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SubjectRe: [Patch 3/3] net: reserve ports for applications using fixed port numbers
Cong Wang wrote:
> Tetsuo Handa wrote:
>> Hello.
>>
>>> --- linux-2.6.orig/drivers/infiniband/core/cma.c
>>> +++ linux-2.6/drivers/infiniband/core/cma.c
>>> @@ -1980,6 +1980,8 @@ retry:
>>> /* FIXME: add proper port randomization per like inet_csk_get_port */
>>> do {
>>> ret = idr_get_new_above(ps, bind_list, next_port, &port);
>>> + if (!ret && inet_is_reserved_local_port(port))
>>> + ret = -EAGAIN;
>>> } while ((ret == -EAGAIN) && idr_pre_get(ps, GFP_KERNEL));
>>>
>>> if (ret)
>>>
>> I think above part is wrong. Below program
> ...
>> This result suggests that above loop will continue until idr_pre_get() fails
>> due to out of memory if all ports were reserved.
>>
>> Also, if idr_get_new_above() returned 0, bind_list (which is a kmalloc()ed
>> pointer) is already installed into a free slot (see comment on
>> idr_get_new_above_int()). Thus, simply calling idr_get_new_above() again will
>> install the same pointer into multiple slots. I guess it will malfunction later.
>
> Thanks for testing!
>
> How about:
>
> + if (!ret && inet_is_reserved_local_port(port))
> + ret = -EBUSY;
>
> ? So that it will break the loop and return error.
>

Or use the similar trick:

int tries = 10;
...

if(!ret && inet_is_reserved_local_port(port)) {
if (tries--)
ret = -EAGAIN;
else
ret = -EBUSY;
}

Any comments?


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