Tune for low-end devices

This page has not been written. EdgeVPN has a full set of resource-limiting flags and none of them are explained beyond their --help line. There is no guidance on which to reach for on a Raspberry Pi, a router or a container with a tight memory cgroup.

What is missing, and where the source is:

• --low-profile (env EDGEVPNLOWPROFILE) is on by default, which is itself undocumented, and its name promises more than it does: in pkg/config/config.go the flag’s only effect is dht.BucketSize(20). A second, unrelated vpn.LowProfile library option in pkg/vpn/config.go swaps in a bounded stream manager (pkg/vpn/vpn.go) and is not wired to the CLI flag. The difference needs writing up.
• The ten limit-* flags in cmd/util.go, which configure the libp2p resource manager: --limit-enable (off by default — the others do nothing until it is on), --limit-file, --limit-scope, --limit-config-streams, --limit-config-streams-inbound, --limit-config-streams-outbound, --limit-config-conn, --limit-config-conn-inbound, --limit-config-conn-outbound and --limit-config-fd. Their defaults (200/30/30, 200/30/30, 30) are not documented and their relationship to --limit-scope is not explained.
• Connection water marks. --connection-high-water and --connection-low-water (env EDGEVPN_CONNECTION_HIGH_WATER / EDGEVPN_CONNECTION_LOW_WATER) both default to 0, and what 0 means is not stated anywhere. --max-connections (env EDGEVPNMAXCONNS) is a third knob in the same area.
• What to turn off. --dht, --mdns, --natservice, --natmap, --autorelay and --relay-service are all on by default and all cost something; --relay-service=false in particular stops the node carrying other peers’ traffic. See relays and hop nodes.

Contributions welcome — see contributing.