Retire tailscale-optimize-router.sh to unused/

Tailscale's UDP GRO forwarding tuning applies to the machine running
tailscaled. That is VM 100 (ts-subnet-rtr), a KVM guest with its own kernel
and netdevs, so ethtool on the Proxmox host cannot affect its forwarding
path. Host-side tuning would only have been the right lever for a tailscaled
running in an LXC container, which shares the host kernel.

The interfaces were wrong in any case. VM 100 is on vmbr7, backed by
enp4s0f7np7. vmbr0 is backed by enp4s0f0np0 and carries unrelated guests, and
enp4s1f12np12 is the host's own routing NIC and not a bridge port at all.

It never ran: the header says to run it from root's crontab, and root has no
crontab. Both offloads were still off on every interface it named.

Kept with a header recording where the tuning actually belongs.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tailscale-optimize-router.sh

@@ -1,4 +0,0 @@
-#!/bin/sh
-# run from root's crontab
-/usr/sbin/ethtool -K vmbr0 rx-udp-gro-forwarding on rx-gro-list off
-/usr/sbin/ethtool -K enp4s1f12np12 rx-udp-gro-forwarding on rx-gro-list off

unused/tailscale-optimize-router.sh

@@ -0,0 +1,24 @@
+#!/bin/sh
+# RETIRED. Kept for reference only.
+#
+# Tailscale's UDP GRO forwarding tuning belongs on the machine running
+# tailscaled. Here that is VM 100 (ts-subnet-rtr), a KVM guest with its own
+# kernel and its own netdevs, so setting it on the Proxmox host cannot affect
+# it. Apply it inside that VM instead, on its default-route interface:
+#
+#   NETDEV=$(ip -o route get 8.8.8.8 | cut -f 5 -d " ")
+#   ethtool -K "$NETDEV" rx-udp-gro-forwarding on rx-gro-list off
+#
+# Host-side tuning would have been the right lever only if tailscaled ran in an
+# LXC container, which shares the host kernel.
+#
+# The interfaces below were wrong regardless. VM 100 sits on vmbr7, backed by
+# enp4s0f7np7; vmbr0 is backed by enp4s0f0np0 and carries different guests,
+# and enp4s1f12np12 is the host's own routing NIC, not a bridge port.
+#
+# It was also never in service: the header said "run from root's crontab", but
+# root has no crontab.
+
+# run from root's crontab
+/usr/sbin/ethtool -K vmbr0 rx-udp-gro-forwarding on rx-gro-list off
+/usr/sbin/ethtool -K enp4s1f12np12 rx-udp-gro-forwarding on rx-gro-list off