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Message-ID: <52A5D9FB.5020003@gmail.com>
Date: Mon, 09 Dec 2013 09:55:55 -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 10:28 PM, Wang Weidong wrote:
> On 2013/12/9 10:40, Vlad Yasevich wrote:
>> 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
>
> Hi vald,
>
> I found that we had checked the value of 0 in sctp_setsockopt_rtoinfo.
> So I only do this:
>
> if (asoc) {
> + if (msecs_to_jiffies(rtoinfo.srto_min) >
> + msecs_to_jiffies(rtoinfo.srto_max))
> + return -EINVAL;
> ...
What if the value in rtoinfo is 0? Right now, the doesn't do any
comparisons and just assigns values into the assoc or sp as long
as the user provided a non-0 value.
Now imagine the user did this:
rtoinfo.srto_min = 0
rtoinfo.srto_max = 5;
setsockopt();
.... later on...
rtoinfo.srto_min = 8;
rtoinfo.srto_max = 0;
setsockopt();
No you have a situation where min > max. However both calls were valid.
My suggestion to you, split the sysctl change into a separate patch and
and do socket option handling in its own patch. Also, please be sure
to test it with different variants of the calls.
-vlad
> } else {
> ...
> + if (rtoinfo.srto_min > rtoinfo.srto_max)
> + return -EINVAL;
> ...
> }
>
> There because we set value to asoc and sp is not same. So I add the
> check into two path.
>
> Regards.
> Wang
>
>>>
>>> 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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