How libcurl upgrade works

Workflow

These stages describe the transaction flow for HTTP requests by using the upgraded libcurl library:

1. An application component, such as Smart Licensing, Install Manager, Zero Touch Provisioning, or the Copy utility, starts an HTTP or HTTPS request by calling the HTTP client library API.

   • The API remains unchanged, so existing feature components continue to work without modification.

   • The HTTP client library receives and processes the request.

2. The HTTP client library packages the request, adds required parameters, and sends the request asynchronously to the HTTP client process.

   • Asynchronous interprocess communication prevents operations from blocking.

   • Request details, such as VRF information and metadata, are included for execution.

   • The HTTP client process receives the prepared request.

3. The HTTP client process manages the request by queuing transactions and maintaining session state for multiple requests.

   • The process uses the libcurl multi interface to scale concurrent requests efficiently.

   • The process performs error handling and allocates required system resources.

   • Requests are sequenced and validated before dispatch to the communication layer. The process then prepares to call libcurl for protocol execution.

4. The HTTP client process calls the curl_multi_perform API for efficient asynchronous network operations.

   • Handles XR-custom socket management, VRF context, and SSL using Cisco extensions.

   • Manages concurrency by using select and the libcurl multi interface.

   This stage provides reliable, efficient transaction processing. Network protocol negotiation and TLS setup occur in the updated, security-patched libcurl library.

5. The libcurl library establishes the network connection, negotiates SSL or TLS as needed, and completes the HTTP transaction by using HTTP/1.0 or HTTP/1.1.

   • Maintains socket management, SSL via libssl_xr/libcrypto_xr, and TCP settings.

   • Security patches and protocol improvements are applied in this stage.

   • The library sends response and transaction state information to the HTTP client process.

6. The HTTP client process parses the libcurl response, updates transaction status, logs actions or errors, and tracks operational state.

   • Uses standardized error codes and logging to simplify troubleshooting and monitoring.

   • Makes status information available through show commands.

   Transaction results are passed to the client library. The HTTP client library supplies the response and status to the application.

7. The application receives the response from the HTTP client library and continues normal operation.

   The HTTP transaction process completes, and resources are released. No user or application-level awareness or adaptation is needed for the upgrade.