examples(iroh): add --logs and --mode ping features to transfer example

[Frando]

Description

More improvements to our transport example to ease dogfooding:

• new --logs flag (for both provide and fetch) for simple file logging:
  • without further config, creates a directory ./logs/transfer-{cmd}-{date}-{endpoint_id} and saves logs with iroh=trace,transfer=trace to a logs file in that directory.
  • different log level can be set with RUST_LOG
  • different path can be set with --logs-path
  • qlog files are also written to that directory if the qlog feature is enabled
• New --mode ping option for fetch command: instead of transferring as much data as possible, this just keeps the connection open until the --duration is expired (default: 10s). This gives much smaller log files (both tracing and qlog) so easier to debug when looking for connection changes only.
• Regular output now includes the time since start after each line. Useful to interpret the "switched to direct" etc lines after the fact (they didn't have any time indication so far)
• Better formatting for durations
• Better spans on accept side. Each connection gets an id now that easily allows to grep for that connection through both iroh and quinn logs
• Print path ids with the paths stats and changes. This allows to correlate with the tracing logs now.

With both logs and qlog in a single dir it's now really straightforward to share it eg with sendme.

Breaking Changes

Notes & open questions

Should --logs include iroh_quinn=trace by default or not?

Change checklist

• Self-review.
• Documentation updates following the style guide, if relevant.
• Tests if relevant.
• All breaking changes documented.
  • List all breaking changes in the above "Breaking Changes" section.
  • Open an issue or PR on any number0 repos that are affected by this breaking change. Give guidance on how the updates should be handled or do the actual updates themselves. The major ones are:
    • quic-rpc
    • iroh-gossip
    • iroh-blobs
    • dumbpipe
    • sendme

[github-actions]

Documentation for this PR has been generated and is available at: https://n0-computer.github.io/iroh/pr/3893/docs/iroh/

Last updated: 2026-02-09T15:03:58Z