Date: Sat, 7 Jul 2018 13:29:05 +0200 From: Michael Tuexen <Michael.Tuexen@lurchi.franken.de> To: Pieter de Goeje <pieter@degoeje.nl> Cc: freebsd-net@freebsd.org Subject: Re: Does TCP_FASTOPEN actually work? Message-ID: <AE051217-6BFC-4BDA-ABE3-CB63FD1C3DBB@lurchi.franken.de> In-Reply-To: <b85877d5-e783-6e2b-253e-3e755df28af7@degoeje.nl> References: <8f67a706-a650-bba2-a7dc-c25e676e1c97@degoeje.nl> <9B19385C-CBD4-4C12-9E84-E12CAAF23092@lurchi.franken.de> <b85877d5-e783-6e2b-253e-3e755df28af7@degoeje.nl>
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> On 6. Jul 2018, at 19:50, Pieter de Goeje <pieter@degoeje.nl> wrote: > > Op 2018-07-05 om 20:33 schreef Michael Tuexen: >>> On 5. Jul 2018, at 17:23, Pieter de Goeje <pieter@degoeje.nl> wrote: >>> >>> I'm trying to test this new feature, but I have trouble getting the client to actually send a cached cookie. It keeps requesting new ones and as a consequence it never sends data in the initial SYN packet. Tcpdump shows that the server correctly replies to a cookie request with a cookie. >> Can you provide a tracefile? > > See http://lux.student.utwente.nl/~pyotr/dump/tfo.pcap which was taken on the client host, by running tfo-client 3 times in quick succession. > >>> >>> Or am I misunderstanding how it should work and is the cookie cache per-process instead of system wide? >> No, the cache is system wide. You can use >> https://reviews.freebsd.org/D14554 >> to see the entries. > > No entries appear in the cache. > I've verified that the kernel actually does receive the cookie by adding a printf() to tcp_input.c just before tcp_fastopen_update_cache() is called. The kernel finds the cookie and attempts to update the cache, and then it is apparently black-holed. > >>> >>> I'm using the test programs from https://people.freebsd.org/~pkelsey/tfo-tools/ for this purpose. >> How are you using the client and server? > > On the server I run tfo-srv without arguments, on the client I run "tfo-client $host 22222" multiple times in quick succession. My expectation is that after the first run the cookie is retrieved and used. > >>> >>> Server and client run on r335760 or later, with no changes to net.inet.tcp.fastopen except that server_enable was set to 1. >> Is client_enable = 1? > > Yes (by default). I can confirm that there was a bug. It was unmasked by https://svnweb.freebsd.org/changeset/base/335610 which enabled the TCP FO handling on the client side per default. I have committed a fix in https://svnweb.freebsd.org/changeset/base/336057 Thanks a lot for reporting the issue. I'm aware of some other issues, but please report any issues you find! Best regards Michael > > - Pieter
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