[olsr-dev] questions on olsrd IPC protocol

[Andreas Tønnesen]

Yes there seems to be something supsicious going on there. But the
whole IPC scheme is not maintained any longer as it is about to be
replaced. The whole IPC/GUI code is pretty awfull and was initially
just a hack to have something GUIihs to show non-tech people ;)
For a front-end the httpinfo plugin is recomended for now.

- Andreas

Yuri Karaban wrote:
> Hello
> 
> I'm learning olsrd IPC protocol and found some inconsistency (or most
> probably I missed something).
> 
> (I'm talking about olsrd distribution version 0.4.9)
> 
> In linux-gtk/src/ipc.c in function `ipc_read', line 176:
> 
> Packet length checked with the following expression:
> 
> <code>
>               while(ntohs(msg->v4.olsr_msgsize) < bytes)
>                 {
>                   ipc_evaluate_message(msg);
> </code>
> 
> 
> And passed to `ipc_evaluate_message'.
> 
> In `ipc_evaluate_message', `union olsr_message *' can be casted to
> `struct routemsg *' (line 321) or `struct netmsg *' (line 326).
> 
> If compare `union olsr_message' with `struct routemsg' or `struct
> netmsg' possible to notice that `message size' member located on different offsets:
> 
> struct olsrmsg
> {
>   olsr_u8_t     olsr_msgtype;
>   olsr_u8_t     olsr_vtime;
>   olsr_u16_t    olsr_msgsize;
> ...
> };
> 
> struct netmsg
> {
>   olsr_u8_t      msgtype;
>   olsr_u16_t     size;
> ...
> };
> 
> struct routemsg 
> {
>   olsr_u8_t      msgtype;
>   olsr_u16_t     size;
> ...
> };
> 
> In `struct olsrmsg` (which is the member of `union olsr_message`) size
> memeber is located on base + 2, and in `struct netmsg' and `struct
> routemsg' it located at base + 1. (This offsets are valid for packed
> structure).
> 
> linux-gtk gui works, I can suppouse because not specified that
> structure is packed gcc align uint16_t members on 2 byte boundary. But
> it is fortunity and it is not good to rely on it.
> 
> Please explain me where I can mistake or if I right please make more
> determinate specifications of this strucures (with __attribute__
> ((packed)) for gcc). And insert dummy one byte wide filler before
> `size' member in `netmsg' and `routemsg' structures.
> 
> PS. Please CC me your questions. Because I'm not subscriber and can
> only to watch archives of mailinglist.
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-- 
Andreas Tønnesen
http://www.olsr.org