What causes "are you connected to the network?" in juicedata/juicefs?

Verify the host has an up, non-loopback interface with an IP address (ip addr / ifconfig).

are you connected to the network?

Error message

are you connected to the network?

What it means

The libjfs local IP discovery helper enumerates the host's network interfaces looking for an address matching a given mask, and returns "are you connected to the network?" when no usable address is found — i.e. no interface has an IP matching the mask (or no non-loopback IP exists at all).

Source

Thrown at sdk/java/libjfs/main.go:2120

			case *net.IPNet:
				ip = v.IP
			case *net.IPAddr:
				ip = v.IP
			}
			if ip == nil || ip.IsLoopback() {
				continue
			}
			ip = ip.To4()
			if ip == nil {
				continue // not an ipv4 address
			}
			if !strings.HasPrefix(ip.String(), mask) {
				continue
			}
			return ip.String(), nil
		}
	}
	return "", errors.New("are you connected to the network?")
}

//export jfs_get_token
func jfs_get_token(h int64, cname *C.char, buf uintptr, count int32, renewer *C.char) int32 {
	w := F(h)
	if w == nil {
		return EINVAL
	}
	id, t, eno := kerb.issue(w.ctx, w.Meta(), C.GoString(cname), w.user, C.GoString(renewer))
	if eno != 0 {
		logger.Errorf("get token for %s: %s", w.volname, eno)
		return errno(eno)
	}
	wb := utils.NewNativeBuffer(toBuf(buf, count))
	wb.Put32(id)
	wb.Put64(uint64(t.Issued))
	wb.Put64(uint64(t.Expire))
	wb.Put([]byte(t.Password))

View on GitHub (pinned to c9a67b23e8)

Solutions

Verify the host has an up, non-loopback interface with an IP address (ip addr / ifconfig).
Check the mask/prefix argument actually matches one of the host's subnets.
Ensure containers have networking configured (docker run --network, CNI setup) before the lookup runs.
If interfaces come up asynchronously, retry the lookup after a short delay.

Defensive patterns

Strategy: try-catch

Validate before calling

func hasUsableIP() bool {
	ifaces, err := net.Interfaces()
	if err != nil { return false }
	for _, i := range ifaces {
		if i.Flags&net.FlagUp == 0 || i.Flags&net.FlagLoopback != 0 { continue }
		addrs, _ := i.Addrs()
		if len(addrs) > 0 { return true }
	}
	return false
}

Try / catch

ip, err := localIP(mask)
if err != nil {
	log.Printf("no matching local IP for mask %s: %v; retrying", mask, err)
	time.Sleep(time.Second)
	ip, err = localIP(mask)
}

Prevention

Wait for network readiness (interface up) before IP discovery in containers/VMs
Pass a mask that matches an actual host subnet; verify with `ip addr`
Avoid running IP-dependent code in loopback-only namespaces
Log all interface addresses when lookup fails to ease diagnosis

When it happens

Trigger: Calling the IP-lookup function on a host whose interfaces are all down or loopback-only; an interface whose IP does not match the supplied subnet mask; running inside a network namespace/container with no configured interfaces; IPv6-only environments where the mask comparison against IPv4 strings never matches.

Common situations: Containers or VMs started before the network is up, hosts with only a loopback device, sandboxed CI runners without network configuration, or a wrong subnet mask passed that matches no interface.

Related errors

AI-assisted analysis of juicedata/juicefs@c9a67b23e8 (2026-09-06). Data as JSON: /api/errors/df85f55809d11495. Report an issue: GitHub.