Revert "Don't use modules"

This reverts commit bffe99aeadae09abd02f2bd3184925af6b680535.

2 files changed, 247 insertions, 0 deletions

diff --git a/internal/ratelimiter/ratelimiter.go b/internal/ratelimiter/ratelimiter.go
new file mode 100644
index 0000000..006900a
--- /dev/null
+++ b/internal/ratelimiter/ratelimiter.go
@@ -0,0 +1,149 @@
+package ratelimiter
+
+/* Copyright (C) 2015-2017 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. */
+
+/* This file contains a port of the rate-limiter from the linux kernel version */
+
+import (
+	"net"
+	"sync"
+	"time"
+)
+
+const (
+	packetsPerSecond   = 20
+	packetsBurstable   = 5
+	garbageCollectTime = time.Second
+	packetCost         = 1000000000 / packetsPerSecond
+	maxTokens          = packetCost * packetsBurstable
+)
+
+type RatelimiterEntry struct {
+	mutex    sync.Mutex
+	lastTime time.Time
+	tokens   int64
+}
+
+type Ratelimiter struct {
+	mutex     sync.RWMutex
+	stop      chan struct{}
+	tableIPv4 map[[net.IPv4len]byte]*RatelimiterEntry
+	tableIPv6 map[[net.IPv6len]byte]*RatelimiterEntry
+}
+
+func (rate *Ratelimiter) Close() {
+	rate.mutex.Lock()
+	defer rate.mutex.Unlock()
+
+	if rate.stop != nil {
+		close(rate.stop)
+	}
+}
+
+func (rate *Ratelimiter) Init() {
+	rate.mutex.Lock()
+	defer rate.mutex.Unlock()
+
+	// stop any ongoing garbage collection routine
+
+	if rate.stop != nil {
+		close(rate.stop)
+	}
+
+	rate.stop = make(chan struct{})
+	rate.tableIPv4 = make(map[[net.IPv4len]byte]*RatelimiterEntry)
+	rate.tableIPv6 = make(map[[net.IPv6len]byte]*RatelimiterEntry)
+
+	// start garbage collection routine
+
+	go func() {
+		timer := time.NewTimer(time.Second)
+		for {
+			select {
+			case <-rate.stop:
+				return
+			case <-timer.C:
+				func() {
+					rate.mutex.Lock()
+					defer rate.mutex.Unlock()
+
+					for key, entry := range rate.tableIPv4 {
+						entry.mutex.Lock()
+						if time.Now().Sub(entry.lastTime) > garbageCollectTime {
+							delete(rate.tableIPv4, key)
+						}
+						entry.mutex.Unlock()
+					}
+
+					for key, entry := range rate.tableIPv6 {
+						entry.mutex.Lock()
+						if time.Now().Sub(entry.lastTime) > garbageCollectTime {
+							delete(rate.tableIPv6, key)
+						}
+						entry.mutex.Unlock()
+					}
+				}()
+				timer.Reset(time.Second)
+			}
+		}
+	}()
+}
+
+func (rate *Ratelimiter) Allow(ip net.IP) bool {
+	var entry *RatelimiterEntry
+	var KeyIPv4 [net.IPv4len]byte
+	var KeyIPv6 [net.IPv6len]byte
+
+	// lookup entry
+
+	IPv4 := ip.To4()
+	IPv6 := ip.To16()
+
+	rate.mutex.RLock()
+
+	if IPv4 != nil {
+		copy(KeyIPv4[:], IPv4)
+		entry = rate.tableIPv4[KeyIPv4]
+	} else {
+		copy(KeyIPv6[:], IPv6)
+		entry = rate.tableIPv6[KeyIPv6]
+	}
+
+	rate.mutex.RUnlock()
+
+	// make new entry if not found
+
+	if entry == nil {
+		rate.mutex.Lock()
+		entry = new(RatelimiterEntry)
+		entry.tokens = maxTokens - packetCost
+		entry.lastTime = time.Now()
+		if IPv4 != nil {
+			rate.tableIPv4[KeyIPv4] = entry
+		} else {
