Re: SCTP sysctl /proc/sys/net/sctp/rto_min/initial/max variables

[Dilip Daya <dilip.daya@hp.com>]

Hi Vlad / Niel,

Please disregard this issue. I extracted sctp from kernel linux-3.2.34
and it does not seem to be a problem. Looks like the sctp I have in
3.2.32 is the problem.

Once again, I very sorry to engage you in this.

Thanking you in advance for all your time and effort.
-DilipD.


On Thu, 2012-11-29 at 16:33 -0500, Dilip Daya wrote:
> Hi Vlad,
> 
> On Thu, 2012-11-29 at 15:49 -0500, Vlad Yasevich wrote:
> > On 11/29/2012 03:35 PM, Dilip Daya wrote:
> > > Hi,
> > >
> > > Testing kernel 3.2.32 x86_64 environment show the sctp sysctl variables:
> > >
> > >   - net.sctp.rto_initial,
> > >   - net.sctp.rto_min,
> > >   - net.sctp.rto_max
> > >
> > > are not overriding the hard-coded recommended values of:
> > > - http://lxr.linux.no/linux+v3.2.34/include/net/sctp/constants.h#L276
> > >
> > > I've confirmed the following values are correct to what I need modified:
> > >   - /proc/sys/net/sctp/rto_initial
> > >   - /proc/sys/net/sctp/rto_min
> > >   - /proc/sys/net/sctp/rto_max
> > >
> > > If I change the hard-coded values and rebuild sctp they take effect. Is
> > > this an issue on my end or is this a sctp sysctl issue?
> > >
> > > Thanks,
> > > -DilipD.
> > >
> > 
> > Dilip
> > 
> > I am not sure what you mean...   Are you saying that issuing
> > 	sysctl -w net.sctp.rto_initial\x100
> > doesn't change the value of rto_initial shown in /proc/sys/net/sctp?
> 
> No, it does change the value in /proc/sys/net/sctp but not picked up by
> sctp associations. Only default recommended values are picked up, i.e.
> 
> # sysctl -a 2>/dev/null | grep ".rto_"
> net.ipv4.tcp_frto_response = 0
> net.sctp.rto_initial = 25
> net.sctp.rto_min = 20
> net.sctp.rto_max = 30
> net.sctp.rto_alpha_exp_divisor = 3
> net.sctp.rto_beta_exp_divisor = 2
> 
> # cat /proc/sys/net/sctp/rto_max
> 30
> 
> # cat /proc/sys/net/sctp/rto_min 
> 20
> 
> # cat /proc/sys/net/sctp/rto_initial 
> 25
> 
> Selective sctp debug:
> [  206.783286] sctp_init_sock: net_params->rto_min: 1000,
> net_params->rto_initial: 3000, net_params->rto_max: 60000
> [  206.783291] sctp_init_sock: sp->rtoinfo.srto_min: 1000,
> sp->rtoinfo.srto_initial: 3000, sp->rtoinfo.srto_max: 60000
> [  206.783403] sctp_association_init: sp->rtoinfo.srto_min: 1000,
> sp->rtoinfo.srto_initial: 3000, sp->rtoinfo.srto_max: 60000
> [  206.783407] sctp_association_init: asoc->rto_min: 250,
> asoc->rto_initial: 750, asoc->rto_max: 15000
> [  206.783426] sctp_transport_init: net_params->rto_initial: 3000,
> peer->rto: 750
> [  206.783993] sctp_transport_init: net_params->rto_initial: 3000,
> peer->rto: 750
> [  206.784008] sctp_transport_init: net_params->rto_initial: 3000,
> peer->rto: 750
> [  206.784019] sctp_transport_init: net_params->rto_initial: 3000,
> peer->rto: 750
> [  206.784028] sctp_transport_init: net_params->rto_initial: 3000,
> peer->rto: 750
> [  206.784038] sctp_transport_init: net_params->rto_initial: 3000,
> peer->rto: 750
> [  206.784047] sctp_transport_init: net_params->rto_initial: 3000,
> peer->rto: 750
> [  206.784731] sctp_transport_update_rto: transport: ffff88011e1b0400,
> rtt: 0, srtt: 0 rttvar: 1, rto: 250, rto-msecs: 1000, rto_min: 250,
> rto_max: 15000
> ...
> 
> # cat /proc/net/sctp/remaddr 
> ADDR ASSOC_ID HB_ACT RTO MAX_PATH_RTX REM_ADDR_RTX  START
> 192.168.2.62  1 1 250 5 0 0
> 
> # cat /proc/net/sctp/assocs_info | grep "R:"
> R:192.168.2.62  1 1500 0 5 11832 0 21040 250 0 1 0
> 
> i.e.
> 
> Default hard-coded recommended values are:
> rto_min     = 1000  msec = 1000/4  =   250 jiffies
> rto_initial = 3000  msec = 3000/4  =   750 jiffies
> rto_max     = 60000 msec = 60000/4 = 15000 jiffies
> 
> 
> => Seems sctp sysctl rto_ variables do not effect.
> 
> -DilipD.
> 
> > 
> > -vlad
> > 
> > > --
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