[openbeosnetteam] Re: Network stack question
- From: Ivo Vachkov <ivo@xxxxxxxxxxx>
- To: openbeosnetteam@xxxxxxxxxxxxx
- Date: Tue, 10 Jul 2007 13:41:02 +0300
Axel Dörfler wrote:
Looking at the BONE headers, there are the following two functions in
what would be net_protocol_module_info in our stack (and I copied them
into our's, too):
/*
* interface for error codes (ICMP, etc) to be passed back to
protocols
* from the network layer
*/
status_t (*error)(int32 error_code, bone_data_t *error_data);
/*
* interface for error replies (ICMP, etc) to be sent from
protocols
* to other sites. Error codes can be passed, or a data ptr and
length
* may be passed. If error_data is non-0 error_code will be
assumed to
* be a length, otherwise a code.
*/
status_t (*error_reply)(struct bone_proto_node *you, bone_data_t *
caused_error, uint32 error_code, void *error_data);
I'd propose that the ICMPv4 module will call error() on the domain
protocol (which we could rename to receive_error(), as it's pretty
similar to what receive_data() does) if it doesn't handle the packet
itself (ie. like echo).
Then, IPv4 will either handle the error itself, or pass it on to the
protocols, just like it would do in receive_data() - but of course it
will also call the protocol's receive_error() method.
On the sending side of things, ICMP should register itself as the error
handling protocol for the domain (via new stack methods to do that). I
am not yet sure how to go from there - probably, there has to be a
stack function send_error() that gets the protocol module as well as
the data as error_reply() above, and will then call the error handler
(ie. ICMPv4) to build a reply buffer then is then pushed down the stack
using error_reply() - which I would then rename to send_error() as
well. It will probably also need to know where to send the error to -
either from the error-causing buffer, or from some route that the
stack's send_error() would then also need to get.
I am a bit confused. So I'll try to explain my understanding of the
following like this:
1. Handling Received ICMP info/error messages:
in IP module:
- we see it's an ICMP packet
- we send it to icmp receive_data()
in ICMP module:
- we check if we can deal with that packet
- if we can deal - we handle it appropriately (like
echo/timestamp/information replies)
- if we can not:
- set a module pointer to the appropriate protocol module
- call module->error();
2. Generating/Sending ICMP error messages:
in IP module:
- module->receive_data() returns error
- we call module->error_reply()
in module->error_reply():
- set a pointer to the icmp protocol module
- call icmp_module->error_reply()
Is this the proper way ? Am I missing something ?
/ipv
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