Subject: Re: v3 for tcp friends?

From: Weiping Pan <[email-masked]>
Date: Wed, 23 Jan 2013 21:16:58 +0800

On 01/23/2013 05:52 PM, Li Yu wrote:
> 于 2013年01月23日 17:39, Li Yu 写道:
>> 于 2013年01月23日 15:58, Li Yu 写道:
>>> 于 2013年01月23日 15:21, Li Yu 写道:
>>>> 于 2013年01月23日 14:46, Eric Dumazet 写道:
>>>>> On Wed, 2013-01-23 at 14:12 +0800, Li Yu wrote:
>>>>>> Oops, this hang is not since TCP friends patch!
>>>>>>
>>>>>> sk_sndbuf_get() is broken by 32 bits integer overflow
>>>>>> because of so large value in net.ipv4.tcp_{rmem,wmem}.
>>>>>>
>>>>>> but this hang also can be found in net-next.git
>>>>>> (3.8.0-rc3+), if we run below commands, then all new
>>>>>> TCP connections stop working!
>>>>>>
>>>>>> # when TCP friends is disabled
>>>>>> sysctl -w net.ipv4.tcp_rmem="4096 4294967296 4294967296" # 4GB
>>>>>> sysctl -w net.ipv4.tcp_wmem="4096 4294967296 4294967296"
>>>>>
>>>>> Right we need to make sure we dont overflow.
>>>>>
>>>>> Try the following fix :
>>>>>
>>>>> diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
>>>>> index a25e1d2..1459145 100644
>>>>> --- a/net/ipv4/sysctl_net_ipv4.c
>>>>> +++ b/net/ipv4/sysctl_net_ipv4.c
>>>>> @@ -549,14 +549,16 @@ static struct ctl_table ipv4_table[] = {
>>>>>           .data        = &sysctl_tcp_wmem,
>>>>>           .maxlen        = sizeof(sysctl_tcp_wmem),
>>>>>           .mode        = 0644,
>>>>> -        .proc_handler    = proc_dointvec
>>>>> +        .extra1        = &zero,
>>
>> If we added below:
>>
>> +static int one = 1;
>> +static int int_max = INT_MAX;
>> ....
>> +               .extra1     = &one,
>> +        .extra2        = &int_max,
>>
>
> The "int_max" may be unnecessary here :)
Hi, Li Yu,

I tested that your patch works fine.
Can you post a complete patch ?

thanks
Weiping Pan