376 lines
11 KiB
Go
376 lines
11 KiB
Go
package customerrors
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import (
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"bufio"
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"context"
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"fmt"
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"net"
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"net/http"
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"net/url"
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"strconv"
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"strings"
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"github.com/opentracing/opentracing-go/ext"
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"github.com/traefik/traefik/v2/pkg/config/dynamic"
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"github.com/traefik/traefik/v2/pkg/log"
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"github.com/traefik/traefik/v2/pkg/middlewares"
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"github.com/traefik/traefik/v2/pkg/tracing"
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"github.com/traefik/traefik/v2/pkg/types"
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"github.com/vulcand/oxy/v2/utils"
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)
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// Compile time validation that the response recorder implements http interfaces correctly.
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var (
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// TODO: maybe remove at least for codeModifierWithCloseNotify.
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_ middlewares.Stateful = &codeModifierWithCloseNotify{}
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_ middlewares.Stateful = &codeCatcherWithCloseNotify{}
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)
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const typeName = "customError"
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type serviceBuilder interface {
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BuildHTTP(ctx context.Context, serviceName string) (http.Handler, error)
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}
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// customErrors is a middleware that provides the custom error pages.
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type customErrors struct {
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name string
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next http.Handler
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backendHandler http.Handler
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httpCodeRanges types.HTTPCodeRanges
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backendQuery string
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}
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// New creates a new custom error pages middleware.
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func New(ctx context.Context, next http.Handler, config dynamic.ErrorPage, serviceBuilder serviceBuilder, name string) (http.Handler, error) {
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log.FromContext(middlewares.GetLoggerCtx(ctx, name, typeName)).Debug("Creating middleware")
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httpCodeRanges, err := types.NewHTTPCodeRanges(config.Status)
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if err != nil {
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return nil, err
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}
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backend, err := serviceBuilder.BuildHTTP(ctx, config.Service)
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if err != nil {
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return nil, err
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}
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return &customErrors{
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name: name,
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next: next,
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backendHandler: backend,
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httpCodeRanges: httpCodeRanges,
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backendQuery: config.Query,
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}, nil
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}
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func (c *customErrors) GetTracingInformation() (string, ext.SpanKindEnum) {
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return c.name, tracing.SpanKindNoneEnum
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}
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func (c *customErrors) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
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ctx := middlewares.GetLoggerCtx(req.Context(), c.name, typeName)
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logger := log.FromContext(ctx)
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if c.backendHandler == nil {
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logger.Error("Error pages: no backend handler.")
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tracing.SetErrorWithEvent(req, "Error pages: no backend handler.")
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c.next.ServeHTTP(rw, req)
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return
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}
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catcher := newCodeCatcher(rw, c.httpCodeRanges)
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c.next.ServeHTTP(catcher, req)
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if !catcher.isFilteredCode() {
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return
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}
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// check the recorder code against the configured http status code ranges
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code := catcher.getCode()
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logger.Debugf("Caught HTTP Status Code %d, returning error page", code)
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var query string
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if len(c.backendQuery) > 0 {
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query = "/" + strings.TrimPrefix(c.backendQuery, "/")
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query = strings.ReplaceAll(query, "{status}", strconv.Itoa(code))
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query = strings.ReplaceAll(query, "{url}", url.QueryEscape(req.URL.String()))
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}
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pageReq, err := newRequest("http://" + req.Host + query)
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if err != nil {
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logger.Error(err)
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http.Error(rw, http.StatusText(code), code)
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return
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}
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utils.CopyHeaders(pageReq.Header, req.Header)
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c.backendHandler.ServeHTTP(newCodeModifier(rw, code),
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pageReq.WithContext(req.Context()))
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}
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func newRequest(baseURL string) (*http.Request, error) {
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u, err := url.Parse(baseURL)
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if err != nil {
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return nil, fmt.Errorf("error pages: error when parse URL: %w", err)
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}
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req, err := http.NewRequest(http.MethodGet, u.String(), nil)
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if err != nil {
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return nil, fmt.Errorf("error pages: error when create query: %w", err)
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}
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req.RequestURI = u.RequestURI()
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return req, nil
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}
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type responseInterceptor interface {
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http.ResponseWriter
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http.Flusher
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getCode() int
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isFilteredCode() bool
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}
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// codeCatcher is a response writer that detects as soon as possible
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// whether the response is a code within the ranges of codes it watches for.
