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/api/openapi.yml

@@ -247,10 +247,15 @@ components:
           description: (Cloud only) Indicates whether peer needs approval
           type: boolean
           example: true
+        ipv6_enabled:
+          type: string
+          enum: [enabled, disabled, auto]
+          example: auto
       required:
         - name
         - ssh_enabled
         - login_expiration_enabled
+        - ipv6_enabled
     PeerBase:
       allOf:
         - $ref: '#/components/schemas/PeerMinimum'
@@ -264,6 +269,10 @@ components:
               description: Peer's public connection IP address
               type: string
               example: 35.64.0.1
+            ip6:
+              description: Peer's IPv6 address
+              type: string
+              example: 2001:db8::0123:4567:890a:bcde
             connected:
               description: Peer to Management connection status
               type: boolean
@@ -310,6 +319,15 @@ components:
               description: Peer's desktop UI version
               type: string
               example: 0.14.0
+            ipv6_supported:
+              description: Whether this peer supports IPv6
+              type: boolean
+              example: true
+            ipv6_enabled:
+              description: Whether IPv6 is enabled for this peer.
+              type: string
+              enum: [enabled, disabled, auto]
+              example: auto
             dns_label:
               description: Peer's DNS label is the parsed peer name for domain resolution. It is used to form an FQDN by appending the account's domain to the peer label. e.g. peer-dns-label.netbird.cloud
               type: string
@@ -352,6 +370,8 @@ components:
             - kernel_version
             - last_login
             - last_seen
+            - ipv6_supported
+            - ipv6_enabled
             - login_expiration_enabled
             - login_expired
             - os
@@ -627,8 +647,12 @@ components:
           items:
             type: string
             example: "ch8i4ug6lnn4g9hqv7m1"
+        ipv6_enabled:
+          description: Whether IPv6 should be enabled for all members with IPv6 set to "auto"
+          type: boolean
       required:
         - name
+        - ipv6_enabled
     Group:
       allOf:
         - $ref: '#/components/schemas/GroupMinimum'
@@ -639,8 +663,12 @@ components:
               type: array
               items:
                 $ref: '#/components/schemas/PeerMinimum'
+            ipv6_enabled:
+              description: Whether IPv6 should be enabled for all members with IPv6 set to "auto"
+              type: boolean
           required:
             - peers
+            - ipv6_enabled
     PolicyRuleMinimum:
       type: object
       properties: