netlink: read missing attributes from sysfs (prometheus#2669)

Read missing dev_id, name_assign_type, and addr_assign_type
from sysfs, since they only take a device-specific lock and
not the whole RTNL lock. This means reading them is much less
impactful on other system processes than many of the other
attributes in sysfs that do take the RTNL lock.

Signed-off-by: Dan Williams <dcbw@redhat.com>

collector/netclass_rtnl_linux.go

@@ -20,12 +20,14 @@ import (
 	"errors"
 	"fmt"
 	"io/fs"
+	"path/filepath"
 
 	"github.com/alecthomas/kingpin/v2"
 	"github.com/go-kit/log/level"
 	"github.com/jsimonetti/rtnetlink"
 	"github.com/mdlayher/ethtool"
 	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/procfs/sysfs"
 )
 
 var (
@@ -57,14 +59,27 @@ func (c *netClassCollector) netClassRTNLUpdate(ch chan<- prometheus.Metric) erro
 		}
 	}
 
+	// Get most attributes from Netlink
 	lMsgs, err := c.getNetClassInfoRTNL()
 	if err != nil {
 		return fmt.Errorf("could not get net class info: %w", err)
 	}
+
+	relevantLinks := make([]rtnetlink.LinkMessage, 0, len(lMsgs))
 	for _, msg := range lMsgs {
-		if c.ignoredDevicesPattern.MatchString(msg.Attributes.Name) {
-			continue
+		if !c.ignoredDevicesPattern.MatchString(msg.Attributes.Name) {
+			relevantLinks = append(relevantLinks, msg)
 		}
+	}
+
+	// Read sysfs for attributes that Netlink doesn't expose
+	sysfsAttrs, err := getSysfsAttributes(relevantLinks)
+	if err != nil {
+		return fmt.Errorf("could not get sysfs device info: %w", err)
+	}
+
+	// Parse all the info and update metrics
+	for _, msg := range relevantLinks {
 		upDesc := prometheus.NewDesc(
 			prometheus.BuildFQName(namespace, c.subsystem, "up"),
 			"Value is 1 if operstate is 'up', 0 otherwise.",
@@ -96,12 +111,16 @@ func (c *netClassCollector) netClassRTNLUpdate(ch chan<- prometheus.Metric) erro
 			duplex = lm.Duplex.String()
 		}
 
+		ifaceInfo := sysfsAttrs[msg.Attributes.Name]
+
 		ch <- prometheus.MustNewConstMetric(infoDesc, prometheus.GaugeValue, infoValue, msg.Attributes.Name, msg.Attributes.Address.String(), msg.Attributes.Broadcast.String(), duplex, operstateStr[int(msg.Attributes.OperationalState)], ifalias)
 
+		pushMetric(ch, c.getFieldDesc("address_assign_type"), "address_assign_type", ifaceInfo.AddrAssignType, prometheus.GaugeValue, msg.Attributes.Name)
 		pushMetric(ch, c.getFieldDesc("carrier"), "carrier", msg.Attributes.Carrier, prometheus.GaugeValue, msg.Attributes.Name)
 		pushMetric(ch, c.getFieldDesc("carrier_changes_total"), "carrier_changes_total", msg.Attributes.CarrierChanges, prometheus.CounterValue, msg.Attributes.Name)
 		pushMetric(ch, c.getFieldDesc("carrier_up_changes_total"), "carrier_up_changes_total", msg.Attributes.CarrierUpCount, prometheus.CounterValue, msg.Attributes.Name)
 		pushMetric(ch, c.getFieldDesc("carrier_down_changes_total"), "carrier_down_changes_total", msg.Attributes.CarrierDownCount, prometheus.CounterValue, msg.Attributes.Name)
+		pushMetric(ch, c.getFieldDesc("device_id"), "device_id", ifaceInfo.DevID, prometheus.GaugeValue, msg.Attributes.Name)
 		pushMetric(ch, c.getFieldDesc("flags"), "flags", msg.Flags, prometheus.GaugeValue, msg.Attributes.Name)
 		pushMetric(ch, c.getFieldDesc("iface_id"), "iface_id", msg.Index, prometheus.GaugeValue, msg.Attributes.Name)
 		pushMetric(ch, c.getFieldDesc("iface_link_mode"), "iface_link_mode", msg.Attributes.LinkMode, prometheus.GaugeValue, msg.Attributes.Name)
@@ -117,6 +136,7 @@ func (c *netClassCollector) netClassRTNLUpdate(ch chan<- prometheus.Metric) erro
 		}
 
 		pushMetric(ch, c.getFieldDesc("mtu_bytes"), "mtu_bytes", msg.Attributes.MTU, prometheus.GaugeValue, msg.Attributes.Name)
+		pushMetric(ch, c.getFieldDesc("name_assign_type"), "name_assign_type", ifaceInfo.NameAssignType, prometheus.GaugeValue, msg.Attributes.Name)
 		pushMetric(ch, c.getFieldDesc("net_dev_group"), "net_dev_group", msg.Attributes.NetDevGroup, prometheus.GaugeValue, msg.Attributes.Name)
 		pushMetric(ch, c.getFieldDesc("transmit_queue_length"), "transmit_queue_length", msg.Attributes.TxQueueLen, prometheus.GaugeValue, msg.Attributes.Name)
 		pushMetric(ch, c.getFieldDesc("protocol_type"), "protocol_type", msg.Type, prometheus.GaugeValue, msg.Attributes.Name)
@@ -186,3 +206,25 @@ func (c *netClassCollector) getLinkModes() ([]*ethtool.LinkMode, error) {
 
 	return lms, err
 }
+
+// getSysfsAttributes reads attributes that are absent from netlink but provided
+// by sysfs.
+func getSysfsAttributes(links []rtnetlink.LinkMessage) (sysfs.NetClass, error) {
+	netClass := sysfs.NetClass{}
+	for _, msg := range links {
+		interfaceClass := sysfs.NetClassIface{}
+		ifName := msg.Attributes.Name
+		devPath := filepath.Join("/sys", "class", "net", ifName)
+
+		// These three attributes hold a device-specific lock when
+		// accessed, not the RTNL lock, so they are much less impactful
+		// than reading most of the other attributes from sysfs.
+		for _, attr := range []string{"addr_assign_type", "dev_id", "name_assign_type"} {
+			if err := sysfs.ParseNetClassAttribute(devPath, attr, &interfaceClass); err != nil {
+				return nil, err
+			}
+		}
+		netClass[ifName] = interfaceClass
+	}
+	return netClass, nil
+}