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// If it is, it simply drops the data from the response.
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// Otherwise, it forwards it directly to the original client (its responseWriter) without any buffering.
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type codeCatcher struct {
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headerMap http.Header
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code int
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httpCodeRanges types.HTTPCodeRanges
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caughtFilteredCode bool
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responseWriter http.ResponseWriter
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headersSent bool
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}
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func newCodeCatcher(rw http.ResponseWriter, httpCodeRanges types.HTTPCodeRanges) responseInterceptor {
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catcher := &codeCatcher{
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headerMap: make(http.Header),
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code: http.StatusOK, // If backend does not call WriteHeader on us, we consider it's a 200.
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responseWriter: rw,
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httpCodeRanges: httpCodeRanges,
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}
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if _, ok := rw.(http.CloseNotifier); ok {
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return &codeCatcherWithCloseNotify{catcher}
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}
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return catcher
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}
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func (cc *codeCatcher) Header() http.Header {
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if cc.headersSent {
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return cc.responseWriter.Header()
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}
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if cc.headerMap == nil {
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cc.headerMap = make(http.Header)
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}
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return cc.headerMap
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}
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func (cc *codeCatcher) getCode() int {
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return cc.code
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}
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// isFilteredCode returns whether the codeCatcher received a response code among the ones it is watching,
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// and for which the response should be deferred to the error handler.
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func (cc *codeCatcher) isFilteredCode() bool {
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return cc.caughtFilteredCode
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}
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func (cc *codeCatcher) Write(buf []byte) (int, error) {
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// If WriteHeader was already called from the caller, this is a NOOP.
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// Otherwise, cc.code is actually a 200 here.
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cc.WriteHeader(cc.code)
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if cc.caughtFilteredCode {
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// We don't care about the contents of the response,
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// since we want to serve the ones from the error page,
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// so we just drop them.
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return len(buf), nil
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}
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return cc.responseWriter.Write(buf)
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}
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// WriteHeader is, in the specific case of 1xx status codes, a direct call to the wrapped ResponseWriter, without marking headers as sent,
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// allowing so further calls.
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func (cc *codeCatcher) WriteHeader(code int) {
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if cc.headersSent || cc.caughtFilteredCode {
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return
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}
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// Handling informational headers.
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if code >= 100 && code <= 199 {
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// Multiple informational status codes can be used,
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// so here the copy is not appending the values to not repeat them.
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for k, v := range cc.Header() {
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cc.responseWriter.Header()[k] = v
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}
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cc.responseWriter.WriteHeader(code)
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return
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}
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cc.code = code
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for _, block := range cc.httpCodeRanges {
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if cc.code >= block[0] && cc.code <= block[1] {
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cc.caughtFilteredCode = true
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// it will be up to the caller to send the headers,
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// so it is out of our hands now.
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return
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}
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}
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// The copy is not appending the values,
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// to not repeat them in case any informational status code has been written.
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for k, v := range cc.Header() {
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cc.responseWriter.Header()[k] = v
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}
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cc.responseWriter.WriteHeader(cc.code)
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cc.headersSent = true
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}
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// Hijack hijacks the connection.
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func (cc *codeCatcher) Hijack() (net.Conn, *bufio.ReadWriter, error) {
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if hj, ok := cc.responseWriter.(http.Hijacker); ok {
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return hj.Hijack()
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}
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return nil, nil, fmt.Errorf("%T is not a http.Hijacker", cc.responseWriter)
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}
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// Flush sends any buffered data to the client.
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func (cc *codeCatcher) Flush() {
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// If WriteHeader was already called from the caller, this is a NOOP.
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// Otherwise, cc.code is actually a 200 here.
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cc.WriteHeader(cc.code)
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// We don't care about the contents of the response,
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// since we want to serve the ones from the error page,
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// so we just don't flush.
