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

[Andrew Lunn <andrew at lunn dot ch>]

On Fri, Jun 17, 2005 at 12:57:49PM +0200, Sturle Mastberg wrote:
> Gary Thomas wrote:
> >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?

I beleave Nick did this for IPv6. This bigger size allows an IPv6
address to be placed into a sockaddr which you cannot normally do.

        Andrew

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