[8.12](backport #37714) filebeat/input/{tcp,udp}: relax requirements that proc entries be present when an address is

CHANGELOG.next.asciidoc

@@ -70,6 +70,7 @@ https://github.com/elastic/beats/compare/v8.8.1\...main[Check the HEAD diff]
 - Fix handling of Juniper SRX structured data when there is no leading junos element. {issue}36270[36270] {pull}36308[36308]
 - Fix Filebeat Cisco module with missing escape character {issue}36325[36325] {pull}36326[36326]
 - Added a fix for Crowdstrike pipeline handling process arrays {pull}36496[36496]
+- Fix TCP/UDP metric queue length parsing base. {pull}37714[37714]
 
 *Heartbeat*
 
@@ -135,6 +136,7 @@ https://github.com/elastic/beats/compare/v8.8.1\...main[Check the HEAD diff]
 - Added support for Okta OAuth2 provider in the CEL input. {issue}36336[36336] {pull}36521[36521]
 - Added support for new features & removed partial save mechanism in the Azure Blob Storage input. {issue}35126[35126] {pull}36690[36690]
 - Added support for new features and removed partial save mechanism in the GCS input. {issue}35847[35847] {pull}36713[36713]
+- Relax TCP/UDP metric polling expectations to improve metric collection. {pull}37714[37714]
 
 *Auditbeat*
 

filebeat/input/tcp/input.go

@@ -238,31 +238,50 @@ func (m *inputMetrics) poll(addr, addr6 []string, each time.Duration, log *logp.
 	// base level for the rx_queue values and ensures that if the
 	// constructed address values are malformed we panic early
 	// within the period of system testing.
+	want4 := true
 	rx, err := procNetTCP("/proc/net/tcp", addr, hasUnspecified, addrIsUnspecified)
 	if err != nil {
-		log.Warnf("failed to get initial tcp stats from /proc: %v", err)
+		want4 = false
+		log.Infof("did not get initial tcp stats from /proc: %v", err)
 	}
+	want6 := true
 	rx6, err := procNetTCP("/proc/net/tcp6", addr6, hasUnspecified6, addrIsUnspecified6)
 	if err != nil {
-		log.Warnf("failed to get initial tcp6 stats from /proc: %v", err)
+		want6 = false
+		log.Infof("did not get initial tcp6 stats from /proc: %v", err)
+	}
+	if !want4 && !want6 {
+		log.Warnf("failed to get initial tcp or tcp6 stats from /proc: %v", err)
+	} else {
+		m.rxQueue.Set(uint64(rx + rx6))
 	}
-	m.rxQueue.Set(uint64(rx + rx6))
 
 	t := time.NewTicker(each)
 	for {
 		select {
 		case <-t.C:
+			var found bool
 			rx, err := procNetTCP("/proc/net/tcp", addr, hasUnspecified, addrIsUnspecified)
 			if err != nil {
-				log.Warnf("failed to get tcp stats from /proc: %v", err)
-				continue
+				if want4 {
+					log.Warnf("failed to get tcp stats from /proc: %v", err)
+				}
+			} else {
+				found = true
+				want4 = true
 			}
 			rx6, err := procNetTCP("/proc/net/tcp6", addr6, hasUnspecified6, addrIsUnspecified6)
 			if err != nil {
-				log.Warnf("failed to get tcp6 stats from /proc: %v", err)
-				continue
+				if want6 {
+					log.Warnf("failed to get tcp6 stats from /proc: %v", err)
+				}
+			} else {
+				found = true
+				want6 = true
+			}
+			if found {
+				m.rxQueue.Set(uint64(rx + rx6))
 			}
-			m.rxQueue.Set(uint64(rx + rx6))
 		case <-m.done:
 			t.Stop()
 			return
@@ -323,10 +342,10 @@ func procNetTCP(path string, addr []string, hasUnspecified bool, addrIsUnspecifi
 			}
 			found = true
 
-			// queue lengths are decimal, e.g.:
+			// queue lengths are hex, e.g.:
 			// - https://elixir.bootlin.com/linux/v6.2.11/source/net/ipv4/tcp_ipv4.c#L2643
 			// - https://elixir.bootlin.com/linux/v6.2.11/source/net/ipv6/tcp_ipv6.c#L1987
-			v, err := strconv.ParseInt(string(r), 10, 64)
+			v, err := strconv.ParseInt(string(r), 16, 64)
 			if err != nil {
 				return 0, fmt.Errorf("failed to parse rx_queue: %w", err)
 			}

filebeat/input/udp/input.go

@@ -231,33 +231,52 @@ func (m *inputMetrics) poll(addr, addr6 []string, each time.Duration, log *logp.
 	// base level for the rx_queue and drops values and ensures that
 	// if the constructed address values are malformed we panic early
 	// within the period of system testing.
+	want4 := true
 	rx, drops, err := procNetUDP("/proc/net/udp", addr, hasUnspecified, addrIsUnspecified)
 	if err != nil {
-		log.Warnf("failed to get initial udp stats from /proc: %v", err)
+		want4 = false
+		log.Infof("did not get initial udp stats from /proc: %v", err)
 	}
+	want6 := true
 	rx6, drops6, err := procNetUDP("/proc/net/udp6", addr6, hasUnspecified6, addrIsUnspecified6)
 	if err != nil {
-		log.Warnf("failed to get initial udp6 stats from /proc: %v", err)
+		want6 = false
+		log.Infof("did not get initial udp6 stats from /proc: %v", err)
+	}
+	if !want4 && !want6 {
+		log.Warnf("failed to get initial udp or udp6 stats from /proc: %v", err)
+	} else {
+		m.rxQueue.Set(uint64(rx + rx6))
+		m.drops.Set(uint64(drops + drops6))
 	}
-	m.rxQueue.Set(uint64(rx + rx6))
-	m.drops.Set(uint64(drops + drops6))
 
 	t := time.NewTicker(each)
 	for {
 		select {
 		case <-t.C:
+			var found bool
 			rx, drops, err := procNetUDP("/proc/net/udp", addr, hasUnspecified, addrIsUnspecified)
 			if err != nil {
-				log.Warnf("failed to get udp stats from /proc: %v", err)
-				continue
+				if want4 {
+					log.Warnf("failed to get udp stats from /proc: %v", err)
+				}
+			} else {
+				found = true
+				want4 = true
 			}
 			rx6, drops6, err := procNetUDP("/proc/net/udp6", addr6, hasUnspecified6, addrIsUnspecified6)
 			if err != nil {
-				log.Warnf("failed to get udp6 stats from /proc: %v", err)
-				continue
+				if want6 {
+					log.Warnf("failed to get udp6 stats from /proc: %v", err)
+				}
+			} else {
+				found = true
+				want6 = true
+			}
+			if found {
+				m.rxQueue.Set(uint64(rx + rx6))
+				m.drops.Set(uint64(drops + drops6))
 			}
-			m.rxQueue.Set(uint64(rx + rx6))
-			m.drops.Set(uint64(drops + drops6))
 		case <-m.done:
 			t.Stop()
 			return
@@ -321,10 +340,10 @@ func procNetUDP(path string, addr []string, hasUnspecified bool, addrIsUnspecifi
 			}
 			found = true
 
-			// queue lengths and drops are decimal, e.g.:
+			// queue lengths and drops are hex, e.g.:
 			// - https://elixir.bootlin.com/linux/v6.2.11/source/net/ipv4/udp.c#L3110
 			// - https://elixir.bootlin.com/linux/v6.2.11/source/net/ipv6/datagram.c#L1048
-			v, err := strconv.ParseInt(string(r), 10, 64)
+			v, err := strconv.ParseInt(string(r), 16, 64)
 			if err != nil {
 				return 0, 0, fmt.Errorf("failed to parse rx_queue: %w", err)
 			}