Add IAN-based TunnelPinger, refactoring the pinger protocol accordingly.

[acb-mv]

This depends on the IAN changes to wireguard-apple, and implements a Pinger named TunnelPinger which uses the tunnel's WireGuard-based ICMP ECHO capabilities to send and receive pings. The Pinger protocol has been modified, moving the address to the setup phase in accordance with how WireGuard ICMP sockets like it.

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This change is 

[linear]

IOS-753 Create tunnel-based implementation of Pinger

[buggmagnet]

The tests don't compile, please make sure that they do and fix them

Reviewable status: 0 of 10 files reviewed, 5 unresolved discussions (waiting on @acb-mv)

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ios/PacketTunnelCore/Pinger/TunnelPinger.swift line 35 at r1 (raw file):

    }

    var socketHandle: Int32?

This doesn't seem to be used, let's delete it

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ios/PacketTunnelCore/Pinger/TunnelPinger.swift line 37 at r1 (raw file):

    var socketHandle: Int32?

    var pingProvider: ICMPPingProvider

private

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ios/PacketTunnelCore/Pinger/TunnelPinger.swift line 47 at r1 (raw file):

        self.logger = Logger(label: "TunnelPinger")
    }
    

Please make sure to run swiftformat

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ios/PacketTunnelCore/Pinger/TunnelPinger.swift line 79 at r1 (raw file):

            replyQueue.async { [weak self] in
                guard let self else { return }
                // NOTE: we cheat here by returning the destination address we were passed, rather than parsing it from the packet on the other side of the FFI boundary.

This comment doesn't seem to make too much sense here, we should probably move it to the reply = .success part

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ios/PacketTunnelCoreTests/Mocks/PingerMock.swift line 99 at r1 (raw file):

        var isSocketOpen = false
        var onReply: ((PingerReply) -> Void)?
        var destAddress: IPv4Address? = nil

nil assignment is redundant here

[acb-mv]

Reviewable status: 0 of 10 files reviewed, 5 unresolved discussions (waiting on @buggmagnet)

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ios/PacketTunnelCore/Pinger/TunnelPinger.swift line 35 at r1 (raw file):

Previously, buggmagnet wrote…

This doesn't seem to be used, let's delete it

Done.

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ios/PacketTunnelCore/Pinger/TunnelPinger.swift line 37 at r1 (raw file):

Previously, buggmagnet wrote…

private

Done.

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ios/PacketTunnelCore/Pinger/TunnelPinger.swift line 47 at r1 (raw file):

Previously, buggmagnet wrote…

Please make sure to run swiftformat

Done.

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ios/PacketTunnelCore/Pinger/TunnelPinger.swift line 79 at r1 (raw file):

Previously, buggmagnet wrote…

This comment doesn't seem to make too much sense here, we should probably move it to the reply = .success part

Done.

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ios/PacketTunnelCoreTests/Mocks/PingerMock.swift line 99 at r1 (raw file):

Previously, buggmagnet wrote…

nil assignment is redundant here

Done.

[buggmagnet]

Reviewed 4 of 10 files at r1, 4 of 6 files at r2.
Reviewable status: 7 of 11 files reviewed, 1 unresolved discussion

[github-actions]

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