[dnsdist] TCP FastOpen

[Casey Deccio]

> On May 2, 2019, at 3:32 PM, Casey Deccio <casey at deccio.net> wrote:
> 
> 
> 
>> On May 2, 2019, at 11:35 AM, Casey Deccio <casey at deccio.net> wrote:
>> 
>> Hi,
>> 
>> I'm using dnsdist 1.1.0-2+deb9u1 on Debian.  I get the following error when I try to enable TCP Fast Open:
>> 
>>> setLocal("0.0.0.0:53", { tcpFastOpenSize=100 })
>> Unable to convert parameter from no value to N5boost8optionalIbEE
>> 
>> Any suggestions?
>> 
>> The answer might be to upgrade, but I've got a running configuration, and I'm hoping not to have to change it (for now) if possible, due to time constraints.
> 
> Okay, I compiled and ran 1.3.3 to see if that would make a difference.  No error, but I can see that no TFO option is being returned by the server:
> 
> 15:27:59.865296 IP 192.0.2.1.37032 > 192.0.2.2.53: Flags [S], seq 4015346648, win 29200, options [mss 1460,sackOK,TS val 905241474 ecr 0,nop,wscale 7,tfo  cookiereq,nop,nop], length 0
> 15:27:59.865373 IP 192.0.2.2.53 > 192.0.2.1.37032: Flags [S.], seq 4279757276, ack 4015346649, win 28960, options [mss 1460,sackOK,TS val 3783501648 ecr 905241474,nop,wscale 7], length 0
> 
> $ uname -a
> Linux baritone 4.9.0-7-amd64 #1 SMP Debian 4.9.110-1 (2018-07-05) x86_64 GNU/Linux
> 
> $ cat /proc/sys/net/ipv4/tcp_fastopen
> 3
> 
> $ grep -r TCP_FASTOPEN /usr/include/linux/tcp.h 
> #define TCP_FASTOPEN		23	/* Enable FastOpen on listeners */

Well I can confirm that the following did *not* work for me for version 1.3.3:

setLocal("0.0.0.0:53", { tcpFastOpenSize=10 })

But I finally tracked down the older options, and this *did* work for version 1.1.0:

setLocal("0.0.0.0:53", true, false, 10)

FYI.

Casey