jschoubben
8fcfa88fe0
A suspended laptop's connection is dead the moment it wakes, and the socket looks perfectly healthy from inside the process — no error, no close, because nothing has tried to send anything. Heartbeats find out twenty or thirty seconds later. For that time the node believes it is in a mesh it has left, which is the one state this design says must never be indistinguishable from being connected. The machine knew immediately. So being roused ends the current attempt rather than only shortening the wait after it: shortening the wait would do nothing at all, because the process is not waiting — it is sitting inside a connection that will not return. A signal, because nothing may listen on a node (novox/hq ADR 0004). A socket for this would be a control surface on every machine, reachable by anything that can reach the machine, in exchange for saving twenty seconds — and the whole security argument rests on there not being one. Two rouses in the same instant are one: a machine suspending and resuming repeatedly must not build a backlog of reconnections to work through. And the backoff is not reset by being roused — that says the machine changed, not that whatever was refusing the connection has stopped, and a laptop woken on a network with no route would otherwise retry at full speed for as long as somebody keeps opening the lid. The dispatcher acts on the events that change where packets go and not on `down`: the link is already gone there, reconnecting will fail, and the backoff exists for exactly that.
23 lines
1.1 KiB
Bash
Executable File
23 lines
1.1 KiB
Bash
Executable File
#!/bin/sh
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# Rouse the host when this machine's network changes.
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#
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# Installed as a NetworkManager dispatcher script (/etc/NetworkManager/dispatcher.d) and as a
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# networkd-dispatcher one. Both hand the interface and the event as arguments; both are ignored
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# beyond the event, because *which* interface changed does not matter — what matters is that a
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# connection opened over the old route is now pointing at nothing, and that is true whichever
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# interface it was.
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#
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# A machine that moves from wifi to ethernet holds a socket that looks perfectly healthy from
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# inside the process: no error, no close, because nothing has tried to send anything. Heartbeats
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# find it twenty or thirty seconds later. The machine knew immediately.
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set -eu
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event="${2:-}"
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case "$event" in
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up|dhcp4-change|dhcp6-change|connectivity-change|routes-change)
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# Only events that can change where packets go. `down` is deliberately not one: the link is
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# already gone, reconnecting will fail, and the backoff exists for exactly that.
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systemctl start --no-block nox-mesh-host-roused.service 2>/dev/null || true
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;;
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esac
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