Add support for IPv6 networks (on Linux clients) (#1459)

* Feat add basic support for IPv6 networks

Newly generated networks automatically generate an IPv6 prefix of size
64 within the ULA address range, devices obtain a randomly generated
address within this prefix.

Currently, this is Linux only and does not yet support all features
(routes currently cause an error).

* Fix firewall configuration for IPv6 networks

* Fix routing configuration for IPv6 networks

* Feat provide info on IPv6 support for specific client to mgmt server

* Feat allow configuration of IPv6 support through API, improve stability

* Feat add IPv6 support to new firewall implementation

* Fix peer list item response not containing IPv6 address

* Fix nftables breaking on IPv6 address change

* Fix build issues for non-linux systems

* Fix intermittent disconnections when IPv6 is enabled

* Fix test issues and make some minor revisions

* Fix some more testing issues

* Fix more CI issues due to IPv6

* Fix more testing issues

* Add inheritance of IPv6 enablement status from groups

* Fix IPv6 events not having associated messages

* Address first review comments regarding IPv6 support

* Fix IPv6 table being created even when IPv6 is disabled

Also improved stability of IPv6 route and firewall handling on client side

* Fix IPv6 routes not being removed

* Fix DNS IPv6 issues, limit IPv6 nameservers to IPv6 peers

* Improve code for IPv6 DNS server selection, add AAAA custom records

* Ensure IPv6 routes can only exist for IPv6 routing peers

* Fix IPv6 network generation randomness

* Fix a bunch of compilation issues and test failures

* Replace method calls that are unavailable in Go 1.21

* Fix nil dereference in cleanUpDefaultForwardRules6

* Fix nil pointer dereference when persisting IPv6 network in sqlite

* Clean up of client-side code changes for IPv6

* Fix nil dereference in rule mangling and compilation issues

* Add a bunch of client-side test cases for IPv6

* Fix IPv6 tests running on unsupported environments

* Fix import cycle in tests

* Add missing method SupportsIPv6() for windows

* Require IPv6 default route for IPv6 tests

* Fix panics in routemanager tests on non-linux

* Fix some more route manager tests concerning IPv6

* Add some final client-side tests

* Add IPv6 tests for management code, small fixes

* Fix linting issues

* Fix small test suite issues

* Fix linter issues and builds on macOS and Windows again

* fix builds for iOS because of IPv6 breakage

management/server/peer/peer.go

@@ -20,6 +20,8 @@ type Peer struct {
 	SetupKey string
 	// IP address of the Peer
 	IP net.IP `gorm:"serializer:json"`
+	// IPv6 address of the Peer
+	IP6 *net.IP `gorm:"uniqueIndex:idx_peers_account_id_ip6"`
 	// Meta is a Peer system meta data
 	Meta PeerSystemMeta `gorm:"embedded;embeddedPrefix:meta_"`
 	// Name is peer's name (machine name)
@@ -44,10 +46,23 @@ type Peer struct {
 	CreatedAt time.Time
 	// Indicate ephemeral peer attribute
 	Ephemeral bool
-	// Geo location based on connection IP
+	// Geolocation based on connection IP
 	Location Location `gorm:"embedded;embeddedPrefix:location_"`
+	// Whether IPv6 should be enabled or not.
+	V6Setting V6Status
 }
 
+type V6Status string
+
+const (
+	// Inherit IPv6 settings from groups (=> if one group the peer is a member of has IPv6 enabled, it will be enabled).
+	V6Auto V6Status = ""
+	// Enable IPv6 regardless of group settings, as long as it is supported.
+	V6Enabled V6Status = "enabled"
+	// Disable IPv6 regardless of group settings.
+	V6Disabled V6Status = "disabled"
+)
+
 type PeerStatus struct { //nolint:revive
 	// LastSeen is the last time peer was connected to the management service
 	LastSeen time.Time
@@ -96,6 +111,7 @@ type PeerSystemMeta struct { //nolint:revive
 	SystemProductName  string
 	SystemManufacturer string
 	Environment        Environment `gorm:"serializer:json"`
+	Ipv6Supported      bool
 }
 
 func (p PeerSystemMeta) isEqual(other PeerSystemMeta) bool {
@@ -130,7 +146,8 @@ func (p PeerSystemMeta) isEqual(other PeerSystemMeta) bool {
 		p.SystemProductName == other.SystemProductName &&
 		p.SystemManufacturer == other.SystemManufacturer &&
 		p.Environment.Cloud == other.Environment.Cloud &&
-		p.Environment.Platform == other.Environment.Platform
+		p.Environment.Platform == other.Environment.Platform &&
+		p.Ipv6Supported == other.Ipv6Supported
 }
 
 // AddedWithSSOLogin indicates whether this peer has been added with an SSO login by a user.
@@ -150,6 +167,7 @@ func (p *Peer) Copy() *Peer {
 		Key:                    p.Key,
 		SetupKey:               p.SetupKey,
 		IP:                     p.IP,
+		IP6:                    p.IP6,
 		Meta:                   p.Meta,
 		Name:                   p.Name,
 		DNSLabel:               p.DNSLabel,
@@ -162,6 +180,7 @@ func (p *Peer) Copy() *Peer {
 		CreatedAt:              p.CreatedAt,
 		Ephemeral:              p.Ephemeral,
 		Location:               p.Location,
+		V6Setting:              p.V6Setting,
 	}
 }