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

[Sturle Mastberg <sturle.mastberg@tandberg.net>]

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?

Regards,
SM

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