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/http/peers_handler.go

@@ -85,11 +85,17 @@ func (h *PeersHandler) updatePeer(account *server.Account, user *server.User, pe
 		return
 	}
 
+	v6Status := nbpeer.V6Auto
+	if req.Ipv6Enabled != api.PeerRequestIpv6EnabledAuto {
+		v6Status = nbpeer.V6Status(req.Ipv6Enabled)
+	}
+
 	update := &nbpeer.Peer{
 		ID:                     peerID,
 		SSHEnabled:             req.SshEnabled,
 		Name:                   req.Name,
 		LoginExpirationEnabled: req.LoginExpirationEnabled,
+		V6Setting: v6Status,
 	}
 
 	if req.ApprovalRequired != nil {
@@ -284,11 +290,22 @@ func toSinglePeerResponse(peer *nbpeer.Peer, groupsInfo []api.GroupMinimum, dnsD
 		osVersion = peer.Meta.Core
 	}
 
+	var ip6 *string
+	if peer.IP6 != nil {
+		ip6string := peer.IP6.String()
+		ip6 = &ip6string
+	}
+	v6Status := api.PeerIpv6EnabledAuto
+	if peer.V6Setting != nbpeer.V6Auto {
+		v6Status = api.PeerIpv6Enabled(peer.V6Setting)
+	}
+
 	return &api.Peer{
 		Id:                     peer.ID,
 		Name:                   peer.Name,
 		Ip:                     peer.IP.String(),
 		ConnectionIp:           peer.Location.ConnectionIP.String(),
+		Ip6:                    ip6,
 		Connected:              peer.Status.Connected,
 		LastSeen:               peer.Status.LastSeen,
 		Os:                     fmt.Sprintf("%s %s", peer.Meta.OS, osVersion),
@@ -300,6 +317,8 @@ func toSinglePeerResponse(peer *nbpeer.Peer, groupsInfo []api.GroupMinimum, dnsD
 		Hostname:               peer.Meta.Hostname,
 		UserId:                 peer.UserID,
 		UiVersion:              peer.Meta.UIVersion,
+		Ipv6Supported:          peer.Meta.Ipv6Supported,
+		Ipv6Enabled:            v6Status,
 		DnsLabel:               fqdn(peer, dnsDomain),
 		LoginExpirationEnabled: peer.LoginExpirationEnabled,
 		LastLogin:              peer.LastLogin,
@@ -317,12 +336,22 @@ func toPeerListItemResponse(peer *nbpeer.Peer, groupsInfo []api.GroupMinimum, dn
 	if osVersion == "" {
 		osVersion = peer.Meta.Core
 	}
+	var ip6 *string
+	if peer.IP6 != nil {
+		ip6string := peer.IP6.String()
+		ip6 = &ip6string
+	}
+	v6Status := api.PeerBatchIpv6EnabledAuto
+	if peer.V6Setting != nbpeer.V6Auto {
+		v6Status = api.PeerBatchIpv6Enabled(peer.V6Setting)
+	}
 
 	return &api.PeerBatch{
 		Id:                     peer.ID,
 		Name:                   peer.Name,
 		Ip:                     peer.IP.String(),
 		ConnectionIp:           peer.Location.ConnectionIP.String(),
+		Ip6:                    ip6,
 		Connected:              peer.Status.Connected,
 		LastSeen:               peer.Status.LastSeen,
 		Os:                     fmt.Sprintf("%s %s", peer.Meta.OS, osVersion),
@@ -334,6 +363,8 @@ func toPeerListItemResponse(peer *nbpeer.Peer, groupsInfo []api.GroupMinimum, dn
 		Hostname:               peer.Meta.Hostname,
 		UserId:                 peer.UserID,
 		UiVersion:              peer.Meta.UIVersion,
+		Ipv6Supported:          peer.Meta.Ipv6Supported,
+		Ipv6Enabled:            v6Status,
 		DnsLabel:               fqdn(peer, dnsDomain),
 		LoginExpirationEnabled: peer.LoginExpirationEnabled,
 		LastLogin:              peer.LastLogin,