IPv4-mapped IPv6 addresses

[Julio Baixauli]

Julio Baixauli wrote:
> 
>         Hello!
> 
>         I need an explanation about IPv4-mapped addresses...
> 
>         I'm programming a client application for test purposes. Basically, I
> open a socket and connect that socket to an IPv6 address. Next, I read
> characters from that socket.
> 
>         There is no problems when I try to connect to global-scope addresses,
> like 3ffe:XXXXXXXXXX. In this cases I can connect.
>         The problem comes when I try to connect to IPv4-mapped addresses. In
> this cases connect returns 'no route to host' or 'network is
> unreachable'. This is false!! because I add a route to IPv4-mapped
> addresses, and when I ping these addresses I can see, at least, ICMP
> Neighbor Solicitation, for the gateway, on the net.
> 
>         So... what's failing?
>         Do kernel any diferences between raw-sockets (ping) and stream-sockets
> (tcp)?
>         Are there any implications with IPv4-mapped addresses?
>         I've no idea about what happens...
> 
>         Thank you very much, and I'm sorry for my horrible english.


	I've discovered that when I try to connect to IPv4-mapped addresses the
kernel traduces these addresses to the corresponding IPv4 address, and
the results are like we should working in IPv4.
	This seems not wrong, because IPv4-mapped addresses represents
IPv4-only nodes, but what happens in SIIT environment? This algorithm
says that IPv6-only nodes have to use IPv4-mapped addresses to
comunicate with a SIIT translator, which should traduce the packets to
IPv4.
	Implies this that dual nodes can't use SIIT translator to comunicate to
IPv4-only nodes? Are there any form to specify the way to handle IPv6
packets with IPv4-mapped destination address for dual nodes?

	Anybody can see any light at the end of the tunnel?

	Thank you very much!!

-- 
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	Julio Baixauli Garreta
	baixauli@mat.upc.es

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