Re: [tcpdump] Truncated strings

[Francois-Xavier Le Bail <devel.fx.lebail () orange fr>]

On 21/08/2018 17:21, Denis Ovsienko wrote:
> (moving this to tcpdump-workers)
>
>  ---- On Tue, 08 May 2018 14:41:13 +0100 Francois-Xavier Le Bail <devel.fx.lebail () orange fr> wrote ---- 
>  > e.g.: 
>  > proto1_print(...) 
>  > { 
>  >   ndo->ndo_protocol = "proto1"; 
>  >   ... 
>  >   proto2_print(...); 
>  >   ... 
>  > } 
>  >  
>  > proto2_print(...) 
>  > { 
>  >   ndo->ndo_protocol = "proto2"; 
>  >   ... 
>  > } 
>  >  
>  > If proto2_print, a "final protocol" (don't call another function with ndo_protocol assignment), need 
>  > to print truncated string with/without longjmp process: no problem. 
>  >  
>  > If no truncated case occurs in proto2_print, after return, the proto1_print function take the 
>  > control and if truncated case occurs in proto1_print it will print "[|proto2]". 
>  >  
>  > Thus after all calls of function with ndo_protocol assignment, we will need a ndo_protocol re-assign 
>  > like: 
>  >  
>  > proto1_print(...) 
>  > { 
>  >   ndo->ndo_protocol = "proto1"; 
>  >   ... 
>  >   proto2_print(...); 
>  >   ndo->ndo_protocol = "proto1"; 
>  >   ... 
>  > } 
>  >  
>  > It can bring errors (forgetting...). 
>  >  
>  > Could we do things differently ? 
>
> With things done this way it looks like this issue could happen, although it would result in incorrect labeling, not 
> incorrect behaviour.
>
> A possible solution could be some stack structure and a macro to call the next function, which macro would take care 
> to update the stack before and after the function call. But to me such a solution looks more complicated than the 
> problem, I would rather proof-read the source code once and leave it to work.

Agreed. Some ndo_protocol reassignment already done in 6daf3a54 and d8802934.
Perhaps more to do. I will have a look.
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