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Message-ID: <52A52D8F.7010202@gmail.com>
Date: Sun, 08 Dec 2013 21:40:15 -0500
From: Vlad Yasevich <vyasevich@...il.com>
To: Wang Weidong <wangweidong1@...wei.com>, nhorman@...driver.com,
davem@...emloft.net
CC: dborkman@...hat.com, netdev@...r.kernel.org,
linux-sctp@...r.kernel.org
Subject: Re: [PATCH v5 1/2] sctp: check the rto_min and rto_max
On 12/08/2013 09:28 PM, Wang Weidong wrote:
> On 2013/12/9 10:19, Vlad Yasevich wrote:
>> On 12/08/2013 08:53 PM, Wang Weidong wrote:
>>> On 2013/12/8 2:54, Vlad Yasevich wrote:
>>>> On 12/07/2013 02:17 AM, Wang Weidong wrote:
>>>>> rto_min should be smaller than rto_max while rto_max should be larger
>>>>> than rto_min. Add two proc_handler for the checking. Add the check in
>>>>> sctp_setsockopt_rtoinfo.
>>>>>
>>>>> Suggested-by: Vlad Yasevich <vyasevich@...il.com>
>>>>> Signed-off-by: Wang Weidong <wangweidong1@...wei.com>
>>>>> ---
>>>>> include/net/sctp/constants.h | 3 ++
>>>>> net/sctp/socket.c | 5 +++
>>>>> net/sctp/sysctl.c | 73 ++++++++++++++++++++++++++++++++++++++++----
>>>>> 3 files changed, 75 insertions(+), 6 deletions(-)
>>>>>
>>>>> diff --git a/include/net/sctp/constants.h b/include/net/sctp/constants.h
>>>>> index 2f0a565..d276978 100644
>>>>> --- a/include/net/sctp/constants.h
>>>>> +++ b/include/net/sctp/constants.h
>>>>> @@ -279,6 +279,9 @@ enum { SCTP_MAX_GABS = 16 };
>>>>> #define SCTP_RTO_ALPHA 3 /* 1/8 when converted to right shifts. */
>>>>> #define SCTP_RTO_BETA 2 /* 1/4 when converted to right shifts. */
>>>>>
>>>>> +#define SCTP_ONE 1 /* 1 ms */
>>>>> +#define SCTP_TIMER_MAX 86400000 /* ms in one day */
>>>>> +
>>>>> /* Maximum number of new data packets that can be sent in a burst. */
>>>>> #define SCTP_DEFAULT_MAX_BURST 4
>>>>>
>>>>> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
>>>>> index 72046b9..13411ad 100644
>>>>> --- a/net/sctp/socket.c
>>>>> +++ b/net/sctp/socket.c
>>>>> @@ -2818,6 +2818,11 @@ static int sctp_setsockopt_rtoinfo(struct sock *sk, char __user *optval, unsigne
>>>>> if (copy_from_user(&rtoinfo, optval, optlen))
>>>>> return -EFAULT;
>>>>>
>>>>> + if (rtoinfo.srto_min < SCTP_ONE ||
>>>>> + rtoinfo.srto_max > SCTP_TIMER_MAX ||
>>>>> + rtoinfo.srto_max < rtoinfo.srto_min)
>>>>> + return -EINVAL;
>>>>> +
>>>>
>>>> You can not do the check for srto_min < 1. The following is the text
>>>> from the spec:
>>>> All times are given in milliseconds. A value of 0, when modifying
>>>> the parameters, indicates that the current value should not be
>>>> changed.
>>>>
>>> Yes, Your are right, I found it in draft-ietf-tsvwg-sctpsocket-14.txt.
>>> Thanks.
>>>
>>>> So, it is valid for a user to pass in a value of 0. Also, I am not sure
>>>> if it makes sense to bind the upper limit here, as well.
>>>>
>>>> -vlad
>>>>
>>> Here, I am not sure as well. I think it should like what we do to the
>>> init_net.sctp.rto_max when set larger than timer_max. Just not change the value.
>>>
>>
>> So, the basic reason that sysctl is limited is that it is a default
>> for all sctp association on the system. It makes some sense to limit
>> what the max value here could be. Limiting it to double suggested
>> RTO.MAX would only make it 2 minutes and may be insufficient for some
>> of the high latency low-throughput wireless links. Making it about an
>> hour should be fine... This would be a separate patch though...
>>
> Here, you mean that we should use 3600*1000 rather than 86400000? So
> we should use another patch to fix that after my patchs?
>
>> Limiting the user-supplied value is not as appropriate since the
>> assumption is that user application may know better what it's
>> requirements are and it is not up to the stack to limit those. As
>> long as the user value is withing the usable range (and the kernel
>> will already knows how and does limit this range), we should not
>> limit this further.
>>
>> -vlad
>>
> Agree, So I should check like this:
> !srto_min || !srto_max || srto_min > srto_max ?
> And no need to add macros for checking.
No, I think this would have to be a little more complicated :(
Remember it's ok to have srto_min == 0 and srto_max == 0. It just
means that no change happens.
You may need to do something like
unsigned long rto_max, rto_min;
if (rtoinfo.srto_max)
rto_max = msecs_to_jiffies(rtoinfo.srto_max);
else
rto_max = asoc ? asoc->rto_max : sp->rto_max;
if (rtoinfo.srto_min)
rto_min = msecs_to_jiffies(rtoinfo.srto_min);
else
rto_min = asoc ? asoc->rto_min : sp->rto_min;
if (rto_min > rto_max)
return -EINVAL;
if (asoc) {
asoc->rto_min = rto_min;
asoc->rto_max = rto_max;
...
etc....
This way we make sure that the user that supplied just rto_min or just
rto_max didn't set them so that min > max.
