YueGuobin 577be9b94e
docs: pin down the VXLAN MTU derivation and its re-derivation paths
Verified against the running kernel's sources (7.2.6): the 50-byte
headroom is 20 outer IPv4 + 8 UDP + 8 VXLAN + 14 inner Ethernet
header (vxlan_headroom(), include/net/vxlan.h); the vxlan driver has
no NETDEV_CHANGEMTU handler so a live tunnel never follows its lower
device, while the bridge does follow its ports at runtime
(NETDEV_CHANGEMTU -> br_mtu_auto_adjust). Document the operational
consequence: the wiring path re-creates the device on every node
start and link (re)creation, so raising the underlay MTU on both
computes and stop/start-ing the nodes is the fix — no manual
ip link needed.
2026-10-17 14:11:00 +08:00
..