+			rate.tableIPv6[KeyIPv6] = entry
+		}
+		rate.mutex.Unlock()
+		return true
+	}
+
+	// add tokens to entry
+
+	entry.mutex.Lock()
+	now := time.Now()
+	entry.tokens += now.Sub(entry.lastTime).Nanoseconds()
+	entry.lastTime = now
+	if entry.tokens > maxTokens {
+		entry.tokens = maxTokens
+	}
+
+	// subtract cost of packet
+
+	if entry.tokens > packetCost {
+		entry.tokens -= packetCost
+		entry.mutex.Unlock()
+		return true
+	}
+	entry.mutex.Unlock()
+	return false
+}
diff --git a/internal/ratelimiter/ratelimiter_test.go b/internal/ratelimiter/ratelimiter_test.go
new file mode 100644
index 0000000..37339ee
--- /dev/null
+++ b/internal/ratelimiter/ratelimiter_test.go
@@ -0,0 +1,98 @@
+package ratelimiter
+
+import (
+	"net"
+	"testing"
+	"time"
+)
+
+type RatelimiterResult struct {
+	allowed bool
+	text    string
+	wait    time.Duration
+}
+
+func TestRatelimiter(t *testing.T) {
+
+	var ratelimiter Ratelimiter
+	var expectedResults []RatelimiterResult
+
+	Nano := func(nano int64) time.Duration {
+		return time.Nanosecond * time.Duration(nano)
+	}
+
+	Add := func(res RatelimiterResult) {
+		expectedResults = append(
+			expectedResults,
+			res,
+		)
+	}
+
+	for i := 0; i < packetsBurstable; i++ {
+		Add(RatelimiterResult{
+			allowed: true,
+			text:    "inital burst",
+		})
+	}
+
+	Add(RatelimiterResult{
+		allowed: false,
+		text:    "after burst",
+	})
+
+	Add(RatelimiterResult{
+		allowed: true,
+		wait:    Nano(time.Second.Nanoseconds() / packetsPerSecond),
+		text:    "filling tokens for single packet",
+	})
+
+	Add(RatelimiterResult{
+		allowed: false,
+		text:    "not having refilled enough",
+	})
+
+	Add(RatelimiterResult{
+		allowed: true,
+		wait:    2 * (Nano(time.Second.Nanoseconds() / packetsPerSecond)),
+		text:    "filling tokens for two packet burst",
+	})
+
+	Add(RatelimiterResult{
+		allowed: true,
+		text:    "second packet in 2 packet burst",
+	})
+
+	Add(RatelimiterResult{
+		allowed: false,
+		text:    "packet following 2 packet burst",
+	})
+
+	ips := []net.IP{
+		net.ParseIP("127.0.0.1"),
+		net.ParseIP("192.168.1.1"),
+		net.ParseIP("172.167.2.3"),
+		net.ParseIP("97.231.252.215"),
+		net.ParseIP("248.97.91.167"),
+		net.ParseIP("188.208.233.47"),
+		net.ParseIP("104.2.183.179"),
+		net.ParseIP("72.129.46.120"),
+		net.ParseIP("2001:0db8:0a0b:12f0:0000:0000:0000:0001"),
+		net.ParseIP("f5c2:818f:c052:655a:9860:b136:6894:25f0"),
+		net.ParseIP("b2d7:15ab:48a7:b07c:a541:f144:a9fe:54fc"),
+		net.ParseIP("a47b:786e:1671:a22b:d6f9:4ab0:abc7:c918"),
+		net.ParseIP("ea1e:d155:7f7a:98fb:2bf5:9483:80f6:5445"),
+		net.ParseIP("3f0e:54a2:f5b4:cd19:a21d:58e1:3746:84c4"),
+	}
+
+	ratelimiter.Init()
+
+	for i, res := range expectedResults {
+		time.Sleep(res.wait)
+		for _, ip := range ips {
+			allowed := ratelimiter.Allow(ip)
+			if allowed != res.allowed {
+				t.Fatal("Test failed for", ip.String(), ", on:", i, "(", res.text, ")", "expected:", res.allowed, "got:", allowed)
+			}
+		}
+	}
+}