Re: udp packet loss even with large socket buffer

[johnny zhao]

hi,

Since my program is coping with MSN, it's not easy to post a small example. 
But I will try :)

I use the following code to initialize the socket:

*****************************
	session->rtp.loc_addr.sin_family = AF_INET;
	session->rtp.loc_addr.sin_addr.s_addr = INADDR_ANY;
	session->rtp.loc_addr.sin_port = htons (port);
	session->rtp.socket = socket (PF_INET, SOCK_DGRAM, 0);
	g_return_val_if_fail (session->rtp.socket > 0, -1);
	err = bind (session->rtp.socket,
		    (struct sockaddr *) &session->rtp.loc_addr,
		    sizeof (struct sockaddr_in));
	/* set the address reusable */
	err = setsockopt (session->rtp.socket, SOL_SOCKET, SO_REUSEADDR,
			  (void*)&optval, sizeof (optval));

	optval = 8388608;
	int optlen;
	err = setsockopt (session->rtp.socket, SOL_SOCKET, SO_RCVBUF,
	      (void*)&optval, sizeof (optval));
	err = getsockopt (session->rtp.socket, SOL_SOCKET, SO_RCVBUF,
	      (void*)&optval, &optlen);
**************************

the following code is used to receive data:
**************************

     while ( ( error = recvfrom (session->rtp.socket, mp->b_wptr,
					  1500, 0,
					  (struct sockaddr *) &remaddr,
					  &addrlen) ) > 0 )
     {
       mp->b_wptr = mp->b_rptr + error;
       rtp_parse(session, mp);    //this function parses and enqueues the 
received packet
       mp = allocb (1500/*session->max_buf_size*/, 0);   //wang
     }
**************************

These codes are executed in a thread with the highest priority.
Thank you in advance!

Best regards,
Johnny

> From: Denis Vlasenko <vda@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
> To: "johnny zhao" <filamoon2@xxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: udp packet loss even with large socket buffer
> Date: Sat, 28 Feb 2004 23:22:50 +0200
>
> On Saturday 28 February 2004 03:09, johnny zhao wrote:
> > Hi,
> >
> > I have a problem when trying to receive udp packets containing video 
> data
> > sent by Microsoft Windows Messenger. Here is a detailed description:
> >
> > Linux box:
> >     Linux-2.4.21-0.13mdksmp, P4 2.6G HT
> > socket mode:
> >     blocked mode
> > code used:
> >     while ( recvfrom(...) )
> > socket buffer size:
> >     8388608, set by using sysctl -w net.core.rmem_default and rmem_max
> >
> > I used ethereal(using libpcap) to monitor the network traffic. All the
> > packets were transferred and captured by libpcap. But my program 
> constantly
> > suffers from packet loss. According to ethereal, the average time 
> interval
> > between 2 packets  is 70-80ms, and the minimum interval can go down to
> > ~1ms. Each packet is smaller than 1500 bytes (ethernet MTU).
> >
> > Can anybody help me? I googled and found a similar case that had been
> > solved by increasing the socket buffer size. But it doesn't work for me. 
> I
> > think 8M is a crazily large size :(
>
> Post a small program demonstrating your problem.
> (I'd test udp receive with netcat too)
> --
> vda

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