shell: clean up stale ssh.sock on --reconnect when the master is already dead#5165
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AkihiroSuda merged 1 commit intoJul 2, 2026
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AkihiroSuda
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Jun 29, 2026
AkihiroSuda
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Jun 29, 2026
…ady dead `limactl shell --reconnect` failed with `exit status 255` when the SSH ControlMaster socket existed but its master process had already exited (unclean hostagent shutdown: kill -9, OOM, host crash) -- the exact wedged state --reconnect is meant to recover from. Gate the control-socket cleanup on a liveness probe: only remove the socket when no master is listening on it, so a genuine `ssh -O exit` failure against a live master is still surfaced as an error. Add sshutil.IsControlMasterRunning and sshutil.RemoveStaleControlMaster with unit tests, and use the latter in the shell --reconnect path. Fixes lima-vm#4913 Signed-off-by: gaurav0107 <[email protected]>
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Summary
limactl shell --reconnect <inst>is the documented escape hatch (added in #3125) for resetting a wedged SSH multiplexed session. Today it fails withexit status 255when the SSH ControlMaster socket file (<instDir>/ssh.sock) still exists but the master process is already dead — which is exactly the wedged state--reconnectis meant to recover from.sshutil.IsControlMasterExistingis a pureos.Stat; it does not verify the master is alive. After an unclean hostagent exit (kill -9, OOM, host crash, or the Cygwin/msys2 emulation file outliving its process) the socket survives.ssh -O exitthen fails and the error was returned directly, so--reconnectexited non-zero with no recovery.Changes
sshutil.IsControlMasterRunning(instDir)— dials the control socket to check whether a master is actually listening (a stale socket has no listener).sshutil.RemoveStaleControlMaster(instDir)— removes the control socket only when no master is listening; a live master's socket is never touched, and a missing socket is a no-op.cmd/limactl/shell.go, onssh.ExitMasterfailure during--reconnect, remove the socket only if it is confirmed stale; if a master is still alive the original error is still returned.This keeps the behavior unchanged for a live master (a genuine
ssh -O exitfailure is still surfaced) and recovers automatically when the master is already dead.Test plan
pkg/sshutil/sshutil_test.go(TestControlMasterStale):go test ./pkg/sshutil/...go vet ./...gofmt -l(clean)go build ./...Fixes #4913