captivedetection

Documentation

Overview

Package captivedetection provides a way to detect if the system is connected to a network that has a captive portal. It does this by making HTTP requests to known captive portal detection endpoints and checking if the HTTP responses indicate that a captive portal might be present.

Index

• Constants
• type Detector
  • func NewDetector(logf logger.Logf) *Detector
  • func (d *Detector) Detect(ctx context.Context, netMon *netmon.Monitor, derpMap *tailcfg.DERPMap, ...) (found bool)
• type Endpoint
  • func (e Endpoint) Equal(other Endpoint) bool
  • func (e Endpoint) String() string
• type EndpointProvider
  • func (p EndpointProvider) String() string

Constants

const Timeout = 3 * time.Second

Timeout is the timeout for captive portal detection requests. Because the captive portal intercepting our requests is usually located on the LAN, this is a relatively short timeout.

Types

type Detector

type Detector struct {
	// contains filtered or unexported fields
}

Detector checks whether the system is behind a captive portal.

func NewDetector

func NewDetector(logf logger.Logf) *Detector

NewDetector creates a new Detector instance for captive portal detection.

func (*Detector) Detect

func (d *Detector) Detect(ctx context.Context, netMon *netmon.Monitor, derpMap *tailcfg.DERPMap, preferredDERPRegionID int) (found bool)

Detect is the entry point to the API. It attempts to detect if the system is behind a captive portal by making HTTP requests to known captive portal detection Endpoints. If any of the requests return a response code or body that looks like a captive portal, Detect returns true. It returns false in all other cases, including when any error occurs during a detection attempt.

This function might take a while to return, as it will attempt to detect a captive portal on all available interfaces by performing multiple HTTP requests. It should be called in a separate goroutine if you want to avoid blocking.

type Endpoint

type Endpoint struct {
	// URL is the URL that we make an HTTP request to as part of the captive portal detection process.
	URL *url.URL
	// StatusCode is the expected HTTP status code that we expect to see in the response.
	StatusCode int
	// ExpectedContent is a string that we expect to see contained in the response body. If this is non-empty,
	// we will check that the response body contains this string. If it is empty, we will not check the response body
	// and only check the status code.
	ExpectedContent string
	// SupportsTailscaleChallenge is true if the endpoint will return the sent value of the X-Tailscale-Challenge
	// HTTP header in its HTTP response.
	SupportsTailscaleChallenge bool
	// Provider is the source of the endpoint. This is used to prioritize certain endpoints over others
	// (for example, a DERP node in the preferred region should always be used first).
	Provider EndpointProvider
}

Endpoint represents a URL that can be used to detect a captive portal, along with the expected result of the HTTP request.

func (Endpoint) Equal

func (e Endpoint) Equal(other Endpoint) bool

func (Endpoint) String

func (e Endpoint) String() string

type EndpointProvider

type EndpointProvider int

EndpointProvider is an enum that represents the source of an Endpoint.

const (
	// DERPMapPreferred is used for an endpoint that is a DERP node contained in the current preferred DERP region,
	// as provided by the DERPMap.
	DERPMapPreferred EndpointProvider = iota
	// DERPMapOther is used for an endpoint that is a DERP node, but not contained in the current preferred DERP region.
	DERPMapOther
	// Tailscale is used for endpoints that are the Tailscale coordination server or admin console.
	Tailscale
)

func (EndpointProvider) String

func (p EndpointProvider) String() string