fix: Remove dead BsdAsyncIcmpSocket::new; live BSD IPv6 validation (FreeBSD 14.3 + OpenBSD 7.7)

[dweekly]

Live-validated ftr v0.9.0 IPv6 support on real BSD hardware: two arm64 Parallels VMs bridged onto the same Sonic fiber LAN as the existing macOS/Linux/Windows validation environments.

What was validated

FreeBSD 14.3-RELEASE (arm64) — FreeBSD freebsd143 14.3-RELEASE ... GENERIC arm64

• External IPv6: yes. Global SLAAC 2001:5a8:4681:2c00:21c:42ff:fed9:7283, v6 default route via vtnet0, ping6 google.com 0% loss (replies from 2607:f8b0:4005:808::200e, hlim=109, ~3.3ms).
• Build: rust/cargo/cc present, git absent (source shipped as a v0.9.0 tarball); cargo build --release → exit 0, 1,163,584-byte binary.
• Non-root permission path validated (verbatim):

  $ ./target/release/ftr --version
  ftr 0.9.0
  $ ./target/release/ftr -6 ::1        # exit 1
  Error: ftr requires root privileges on freebsd
  This platform does not support unprivileged traceroute.
  $ ./target/release/ftr 8.8.8.8       # exit 1
  Error: ftr requires root privileges on freebsd
  This platform does not support unprivileged traceroute.
  

OpenBSD 7.7 (arm64) — first-ever compile of the cfg(target_os = "openbsd") arm — OpenBSD openbsd7.localdomain 7.7 GENERIC.MP#2 arm64

• External IPv6: no. Only ::1, no global v6, no v6 default route; ping6 google.com 100% loss (ret=-1). OpenBSD v6 traces on this host are limited to loopback.
• Build (headline): the OpenBSD bsd_v6.rs arm compiled for the first time ever, and clean. git clone --branch v0.9.0 + cargo build --release → exit 0 in 2m20s, 1,251,000-byte binary. It emitted exactly one warning — dead code in the shared IPv4 path (see below).

The dead-code fix

The OpenBSD (and any BSD) release build flagged:

warning: associated function `new` is never used
  --> src/socket/bsd.rs:35:12
warning: `ftr` (lib) generated 1 warning

BsdAsyncIcmpSocket::new() had a single caller — its own #[cfg(test)] unit test — so a non-test release build on a BSD flags it. It went unnoticed because CI's FreeBSD job builds in test profile (where the test uses it) and clippy -D warnings runs on Linux/macOS, where bsd.rs is not compiled at all. This is the same class of platform-gated dead code cleaned up earlier for the macOS and Windows arms. The fix removes the redundant new() and points its test at new_with_config(TimingConfig::default()) — the constructor the socket factory actually uses. After the patch, cargo build --release finishes warning-free on both OpenBSD (33.85s) and FreeBSD (7.50s), confirmed by rebuild on the live VMs.

What remains untested (honest)

The live root-gated multi-hop trace was not run this session. Raw ICMPv6 requires root on the BSDs; direct root SSH is disabled on both VMs and no host-sanctioned privilege-escalation path was available, so the run that would finally observe a router-originated ICMPv6 Time Exceeded on FreeBSD first-hand is deferred to a maintainer (recorded in docs/IPV6_DESIGN.md). FreeBSD has confirmed external v6, so the trace is achievable there; OpenBSD's VM has no external v6. Root cargo test on the VMs likewise pending.

Validation

• Host gates: cargo fmt, cargo clippy --all-targets -D warnings, cargo test (228+20+doctests pass), RUSTDOCFLAGS=-D warnings cargo doc — all green. (cargo check --target x86_64-unknown-freebsd fails on openssl-sys header cross-compile, unrelated to this change; bsd.rs isn't reached.)
• Real-hardware: warning-free release rebuild on both FreeBSD 14.3 and OpenBSD 7.7. CI's FreeBSD VM job exercises the changed bsd.rs.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.31%. Comparing base (9be8a93) to head (e58b1b9).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #51   +/-   ##
=======================================
  Coverage   84.31%   84.31%           
=======================================
  Files          36       36           
  Lines        6663     6663           
=======================================
  Hits         5618     5618           
  Misses       1045     1045           

Flag	Coverage Δ
unittests	84.31% <ø> (ø)

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