in-kernel tcp server

[John Polstra]

Julian Elischer wrote:
> Nicolas Cormier wrote:
>> Hi,
>>
>> I'm trying to write a little tcp-server kernel module (like tftp).
>> I didn't find a lot of documents about the kernel network programming,
>> just one thread which talks about netgraph.
>> In the freebsd includes I found /usr/include/sys/socketvar.h (so*).
>>
>> What's the easy way to create a basic tcp server
>> (create/bind/listen/accept/send/recv) : use netgraph's ksocket or so*
>> ?
>>
>> Thanks in advance !
>> PS: the whole job must be done in the kernel.
> 
> 
> 
> yes it can (and has been) done..
> John Polstra did it many years ago.. using netgraph ksockets.
> He had an in-kernel web server.
> At least I THINK it was him :-)

Yes, that's right.  I started out using netgraph ksockets, but later on 
it evolved, mainly for performance reasons.  (I needed it to be really, 
really fast.)  The first change was that I eliminated the ksockets and 
worked directly at the link layer, using ng_ether nodes.  I implemented 
a small, stripped down TCP stack and bypassed the FreeBSD native 
TCP/IP/socket layers.  This was still done with netgraph, using just the 
ng_ether nodes talking to my own ng_webclient / ng_webserver nodes.  It 
improved the performance immensely.

More recently I restructured it quite a bit to get better MP performance 
using FreeBSD 7.x.  (The original version was based on 4.x).  I found 
that the netgraph locking and internode communication mechanism impacted 
performance too much under 7.x.  So I eliminated the ng_ether nodes and 
made the webserver / webclient nodes talk directly to the interfaces via 
the if_input / if_output hooks.  It still uses netgraph, but really only 
as a configuration and management mechanism.  No actual network traffic 
flows between netgraph nodes.  This change also resulted in a big 
performance improvement.

Unfortunately, my contract forbids me to release the source code publicly.

John