No IPv4 Address

Describe the bug
When using OpenVPN 2.6.0, our Windows clients can't assign the IPv4 address given by the server, which results in a later failure when the client tries to set routes dependent on that IPv4 address. The issue does not appear when using the old tap-windows6 driver by setting disable-dco in the client config.

Redacted Log (I hope it is still readable enough):

2023-01-27 13:56:46 Note: --cipher is not set. OpenVPN versions before 2.5 defaulted to BF-CBC as fallback when cipher negotiation failed in this case. If you need this fallback please add '--data-ciphers-fallback BF-CBC' to your configuration and/or add BF-CBC to --data-ciphers.
2023-01-27 13:56:46 OpenVPN 2.6.0 [git:v2.6.0/b999466418dddb89] Windows-MSVC [SSL (OpenSSL)] [LZO] [LZ4] [PKCS11] [AEAD] [DCO] built on Jan 25 2023
2023-01-27 13:56:46 Windows version 10.0 (Windows 10 or greater), amd64 executable
2023-01-27 13:56:46 library versions: OpenSSL 3.0.7 1 Nov 2022, LZO 2.10
2023-01-27 13:56:46 MANAGEMENT: TCP Socket listening on [AF_INET]127.0.0.1:25341
2023-01-27 13:56:46 Need hold release from management interface, waiting...
2023-01-27 13:56:47 MANAGEMENT: Client connected from [AF_INET]127.0.0.1:62515
2023-01-27 13:56:47 MANAGEMENT: CMD 'state on'
2023-01-27 13:56:47 MANAGEMENT: CMD 'log on all'
2023-01-27 13:56:47 MANAGEMENT: CMD 'echo on all'
2023-01-27 13:56:47 MANAGEMENT: CMD 'bytecount 5'
2023-01-27 13:56:47 MANAGEMENT: CMD 'state'
2023-01-27 13:56:47 MANAGEMENT: CMD 'hold off'
2023-01-27 13:56:47 MANAGEMENT: CMD 'hold release'
2023-01-27 13:56:47 MANAGEMENT: >STATE:1674824207,RESOLVE,,,,,,
2023-01-27 13:56:47 TCP/UDP: Preserving recently used remote address: [AF_INET]REMOTE_IP:1194
2023-01-27 13:56:47 ovpn-dco device [OpenVPN Data Channel Offload] opened
2023-01-27 13:56:47 UDP link local: (not bound)
2023-01-27 13:56:47 UDP link remote: [AF_INET]REMOTE_IP:1194
2023-01-27 13:56:47 MANAGEMENT: >STATE:1674824207,WAIT,,,,,,
2023-01-27 13:56:47 MANAGEMENT: >STATE:1674824207,AUTH,,,,,,
2023-01-27 13:56:47 TLS: Initial packet from [AF_INET]REMOTE_IP:1194, sid=xxxxxxxx xxxxxxxx
2023-01-27 13:56:47 VERIFY OK: depth=3, REDACTED
2023-01-27 13:56:47 VERIFY OK: depth=2, REDACTED
2023-01-27 13:56:47 VERIFY OK: depth=1, REDACTED
2023-01-27 13:56:47 VERIFY KU OK
2023-01-27 13:56:47 Validating certificate extended key usage
2023-01-27 13:56:47 ++ Certificate has EKU (str) TLS Web Server Authentication, expects TLS Web Server Authentication
2023-01-27 13:56:47 VERIFY EKU OK
2023-01-27 13:56:47 VERIFY X509NAME OK: REDACTED
2023-01-27 13:56:47 VERIFY OK: depth=0, REDACTED
2023-01-27 13:56:47 Control Channel: TLSv1.3, cipher TLSv1.3 TLS_AES_256_GCM_SHA384, peer certificate: 4096 bit RSA, signature: RSA-SHA256
2023-01-27 13:56:47 [REMOTE_DOMAIN] Peer Connection Initiated with [AF_INET]REMOTE_IP:1194
2023-01-27 13:56:47 TLS: move_session: dest=TM_ACTIVE src=TM_INITIAL reinit_src=1
2023-01-27 13:56:47 TLS: tls_multi_process: initial untrusted session promoted to trusted
2023-01-27 13:56:47 PUSH: Received control message: 'PUSH_REPLY,dhcp-option DNS DNS_v4_IP,dhcp-option DNS6 DNS_v6_IP,dhcp-option NTP NTP_v4_IP_1,dhcp-option NTP NTP_v4_IP_2,dhcp-option DOMAIN COMPANY_DOMAIN,ip-win32 dynamic 0 86400,route COMPANY_IP_NET 255.255.0.0,route-ipv6 COMPANY_IP_NET_v6/48,route remote_host 255.255.255.255 net_gateway,tun-ipv6,route-gateway VPN_CLIENT_IPv4_GATEWAY,topology subnet,ping 15,ping-restart 120,ifconfig-ipv6 VPN_CLIENT_IPv6/64 VPN_CLIENT_IPv6_GATEWAY,ifconfig VPN_CLIENT_IPv4 255.255.255.0,peer-id 3,cipher AES-256-GCM'
2023-01-27 13:56:47 OPTIONS IMPORT: timers and/or timeouts modified
2023-01-27 13:56:47 OPTIONS IMPORT: --ifconfig/up options modified
2023-01-27 13:56:47 OPTIONS IMPORT: route options modified
