On Dec 2, 2013, at 12:56 PM, Neil Horman <nhorman@xxxxxxxxxxxxx> wrote:
> On Mon, Dec 02, 2013 at 02:51:45PM +0800, Wang Weidong wrote:
>> From: Wang Weidong <wangweidong1@xxxxxxxxxx>
>>
>> when I setted the max_burst to 0, do the lksctp-tools I got hang.
>> I found sctp_transport_burst_limited would make the cwnd to 0.
>> so I make the max_burst min value to 1.
>> Signed-off-by: Wang Weidong <wangweidong1@xxxxxxxxxx>
>> ---
>> net/sctp/sysctl.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/sctp/sysctl.c b/net/sctp/sysctl.c
>> index 7637e8e..46832d3 100644
>> --- a/net/sctp/sysctl.c
>> +++ b/net/sctp/sysctl.c
>> @@ -135,7 +135,7 @@ static struct ctl_table sctp_net_table[] = {
>> .maxlen = sizeof(int),
>> .mode = 0644,
>> .proc_handler = proc_dointvec_minmax,
>> - .extra1 = &zero,
>> + .extra1 = &one,
>> .extra2 = &int_max
>> },
>> {
>> --
>> 1.7.12
>>
>>
>
>
> This seems like a band-aid to me. There are a few things wrong:
>
> 1) You can also set the the max_burst via setsockopt, and so this would need to
> be checked in that path as well.
>
> 2) I don't see how having a cwnd of zero would cause a hang. It looks like a
> cwnd of zero would perpetually place the association in a slow start state,
> which is silly but not illegal.
>
> Please investigate the acutally root cause of the problem before just avoiding
> it like this.
I second this.
Please note the using max_burst of in the socket option means that you
deactivate max_burst, not that you actually use the value 0. See
http://tools.ietf.org/html/rfc6458#section-8.1.24
I FreeBSD we use the sysctl variable as the default for sockets. Therefore
max_burst is a valid value, it just disables max_burst.
Best regards
Michael
>
> Thanks!
> Neil
>
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