Support ICMP cellular connectivity probe with undefined host IP

This commit fixes handling of ICMP-based cellular connectivity
probes when the probe host is not specified.
Users can configure periodic connectivity probes for cellular networks,
using either ICMP or TCP. For ICMP, the probe host can be left empty
to use the default target (Google DNS: 8.8.8.8), as was the implicit
behavior in older EVE versions where the probe address was not yet
configurable.

However, it turned out that EVE did not handle the case of an undefined
ICMP probe IP at all. This went unnoticed because parsing errors
(such as "missing endpoint host address for ICMP probe") were only logged,
while the configuration was still applied — and probing happened to work
as intended. With recent improvements in zedagent, parsing failures are
now reported to the controller, and EVE rejects configurations with such
errors.

This commit fixes the parsing logic to correctly accept an undefined ICMP
probe endpoint and ensures it is properly handled by mmagent.

Signed-off-by: Milan Lenco <[email protected]>
(cherry picked from commit e2e5e95)

Author: milan-zededa

pkg/pillar/cmd/zedagent/parseconfig.go

@@ -577,15 +577,28 @@ func parseConnectivityProbe(probe *zconfig.ConnectivityProbe) (
 	case zconfig.ConnectivityProbeMethod_CONNECTIVITY_PROBE_METHOD_ICMP:
 		parsedProbe.Method = types.ConnectivityProbeMethodICMP
 		parsedProbe.ProbeHost = probe.GetProbeEndpoint().GetHost()
-		if parsedProbe.ProbeHost == "" {
-			return parsedProbe, errors.New("missing endpoint host address for ICMP probe")
+		// Undefined host for ICMP probing is allowed - EVE will probe Google DNS
+		// (8.8.8.8) in that case.
+		// However, if host address is defined, it should be a valid IP address.
+		if parsedProbe.ProbeHost != "" {
+			probeIP := net.ParseIP(parsedProbe.ProbeHost)
+			if probeIP == nil {
+				return parsedProbe, fmt.Errorf("invalid IP address for ICMP probe: %s",
+					parsedProbe.ProbeHost)
+			}
 		}
 	case zconfig.ConnectivityProbeMethod_CONNECTIVITY_PROBE_METHOD_TCP:
 		parsedProbe.Method = types.ConnectivityProbeMethodTCP
+		// Host address should be a valid (and non-empty) IP address.
 		parsedProbe.ProbeHost = probe.GetProbeEndpoint().GetHost()
 		if parsedProbe.ProbeHost == "" {
 			return parsedProbe, errors.New("missing endpoint host address for TCP probe")
 		}
+		probeIP := net.ParseIP(parsedProbe.ProbeHost)
+		if probeIP == nil {
+			return parsedProbe, fmt.Errorf("invalid IP address for TCP probe: %s",
+				parsedProbe.ProbeHost)
+		}
 		probePort := probe.GetProbeEndpoint().GetPort()
 		if probePort == 0 {
 			return parsedProbe, errors.New("missing endpoint port number for TCP probe")
@@ -2223,7 +2236,7 @@ func parseNetworkWirelessConfig(ctx *getconfigContext,
 		if err != nil {
 			return wconfig, err
 		}
-		if customProbe.Method == types.ConnectivityProbeMethodNone || err != nil {
+		if customProbe.Method == types.ConnectivityProbeMethodNone {
 			// For backward compatibility.
 			if probeCfg.GetProbeAddress() != "" {
 				customProbe = types.ConnectivityProbe{

pkg/wwan/mmagent/agent.go

@@ -1117,6 +1117,15 @@ func (a *MMAgent) probeModemConnectivity(modem *ModemInfo) error {
 			return nil
 		}
 	case types.ConnectivityProbeMethodICMP:
+		if probeConfig.UserDefinedProbe.ProbeHost == "" {
+			// When ICMP probe is selected but probe host is undefined, we use the default
+			// probing endpoint (Google DNS).
+			err = a.runICMPProbe(modemIP, defaultProbeAddr)
+			if err == nil {
+				return nil
+			}
+			break
+		}
 		// User-configured ICMP probe address.
 		remoteIP := net.ParseIP(probeConfig.UserDefinedProbe.ProbeHost)
 		if remoteIP == nil {