2023-01-27 13:56:47 OPTIONS IMPORT: route-related options modified
2023-01-27 13:56:47 OPTIONS IMPORT: --ip-win32 and/or --dhcp-option options modified
2023-01-27 13:56:47 OPTIONS IMPORT: peer-id set
2023-01-27 13:56:47 OPTIONS IMPORT: data channel crypto options modified
2023-01-27 13:56:47 interactive service msg_channel=572
2023-01-27 13:56:47 GDG6: remote_host_ipv6=n/a
2023-01-27 13:56:47 NOTE: GetBestInterfaceEx returned error: Element nicht gefunden.   (code=1168)
2023-01-27 13:56:47 MANAGEMENT: >STATE:1674824207,ASSIGN_IP,,VPN_CLIENT_IPv4,,,,,VPN_CLIENT_IPv6
2023-01-27 13:56:47 IPv4 MTU set to 1300 on interface 9 using service
2023-01-27 13:56:47 INET6 address service: add VPN_CLIENT_IPv6/128
2023-01-27 13:56:47 add_route_ipv6(VPN_CLIENT_IPv6_NETWORK/64 -> VPN_CLIENT_IPv6 metric 0) IF 9
2023-01-27 13:56:47 IPv6 route addition via service succeeded
2023-01-27 13:56:47 IPv6 dns servers set using service
2023-01-27 13:56:47 IPv6 MTU set to 1300 on interface 9 using service
2023-01-27 13:56:47 C:\WINDOWS\system32\route.exe ADD REMOTE_IP MASK 255.255.255.255 DEFAULT_IPv4_GATEWAY
2023-01-27 13:56:47 Route addition via service succeeded
2023-01-27 13:56:47 C:\WINDOWS\system32\route.exe ADD 0.0.0.0 MASK 128.0.0.0 VPN_CLIENT_IPv4_GATEWAY
2023-01-27 13:56:47 Warning: route gateway is not reachable on any active network adapters: VPN_CLIENT_IPv4_GATEWAY
2023-01-27 13:56:47 C:\WINDOWS\system32\route.exe ADD 128.0.0.0 MASK 128.0.0.0 VPN_CLIENT_IPv4_GATEWAY
2023-01-27 13:56:47 Warning: route gateway is not reachable on any active network adapters: VPN_CLIENT_IPv4_GATEWAY
2023-01-27 13:56:47 MANAGEMENT: >STATE:1674824207,ADD_ROUTES,,,,,,
2023-01-27 13:56:47 C:\WINDOWS\system32\route.exe ADD COMPANY_IP_NET MASK 255.255.0.0 VPN_CLIENT_IPv4_GATEWAY METRIC 200
2023-01-27 13:56:47 Warning: route gateway is not reachable on any active network adapters: VPN_CLIENT_IPv4_GATEWAY
2023-01-27 13:56:47 C:\WINDOWS\system32\route.exe ADD REMOTE_IP MASK 255.255.255.255 DEFAULT_IPv4_GATEWAY METRIC 200
2023-01-27 13:56:47 Route addition via service failed because route exists
2023-01-27 13:56:47 add_route_ipv6(COMPANY_IP_NET_v6/48 -> VPN_CLIENT_IPv6_GATEWAY metric 200) IF 9
2023-01-27 13:56:47 IPv6 route addition via service succeeded
2023-01-27 13:56:47 add_route_ipv6(::/3 -> VPN_CLIENT_IPv6_GATEWAY metric 200) IF 9
2023-01-27 13:56:47 IPv6 route addition via service succeeded
2023-01-27 13:56:47 add_route_ipv6(2000::/4 -> VPN_CLIENT_IPv6_GATEWAY metric 200) IF 9
2023-01-27 13:56:47 IPv6 route addition via service succeeded
2023-01-27 13:56:47 add_route_ipv6(3000::/4 -> VPN_CLIENT_IPv6_GATEWAY metric 200) IF 9
2023-01-27 13:56:47 IPv6 route addition via service succeeded
2023-01-27 13:56:47 add_route_ipv6(fc00::/7 -> VPN_CLIENT_IPv6_GATEWAY metric 200) IF 9
2023-01-27 13:56:47 IPv6 route addition via service succeeded
2023-01-27 13:56:47 Data Channel: using negotiated cipher 'AES-256-GCM'
2023-01-27 13:56:47 Initialization Sequence Completed
2023-01-27 13:56:47 MANAGEMENT: >STATE:1674824207,CONNECTED,ROUTE_ERROR,VPN_CLIENT_IPv4,REMOTE_IP,1194,,,VPN_CLIENT_IPv6

Tested on Windows 10 2004, which should correspond to 20H1. I have also tested the same config on 21H2 with the same results.

Is this an issue in our config or a problem in the new dco driver?

Expected behavior
A working IPv4 address and correctly configured routes

Version information (please complete the following information):

• OS: Windows 10
• OpenVPN version: 2.6.0

No source files or tests are mentioned. Reproduce the connection on Windows 10 with OpenVPN 2.6.0 and DCO enabled, then compare it with the same configuration using disable-dco; done means the IPv4 address is assigned and dependent routes are configured without ROUTE_ERROR.