archive
/
tailscale-android
mirror of https://github.com/tailscale/tailscale-android
1
0
Fork 0
Code Issues Projects Releases Wiki Activity

android: rework NetworkChangeCallback to track all networks

Browse Source 
Instead of just tracking our default network, track all of them and
decide upon each change which is the "best" option.

Updates tailscale/tailscale#13173

Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
pull/500/head
Andrew Dunham 2 weeks ago
parent 33f79deb3a
commit aaecc62e1c
1 changed files with 120 additions and 52 deletions
Show Stats Download Patch File Download Diff File

172
android/src/main/java/com/tailscale/ipn/NetworkChangeCallback.kt
Unescape Escape View File

@ -6,94 +6,162 @@ import android.net.ConnectivityManager
import android.net.LinkProperties
import android.net.Network
import android.net.NetworkCapabilities
import android.net.NetworkRequest
import android.util.Log
import libtailscale.Libtailscale
import java.net.InetAddress
import java.util.concurrent.locks.ReentrantLock
import kotlin.concurrent.withLock
object NetworkChangeCallback {
private const val TAG = "NetworkChangeCallback"
// Cache LinkProperties and NetworkCapabilities since synchronous ConnectivityManager calls are
// prone to races.
// Since there is no guarantee for which update might come first, maybe update DNS configs on
// both.
val networkCapabilitiesCache = mutableMapOf<Network, NetworkCapabilities>()
val linkPropertiesCache = mutableMapOf<Network, LinkProperties>()
// requestDefaultNetworkCallback receives notifications about the default network. Listen for
// changes to the capabilities, which are guaranteed to come after a network becomes available per
// https://developer.android.com/reference/android/net/ConnectivityManager.NetworkCallback#onAvailable(android.net.Network),
// in order to filter on non-VPN networks.
private data class NetworkInfo(
var caps: NetworkCapabilities,
var linkProps: LinkProperties
)
private val lock = ReentrantLock()
private val activeNetworks = mutableMapOf<Network, NetworkInfo>() // keyed by Network
// monitorDnsChanges sets up a network callback to monitor changes to the
// system's network state and update the DNS configuration when interfaces
// become available or properties of those interfaces change.
fun monitorDnsChanges(connectivityManager: ConnectivityManager, dns: DnsConfig) {
val networkConnectivityRequest =
NetworkRequest.Builder()
.addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET)
.addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_VPN)
.build()
connectivityManager.registerDefaultNetworkCallback(
// Use registerNetworkCallback to listen for updates from all networks, and
// then update DNS configs for the best network.
//
// Note that we can't use registerDefaultNetworkCallback because the
// default network used by Tailscale will always show up with capability
// NOT_VPN=false, and we must filter out NOT_VPN networks to avoid routing
// loops.
connectivityManager.registerNetworkCallback(
networkConnectivityRequest,
object : ConnectivityManager.NetworkCallback() {
override fun onAvailable(network: Network) {
super.onAvailable(network)
Log.d(TAG, "onAvailable: network ${network}")
lock.withLock {
activeNetworks[network] = NetworkInfo(NetworkCapabilities(), LinkProperties())
maybeUpdateDNSConfigLocked("onAvailable", dns)
}
}
override fun onCapabilitiesChanged(network: Network, capabilities: NetworkCapabilities) {
super.onCapabilitiesChanged(network, capabilities)
networkCapabilitiesCache[network] = capabilities
val linkProperties = linkPropertiesCache[network]
if (linkProperties != null &&
capabilities.hasCapability(NetworkCapabilities.NET_CAPABILITY_NOT_VPN) &&
capabilities.hasCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET)) {
maybeUpdateDNSConfig(linkProperties, dns)
} else {
if (!capabilities.hasCapability(NetworkCapabilities.NET_CAPABILITY_NOT_VPN) ||
!capabilities.hasCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET)) {
Log.d(
TAG,
"Capabilities changed for network $network.toString(), but not updating DNS config because either this is a VPN network or non-internet network")
} else {
Log.d(
TAG,
"Capabilities changed for network $network.toString(), but not updating DNS config, because the LinkProperties hasn't been gotten yet")
}
lock.withLock {
activeNetworks[network]?.caps = capabilities
maybeUpdateDNSConfigLocked("onCapabilitiesChanged", dns)
}
}
override fun onLinkPropertiesChanged(network: Network, linkProperties: LinkProperties) {
super.onLinkPropertiesChanged(network, linkProperties)