-vlad
>
> Thanks.
>
>>>
>>> Regards.
>>> Wang
>>>
>>>>> asoc = sctp_id2assoc(sk, rtoinfo.srto_assoc_id);
>>>>>
>>>>> /* Set the values to the specific association */
>>>>> diff --git a/net/sctp/sysctl.c b/net/sctp/sysctl.c
>>>>> index 6b36561..33c56c6 100644
>>>>> --- a/net/sctp/sysctl.c
>>>>> +++ b/net/sctp/sysctl.c
>>>>> @@ -40,8 +40,8 @@
>>>>> #include <linux/sysctl.h>
>>>>>
>>>>> static int zero = 0;
>>>>> -static int one = 1;
>>>>> -static int timer_max = 86400000; /* ms in one day */
>>>>> +static int one = SCTP_ONE;
>>>>> +static int timer_max = SCTP_TIMER_MAX;
>>>>> static int int_max = INT_MAX;
>>>>> static int sack_timer_min = 1;
>>>>> static int sack_timer_max = 500;
>>>>> @@ -61,6 +61,13 @@ static int proc_sctp_do_hmac_alg(struct ctl_table *ctl,
>>>>> void __user *buffer, size_t *lenp,
>>>>>
>>>>> loff_t *ppos);
>>>>> +static int proc_sctp_do_rto_min(struct ctl_table *ctl, int write,
>>>>> + void __user *buffer, size_t *lenp,
>>>>> + loff_t *ppos);
>>>>> +static int proc_sctp_do_rto_max(struct ctl_table *ctl, int write,
>>>>> + void __user *buffer, size_t *lenp,
>>>>> + loff_t *ppos);
>>>>> +
>>>>> static struct ctl_table sctp_table[] = {
>>>>> {
>>>>> .procname = "sctp_mem",
>>>>> @@ -102,17 +109,17 @@ static struct ctl_table sctp_net_table[] = {
>>>>> .data = &init_net.sctp.rto_min,
>>>>> .maxlen = sizeof(unsigned int),
>>>>> .mode = 0644,
>>>>> - .proc_handler = proc_dointvec_minmax,
>>>>> + .proc_handler = proc_sctp_do_rto_min,
>>>>> .extra1 = &one,
>>>>> - .extra2 = &timer_max
>>>>> + .extra2 = &init_net.sctp.rto_max
>>>>> },
>>>>> {
>>>>> .procname = "rto_max",
>>>>> .data = &init_net.sctp.rto_max,
>>>>> .maxlen = sizeof(unsigned int),
>>>>> .mode = 0644,
>>>>> - .proc_handler = proc_dointvec_minmax,
>>>>> - .extra1 = &one,
>>>>> + .proc_handler = proc_sctp_do_rto_max,
>>>>> + .extra1 = &init_net.sctp.rto_min,
>>>>> .extra2 = &timer_max
>>>>> },
>>>>> {
>>>>> @@ -342,6 +349,60 @@ static int proc_sctp_do_hmac_alg(struct ctl_table *ctl,
>>>>> return ret;
>>>>> }
>>>>>
>>>>> +static int proc_sctp_do_rto_min(struct ctl_table *ctl, int write,
>>>>> + void __user*buffer, size_t *lenp,
>>>>> + loff_t *ppos)
>>>>> +{
>>>>> + struct net *net = current->nsproxy->net_ns;
>>>>> + int new_value;
>>>>> + struct ctl_table tbl;
>>>>> + unsigned int min = *(unsigned int *) ctl->extra1;
>>>>> + unsigned int max = *(unsigned int *) ctl->extra2;
>>>>> + int ret;
>>>>> +
>>>>> + memset(&tbl, 0, sizeof(struct ctl_table));
>>>>> + tbl.maxlen = sizeof(unsigned int);
>>>>> +
>>>>> + if (write)
>>>>> + tbl.data = &new_value;
>>>>> + else
>>>>> + tbl.data = &net->sctp.rto_min;
>>>>> + ret = proc_dointvec(&tbl, write, buffer, lenp, ppos);
>>>>> + if (write) {
>>>>> + if (ret || new_value > max || new_value < min)
>>>>> + return -EINVAL;
>>>>> + net->sctp.rto_min = new_value;
>>>>> + }
>>>>> + return ret;
>>>>> +}
>>>>> +
>>>>> +static int proc_sctp_do_rto_max(struct ctl_table *ctl, int write,
>>>>> + void __user*buffer, size_t *lenp,
>>>>> + loff_t *ppos)
>>>>> +{
>>>>> + struct net *net = current->nsproxy->net_ns;
>>>>> + int new_value;
>>>>> + struct ctl_table tbl;
>>>>> + unsigned int min = *(unsigned int *) ctl->extra1;
>>>>> + unsigned int max = *(unsigned int *) ctl->extra2;
>>>>> + int ret;
>>>>> +
>>>>> + memset(&tbl, 0, sizeof(struct ctl_table));
>>>>> + tbl.maxlen = sizeof(unsigned int);
>>>>> +
>>>>> + if (write)
>>>>> + tbl.data = &new_value;
>>>>> + else
>>>>> + tbl.data = &net->sctp.rto_max;
>>>>> + ret = proc_dointvec(&tbl, write, buffer, lenp, ppos);
>>>>> + if (write) {
>>>>> + if (ret || new_value > max || new_value < min)
>>>>> + return -EINVAL;
>>>>> + net->sctp.rto_max = new_value;
>>>>> + }
>>>>> + return ret;
>>>>> +}
>>>>> +
>>>>> int sctp_sysctl_net_register(struct net *net)
>>>>> {
>>>>> struct ctl_table *table;
>>>>>
>>>>
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>>>
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>>
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