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// (e.g., To prevent superfluous WriteHeader on request with a
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// `Transfert-Encoding: chunked` header).
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if cc.caughtFilteredCode {
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return
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}
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if flusher, ok := cc.responseWriter.(http.Flusher); ok {
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flusher.Flush()
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}
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}
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type codeCatcherWithCloseNotify struct {
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*codeCatcher
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}
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// CloseNotify returns a channel that receives at most a single value (true)
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// when the client connection has gone away.
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func (cc *codeCatcherWithCloseNotify) CloseNotify() <-chan bool {
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return cc.responseWriter.(http.CloseNotifier).CloseNotify()
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}
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// codeModifier forwards a response back to the client,
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// while enforcing a given response code.
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type codeModifier interface {
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http.ResponseWriter
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}
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// newCodeModifier returns a codeModifier that enforces the given code.
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func newCodeModifier(rw http.ResponseWriter, code int) codeModifier {
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codeMod := &codeModifierWithoutCloseNotify{
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headerMap: make(http.Header),
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code: code,
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responseWriter: rw,
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}
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if _, ok := rw.(http.CloseNotifier); ok {
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return &codeModifierWithCloseNotify{codeMod}
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}
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return codeMod
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}
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type codeModifierWithoutCloseNotify struct {
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code int // the code enforced in the response.
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// headerSent is whether the headers have already been sent,
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// either through Write or WriteHeader.
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headerSent bool
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headerMap http.Header // the HTTP response headers from the backend.
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responseWriter http.ResponseWriter
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}
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// Header returns the response headers.
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func (r *codeModifierWithoutCloseNotify) Header() http.Header {
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if r.headerSent {
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return r.responseWriter.Header()
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}
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if r.headerMap == nil {
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r.headerMap = make(http.Header)
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}
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return r.headerMap
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}
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// Write calls WriteHeader to send the enforced code,
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// then writes the data directly to r.responseWriter.
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func (r *codeModifierWithoutCloseNotify) Write(buf []byte) (int, error) {
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r.WriteHeader(r.code)
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return r.responseWriter.Write(buf)
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}
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// WriteHeader sends the headers, with the enforced code (the code in argument is always ignored),
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// if it hasn't already been done.
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// WriteHeader is, in the specific case of 1xx status codes, a direct call to the wrapped ResponseWriter, without marking headers as sent,
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// allowing so further calls.
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func (r *codeModifierWithoutCloseNotify) WriteHeader(code int) {
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if r.headerSent {
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return
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}
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// Handling informational headers.
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if code >= 100 && code <= 199 {
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// Multiple informational status codes can be used,
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// so here the copy is not appending the values to not repeat them.
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for k, v := range r.headerMap {
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r.responseWriter.Header()[k] = v
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}
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r.responseWriter.WriteHeader(code)
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return
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}
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for k, v := range r.headerMap {
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r.responseWriter.Header()[k] = v
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}
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r.responseWriter.WriteHeader(r.code)
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r.headerSent = true
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}
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// Hijack hijacks the connection.
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func (r *codeModifierWithoutCloseNotify) Hijack() (net.Conn, *bufio.ReadWriter, error) {
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hijacker, ok := r.responseWriter.(http.Hijacker)
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if !ok {
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return nil, nil, fmt.Errorf("%T is not a http.Hijacker", r.responseWriter)
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}
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return hijacker.Hijack()
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}
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// Flush sends any buffered data to the client.
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func (r *codeModifierWithoutCloseNotify) Flush() {
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r.WriteHeader(r.code)
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if flusher, ok := r.responseWriter.(http.Flusher); ok {
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flusher.Flush()
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}
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}
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type codeModifierWithCloseNotify struct {
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*codeModifierWithoutCloseNotify
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}
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// CloseNotify returns a channel that receives at most a single value (true)
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// when the client connection has gone away.
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func (r *codeModifierWithCloseNotify) CloseNotify() <-chan bool {
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return r.responseWriter.(http.CloseNotifier).CloseNotify()
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}
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