From owner-freebsd-hackers  Fri May 18  8:43:54 2001
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From: Archie Cobbs <archie@dellroad.org>
Message-Id: <200105181541.f4IFfoq79682@arch20m.dellroad.org>
Subject: Re: How to transfer data from netgraph node to user program?
In-Reply-To: <Pine.SOL.4.33.0105181351210.6629-100000@abyss.unshadow.net>
 "from Roman V. Palagin at May 18, 2001 02:15:13 pm"
To: "Roman V. Palagin" <romanp@unshadow.net>
Date: Fri, 18 May 2001 08:41:50 -0700 (PDT)
Cc: freebsd-hackers@freebsd.org
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Roman V. Palagin writes:
> When size of collected data about 10Kb, all works fine. But when I need to
> send 400Kb in reply - oops, ng_xxx_show_data() returns ENOBUFS (I think
> because ng_socket receive queue is full, nobody reads from socket). So, I
> don't understand how I can transfer large amount of data :-\ Any ideas?

FreeBSD 4.x will not allow a context switch from within the kernel.
Therefore, it is possible to overflow a socket if you keep adding
data to it without leaving the kernel... because the user process
never gets a chance to read the data.

Maybe you can set a short timeout in your node after writing a
certain amount of data, return, and then write some more when
the timer goes off.

-Archie

__________________________________________________________________________
Archie Cobbs     *     Packet Design     *     http://www.packetdesign.com

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