Ancillary data and 32/64 bit processes
Ancillary data and 32/64 bit processes
- Subject: Ancillary data and 32/64 bit processes
- From: Michael Tuexen <email@hidden>
- Date: Sun, 3 Feb 2008 20:15:34 +0100
Dear all,
I habe a problem using ancillary data on 64-bit processes...
The macro CMSG_DATA ist defined in /usr/include/sys/socket.h as
#define CMSG_DATA(cmsg) ((unsigned char *)(cmsg) + \
__DARWIN_ALIGN(sizeof(struct
cmsghdr)))
__DARWIN_ALIGN behaves different on 32-bit processes and 64-bit
processes.
Therefore the offset of the CMSG_DATA is 12 bytes on 32-bit processes
and 16 byte on 64-bit processes. However, the kernel ignores this
difference
and puts the CMSG_DATA at a 12 byte offset.
Therefore programs using ancillary data work, when compiled for 32-bit,
but do not work when compiled for 64-bit.
I can provide a simple UDP discard server which shows this bug.
Is this a known bug? Should it be fixed by changing the CMSG_DATA
macros to behave the same on 32-bit and 64-bit processes or should
the kernel be changed to adjust the ancillary data?
This problem is crucial for our SCTP NKE, which uses ancillary
data a lot...
Best regards
Michael
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