[tcpm] Beware the ordering of TCP options
"Adam Langley" <agl@imperialviolet.org> Mon, 27 October 2008 17:15 UTC
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Date: Mon, 27 Oct 2008 10:15:45 -0700
From: Adam Langley <agl@imperialviolet.org>
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Subject: [tcpm] Beware the ordering of TCP options
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The general fact that ordering of TCP options can be important is probably old news to many here. However, the specifics may be interesting. With Linux 2.6.27 the kernel changed the default ordering of options. With the default sysctls the ordering changed from: <MSS: 4 bytes><SACK PERM: 2 bytes><Timestamp: 10 bytes> To <SACK Advert: 2 bytes><Timestamp: 10 bytes><MSS: 4 bytes> This was my fault and it broke the world :( Many routers dropped the new packets on the floor, breaking connectivity for many people: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/264019 http://www.ubuntu.com/getubuntu/releasenotes/810 https://qa.mandriva.com/show_bug.cgi?id=43372 http://wiki.mandriva.com/en/2009.0_Errata#TCP_timestamps Disabling the timestamps sysctl fixes the issue. The options in this case looked like: <NOP><NOP><SACK PERM: 2 bytes><MSS: 4 bytes> And that is seemingly ok with these routers. It seems that SACK PERM cannot be the first option. AGL -- Adam Langley agl@imperialviolet.org http://www.imperialviolet.org _______________________________________________ tcpm mailing list tcpm@ietf.org https://www.ietf.org/mailman/listinfo/tcpm
- [tcpm] Beware the ordering of TCP options Adam Langley
- Re: [tcpm] Beware the ordering of TCP options Lars Eggert
- Re: [tcpm] Beware the ordering of TCP options Adam Langley
- Re: [tcpm] Beware the ordering of TCP options David Borman
- Re: [tcpm] Beware the ordering of TCP options Ilpo Järvinen
- Re: [tcpm] Beware the ordering of TCP options Pekka Savola