netstat: Use procfs parsers for netstat, snmp and snmp6

collector/fixtures/proc/10/net

@@ -0,0 +1 @@
+../net

collector/netstat_descs_drift_test.go

@@ -0,0 +1,78 @@
+// Copyright The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package collector
+
+import (
+	"os"
+	"reflect"
+	"regexp"
+	"sort"
+	"testing"
+
+	"github.com/prometheus/procfs"
+)
+
+// TestNetStatDescsInSync guards against drift between the committed descriptor
+// table (netstat_descs_linux.go) and the procfs structs it is generated from.
+// If a procfs upgrade adds or removes statistics fields, this test fails until
+// the table is regenerated with `GOOS=linux go generate ./collector`.
+func TestNetStatDescsInSync(t *testing.T) {
+	src, err := os.ReadFile("netstat_descs_linux.go")
+	if err != nil {
+		t.Fatalf("read netstat_descs_linux.go: %v", err)
+	}
+
+	re := regexp.MustCompile(`"([A-Za-z0-9]+_[A-Za-z0-9]+)": prometheus\.NewDesc`)
+	committed := map[string]bool{}
+	for _, m := range re.FindAllSubmatch(src, -1) {
+		committed[string(m[1])] = true
+	}
+
+	var n procfs.ProcNetstat
+	var s procfs.ProcSnmp
+	var s6 procfs.ProcSnmp6
+	expected := map[string]bool{}
+	for _, v := range []any{
+		n.TcpExt, n.IpExt,
+		s.Ip, s.Icmp, s.IcmpMsg, s.Tcp, s.Udp, s.UdpLite,
+		s6.Ip6, s6.Icmp6, s6.Udp6, s6.UdpLite6,
+	} {
+		tt := reflect.TypeOf(v)
+		for i := 0; i < tt.NumField(); i++ {
+			f := tt.Field(i)
+			if f.Type != reflect.TypeFor[*float64]() {
+				continue
+			}
+			expected[tt.Name()+"_"+f.Name] = true
+		}
+	}
+
+	var missing, extra []string
+	for k := range expected {
+		if !committed[k] {
+			missing = append(missing, k)
+		}
+	}
+	for k := range committed {
+		if !expected[k] {
+			extra = append(extra, k)
+		}
+	}
+	sort.Strings(missing)
+	sort.Strings(extra)
+
+	if len(missing) != 0 || len(extra) != 0 {
+		t.Fatalf("netstat_descs_linux.go is out of sync with procfs (missing=%v extra=%v); run `GOOS=linux go generate ./collector`", missing, extra)
+	}
+}

collector/netstat_descs_gen.go

@@ -0,0 +1,96 @@
+// Copyright The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build ignore
+
+// Command netstat-descs regenerates collector/netstat_descs_linux.go from the
+// procfs netstat/snmp/snmp6 statistics structs.
+//
+// Run from the repository root:
+//
+//	go generate ./collector
+//
+// The output is a table of explicit, source-visible prometheus.Desc literals
+// (one per *float64 field of each statistics struct), keyed by
+// "<Protocol>_<Field>". Keeping the descriptors as literals lets the AST-based
+// documentation tooling read them and avoids allocating descriptors per scrape.
+package main
+
+import (
+	"fmt"
+	"os"
+	"reflect"
+	"strings"
+
+	"github.com/prometheus/procfs"
+)
+
+type entry struct {
+	key  string
+	help string
+}
+
+func main() {
+	var n procfs.ProcNetstat
+	var s procfs.ProcSnmp
+	var s6 procfs.ProcSnmp6
+
+	structs := []any{
+		n.TcpExt, n.IpExt,
+		s.Ip, s.Icmp, s.IcmpMsg, s.Tcp, s.Udp, s.UdpLite,
+		s6.Ip6, s6.Icmp6, s6.Udp6, s6.UdpLite6,
+	}
+
+	var b strings.Builder
+	b.WriteString(`// Code generated by netstat-descs; DO NOT EDIT.
+
+//go:build !nonetstat
+
+package collector
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+// netStatMetricDescs returns the explicit, source-visible metric descriptors
+// for every field of the procfs netstat/snmp/snmp6 statistics structs, keyed by
+// "<Protocol>_<Field>". Descriptors are allocated once; collection looks them up
+// by name instead of calling prometheus.NewDesc on every scrape.
+func netStatMetricDescs() map[string]*prometheus.Desc {
+	return map[string]*prometheus.Desc{
+`)
+
+	count := 0
+	for _, v := range structs {
+		t := reflect.TypeOf(v)
+		proto := t.Name()
+		for i := 0; i < t.NumField(); i++ {
+			f := t.Field(i)
+			if f.Type != reflect.TypeFor[*float64]() {
+				continue
+			}
+			key := proto + "_" + f.Name
+			help := "Statistic " + proto + f.Name + "."
+			fmt.Fprintf(&b, "\t\t%q: prometheus.NewDesc(\n\t\t\tprometheus.BuildFQName(namespace, netStatsSubsystem, %q),\n\t\t\t%q,\n\t\t\tnil, nil),\n", key, key, help)
+			count++
+		}
+	}
+
+	b.WriteString("\t}\n}\n")
+
+	if err := os.WriteFile("netstat_descs_linux.go", []byte(b.String()), 0o644); err != nil {
+		fmt.Fprintln(os.Stderr, "write netstat_descs_linux.go:", err)
+		os.Exit(1)
+	}
+	fmt.Fprintf(os.Stderr, "wrote netstat_descs_linux.go (%d descriptors)\n", count)
+}