Re: can we increase the send buffer size of rfcomm socket?

Hi Marcel,

2009/8/27 Marcel Holtmann [off-list ref]:

Hi Zhu,

quoted

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(...)
{
=A0 =A0...
=A0 =A0 =A0 =A0 =A0 =A0 =A0 skb =3D sock_alloc_send_skb(sk, size + RFCOM=

M_SKB_RESERVE,

quoted

=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 msg->msg_fla=

gs & MSG_DONTWAIT, &err);

quoted

=A0 =A0 =A0 =A0 =A0 =A0 =A0 if (!skb)
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 break;
=A0 =A0...
}

Looks the send buffer is not adequate. Then I increased the send
buffer size in function rfcomm_sock_alloc(), =A0build 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 =A0tcp/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 =3D RFCOMM_MAX_CREDITS * RFCOMM_DEFAULT_MTU * 10
to
sk->sk_sndbuf =3D RFCOMM_MAX_CREDITS * RFCOMM_DEFAULT_MTU * 20

Thanks,
Zhu Lan