"Chris Zhang" <[EMAIL PROTECTED]> writes:
As Alex asked, your problem description is unclear. Since I have some
different questions to what he asked, and you answered, I include them:
> Suppose I have two NICs on one host, NIC A and NIC B. Is it possible
> to get all traffic to use A,
When you say "to use A", what specifically do you mean:
* to use the IP address that you assigned to NIC A[1]
* to leave the computer and hit the wire out NIC A
* something else?
> and then route them through B,
My best guess here is that you expect the packet to:
1. Exit to the wire via NIC A
2. Return to the host via NIC B
3. Exit to the outside world via some unmentioned, third, interface
Is that correct?
> and finally to outside? without the aid of iptables or anything
> similar, e.g. just changing the routing table? Suppose ip forwarding
> works.
Why the restriction?
Is this, specifically, because you want to achieve some VoIP and
tunnelling related goal with the iPhone, and it only provides a standard
routing stack?
I ask, because the Linux IP stack is extremely flexible and can do a
wide range of things that a more traditional BSD stack, well, can't.
Anyway, assuming that my best guess is, in fact, correct -- which
I think it probably is from the iPhone bit below -- then, no.
What you are asking is impossible without the addition of NAT, packet
marking, or some other method to identify the packet beyond what you get
in the standard facility.
The routing table doesn't include a lot of "if" for an individual
packet, and retains no state -- you can't say "if this is the second
time I have seen ..."
> Just out of curiosity, does anyone know how iPhone restricts VOIP
> traffic over 3G technically?
It is done for profit, and by the request of customers. (The real
customers, the telecoms companies, not you and the other end users who
hold the physical device...)
> Suppose one can make a tunnel, e.g. IPSec, PPTP (which iPhone has
> native support), to a VPN endpoint, e.g. home computer through
> 3G. Is it possible to then run a VOIP app inside the tunnel?
Not if Apple and their customers have any say in the matter, no. Not
reliably, in the long term, because it some something other than what
Apple have approved of your doing with their iPhone.[2]
Regards,
Daniel
Footnotes:
[1] ...which, under Linux, is actually a property of the computer, not
the network card, and is equally valid as an outbound address for
any interface, technically speaking.
[2] Since you don't actually have any particular control of the device
I wouldn't really call you the owner of it. You may have paid for
it, but Apple still run the show...
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