IPv6 UDP sends hit ENOBUFS much faster than IPv4 (smaller kernel
buffers, NDP overhead). Fixed:
- Adaptive backoff: 200us→10ms as errors accumulate, resets on success
- Higher error threshold: 50k instead of 1k before stopping
- Yield with sleep when errors have been seen recently
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>