feat(dns): enhance dns hijack with fake IP enabled

[ibigbug]

🤔 This is a ...

• New feature
• Bug fix
• Performance optimization
• Enhancement feature
• Refactoring
• Code style optimization
• Test Case
• Branch merge
• Workflow
• Other (about what?)

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[Itsusinn]

@Watfaq/clash-rs-devs
There is actually another solution for global states (axum is using something similiar).

Define a struct named AppConext where we store states that maybe global
And a static var for global useage

struct AppConext {
    mark: u64
    name: String
    tun: tunState
}
static GLOBAL_CONTEXT: ArcSwapOption<AppConext> = todo!()
// or ...
static GLOBAL_CONTEXT: RwLock<AppConext> = todo!()

// if we want more fine-grained lock
struct AppConext {
    mark: AtomicU64
    name: ArcSwap<String>
    other: RwLock<AnotherState>
}
static GLOBAL_CONTEXT: Lazy<AppConext> = todo!()

Where we use global states:

fn apply_socket_opts(){
    apply_socket_opts_with_ctx(GLOBAL_CONTEXT.get())
}
fn apply_socket_opts_with_ctx(ctx: AppContext){
    todo!()
}

when we use *_with_ctx funtcions ?

• a. when define another with_ctx function

fn bind_interface(){
    bind_interface_with_ctx(GLOBAL_CONTEXT.get())
}
fn bind_interface_with_ctx(ctx: AppContext){
    todo!()
}
// we must caller's Context

• b. when we writing parallel tests

#[test]
fn test_1(){
    GLOBAL_CONTEXT.init(AppConext { mark:41 })
    apply_socket_opts()
}
#[test]
fn test_2(){
    GLOBAL_CONTEXT.init(AppConext { mark:34 })
    apply_socket_opts()
}
// that may cause
// 1. panic due to multi init if we use lazy
// 2. actual GLOBAL_CONTEXT not clear, `mark` maybe 34 in test_1 or 41 in test_2


#[test]
fn test_1(){
    let ctx = AppConext { mark:41 }
    apply_socket_opts_with_ctx(ctx)
}
#[test]
fn test_2(){
    let ctx = AppConext { mark:34 }
    apply_socket_opts_with_ctx(ctx)
}

when we use funtcions without _with_ctx ?

Actually saying... I dont know, we could pass ctx everywhere

fn main(){
    let ctx = AppContext {
        ..
    }
    func_1_ctx(ctx);
    func_2_ctx(ctx);
}
fn func_1_with_ctx(ctx:Context){
}
fn func_2_with_ctx(ctx:Context){
}

or we dont use ctx only in top-level?

fn main(){
    let ctx = AppContext {
        ..
    }
    GLOBAL_CONTEXT.init(ctx);
    func_1();
    func_2();
}

[ibigbug]

Sure. That's def a more elegant solution.

There's probably some issues with the current tun udp handling concurrent reqs that I'm still trying to figure out.

[Itsusinn]

There's probably some issues with the current tun udp handling concurrent reqs that I'm still trying to figure out.

TUN UDP + FAKE-IP + DNS hijack ?

[ibigbug]

Likely. Haven't test other scenarios tho.

[Itsusinn]

On android TUN + dns-hijack works well (master branch). It might be route problems?

[ibigbug]

I'll make another PR to apply the global state refactor

[Itsusinn]

I'll make another PR to apply the global state refactor

I think we can just pass context everywhere

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