Hello, We are running C++ software that uses libCurl 8.5 on Windows 10 and 11 that perform HTTP operations.
During testing I notice a difference in some rare situations when running the software in Window 11 and in a virtual machine. The virtual machine is Oracle Virtual Box with Windows 11 host and Windows 10 guest OS). We enabled CURLOPT_VERBOSE to debug the issue when the software attempts to perform a HTTP post operation. Here is the output from Windows 11; 1. Host localhost:8010 was resolved 2. IPv6: ::1 3. IPv4: 127.0.0.1 4. Trying [::1]:8010... 5. Trying 127.0.0.1:8010... 6. Connect to localhost (127.0.0.1) port 8010 Step 4 in the above list uses approximately 200ms to execute before moving on to trying 127.0.0.1. Here is the output from Windows 10 inside Oracle Virtual Box; 1. Host localhost:8010 was resolved 2. IPv6: ::1 3. IPv4: 127.0.0.1 4. Trying [::1]:8010... 5. ipv6 connect timeout after 2985ms, move on 6. Connection timeout after 3378 ms 7. Close connection Step 4 in the above list uses approximately 2985ms to execute before moving on ... Windows 11 has the following interfaces (according to "route print" command) * Intel(R) Ethernet Connection * VirtalBox Host-only Ethernet Adpter * Software Loopback Interface Windows 10 inside VirtualBox has the following interfaces (according to "route print" command) * Intel(R) PRO/1000 MT * Software Loopback Interface Why does Windows 10 inside a virtual machine use 15 times as much time to try IPv6 before moving on? How can I possible reduce or remove this difference? I have read above CURLOPT_IPRESOVE but really need to understand the problem before considering this solution. Appreciate any input Regards, Lars
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