IPv6 address 28 bytes length???

Max

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Dec 18, 2003, 6:37:38 AM12/18/03

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My task is to get all ip addresses of all interfaces on
local computer

I'm using GetAdaptersAddresses functions and I've got as
a result unicast addresses not only 16 bytes long, but
also 28 bytes long!!!

Some results:
Automatic Tunneling Pseudo-Interface
17.0.0.0.0.0.0.0.FE.80.0.0.0.0.0.0.0.0.5E.FE.C0.A8.0.4.2.0
.0.0
Loopback Pseudo-Interface
17.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.0.0.0.0 -
this is ::1 but with prefixes and posfixes!!!

Flag GAA_FLAG_INCLUDE_PREFIX not set. How to extract real
address? How can I determine how long prefix and postfix
are?

Also I've got some problems, while getting IPv4 addresses
via the same function - it looks like
2.0.0.0.C0.A8.0.4.0.0.0.0.0.0.0.0. My IPv4 address is
inside that IPv6 address. Is positions of v4 address
inside v6 address fixed?

Bob Bradley

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Dec 18, 2003, 7:30:24 PM12/18/03

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In article <060301c3c55b$56e415b0$a401...@phx.gbl>,
"Max" <anon...@discussions.microsoft.com> wrote:

> I'm using GetAdaptersAddresses functions and I've got as
> a result unicast addresses not only 16 bytes long, but
> also 28 bytes long!!!

The address that is returned is a sockaddr variant, not a raw IP
address. 28 bytes is the size of the entire sockaddr_in6, but to get
just the address you need to look at sockaddr_in6.sin6_addr.

When you are iterating through the addresses in the IP_ADAPTER_ADDRESSES
structure (e.g. starting with IP_ADAPTER_ADDRESSES.FirstUnicastAddress),
you should look at SOCKADDR->lpSockAddr->sa_family and if it is
AF_INET6, then cast the pointer as a sockaddr_in6 * and access the
IPv6-specific fields that way (similarly with sockaddr_in * for AF_INET).

> Also I've got some problems, while getting IPv4 addresses
> via the same function - it looks like
> 2.0.0.0.C0.A8.0.4.0.0.0.0.0.0.0.0. My IPv4 address is
> inside that IPv6 address. Is positions of v4 address
> inside v6 address fixed?

You may be seeing an IPv4-mapped IPv6 address. For example, the
Automatic Tunneling Pseudo-Interface on my machine reports an
IPv4-mapped IPv6 address (e.g. fe80:5efe:1.2.3.4%2).

Morozov Max

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Dec 19, 2003, 5:25:28 AM12/19/03

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> When you are iterating through the addresses in the IP_ADAPTER_ADDRESSES
> structure (e.g. starting with IP_ADAPTER_ADDRESSES.FirstUnicastAddress),
> you should look at SOCKADDR->lpSockAddr->sa_family and if it is
> AF_INET6, then cast the pointer as a sockaddr_in6 * and access the
> IPv6-specific fields that way (similarly with sockaddr_in * for AF_INET).

Great!!! Big thanx :))))

Morozov Max

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Dec 19, 2003, 6:16:51 AM12/19/03

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> Also I've got some problems, while getting IPv4 addresses
> via the same function - it looks like
> 2.0.0.0.C0.A8.0.4.0.0.0.0.0.0.0.0. My IPv4 address is
> inside that IPv6 address. Is positions of v4 address
> inside v6 address fixed?

According to Bob Bradley's answer, this byte array must be converted into
sockaddr_in structure and we'll got:
sin_family=2 (AF_INET)
sin_port=0
sin_addr=/*192.168.0.4*/
sin_zero={0,...0}

Addresses returned by GetAdaptersAddresses are sockaddr structures of
WinSock

Big thanx to Bob Bradley!!