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package main
import (
"net"
"net/http"
"strings"
"sync"
"time"
)
type limiter struct {
mu sync.Mutex
hits map[string][]time.Time
max int
window time.Duration
}
func newLimiter(max int, window time.Duration) *limiter {
return &limiter{hits: map[string][]time.Time{}, max: max, window: window}
}
func (l *limiter) prune(key string, now time.Time) []time.Time {
cutoff := now.Add(-l.window)
kept := l.hits[key][:0]
for _, t := range l.hits[key] {
if t.After(cutoff) {
kept = append(kept, t)
}
}
if len(kept) == 0 {
delete(l.hits, key)
} else {
l.hits[key] = kept
}
if len(l.hits) > 10000 {
for k, v := range l.hits {
if !v[len(v)-1].After(cutoff) {
delete(l.hits, k)
}
}
}
return kept
}
func (l *limiter) blocked(key string) bool {
l.mu.Lock()
defer l.mu.Unlock()
return len(l.prune(key, time.Now())) >= l.max
}
func (l *limiter) fail(key string) {
l.mu.Lock()
defer l.mu.Unlock()
now := time.Now()
l.hits[key] = append(l.prune(key, now), now)
}
var trustedProxies []*net.IPNet
func trustedProxy(ip net.IP) bool {
if ip.IsLoopback() {
return true
}
for _, n := range trustedProxies {
if n.Contains(ip) {
return true
}
}
return false
}
func clientIP(r *http.Request) string {
host, _, err := net.SplitHostPort(r.RemoteAddr)
if err != nil {
host = r.RemoteAddr
}
if ip := net.ParseIP(host); ip != nil && trustedProxy(ip) {
if xff := r.Header.Get("X-Forwarded-For"); xff != "" {
hops := strings.Split(xff, ",")
return strings.TrimSpace(hops[len(hops)-1])
}
}
return host
}
type bucket struct {
tokens float64
last time.Time
}
type buckets struct {
mu sync.Mutex
m map[string]*bucket
rate float64
burst float64
}
func newBuckets(rate, burst float64) *buckets {
return &buckets{m: map[string]*bucket{}, rate: rate, burst: burst}
}
func (b *buckets) allow(key string) bool {
b.mu.Lock()
defer b.mu.Unlock()
now := time.Now()
k, ok := b.m[key]
if !ok {
if len(b.m) >= 20000 {
for name, v := range b.m {
if v.tokens+now.Sub(v.last).Seconds()*b.rate >= b.burst {
delete(b.m, name)
}
}
if len(b.m) >= 20000 {
return false
}
}
k = &bucket{tokens: b.burst, last: now}
b.m[key] = k
}
k.tokens = min(b.burst, k.tokens+now.Sub(k.last).Seconds()*b.rate)
k.last = now
if k.tokens < 1 {
return false
}
k.tokens--
return true
}
func heavyRequest(r *http.Request) bool {
p := r.URL.Path
q := r.URL.Query()
return p == "/search" || strings.Contains(p, "/archive/") || strings.Contains(p, "/blame/") ||
strings.Contains(p, "/interdiff") || (strings.HasSuffix(p, "/search") && q.Get("q") != "") ||
(strings.Contains(p, "/log") && q.Get("q") != "") || p == "/login" || p == "/register"
}
func (s *Server) throttle(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
if strings.HasPrefix(r.URL.Path, "/static/") {
next.ServeHTTP(w, r)
return
}
ip := clientIP(r)
if !s.requests.allow(ip) || (heavyRequest(r) && !s.heavy.allow(ip)) {
w.Header().Set("Retry-After", "10")
http.Error(w, "too many requests, slow down", http.StatusTooManyRequests)
return
}
next.ServeHTTP(w, r)
})
}
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