ip6tables: always install service and mangle rules regardless of ipv6_default_router

Previously configure_ip6tables() returned early when ipv6_default_router
was not set. This left nodes without IPv6 TCPMSS clamping for forwarded
mesh traffic, causing MTU black holes. Now ip6tables.service and mangle
rules are always installed; the nat table is only added when
ipv6_default_router is set.

Also includes link status monitor improvements: cost hysteresis,
congestion-aware metric capping, TX rate tracking, and disconnect
recovery with EWMA history clearing.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
2 files changed
tree: 30659fec3c8ae150abaaa524d7dde04d87321ae6
  1. .gitignore
  2. .gitmodules
  3. config.examples/
  4. src/
  5. support.sh
  6. systemd-units/