Add collector for netstats tcp packet counters for FreeBSD. (#3177)

* Add collector for netstats tcp packet counters for FreeBSD.

Signed-off-by: K Rin <rin@sandb0x.tw>

* Update collector/netstat_freebsd.go to keep the naming convention

Co-authored-by: Ben Kochie <superq@gmail.com>
Signed-off-by: K Rin <sandb0x.tw0913@gmail.com>

---------

Signed-off-by: K Rin <rin@sandb0x.tw>
Signed-off-by: K Rin <sandb0x.tw0913@gmail.com>
Co-authored-by: Ben Kochie <superq@gmail.com>

collector/netstat_freebsd.go

@@ -0,0 +1,108 @@
+// Copyright 2024 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 freebsd
+// +build freebsd
+
+package collector
+
+import (
+	"errors"
+	"fmt"
+	"log/slog"
+	"unsafe"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"golang.org/x/sys/unix"
+)
+
+/*
+#include <sys/types.h>
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <netinet/tcp.h>
+#include <netinet/tcp_var.h>
+#include <netinet/udp.h>
+*/
+import "C"
+
+var (
+	bsdNetstatTcpSendPacketsTotal = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, "netstat", "tcp_transmit_packets_total"),
+		"TCP packets sent",
+		nil, nil,
+	)
+
+	bsdNetstatTcpRecvPacketsTotal = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, "netstat", "tcp_receive_packets_total"),
+		"TCP packets received",
+		nil, nil,
+	)
+)
+
+type netStatCollector struct {
+	netStatMetric *prometheus.Desc
+}
+
+func init() {
+	registerCollector("netstat", defaultEnabled, NewNetStatCollector)
+}
+
+func NewNetStatCollector(logger *slog.Logger) (Collector, error) {
+	return &netStatCollector{}, nil
+}
+
+func (c *netStatCollector) Describe(ch chan<- *prometheus.Desc) {
+	ch <- c.netStatMetric
+}
+
+func (c *netStatCollector) Collect(ch chan<- prometheus.Metric) {
+	_ = c.Update(ch)
+}
+
+func getData(queryString string) ([]byte, error) {
+	data, err := unix.SysctlRaw(queryString)
+	if err != nil {
+		fmt.Println("Error:", err)
+		return nil, err
+	}
+
+	if len(data) < int(unsafe.Sizeof(C.struct_tcpstat{})) {
+		return nil, errors.New("Data Size mismatch")
+	}
+	return data, nil
+}
+
+func (c *netStatCollector) Update(ch chan<- prometheus.Metric) error {
+
+	tcpData, err := getData("net.inet.tcp.stats")
+	if err != nil {
+		return err
+	}
+
+	tcpStats := *(*C.struct_tcpstat)(unsafe.Pointer(&tcpData[0]))
+
+	ch <- prometheus.MustNewConstMetric(
+		bsdNetstatTcpSendPacketsTotal,
+		prometheus.CounterValue,
+		float64(tcpStats.tcps_sndtotal),
+	)
+
+	ch <- prometheus.MustNewConstMetric(
+		bsdNetstatTcpRecvPacketsTotal,
+		prometheus.CounterValue,
+		float64(tcpStats.tcps_rcvtotal),
+	)
+
+	return nil
+}

collector/netstat_freebsd_test.go

@@ -0,0 +1,77 @@
+// Copyright 2024 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 freebsd
+// +build freebsd
+
+package collector
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+	"golang.org/x/sys/unix"
+	"testing"
+	"unsafe"
+)
+
+func TestNetStatCollectorDescribe(t *testing.T) {
+	ch := make(chan *prometheus.Desc, 1)
+	collector := &netStatCollector{
+		netStatMetric: prometheus.NewDesc("dummy_metric", "dummy", nil, nil),
+	}
+	collector.Describe(ch)
+	desc := <-ch
+
+	if want, got := "dummy_metric", desc.String(); want != got {
+		t.Errorf("want %s, got %s", want, got)
+	}
+}
+
+func TestGetData(t *testing.T) {
+	data, err := getData("net.inet.tcp.stats")
+	if err != nil {
+		t.Fatal("unexpected error:", err)
+	}
+
+	if got, want := len(data), int(unsafe.Sizeof(unix.TCPStats{})); got < want {
+		t.Errorf("data length too small: want >= %d, got %d", want, got)
+	}
+}
+
+func TestNetStatCollectorUpdate(t *testing.T) {
+	ch := make(chan prometheus.Metric, len(metrics))
+	collector := &netStatCollector{
+		netStatMetric: prometheus.NewDesc("netstat_metric", "NetStat Metric", nil, nil),
+	}
+	err := collector.Update(ch)
+	if err != nil {
+		t.Fatal("unexpected error:", err)
+	}
+
+	if got, want := len(ch), len(metrics); got != want {
+		t.Errorf("metric count mismatch: want %d, got %d", want, got)
+	}
+
+	for range metrics {
+		<-ch
+	}
+}
+
+func TestNewNetStatCollector(t *testing.T) {
+	collector, err := NewNetStatCollector(nil)
+	if err != nil {
+		t.Fatal("unexpected error:", err)
+	}
+	if collector == nil {
+		t.Fatal("collector is nil, want non-nil")
+	}
+}