FreeLists / openbeosnetteam / [openbeosnetteam] Re: Network stack question

[Ivo Vachkov <ivo@xxxxxxxxxxx>]

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