[DCO 2.8.2.0] [WINDOWS 10 Pro 10.0.19044] crypto_alg: CHACHA20-POLY1305: bad cipher for data channel use
Tested DCO on Windows 10 and Windows 11 with the same version of DCO and OpenVPN Connect. Used the same *.ovpn configuration file.
On Windows 11 DCO passed.
On Windows 10 DCO fails. Error:
` Client exception in transport_recv: crypto_alg: CHACHA20-POLY1305: bad cipher for data channel use`
Details provided below.
`OpenVPN Connect 3.8.0 (4528)`
`OpenVPN core 3.11.3 win x86_64 64-bit OVPN-DCO built on Sep 16 2025 15:58:53`
`OpenVPN Data Channel Offload 2.8.2.0`
```
OS Name: Microsoft Windows 10 Pro
OS Version: 10.0.19044 N/A Build 19044
```
```
[Feb 28, 2026, 18:42:23] EVENT: DISCONNECTED
[Feb 28, 2026, 18:42:23] WinCommandAgent: transmitting bypass route to <REMOTE_IP>
{
"host" : "<REMOTE_IP>",
"ipv6" : false
}
[Feb 28, 2026, 18:42:23] {
"allow_local_dns_resolvers" : false,
"confirm_event" : "600f000000000000",
"destroy_event" : "480a000000000000"
}
POST np://[\\.\pipe\agent_ovpnconnect]/tun-open : 200 OK
Destroyed previous TAP instance
TAP ADAPTERS:
guid='{9E0F7192-213E-4039-83C6-E8AC4C6FD211}' index=44 name='OpenVPN Connect DCO Adapter'
guid='{F2CAA5A1-9DC4-4CE5-B2ED-99CD508B2E08}' index=111 name='OpenVPN Data Channel Offload'
Open TAP device "OpenVPN Connect DCO Adapter" PATH="\\?\ROOT#NET#0001#{cac88484-7515-4c03-82e6-71a87abac361}\ovpn-dco" SUCCEEDED
TAP handle: 480a000000000000
[Feb 28, 2026, 18:42:22] EVENT: RESOLVE
[Feb 28, 2026, 18:42:22] EVENT: RECONNECTING
[Feb 28, 2026, 18:42:20] Client terminated, restarting in 2000 ms...
[Feb 28, 2026, 18:42:20] Client exception in transport_recv: crypto_alg: CHACHA20-POLY1305: bad cipher for data channel use
[Feb 28, 2026, 18:42:20] EVENT: CONNECTING
[Feb 28, 2026, 18:42:20] Connecting to [<REMOTE_IP>]:<REMOTE_PORT> (<REMOTE_IP>) via UDPv4-DCO
[Feb 28, 2026, 18:42:20] WinCommandAgent: transmitting bypass route to <REMOTE_IP>
{
"host" : "<REMOTE_IP>",
"ipv6" : false
}
[Feb 28, 2026, 18:42:20] {
"allow_local_dns_resolvers" : false,
"confirm_event" : "4c0a000000000000",
"destroy_event" : "480a000000000000"
}
POST np://[\\.\pipe\agent_ovpnconnect]/tun-open : 200 OK
Destroyed previous TAP instance
TAP ADAPTERS:
guid='{9E0F7192-213E-4039-83C6-E8AC4C6FD211}' index=44 name='OpenVPN Connect DCO Adapter'
guid='{F2CAA5A1-9DC4-4CE5-B2ED-99CD508B2E08}' index=111 name='OpenVPN Data Channel Offload'
Open TAP device "OpenVPN Connect DCO Adapter" PATH="\\?\ROOT#NET#0001#{cac88484-7515-4c03-82e6-71a87abac361}\ovpn-dco" SUCCEEDED
TAP handle: 480a000000000000
[Feb 28, 2026, 18:42:19] EVENT: RESOLVE
[Feb 28, 2026, 18:42:19] EVENT: RECONNECTING
[Feb 28, 2026, 18:42:17] Client terminated, restarting in 2000 ms...