linkPropertiesCache[network] = linkProperties
val capabilities = networkCapabilitiesCache[network]
if (capabilities != null &&
capabilities.hasCapability(NetworkCapabilities.NET_CAPABILITY_NOT_VPN) &&
capabilities.hasCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET)) {
maybeUpdateDNSConfig(linkProperties, dns)
} else {
if (capabilities == null) {
Log.d(
TAG,
"Capabilities changed for network $network.toString(), but not updating DNS config because capabilities haven't been gotten for this network yet")
} else {
Log.d(
TAG,
"Capabilities changed for network $network.toString(), but not updating DNS config, because this is a VPN network or non-Internet network")
}
lock.withLock {
activeNetworks[network]?.linkProps = linkProperties
maybeUpdateDNSConfigLocked("onLinkPropertiesChanged", dns)
}
}
override fun onLost(network: Network) {
super.onLost(network)
if (dns.updateDNSFromNetwork("")) {
Libtailscale.onDNSConfigChanged("")
Log.d(TAG, "onLost: network ${network}")
lock.withLock {
activeNetworks.remove(network)
maybeUpdateDNSConfigLocked("onLost", dns)
}
}
})
}
fun maybeUpdateDNSConfig(linkProperties: LinkProperties, dns: DnsConfig) {
// pickNonMetered returns the first non-metered network in the list of
// networks, or the first network if none are non-metered.
private fun pickNonMetered(networks: Map<Network, NetworkInfo>): Network? {
for ((network, info) in networks) {
if (info.caps.hasCapability(NetworkCapabilities.NET_CAPABILITY_NOT_METERED)) {
return network
}
}
return networks.keys.firstOrNull()
}
// pickDefaultNetwork returns a non-VPN network to use as the 'default'
// network; one that is used as a gateway to the internet and from which we
// obtain our DNS servers.
private fun pickDefaultNetwork(): Network? {
// Filter the list of all networks to those that have the INTERNET
// capability, are not VPNs, and have a non-zero number of DNS servers
// available.
val networks = activeNetworks.filter { (_, info) ->
info.caps.hasCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET) &&
info.caps.hasCapability(NetworkCapabilities.NET_CAPABILITY_NOT_VPN) &&
info.linkProps.dnsServers.isNotEmpty() == true
}
// If we have one; just return it; otherwise, prefer networks that are also
// not metered (i.e. cell modems).
val nonMeteredNetwork = pickNonMetered(networks)
if (nonMeteredNetwork != null) {
return nonMeteredNetwork
}
// Okay, less good; just return the first network that has the INTERNET and
// NOT_VPN capabilities; even though this interface doesn't have any DNS
// servers set, we'll use our DNS fallback servers to make queries. It's
// strictly better to return an interface + use the DNS fallback servers
// than to return nothing and not be able to route traffic.
for ((network, info) in activeNetworks) {
if (info.caps.hasCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET) &&
info.caps.hasCapability(NetworkCapabilities.NET_CAPABILITY_NOT_VPN)) {
Log.w(TAG, "no networks available that also have DNS servers set; falling back to first network ${network}")
return network
}
}
// Otherwise, return nothing; we don't want to return a VPN network since
// it could result in a routing loop, and a non-INTERNET network isn't
// helpful.
Log.w(TAG, "no networks available to pick a default network")
return null
}
// maybeUpdateDNSConfig will maybe update our DNS configuration based on the
// current set of active Networks.
//
// 'lock' must be held.
private fun maybeUpdateDNSConfigLocked(why: String, dns: DnsConfig) {
val defaultNetwork = pickDefaultNetwork()
if (defaultNetwork == null) {
Log.d(TAG, "${why}: no default network available; not updating DNS config")
return
}
val info = activeNetworks[defaultNetwork]
if (info == null) {
Log.w(TAG, "${why}: [unexpected] no info available for default network; not updating DNS config")
return
}
val sb = StringBuilder()
val dnsList: MutableList<InetAddress> = linkProperties.dnsServers ?: mutableListOf()
for (ip in dnsList) {
for (ip in info.linkProps.dnsServers) {
sb.append(ip.hostAddress).append(" ")
}
val searchDomains: String? = linkProperties.domains
val searchDomains: String? = info.linkProps.domains
if (searchDomains != null) {
sb.append("\n")
sb.append(searchDomains)
}
if (dns.updateDNSFromNetwork(sb.toString())) {
Libtailscale.onDNSConfigChanged(linkProperties.interfaceName)
Log.d(TAG, "${why}: updated DNS config for network ${defaultNetwork} (${info.linkProps.interfaceName})")
Libtailscale.onDNSConfigChanged(info.linkProps.interfaceName)
}
}
}

Write Preview
Loading…
Cancel
Save