How to Read and Interpret VRCP DrvInfo Logs

VRCP DrvInfo: Complete Guide to Driver Information and TroubleshootingVRCP (Virtual Router Control Protocol) DrvInfo is a diagnostic and telemetry component commonly used in environments that manage virtual routing and driver-level networking components. This guide explains what DrvInfo contains, how to collect and interpret its data, common problems that show up in DrvInfo reports, and step-by-step troubleshooting procedures to resolve driver and virtual-router issues.

What is VRCP DrvInfo?

VRCP DrvInfo is a structured set of driver- and interface-related information produced by the VRCP subsystem (or by complementary diagnostics tools) to show the current state, capabilities, and recent events for networking drivers and virtual routing interfaces. It typically includes versioning details, configuration flags, runtime statistics, error counters, and timestamps of notable events.

Typical uses:

• Debugging driver failures or misconfiguration.
• Auditing environment consistency across hosts.
• Feeding automation for monitoring and alerting.
• Forensics after an outage to trace root cause.

Common DrvInfo fields and what they mean

Below are frequently encountered fields in DrvInfo outputs and how to interpret them.

• DriverName / Module: identifies the kernel or user-space driver handling the virtual interface.
• Version / Build: driver version and build hashes — important when matching bug reports or vendor advisories.
• DeviceID / PCI / BusInfo: hardware identifiers used for mapping virtual interfaces to physical NICs.
• MTU: maximum transmission unit configured for the interface — mismatch between ends can cause fragmentation or drops.
• MAC Address: hardware/virtual address used for layer-2 communication.
• AdminState / OperState: administrative (configured) state vs. operational (actual) state. Discrepancies indicate link, authentication, or policy issues.
• Rx/Tx Counters: cumulative packet and byte counts; high error/collision counts are red flags.
• Error Counters: CRC errors, dropped packets, buffer overruns — each suggests particular failure modes.
• Flags / Capabilities: offload capabilities (checksum offload, TSO, GRO), VLAN offload, SR-IOV, etc. Incorrect/off mismatches can affect performance.
• Timestamps / LastEvent: when driver was loaded, last reset, or last error — useful for correlating with system logs.
• Configuration Hash / Checksum: a digest of configuration used to detect drift between nodes.

How to collect DrvInfo

Collection methods depend on environment and tooling. Common approaches:

• Command-line tool: many VRCP deployments provide a cli command (e.g., vrcp drvinfo show) that prints structured DrvInfo.
• System logs: dmesg / journalctl often include driver load/unload events and error messages referenced by DrvInfo timestamps.
• Telemetry agents: monitoring agents can periodically pull DrvInfo and send it to central collectors (Prometheus exporters, ELK, etc.).
• Vendor diagnostics: NIC and hypervisor vendors may provide utilities that export richer driver diagnostics.

When collecting:

• Gather both the DrvInfo output and system logs from the same time window.
• Capture environment details: kernel version, hypervisor version, and recent configuration changes.
• Use structured (JSON/YAML) output if available for easier parsing and automation.

Interpreting common DrvInfo entries and patterns

1. AdminState=up, OperState=down

   • Likely causes: physical link down, switch port disabled, VLAN mismatch, authentication failure (802.1X), or driver failure.
   • Check: switch port status, cable/physical link, and port security settings; inspect driver logs for link negotiation errors.

2. High Rx drops / Rx errors

   • Likely causes: buffer exhaustion, mismatched MTU leading to fragmentation, corrupted frames (bad cabling), or hardware faults.
   • Check: socket buffer and ring sizes, MTU configuration on both ends, NIC hardware diagnostics.

3. Frequent driver resets (LastReset timestamp repeatedly updates)

   • Likely causes: driver crashes due to firmware bugs, power management issues, or transient hardware errors.
   • Check: kernel logs for oops/panic, firmware/driver compatibility, rollback to a known-good driver or firmware.

4. Offload capabilities listed but not used (e.g., checksum offload reported but high CPU)

   • Likely causes: packet path bypassed hardware (encapsulation, tunneling), or OS/kernel configuration disabling offloads.
   • Check: ensure kernel networking stack and virtual switching allow offloads; verify tunnel/GSO settings and drivers for compatibility.

5. MAC or VLAN learning issues (stale MAC, wrong VLAN)

   • Likely causes: duplicated MACs, VM migration with incorrect flush, switch configuration issue.
   • Check: clear MAC tables, ensure correct migration procedures, and verify VLAN tagging consistency.

Step-by-step troubleshooting workflow

1. Reproduce and capture:

   • Capture current DrvInfo (structured output), system logs, and network-level packet traces if possible.
   • Note the timestamp and correlate across sources.

2. Check obvious configuration mismatches:

   • Confirm MTU, VLAN, and link speed/duplex match across peer endpoints.
   • Verify admin vs. oper state differences.

3. Inspect driver and kernel logs:

   • Use journalctl, dmesg, and vendor driver logs for backtraces, reset messages, and firmware errors.

4. Check hardware health:

   • Run NIC vendor diagnostics and check for SFP/QSFP errors, link flaps, or thermal issues.
   • For virtualized NICs, inspect hypervisor host health and VM host mappings.

5. Isolate the problem:

   • Move the VM/interface to a different host or attach to a different physical NIC to narrow whether it’s hardware, host, or configuration related.
   • Temporarily disable advanced offloads or power management features to see if stability improves.

6. Apply mitigations:

   • Increase rx/tx ring sizes, adjust buffer sizes.
   • Disable problematic offloads (TSO/GSO) if they cause corruption.
   • Roll back to a previous stable driver/firmware if a recent upgrade correlates with the issue.

7. Long-term fixes:

   • Patch drivers/firmware where vendor provides fixes.
   • Add monitoring/alerts on specific DrvInfo counters (CRC errors, resets).
   • Automate consistent configuration enforcement (configuration management, periodic checksums of config).

Examples: real-world scenarios

• Scenario A — Intermittent packet loss on VMs: DrvInfo showed rising RxDrops and repeated driver resets. Root cause: faulty SFP causing CRC errors. Replacement fixed the issue; monitoring alerted on CRC errors going forward.
• Scenario B — High CPU for small packets: DrvInfo reported offload capabilities but encapsulated traffic prevented offload usage. Solution: enable offload-compatible encapsulation or use vSwitch features that preserve offload.
• Scenario C — After a kernel update, multiple hosts saw link flaps; DrvInfo indicated a driver incompatibility. Rolling back kernel/driver on one host confirmed the cause; vendor patch later resolved it.

Automation and monitoring recommendations

• Export DrvInfo fields as metrics (e.g., via Prometheus exporters) for trend analysis and thresholds.
• Alert on sudden increases in error counters, driver resets, or admin/oper mismatches.
• Store periodic snapshots of DrvInfo in an indexed store (Elasticsearch, object store) to enable historical correlation.
• Use configuration hash fields to detect drift and trigger automated remediation or alerts.

When to involve vendor support

Contact vendor support when:

• You have driver crash logs, oopses, or firmware errors that match vendor-known issues.
• The problem persists after isolating hardware vs host-level issues.
• You need firmware or driver updates not publicly available. Provide vendor with:
• DrvInfo output, correlated system logs, timestamps, and steps to reproduce.

Summary

• DrvInfo aggregates driver, interface, and runtime telemetry useful for diagnosing virtual routing and NIC issues.
• Collect structured DrvInfo plus logs, traces, and environment versions.
• Focus troubleshooting on state mismatches, error counters, driver resets, and offload/capability mismatches.
• Use automation to monitor important counters and configuration drift; involve vendors when diagnostics point to firmware/driver bugs.