Is it possible to split tunnel using system extensions based NE Transparent Proxy in Catalina?

So I call BSD

bind

to Wifi address,

connect

to IP1, then transfer data between flow and the new connection (via Wifi). Is it possbile to do it in this way?

I can’t see why not. Apple’s networking stack supports scoped routing, so if a connection is bound to a specific interface then its traffic will run over that interface. Did you try this? What happened?

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—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"

Yes. I did try it. But connect() API call failed.

I set IP1 to NETransparentProxyNetworkSettings.includedNetworkRules, then set network setting using [MYNEAppProxyProvider setTunnelNetworkSettings] method, so in [MyNEAppProxyProvider handleNewFlow:flow] I can get the flow connecting to IP1. The bind() to Wifi address success, however, connect() to IP1 failure immedaitely with error 49 which is EADDRNOTAVAIL (Can't assign requested address). I tried call [flow openWithLocalEndpoint:IP1Address completionHandler:^(){NSError *error}] before establishing new connection via Wifi, [flow openWithLocalEndpoint] is success, but connect() failed with same error. If I didn't call bind() before connect(), then the connection will go through LAN instead of Wifi I think because LAN is primaryInterface.

I have a couple of things you might try:

• Rather than binding to the interface’s source address, trying binding to the interface directly, that is, using

  IP_BOUND_IF

  .

• You wrote:

I set IP1 to

NETransparentProxyNetworkSettings.includedNetworkRules

Just for the sake of experiment, try catching this connection via other means. For example, use a rule that matches a wildcard address and the destination port. Does the

bind

connect

Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"

IP_BOUND_IF works! Thank you so much!