netstack

type Impl struct {
	// GetTCPHandlerForFlow conditionally handles an incoming TCP flow for the
	// provided (src/port, dst/port) 4-tuple.
	//
	// A nil value is equivalent to a func returning (nil, false).
	//
	// If func returns intercept=false, the default forwarding behavior (if
	// ProcessLocalIPs and/or ProcesssSubnetIPs) takes place.
	//
	// When intercept=true, the behavior depends on whether the returned handler
	// is non-nil: if nil, the connection is rejected. If non-nil, handler takes
	// over the TCP conn.
	GetTCPHandlerForFlow func(src, dst netip.AddrPort) (handler func(net.Conn), intercept bool)

	// GetUDPHandlerForFlow conditionally handles an incoming UDP flow for the
	// provided (src/port, dst/port) 4-tuple.
	//
	// A nil value is equivalent to a func returning (nil, false).
	//
	// If func returns intercept=false, the default forwarding behavior (if
	// ProcessLocalIPs and/or ProcesssSubnetIPs) takes place.
	//
	// When intercept=true, the behavior depends on whether the returned handler
	// is non-nil: if nil, the connection is rejected. If non-nil, handler takes
	// over the UDP flow.
	GetUDPHandlerForFlow func(src, dst netip.AddrPort) (handler func(nettype.ConnPacketConn), intercept bool)

	// CheckLocalTransportEndpoints, if true, causes netstack to check if gVisor
	// has a registered endpoint for incoming packets to local IPs. This is used
	// by tsnet to intercept packets for registered listeners and outbound
	// connections when ProcessLocalIPs is false (i.e., when using a TUN).
	// It can only be set before calling Start.
	// TODO(raggi): refactor the way we handle both CheckLocalTransportEndpoints
	// and the earlier netstack registrations for serve, funnel, peerAPI and so
	// on. Currently this optimizes away cost for tailscaled in TUN mode, while
	// enabling extension support when using tsnet in TUN mode. See #18423.
	CheckLocalTransportEndpoints bool

	// ProcessLocalIPs is whether netstack should handle incoming
	// traffic directed at the Node.Addresses (local IPs).
	// It can only be set before calling Start.
	ProcessLocalIPs bool

	// ProcessSubnets is whether netstack should handle incoming
	// traffic destined to non-local IPs (i.e. whether it should
	// be a subnet router).
	// It can only be set before calling Start.
	ProcessSubnets bool
	// contains filtered or unexported fields
}

type LocalBackend = any