Re: [ECOS] Possible fix for duplicated ARP entries in the FreeBSD stack

[Gary Thomas <gary@mlbassoc.com>]

On Fri, 2005-06-17 at 10:52 +0200, Sturle Mastberg wrote:
> Hello,
> 
> For some time I've had problem with duplicated ARP entries that have 
> caused all sorts of problems. I searched the archive and discovered that 
> the problem had been reported before:
>  
> 
> http://sourceware.org/ml/ecos-discuss/2004-11/msg00097.html
>  
> 
> My proposal to a fix is to make the sockaddr_inarp struct 
> (include/netinet/if_ether.h) equal in size to the sockaddr struct by 
> padding it at the end. This is exactly what is done to the sockaddr_in 
> struct (include/netinet/in.h) for different reasons.
>  
> 
> I reached this conclusion after I discovered that two virutally 
> identical calls to rtalloc1 (net/route.c) returned different results. 
> The first instance appears in arplookup (netinet/if_ether.c) where the 
> first parameter to rtalloc1 is a struct sockaddr_inarp cast to a struct 
> sockaddr. The second instance appears in ip_output (netinet/ip_output) 
> via rtalloc_ign (net/route.c) where the first parameter to rtalloc1 is 
> an actual struct sockaddr. The rtalloc1 function does a radix tree 
> search with a call to the rn_match function (net/radix.c). A closer look 
> at this code reveals that it does indeed depend on the size of the 
> supplied struct.
>  
> 
> The only conclusion a can draw from this is that the three structs: 
> sockaddr, sockaddr_in and sockaddr_inarp must all be of equal size. I 
> have checked the FreeBSD source repository that this is the case for the 
> original code.
>  
> 
> While browsing the FreeBSD source repository I discovered that the 
> sa_data character array member of the sockaddr struct was increased in 
> size in the eCos FreeBSD stack. Does anyone know why this increase was 
> introduced in eCos?

Can you provide the details of what you found?  i.e. exactly how
these structures were modified during the port?  [more likely, you're
looking at a newer version of the FreeBSD code than I used and the 
changes happened in the BSD codebase]  In any case, then we can analyze
how things are different and what might need to be done.

Thanks


-- 
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Gary Thomas                 |  Consulting for the
MLB Associates              |    Embedded world
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