On Sun, Jan 15, 2006 at 12:50:38PM +0100, Willem de Bruijn ([EMAIL PROTECTED])
wrote:
> > I wonder if can anybody can say what is the advantages/disadvantages
> > of the linux networking kernel layer comapred to STREAMS network layer
> > (of Solaris for examples).
>
> hi John,
>
> I'll take a stab at this question, since I'm working on a stream-like
> framework in/op top of Linux anyway. First of all, though, to everyone else:
> hi. I don't normally post here because I don't develop mainline kernel code,
> instead I write code for a network project outside the kerneltree. If this
> question doesn't belong on this list let me know, we can take it offline.
>
> First some background info: the original STREAMS by Dennis Ritchie stacks
> processing elements in the kernel. More recent derivates are Click and
> ScoutOS. You can find a Linux port of the last online, search for 'Scout in
> the Linux Kernel', aka SILK.
>
> The major architectural difference between streamlike architectures and
> functional architectures (like the Linux kernel) is that in the first paths
> are transient while in the latter they're hardcoded (as functions). You can
> setup a streams environment in general by calling
>
> create_processor("ip"),
> create_processor("tcp"),
> link_processors("ip", "tcp")
>
> In functional methods, on the other hand, you have to know the exact function
> name to call at compile time, i.e.:
>
> int tcp(char * pkt, int plen){
> if (!ip(pkt, plen))
> return -1;
> //[... process tcp stuff ..]
> return 0;
> }
Just for clarification.
Linux networking code never calls such hardcoded methods.
It always does following [very roughly]:
sys_send() -> sock_sendmsg() -> sock->ops->sendmsg()
[for example it can be pointer to inet_sendmsg() ], which in turn calls
sk->sk_prot->sendmsg() which for example could be a pointer to
tcp_sendmsg().
So you already have above create_processor... , it is transformed
into inet_register_protosw(SOCK_STREAM, IPPROTO_TCP) and so on...
Concider also dst_output()/dst_input() stackable technique which is
widely used in Linux networking code which makes it so flexible.
--
Evgeniy Polyakov
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