On Thu, 22 Jun 2006, Wes Hardaker wrote:
It's not that simple, I'm afraid. Much of the time it's also how the
structures used by the kernel store them. I'm pretty sure that some
systems are storing them in host order and others in network order,
which means you sometimes need to apply htonl and other times you
don't. That's what's truly broken.
But you're right, we should have a policy about how things are stored.
I say host-order. Or maybe network.
We had this discussion in October 2005, thread was named "Endian - ness
issue". I just wish to repeat the recommendation I made at that time:
The policy should be to store IPv4 address as u_char[4].
Forget about host-order vs network-order. Both are artifacts of the
misbegotten idea about storing IPv4 address as integer. An IPv4 address
is a sequence of 4 unsigned bytes: store it as such and you will localize
the ordering problems to the (very few) places where you have to interact
with interfaces that use this misbegotten representation. One of these,
unfortunately, is the classic socket interface; as this is a widely
known interface it has unfortunately added to the misconception that
this is "how the kernel store them". It isn't: it is just "how the
kernel present them through the socket interface".
Coding details and further arguments of my recommendation can be found in
the mail archive.
(Actually, in the deepest analysis, because of the way IP routing works,
an IPv4 address is best described as a sequence of 32 bits - but there
seems be a consensus among processor vendors about which bits are first in
a byte, so the "sequence of bytes" model does not introduce coding
problems, as does the "integer" model).
best regards
--
Peder Chr. Nørgaard Senior System Developer, M. Sc.
Ericsson Denmark A/S, Telebit Division
Skanderborgvej 232 tel: +45 30 91 84 31
DK-8260 Viby J, Denmark fax: +45 89 38 51 01
e-mail: [EMAIL PROTECTED]
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