[Feb 28, 2026, 18:42:17] Client exception in transport_recv: crypto_alg: CHACHA20-POLY1305: bad cipher for data channel use
[Feb 28, 2026, 18:42:17] EVENT: CONNECTING
[Feb 28, 2026, 18:42:17] Connecting to [<REMOTE_IP>]:<REMOTE_PORT> (<REMOTE_IP>) via UDPv4-DCO
[Feb 28, 2026, 18:42:17] WinCommandAgent: transmitting bypass route to <REMOTE_IP>
{
"host" : "<REMOTE_IP>",
"ipv6" : false
}
[Feb 28, 2026, 18:42:17] {
"allow_local_dns_resolvers" : false,
"confirm_event" : "a40f000000000000",
"destroy_event" : "0c0f000000000000"
}
POST np://[\\.\pipe\agent_ovpnconnect]/tun-open : 200 OK
Destroyed previous TAP instance
TAP ADAPTERS:
guid='{9E0F7192-213E-4039-83C6-E8AC4C6FD211}' index=44 name='OpenVPN Connect DCO Adapter'
guid='{F2CAA5A1-9DC4-4CE5-B2ED-99CD508B2E08}' index=111 name='OpenVPN Data Channel Offload'
Open TAP device "OpenVPN Connect DCO Adapter" PATH="\\?\ROOT#NET#0001#{cac88484-7515-4c03-82e6-71a87abac361}\ovpn-dco" SUCCEEDED
TAP handle: 0c0f000000000000
[Feb 28, 2026, 18:42:16] EVENT: RESOLVE
[Feb 28, 2026, 18:42:16] EVENT: RECONNECTING
[Feb 28, 2026, 18:42:14] Client terminated, restarting in 2000 ms...
[Feb 28, 2026, 18:42:14] Client exception in transport_recv: crypto_alg: CHACHA20-POLY1305: bad cipher for data channel use
[Feb 28, 2026, 18:42:14] EVENT: CONNECTING
[Feb 28, 2026, 18:42:14] Connecting to [<REMOTE_IP>]:<REMOTE_PORT> (<REMOTE_IP>) via UDPv4-DCO
[Feb 28, 2026, 18:42:14] WinCommandAgent: transmitting bypass route to <REMOTE_IP>
{
"host" : "<REMOTE_IP>",
"ipv6" : false
}
[Feb 28, 2026, 18:42:14] {
"allow_local_dns_resolvers" : false,
"confirm_event" : "440f000000000000",
"destroy_event" : "ac0e000000000000"
}
POST np://[\\.\pipe\agent_ovpnconnect]/tun-open : 200 OK
Destroyed previous TAP instance
TAP ADAPTERS:
guid='{9E0F7192-213E-4039-83C6-E8AC4C6FD211}' index=44 name='OpenVPN Connect DCO Adapter'
guid='{F2CAA5A1-9DC4-4CE5-B2ED-99CD508B2E08}' index=111 name='OpenVPN Data Channel Offload'
Open TAP device "OpenVPN Connect DCO Adapter" PATH="\\?\ROOT#NET#0001#{cac88484-7515-4c03-82e6-71a87abac361}\ovpn-dco" SUCCEEDED
TAP handle: 480f000000000000
[Feb 28, 2026, 18:42:13] EVENT: RESOLVE
[Feb 28, 2026, 18:42:13] EVENT: RECONNECTING
[Feb 28, 2026, 18:42:11] Client terminated, restarting in 2000 ms...
[Feb 28, 2026, 18:42:11] Client exception in transport_recv: crypto_alg: CHACHA20-POLY1305: bad cipher for data channel use
[Feb 28, 2026, 18:42:11] EVENT: CONNECTING
[Feb 28, 2026, 18:42:11] Connecting to [<REMOTE_IP>]:<REMOTE_PORT> (<REMOTE_IP>) via UDPv4-DCO
[Feb 28, 2026, 18:42:10] WinCommandAgent: transmitting bypass route to <REMOTE_IP>
{
"host" : "<REMOTE_IP>",
"ipv6" : false
}
[Feb 28, 2026, 18:42:10] {
"allow_local_dns_resolvers" : false,
"confirm_event" : "480f000000000000",
"destroy_event" : "4c0f000000000000"
}
POST np://[\\.\pipe\agent_ovpnconnect]/tun-open : 200 OK
Destroyed previous TAP instance
TAP ADAPTERS:
guid='{9E0F7192-213E-4039-83C6-E8AC4C6FD211}' index=44 name='OpenVPN Connect DCO Adapter'
guid='{F2CAA5A1-9DC4-4CE5-B2ED-99CD508B2E08}' index=111 name='OpenVPN Data Channel Offload'
Open TAP device "OpenVPN Connect DCO Adapter" PATH="\\?\ROOT#NET#0001#{cac88484-7515-4c03-82e6-71a87abac361}\ovpn-dco" SUCCEEDED
TAP handle: 540f000000000000
[Feb 28, 2026, 18:42:09] EVENT: RESOLVE
[Feb 28, 2026, 18:42:09] EVENT: RECONNECTING
[Feb 28, 2026, 18:42:07] Client terminated, restarting in 2000 ms...
