Bug 79891

Summary:	Router causes TCP retransmits for windows hosts after "ip_forward: fix inverted local_df test"
Product:	Networking	Reporter:	Theodor Milkov (tm)
Component:	IPV4	Assignee:	Stephen Hemminger (stephen)
Status:	NEW ---
Severity:	normal	CC:	fw, szg00000
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:	3.2.60	Subsystem:
Regression:	No	Bisected commit-id:
Attachments:	TCP retransmissions from a windows host

Description Theodor Milkov 2014-07-10 13:20:06 UTC

Created attachment 142651 [details]
TCP retransmissions from a windows host

After upgrading a router to Linux 3.2.60 most windows machines behind it started experiencing connection stalls. Downgrade to 3.2.59 resolved the problem. Using git bisect I pinpointed it to "59d9f389df3cdf72833d5ee17c3fe959b6bdc792 is the first bad commit", which entered the kernel from here http://marc.info/?l=linux-netdev&m=139949081418806&w=2

No connection problems for Linux hosts at all – only windows. Please, find attached tcpdump packet capture demonstrating the bad behaviour.

Comment 1 Theodor Milkov 2014-07-11 05:44:45 UTC

I wonder if this is the same bug discussed in the Debian bug tracker: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=754294

Comment 2 Florian Westphal 2014-07-11 21:57:28 UTC

I guess it would be fixed by applying

commit 21d1196a35f5686c4323e42a62fdb4b23b0ab4a3
ipv4: set transport header earlier

to 3.4 series.

Comment 3 Theodor Milkov 2014-07-12 10:35:59 UTC

Latest development: http://marc.info/?l=linux-netdev&m=140511646508963&w=2