From 13ec5ee4044889e547df2a21420bdfec68463430 Mon Sep 17 00:00:00 2001
From: Aditya Mukerjee <dev@chimeracoder.net>
Date: Tue, 17 Oct 2017 17:06:24 -0400
Subject: [PATCH] Add function to expose /proc/softnet_stat data

---
 networking.go      | 82 ++++++++++++++++++++++++++++++++++++++++++++++
 networking_test.go | 53 ++++++++++++++++++++++++++++++
 2 files changed, 135 insertions(+)

diff --git a/networking.go b/networking.go
index f0412fdbd..63aada593 100644
--- a/networking.go
+++ b/networking.go
@@ -2,9 +2,13 @@ package veneur
 
 import (
 	"crypto/tls"
+	"encoding/csv"
 	"fmt"
+	"io"
 	"net"
 	"os"
+	"path/filepath"
+	"strconv"
 	"sync"
 
 	"github.com/sirupsen/logrus"
@@ -191,3 +195,81 @@ func startSSFUnix(s *Server, addr *net.UnixAddr) <-chan struct{} {
 	}()
 	return done
 }
+
+type SoftnetData struct {
+	Processors []SoftnetDataProcessor
+}
+
+type SoftnetDataProcessor struct {
+	Processed      int64
+	Dropped        int64
+	TimeSqueeze    int64
+	CPUCollision   int64
+	ReceivedRPS    int64
+	FlowLimitCount int64
+}
+
+// SoftnetStat provides information about UDP traffic, as provided
+// on Linux machines by /proc/net/softnet_stat. Its behavior on other
+// operating systems is undefined.
+func SoftnetStat() (SoftnetData, error) {
+	f, err := os.Open(filepath.Join("/proc", "net", "softnet_stat"))
+	if err != nil {
+		return SoftnetData{}, err
+	}
+	return parseSoftnet(f)
+}
+
+func parseSoftnet(r io.Reader) (SoftnetData, error) {
+	// softnet_stat output consists of 11 columns.
+	// The first two refer to the number of packets processed and dropped.
+	// The third is the number of times "squeezing" occurred (work was remaining
+	// when netdev_budget or the time slice expired).
+	// The next five fields are always 0 for current kernel versions (they previously
+	// were used for fastroute, which is no longer supported).
+	// The last three columns provide the number of cpu collisions (when two CPUs attempted
+	// to acquire the device queue lock simultaneously), the number of times the CPU was woken
+	// up by an inter-processor interrupt, and the number of times the flow limit has been reached.
+	const columns = 11
+	cr := csv.NewReader(r)
+	cr.Comma = ' '
+	cr.FieldsPerRecord = columns
+
+	records, err := cr.ReadAll()
+	if err != nil {
+		return SoftnetData{}, err
+	}
+
+	sd := SoftnetData{}
+	sd.Processors = make([]SoftnetDataProcessor, len(records))
+	for i, processor := range records {
+		fields, err := parseSoftnetRecord(processor)
+		if err != nil {
+			return SoftnetData{}, err
+		}
+		sdp := SoftnetDataProcessor{
+			Processed:      fields[0],
+			Dropped:        fields[1],
+			TimeSqueeze:    fields[2],
+			CPUCollision:   fields[8],
+			ReceivedRPS:    fields[9],
+			FlowLimitCount: fields[10],
+		}
+		sd.Processors[i] = sdp
+	}
+	return sd, nil
+}
+
+// parseSoftnetRecord parses a single row
+func parseSoftnetRecord(processorRecord []string) ([]int64, error) {
+	const base = 16
+	r := make([]int64, len(processorRecord))
+	for i, c := range processorRecord {
+		n, err := strconv.ParseInt(c, base, 64)
+		if err != nil {
+			return nil, err
+		}
+		r[i] = n
+	}
+	return r, nil
+}
diff --git a/networking_test.go b/networking_test.go
index 575ae286a..b4eee39d5 100644
--- a/networking_test.go
+++ b/networking_test.go
@@ -3,6 +3,7 @@ package veneur
 import (
 	"fmt"
 	"net"
+	"strings"
 	"testing"
 	"time"
 
@@ -92,3 +93,55 @@ func TestConnectUNIX(t *testing.T) {
 	}
 	close(srv.shutdown)
 }
+
+func TestParseSoftnet(t *testing.T) {
+	const input = `
+00058bcf 00000001 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
+0004c22d 00000000 00000004 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
+00042d39 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
+00052ffe 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
+00015a54 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
+0001897c 00000000 00000000 00000000 00000000 00000000 00000000 00000000 000000c2 00000000 00000000
+00233be1 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 000000d0 00000000
+0025ec50 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000f00`
+
+	expected := SoftnetData{
+		Processors: []SoftnetDataProcessor{
+			{
+				Processed: 0x00058bcf,
+				Dropped:   0x1,
+			},
+			{
+				Processed:   0x0004c22d,
+				TimeSqueeze: 0x4,
+			},
+			{
+				Processed: 0x00042d39,
+			},
+			{
+				Processed: 0x00052ffe,
+			},
+			{
+				Processed: 0x00015a54,
+			},
+			{
+				Processed:    0x0001897c,
+				CPUCollision: 0xc2,
+			},
+			{
+				Processed:   0x00233be1,
+				ReceivedRPS: 0xd0,
+			},
+			{
+				Processed:      0x0025ec50,
+				FlowLimitCount: 0xf00,
+			},
+		},
+	}
+
+	r := strings.NewReader(input)
+	sd, err := parseSoftnet(r)
+	assert.NoError(t, err, "Could not parse valid softnet_stat data")
+
+	assert.Equal(t, sd, expected)
+}