Return-Path: <cyrus@holtmann.org>
Subject: Re: can we increase the send buffer size of rfcomm socket?
From: Marcel Holtmann <marcel@holtmann.org>
To: Lan Zhu <zhu.lan.cn@gmail.com>
Cc: linux-bluetooth@vger.kernel.org
In-Reply-To: <113d36d80908260307g59eead24v9311d612c8541ad0@mail.gmail.com>
References: <113d36d80908260307g59eead24v9311d612c8541ad0@mail.gmail.com>
Content-Type: text/plain
Date: Wed, 26 Aug 2009 11:04:07 -0700
Message-Id: <1251309847.2950.96.camel@localhost.localdomain>
Mime-Version: 1.0
Sender: linux-bluetooth-owner@vger.kernel.org
List-ID: <linux-bluetooth.vger.kernel.org>

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