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Possible fix for duplicated ARP entries in the FreeBSD stack
- From: Sturle Mastberg <sturle dot mastberg at tandberg dot net>
- To: ecos-discuss at sources dot redhat dot com
- Date: Fri, 17 Jun 2005 10:52:00 +0200
- Subject: [ECOS] Possible fix for duplicated ARP entries in the FreeBSD stack
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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