package middleware import ( "fmt" "io" "math/rand" "net" "net/http" "net/url" "regexp" "sync" "sync/atomic" "time" "github.com/labstack/echo/v4" ) // TODO: Handle TLS proxy type ( // ProxyConfig defines the config for Proxy middleware. ProxyConfig struct { // Skipper defines a function to skip middleware. Skipper Skipper // Balancer defines a load balancing technique. // Required. Balancer ProxyBalancer // Rewrite defines URL path rewrite rules. The values captured in asterisk can be // retrieved by index e.g. $1, $2 and so on. // Examples: // "/old": "/new", // "/api/*": "/$1", // "/js/*": "/public/javascripts/$1", // "/users/*/orders/*": "/user/$1/order/$2", Rewrite map[string]string // RegexRewrite defines rewrite rules using regexp.Rexexp with captures // Every capture group in the values can be retrieved by index e.g. $1, $2 and so on. // Example: // "^/old/[0.9]+/": "/new", // "^/api/.+?/(.*)": "/v2/$1", RegexRewrite map[*regexp.Regexp]string // Context key to store selected ProxyTarget into context. // Optional. Default value "target". ContextKey string // To customize the transport to remote. // Examples: If custom TLS certificates are required. Transport http.RoundTripper // ModifyResponse defines function to modify response from ProxyTarget. ModifyResponse func(*http.Response) error } // ProxyTarget defines the upstream target. ProxyTarget struct { Name string URL *url.URL Meta echo.Map } // ProxyBalancer defines an interface to implement a load balancing technique. ProxyBalancer interface { AddTarget(*ProxyTarget) bool RemoveTarget(string) bool Next(echo.Context) *ProxyTarget } commonBalancer struct { targets []*ProxyTarget mutex sync.RWMutex } // RandomBalancer implements a random load balancing technique. randomBalancer struct { *commonBalancer random *rand.Rand } // RoundRobinBalancer implements a round-robin load balancing technique. roundRobinBalancer struct { *commonBalancer i uint32 } ) var ( // DefaultProxyConfig is the default Proxy middleware config. DefaultProxyConfig = ProxyConfig{ Skipper: DefaultSkipper, ContextKey: "target", } ) func proxyRaw(t *ProxyTarget, c echo.Context) http.Handler { return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { in, _, err := c.Response().Hijack() if err != nil { c.Set("_error", fmt.Sprintf("proxy raw, hijack error=%v, url=%s", t.URL, err)) return } defer in.Close() out, err := net.Dial("tcp", t.URL.Host) if err != nil { c.Set("_error", echo.NewHTTPError(http.StatusBadGateway, fmt.Sprintf("proxy raw, dial error=%v, url=%s", t.URL, err))) return } defer out.Close() // Write header err = r.Write(out) if err != nil { c.Set("_error", echo.NewHTTPError(http.StatusBadGateway, fmt.Sprintf("proxy raw, request header copy error=%v, url=%s", t.URL, err))) return } errCh := make(chan error, 2) cp := func(dst io.Writer, src io.Reader) { _, err = io.Copy(dst, src) errCh <- err } go cp(out, in) go cp(in, out) err = <-errCh if err != nil && err != io.EOF { c.Set("_error", fmt.Errorf("proxy raw, copy body error=%v, url=%s", t.URL, err)) } }) } // NewRandomBalancer returns a random proxy balancer. func NewRandomBalancer(targets []*ProxyTarget) ProxyBalancer { b := &randomBalancer{commonBalancer: new(commonBalancer)} b.targets = targets return b } // NewRoundRobinBalancer returns a round-robin proxy balancer. func NewRoundRobinBalancer(targets []*ProxyTarget) ProxyBalancer { b := &roundRobinBalancer{commonBalancer: new(commonBalancer)} b.targets = targets return b } // AddTarget adds an upstream target to the list. func (b *commonBalancer) AddTarget(target *ProxyTarget) bool { for _, t := range b.targets { if t.Name == target.Name { return false } } b.mutex.Lock() defer b.mutex.Unlock() b.targets = append(b.targets, target) return true } // RemoveTarget removes an upstream target from the list. func (b *commonBalancer) RemoveTarget(name string) bool { b.mutex.Lock() defer b.mutex.Unlock() for i, t := range b.targets { if t.Name == name { b.targets = append(b.targets[:i], b.targets[i+1:]...) return true } } return false } // Next randomly returns an upstream target. func (b *randomBalancer) Next(c echo.Context) *ProxyTarget { if b.random == nil { b.random = rand.New(rand.NewSource(int64(time.Now().Nanosecond()))) } b.mutex.RLock() defer b.mutex.RUnlock() return b.targets[b.random.Intn(len(b.targets))] } // Next returns an upstream target using round-robin technique. func (b *roundRobinBalancer) Next(c echo.Context) *ProxyTarget { b.i = b.i % uint32(len(b.targets)) t := b.targets[b.i] atomic.AddUint32(&b.i, 1) return t } // Proxy returns a Proxy middleware. // // Proxy middleware forwards the request to upstream server using a configured load balancing technique. func Proxy(balancer ProxyBalancer) echo.MiddlewareFunc { c := DefaultProxyConfig c.Balancer = balancer return ProxyWithConfig(c) } // ProxyWithConfig returns a Proxy middleware with config. // See: `Proxy()` func ProxyWithConfig(config ProxyConfig) echo.MiddlewareFunc { // Defaults if config.Skipper == nil { config.Skipper = DefaultProxyConfig.Skipper } if config.Balancer == nil { panic("echo: proxy middleware requires balancer") } if config.Rewrite != nil { if config.RegexRewrite == nil { config.RegexRewrite = make(map[*regexp.Regexp]string) } for k, v := range rewriteRulesRegex(config.Rewrite) { config.RegexRewrite[k] = v } } return func(next echo.HandlerFunc) echo.HandlerFunc { return func(c echo.Context) (err error) { if config.Skipper(c) { return next(c) } req := c.Request() res := c.Response() tgt := config.Balancer.Next(c) c.Set(config.ContextKey, tgt) if err := rewriteURL(config.RegexRewrite, req); err != nil { return err } // Fix header // Basically it's not good practice to unconditionally pass incoming x-real-ip header to upstream. // However, for backward compatibility, legacy behavior is preserved unless you configure Echo#IPExtractor. if req.Header.Get(echo.HeaderXRealIP) == "" || c.Echo().IPExtractor != nil { req.Header.Set(echo.HeaderXRealIP, c.RealIP()) } if req.Header.Get(echo.HeaderXForwardedProto) == "" { req.Header.Set(echo.HeaderXForwardedProto, c.Scheme()) } if c.IsWebSocket() && req.Header.Get(echo.HeaderXForwardedFor) == "" { // For HTTP, it is automatically set by Go HTTP reverse proxy. req.Header.Set(echo.HeaderXForwardedFor, c.RealIP()) } // Proxy switch { case c.IsWebSocket(): proxyRaw(tgt, c).ServeHTTP(res, req) case req.Header.Get(echo.HeaderAccept) == "text/event-stream": default: proxyHTTP(tgt, c, config).ServeHTTP(res, req) } if e, ok := c.Get("_error").(error); ok { err = e } return } } }