Badalian to Cc:. He's using 3c905C (3c59x.c, > allegedly maintained by myself). > > (Badalian, please use emailed reply-to-all rather than the bugzilla > interface for the remainder of this discussion, thanks). > There is an ancient patch on this page: http://www.bewley.net/linux/vlan/patches/ I have no idea if this would apply or if it has already been put into the kernel. I also don't have any 3com nics to test with, but there are probably folks on the vlan mailing list that could try patches... Thanks, Ben
On Fri, 05 May 2006 21:39:14 -0700 Ben Greear <greearb@candelatech.com> wrote: > Andrew Morton wrote: > > > Sorry, I should have added Badalian to Cc:. He's using 3c905C (3c59x.c, > > allegedly maintained by myself). > > > > (Badalian, please use emailed reply-to-all rather than the bugzilla > > interface for the remainder of this discussion, thanks). > > > > There is an ancient patch on this page: > > http://www.bewley.net/linux/vlan/patches/ > > I have no idea if this would apply or if it has already been put into the > kernel. I also don't have any 3com nics to test with, but there are probably > folks on the vlan mailing list that could try patches... > Yeah, that was merged ages ago. I guess I can type simple commands and add printks. Do you have time to take a look at the driver and suggest what I should be looking for?
Andrew Morton wrote: > I guess I can type simple commands and add printks. Do you have time to > take a look at the driver and suggest what I should be looking for? I can only offer vague hints: TX usually works, but RX often has isues. There is usually a bit or two that needs setting to enable the larger than MTU pkt RX. It seems some older chipsets had issues with doing checksum offload for VLAN packets, so could try disabling the UDP/TCP checksum logic and see if that helps. Thanks, Ben
This appears to be a bug with the 3com NIC driver. I do not own this hardware or know the driver, so it is unlikely I will ever be able to fix this problem. Assigning to the 3com driver maintainer. If the driver is not going to be fixed, then I will update my VLAN page with a note that the 3c905 driver can only run VLANs with MTU of 1496, and that users needing 1500 MTU vlans must use a different piece of harder.
If no objections, this bug should be closed as Documented. Thanks.