[Feb 28, 2026, 18:42:07] Client exception in transport_recv: crypto_alg: CHACHA20-POLY1305: bad cipher for data channel use
[Feb 28, 2026, 18:42:07] EVENT: CONNECTING
[Feb 28, 2026, 18:42:07] Connecting to [<REMOTE_IP>]:<REMOTE_PORT> (<REMOTE_IP>) via UDPv4-DCO
[Feb 28, 2026, 18:42:07] WinCommandAgent: transmitting bypass route to <REMOTE_IP>
{
"host" : "<REMOTE_IP>",
"ipv6" : false
}
[Feb 28, 2026, 18:42:07] {
"allow_local_dns_resolvers" : false,
"confirm_event" : "4c0f000000000000",
"destroy_event" : "480f000000000000"
}
POST np://[\\.\pipe\agent_ovpnconnect]/tun-open : 200 OK
Destroyed previous TAP instance
TAP ADAPTERS:
guid='{9E0F7192-213E-4039-83C6-E8AC4C6FD211}' index=44 name='OpenVPN Connect DCO Adapter'
guid='{F2CAA5A1-9DC4-4CE5-B2ED-99CD508B2E08}' index=111 name='OpenVPN Data Channel Offload'
Open TAP device "OpenVPN Connect DCO Adapter" PATH="\\?\ROOT#NET#0001#{cac88484-7515-4c03-82e6-71a87abac361}\ovpn-dco" SUCCEEDED
TAP handle: ec0f000000000000
[Feb 28, 2026, 18:42:06] EVENT: RESOLVE
[Feb 28, 2026, 18:42:06] EVENT: RECONNECTING
[Feb 28, 2026, 18:42:04] Client terminated, restarting in 2000 ms...
[Feb 28, 2026, 18:42:04] Client exception in transport_recv: crypto_alg: CHACHA20-POLY1305: bad cipher for data channel use
[Feb 28, 2026, 18:42:04] EVENT: CONNECTING
[Feb 28, 2026, 18:42:04] Connecting to [<REMOTE_IP>]:<REMOTE_PORT> (<REMOTE_IP>) via UDPv4-DCO
[Feb 28, 2026, 18:42:04] WinCommandAgent: transmitting bypass route to <REMOTE_IP>
{
"host" : "<REMOTE_IP>",
"ipv6" : false
}
[Feb 28, 2026, 18:42:04] {
"allow_local_dns_resolvers" : false,
"confirm_event" : "e40f000000000000",
"destroy_event" : "e80f000000000000"
}
POST np://[\\.\pipe\agent_ovpnconnect]/tun-open : 200 OK
Destroyed previous TAP instance
TAP ADAPTERS:
guid='{9E0F7192-213E-4039-83C6-E8AC4C6FD211}' index=44 name='OpenVPN Connect DCO Adapter'
guid='{F2CAA5A1-9DC4-4CE5-B2ED-99CD508B2E08}' index=111 name='OpenVPN Data Channel Offload'
Open TAP device "OpenVPN Connect DCO Adapter" PATH="\\?\ROOT#NET#0001#{cac88484-7515-4c03-82e6-71a87abac361}\ovpn-dco" SUCCEEDED
TAP handle: 7c0f000000000000
[Feb 28, 2026, 18:42:03] EVENT: RESOLVE
[Feb 28, 2026, 18:42:03] 4 [persist-tun]
[Feb 28, 2026, 18:42:03] 3 [tcp-nodelay]
[Feb 28, 2026, 18:42:03] 2 [connect-retry] [2] [300]
[Feb 28, 2026, 18:42:03] 1 [resolv-retry] [infinite]
[Feb 28, 2026, 18:42:03] 0 [data-ciphers] [CHACHA20-POLY1305]
[Feb 28, 2026, 18:42:03] Unsupported option (ignored)
[Feb 28, 2026, 18:42:03] NOTE: This configuration contains options that were not used:
[Feb 28, 2026, 18:42:03] Frame=512/2112/512 mssfix-ctrl=1250
[Feb 28, 2026, 18:42:03] OpenVPN core 3.11.3 win x86_64 64-bit OVPN-DCO built on Sep 16 2025 15:58:53
```
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