fix(net): reject IPv4-compatible addresses in is_advertisable_ipv6 (#1955) - #144
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IPv6 addresses derived from IPv4 (both IPv4-mapped ::ffff:a.b.c.d and IPv4-compatible ::a.b.c.d forms) are not routable global addresses and must not be advertised as peer candidates. Previously only the mapped form was filtered; now both forms are rejected via to_ipv4().is_some(), which matches both the ::/96 IPv4-compatible block and the ::ffff:0:0/96 IPv4-mapped block. Adds three unit tests: IPv4-compatible rejection, regression guard for IPv4-mapped, and guard against over-rejecting real global addresses. Fixes #1955. Co-Authored-By: Claude <noreply@anthropic.com>
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What changed
Closes DIG-Network/dig_ecosystem#1955.
is_advertisable_ipv6(crates/dig-node-core/src/seams/dig_peer/net.rs) decides whether anIpv6Addris a global-unicast address worth advertising to peers. It folded out IPv4-mapped addresses (::ffff:a.b.c.d) viato_ipv4_mapped().is_some(), but missed the IPv4-compatible form (::a.b.c.d, the::/96block). An IPv4-compatible address is an IPv4 address in disguise — not a dialable global IPv6 — so advertising it as a routable IPv6 candidate is wrong (§5.2 IPv6-first: IPv4-in-any-form must not masquerade as a global IPv6 peer address).Fix:
ip.to_ipv4_mapped().is_some()→ip.to_ipv4().is_some().to_ipv4()returnsSomefor both the mapped and the compatible forms, so both are now rejected.::(unspecified) and::1(loopback) remain caught by the earlieris_unspecified()/is_loopback()checks in the same expression, so the change adds only the compatible-form rejection — it never over-rejects a genuine global address (to_ipv4()returnsNonefor e.g.2001:db8::1). The doc comment is updated to say "not an IPv4-mapped OR IPv4-compatible address".Verification
ipv4_compatible_is_not_advertisable—::1.2.3.4(::0102:0304) →false(RED underto_ipv4_mapped, GREEN after the fix).ipv4_mapped_is_still_not_advertisable—::ffff:1.2.3.4→false(regression guard).a_real_global_unicast_ipv6_is_advertisable—2001:db8::1→true(no over-rejection).local_ipv6_addr→advertised_socket_addrs).cargo fmt --all -- --check→ 0 ·cargo clippy -p dig-node-core --all-targets --all-features -- -D warnings→ 0 ·cargo test -p dig-node-coregreen (the only failure being the known env-limiteddual_stackport-bind test, #1961).Version
fix:(correctness — a more-restrictive address filter; no public-API/behaviour break for legitimate addresses) →[workspace.package].version0.75.2 → 0.75.3.Cargo.lockupdated + committed.Generated by Claude Code