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thinca
dd989ec9ca
Problem: When ch_open() tries to connect to a hostname that resolves to
multiple addresses (e.g., both IPv6 and IPv4), it uses a
single waittime for all connection attempts. If the first IPv6
connection attempt times out, it consumes almost all of the
waittime, leaving insufficient time (often just 1ms) for the
IPv4 attempt to succeed. (reporter)
Solution: Implement a simplified version of Happy Eyeballs (RFC 8305) to
improve connection fallback behavior when IPv6 is unavailable
or slow (thinca).
Distribute the waittime across multiple addresses:
- First address: use up to 250ms (RFC 8305 Connection Attempt Delay) or
half of the total waittime, whichever is smaller
- Middle addresses: divide remaining time equally
- Last address: use all remaining time
This ensures that IPv4 fallback has sufficient time to succeed even when
IPv6 connection attempts fail or timeout.
closes: #19233
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
Signed-off-by: thinca <thinca@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
