Hi Marcel,
2009/8/28 Marcel Holtmann <marcel@xxxxxxxxxxxx>:
> Hi Zhu,
>
>> >> We tried to write a 64k data to rfcomm socket, but it will break
>> >> before sending all of the data out. The problem is in function
>> >> rfcomm_sock_sendmsg() in net/bluetooth/rfcomm/sock.c, it breaks after
>> >> calling sock_alloc_send_skb().
>> >>
>> >> static int rfcomm_sock_sendmsg(...)
>> >> {
>> >> ...
>> >> skb = sock_alloc_send_skb(sk, size + RFCOMM_SKB_RESERVE,
>> >> msg->msg_flags & MSG_DONTWAIT, &err);
>> >> if (!skb)
>> >> break;
>> >> ...
>> >> }
>> >>
>> >> Looks the send buffer is not adequate. Then I increased the send
>> >> buffer size in function rfcomm_sock_alloc(), build kernel and try
>> >> again, this time the sendmsg can complete sending all the data.
>> >>
>> >> Can we use the setsockopt() method to change the socket's send/receive
>> >> buffer size, just like the usual tcp/ip socket?
>> >
>> > yes we can. Send a patch for it and I am going to review it.
>> >
>> > Regards
>> >
>> > Marcel
>> >
>> >
>> >
>>
>> Today I changed the send buffer size but found kernel become very
>> unstable. It usually crash during sending rfcomm data. Do you know
>> what's the reason?
>>
>> Below is what I changed in net/bluetooth/rfcomm/sock.c.
>>
>> in function rfcomm_sock_alloc(),
>>
>> change sk->sndbuf
>> from
>> sk->sk_sndbuf = RFCOMM_MAX_CREDITS * RFCOMM_DEFAULT_MTU * 10
>> to
>> sk->sk_sndbuf = RFCOMM_MAX_CREDITS * RFCOMM_DEFAULT_MTU * 20
>
> which kernel is this? There have been some fixes in the network stack
> for this. Also I need oopses to see what might happen here.
>
> Regards
>
> Marcel
>
>
>
Yes, it's our kernel's problem. We used another version and it worked
fine. Here the change in rfcomm_sock_alloc() is only for testing. What
I'm doing now is adding a case for RFCOMM_SNDBUF in the function
rfcomm_sock_setsockopt_old(), as below.
case RFCOMM_SNDBUF:
sk->sk_sndbuf = opt;
break;
I'm thinking to add a limitation for a maximum buffer size, but don't
know what maximum size is appropriate here. Do you have any idea?
Thanks,
Zhu Lan
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