On Feb 9, 2012, at 5:05 AM, David Laight wrote:
> There is a report on one of the netbsd lists (might have
> been a developer-only list) that tcpdump (etc) aren't
> working on 64bit netbsd platforms.
>
> IIRC it had something to do with 'struct timeval' and friends.
>
> I'm not sure of the full details but it might be related to:
> 1) NetBSD recently changing from 32bit to 64bit time_t.
> 2) 'struct timeval' being 48bits for i386 but 64bits for amd64,
> and someone trying to run the 32bit pcap code on a 64bit system.
From a quick look at the top-of-trunk bpf.c and bpf.h:
$ ident bpf.[ch]
bpf.c:
$NetBSD: bpf.c,v 1.168 2011/12/16 03:05:23 christos Exp $
$NetBSD: bpf.c,v 1.168 2011/12/16 03:05:23 christos Exp $
bpf.h:
$NetBSD: bpf.h,v 1.58 2011/08/30 14:22:22 bouyer Exp $
it looks as if the BPF driver attempts to provide 32-bit-compatible bufferfuls
of packets to 32-bit processes.
*However*, that's not the only place where structures involving times get
passed between the kernel and userland. They *also* get passed in the
BIOCGRTIMEOUT and BIOCSRTIMEOUT ioctls, the argument to which is a pointer to a
struct timeval. This being a BSD-flavored OS, the ioctl cookie includes the
size of the structure, so an ioctl with a 32-bit struct timeval will have a
different ioctl cookie from an ioctl with a 64-bit struct timeval.
>From a quick look at the top of the trunk, _BSD_TIME_T_ is always defined as
>__int64_t and _BSD_SUSECONDS_T_ is always defined as int, so struct timeval
>would, *modulo padding at the end* (I presume that's the "48bits for i386 and
>64bits for amd64" - presumably meaning "48 bits for 32-bit platforms and 64
>bits for 64-bit platforms"), be laid out the same, so that should work as well.
As for pcap files, the time stamp in them is defined to have a 32-bit
time-in-seconds value, which will just get padded out to 64 bits when reading
and chopped to the lower 32 bits when writing on a system with a 64-bit
time-in-seconds type, so that should work as well.
So there's not much I can do here without more details about the exact problem,
including, for example, whether somebody's running binaries built on a NetBSD
system with a 32-bit time_t on a NetBSD system with a 64-bit time_t.-
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