# Building nginx with TCP\_FASTOPEN enabled **URL:** \ **Category:** NGINX\ **Created:** [August 9, 2014, 8:19pm UTC](https://www.ruby-forum.com/t/building-nginx-with-tcp-fastopen-enabled/231467 "2014-08-09T20:19:58Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\ **Post date:** [August 9, 2014, 8:19pm UTC](https://www.ruby-forum.com/t/building-nginx-with-tcp-fastopen-enabled/231467/1 "2014-08-09T20:19:58Z")
Hello, I’ve tried to use “fastopen” in the listen directive but nginx gave me an error that the option is unkown. I’m using nginx 1.7.4 on Debian Wheezy 3.14.13 kernel. I’ve compiled nginx myself. When I run the configure command, I get: “checking for TCP\_FASTOPEN … not found” ‘cat /proc/sys/net/ipv4/tcp\_fastopen’ gives me “3” - I also tried it with the value “2”. Why does my system not support TCP fastopen? My kernel is recent enough… thank you, Can Posted at Nginx Forum: > **[Building nginx with TCP\_FASTOPEN enabled](https://forum.nginx.org/read.php?2,252447,252447#msg-252447)** > > Hello, I've tried to use "fastopen" in the listen directive but nginx gave me an error that the option is unkown. I'm using nginx 1.7.4 on Debian Wheezy 3.14.13 kernel. I've compiled nginx myself. When I run the configure command, I get: ---
**Author:** ![mastercan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/a698b9/32.png) [@mastercan](https://www.ruby-forum.com/u/mastercan)\ **Post date:** [August 10, 2014, 2:33am UTC](https://www.ruby-forum.com/t/building-nginx-with-tcp-fastopen-enabled/231467/2 "2014-08-10T02:33:45Z")
Hello! On Sat, Aug 09, 2014 at 02:19:32PM -0400, mastercan wrote: > ‘cat /proc/sys/net/ipv4/tcp\_fastopen’ gives me “3” - I also tried it with > the value “2”. > > Why does my system not support TCP fastopen? My kernel is recent enough… Try looking into objs/autoconf.err, it has details about configure test failures. Most likely, the TCP\_FASTOPEN constant isn’t defined since your glibc isn’t recent enough, something like 2.18+ is needed. – Maxim D. > **[nginx](http://nginx.org/)** ---
**Author:** ![mastercan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/a698b9/32.png) [@mastercan](https://www.ruby-forum.com/u/mastercan)\ **Post date:** [August 10, 2014, 1:59pm UTC](https://www.ruby-forum.com/t/building-nginx-with-tcp-fastopen-enabled/231467/3 "2014-08-10T13:59:43Z")
Maxim D. Wrote: > Try looking into objs/autoconf.err, it has details about configure > test failures. Most likely, the TCP\_FASTOPEN constant isn’t > defined since your glibc isn’t recent enough, something like 2.18+ > is needed. Yes, you’re right. glibc was the problem. I tried to build an nginx deb package on a development machine with updated glibc libs and installed it on the production server. Unfortunately I get this error when trying to start nginx: “/lib/x86\_64-linux-gnu/libc.so.6: version `GLIBC\_2.14’ not found (required by /usr/sbin/nginx)” So I guess I must upgrade glibc on the production server as well…which might break dependencies… Posted at Nginx Forum: [http://forum.nginx.org/read.php?2,252447,252458#msg-252458](http://forum.nginx.org/read.php?2,252447,252458#msg-252458) ---
**Author:** ![mastercan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/a698b9/32.png) [@mastercan](https://www.ruby-forum.com/u/mastercan)\ **Post date:** [August 10, 2014, 2:49pm UTC](https://www.ruby-forum.com/t/building-nginx-with-tcp-fastopen-enabled/231467/4 "2014-08-10T14:49:42Z")
Lukas T. Wrote: > Don’t upgrade libc because of this (it will mess your system up). > > Just define it manually when compiling nginx by passing it to the > compiler: > -DTCP\_FASTOPEN=23 Which command accepts the -D flag? Where exactly do I set this option? Thanks in advance Posted at Nginx Forum: [http://forum.nginx.org/read.php?2,252447,252460#msg-252460](http://forum.nginx.org/read.php?2,252447,252460#msg-252460) ---
**Author:** ![mastercan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/a698b9/32.png) [@mastercan](https://www.ruby-forum.com/u/mastercan)\ **Post date:** [August 10, 2014, 2:25pm UTC](https://www.ruby-forum.com/t/building-nginx-with-tcp-fastopen-enabled/231467/5 "2014-08-10T14:25:18Z")
> Yes, you’re right. glibc was the problem. I tried to build an nginx deb > package on a development machine with updated glibc libs and installed it > on the production server. Don’t upgrade libc because of this (it will mess your system up). Just define it manually when compiling nginx by passing it to the compiler: -DTCP\_FASTOPEN=23 Regards, Lukas ---
**Author:** ![mastercan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/a698b9/32.png) [@mastercan](https://www.ruby-forum.com/u/mastercan)\ **Post date:** [August 10, 2014, 2:54pm UTC](https://www.ruby-forum.com/t/building-nginx-with-tcp-fastopen-enabled/231467/6 "2014-08-10T14:54:27Z")
❦ 10 août 2014 07:59 -0400, “mastercan” [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) : > “/lib/x86\_64-linux-gnu/libc.so.6: version `GLIBC\_2.14’ not found (required > by /usr/sbin/nginx)” > > So I guess I must upgrade glibc on the production server as well…which > might break dependencies… There is nothing in this feature that needs a recent glibc except the definition of TCP\_FASTOPEN constant. On the machine where you compile, you can just add the constant in /usr/include/linux/tcp.h and /usr/include/netinet/tcp.h. The resulting binary will work on another machine without this modification. ## nginx should just define this symbol when not available. The remaining of the code is already detecting at runtime if this feature is available or not. Localise input and output in subroutines. - The Elements of Programming Style (Kernighan & Plauger) ---
**Author:** ![mastercan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/a698b9/32.png) [@mastercan](https://www.ruby-forum.com/u/mastercan)\ **Post date:** [August 10, 2014, 3:01pm UTC](https://www.ruby-forum.com/t/building-nginx-with-tcp-fastopen-enabled/231467/7 "2014-08-10T15:01:01Z")
Lukas T. Wrote: > Don’t upgrade libc because of this (it will mess your system up). > > Just define it manually when compiling nginx by passing it to the > compiler: > -DTCP\_FASTOPEN=23 Thank you! This seems to define the constant. I simply added –with-cc-opt=“-DTCP\_FASTOPEN=23” to my configure command. I think this will work (I’m compiling it right now…) Posted at Nginx Forum: [http://forum.nginx.org/read.php?2,252447,252462#msg-252462](http://forum.nginx.org/read.php?2,252447,252462#msg-252462)