Support get signal sender pid in signal::recv

[taikulawo]

Is your feature request related to a problem? Please describe.
We want to know signal sender pid to do some logic.

Describe the solution you'd like
https://docs.rs/tokio/latest/tokio/signal/unix/struct.Signal.html#method.recv
change signature from

pub async fn recv(&mut self) -> Option<()>{}

to

pub async fn recv(&mut self) -> Option<SignalInfo>{}

SigInfo should have kernel siginfo_t##_pid
https://elixir.bootlin.com/linux/v6.13.1/source/include/uapi/asm-generic/siginfo.h#L40
Additional context
https://stackoverflow.com/questions/11508427/linux-c-upon-receiving-a-signal-is-it-possible-to-know-the-pid-of-the-sender

[Darksonn]

cc @ipetkov

[ipetkov]

This would unfortunately require a breaking change, with the alternative being to introduce a new method to return the signal itself.

Though FWIW a signal handler will always fire on the signal it was registered with (and this cannot be changed after the fact), so the caller can always add their own wrapper to return the originally-registered-signal as a workaround

[Darksonn]

Yes, a new API would probably be required.

Though FWIW a signal handler will always fire on the signal it was registered with (and this cannot be changed after the fact), so the caller can always add their own wrapper to return the originally-registered-signal as a workaround

Isn't this about getting the pid that sent the signal, rather than which signal it is?

[hamidrezakp]

I'd like to implement this feature.
How would you like the API to look like? because the origin pid is not available in all signals.

One way is to return a SignalInfo struct with optional fields and also provide the raw siginfo_t struct as an unsafe ptr for other uses.

pub async fn recv(&mut self) -> Option<SignalInfo>

struct SignalInfo {
    raw: *const siginfo_t,
    pub origin: Option<SignalOrigin>
}

enum SignalOrigin {
    Kernel
    Process(pid)
}

impl SignalInfo {
    pub unsafe fn raw_ptr(&self) -> *const libc::siginfo_t
}