Most recent kernel where this bug did not occur: Distribution: Ubuntu Hardware Environment: Laptop Acer Aspire 3500 Software Environment: Problem Description: Performing ftp upload on a network that has an MTU of 1400 along the way. Local interface MTU is set to 1500. Laptop receives from the network ICMP Destination Unreachable (Fragmentation Needed), MTU of next hop 1400, but i see no reduction on the IP packet size sent by the Laptop. Because the IP MTU Path Discovery mechanism is enabled, all the outoing packets have the DF flag set, causing this TCP session to stall. Steps to reproduce:
Created attachment 6590 [details] Traffic capture file showing the problem
What network driver is used? Is TCP Segmentation Offload enabled for the network interface? ethtool -k eth0
Driver is sis900, compiled into the kernel. ferrao@meter:~$ sudo ethtool -k eth0 Offload parameters for eth0: Cannot get device rx csum settings: Operation not supported Cannot get device tx csum settings: Operation not supported Cannot get device scatter-gather settings: Operation not supported Cannot get device tcp segmentation offload settings: Operation not supported no offload info available
According to my ethtool (compiled latest version) docs, the only thing i seem to be able to do on this driver is : ferrao@meter:/usr/share/doc/ethtool$ sudo ethtool -i eth0 driver: sis900 version: v1.08.08 Jan. 22 2005 firmware-version: bus-info: 0000:00:04.0
My email is getting rejected at due to administrative prohibition, so i'm answering here. I can try to capture it again, but won't tcpdump -nr trace_file.cap -x give you the same result? Thanx Herbert Xu wrote: >>David S. Miller wrote: >> >> > >>>>Alternatively, we're ignoring the PMTU message for one reason or >>>>another. Perhaps the quoted TCP packet in the ICMP pmtu message >>>>has an incorrect sequence number or is truncated for some reason. >>>> >>>> > >> >>That's what I think too. >> >>Can we please get the same packet dump with -x? >> >>Thanks, >>
This bug is getting little attention, does it still exist with 2.6.16 or 2.6.17-rc?
Please reopen this bug if it's still present in kernel 2.6.17.