libgo/go/net/http/fcgi/child.go - gofrontend - Git at Google

 // Copyright 2011 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 package fcgi

 // This file implements FastCGI from the perspective of a child process.

 import (
 	"context"
 	"errors"
 	"fmt"
 	"io"
 	"net"
 	"net/http"
 	"net/http/cgi"
 	"os"
 	"strings"
 	"sync"
 	"time"
 )

 // request holds the state for an in-progress request. As soon as it's complete,
 // it's converted to an http.Request.
 type request struct {
 	pw        *io.PipeWriter
 	reqId     uint16
 	params    map[string]string
 	buf       [1024]byte
 	rawParams []byte
 	keepConn  bool
 }

 // envVarsContextKey uniquely identifies a mapping of CGI
 // environment variables to their values in a request context
 type envVarsContextKey struct{}

 func newRequest(reqId uint16, flags uint8) *request {
 	r := &request{
 		reqId:    reqId,
 		params:   map[string]string{},
 		keepConn: flags&flagKeepConn != 0,
 	}
 	r.rawParams = r.buf[:0]
 	return r
 }

 // parseParams reads an encoded []byte into Params.
 func (r *request) parseParams() {
 	text := r.rawParams
 	r.rawParams = nil
 	for len(text) > 0 {
 		keyLen, n := readSize(text)
 		if n == 0 {
 			return
 		}
 		text = text[n:]
 		valLen, n := readSize(text)
 		if n == 0 {
 			return
 		}
 		text = text[n:]
 		if int(keyLen)+int(valLen) > len(text) {
 			return
 		}
 		key := readString(text, keyLen)
 		text = text[keyLen:]
 		val := readString(text, valLen)
 		text = text[valLen:]
 		r.params[key] = val
 	}
 }

 // response implements http.ResponseWriter.
 type response struct {
 	req            *request
 	header         http.Header
 	code           int
 	wroteHeader    bool
 	wroteCGIHeader bool
 	w              *bufWriter
 }

 func newResponse(c *child, req *request) *response {
 	return &response{
 		req:    req,
 		header: http.Header{},
 		w:      newWriter(c.conn, typeStdout, req.reqId),
 	}
 }

 func (r *response) Header() http.Header {
 	return r.header
 }

 func (r *response) Write(p []byte) (n int, err error) {
 	if !r.wroteHeader {
 		r.WriteHeader(http.StatusOK)
 	}
 	if !r.wroteCGIHeader {
 		r.writeCGIHeader(p)
 	}
 	return r.w.Write(p)
 }

 func (r *response) WriteHeader(code int) {
 	if r.wroteHeader {
 		return
 	}
 	r.wroteHeader = true
 	r.code = code
 	if code == http.StatusNotModified {
 		// Must not have body.
 		r.header.Del("Content-Type")
 		r.header.Del("Content-Length")
 		r.header.Del("Transfer-Encoding")
 	}
 	if r.header.Get("Date") == "" {
 		r.header.Set("Date", time.Now().UTC().Format(http.TimeFormat))
 	}
 }

 // writeCGIHeader finalizes the header sent to the client and writes it to the output.
 // p is not written by writeHeader, but is the first chunk of the body
 // that will be written. It is sniffed for a Content-Type if none is
 // set explicitly.
 func (r *response) writeCGIHeader(p []byte) {
 	if r.wroteCGIHeader {
 		return
 	}
 	r.wroteCGIHeader = true
 	fmt.Fprintf(r.w, "Status: %d %s\r\n", r.code, http.StatusText(r.code))
 	if _, hasType := r.header["Content-Type"]; r.code != http.StatusNotModified && !hasType {
 		r.header.Set("Content-Type", http.DetectContentType(p))
 	}
 	r.header.Write(r.w)
 	r.w.WriteString("\r\n")
 	r.w.Flush()
 }

 func (r *response) Flush() {
 	if !r.wroteHeader {
 		r.WriteHeader(http.StatusOK)
 	}
 	r.w.Flush()
 }

 func (r *response) Close() error {
 	r.Flush()
 	return r.w.Close()
 }

 type child struct {
 	conn    *conn
 	handler http.Handler

 	mu       sync.Mutex          // protects requests:
 	requests map[uint16]*request // keyed by request ID
 }

 func newChild(rwc io.ReadWriteCloser, handler http.Handler) *child {
 	return &child{
 		conn:     newConn(rwc),
 		handler:  handler,
 		requests: make(map[uint16]*request),
 	}
 }

 func (c *child) serve() {
 	defer c.conn.Close()
 	defer c.cleanUp()
 	var rec record
 	for {
 		if err := rec.read(c.conn.rwc); err != nil {
 			return
 		}
 		if err := c.handleRecord(&rec); err != nil {
 			return
 		}
 	}
 }

 var errCloseConn = errors.New("fcgi: connection should be closed")

 var emptyBody = io.NopCloser(strings.NewReader(""))

 // ErrRequestAborted is returned by Read when a handler attempts to read the
 // body of a request that has been aborted by the web server.
 var ErrRequestAborted = errors.New("fcgi: request aborted by web server")

 // ErrConnClosed is returned by Read when a handler attempts to read the body of
 // a request after the connection to the web server has been closed.
 var ErrConnClosed = errors.New("fcgi: connection to web server closed")

 func (c *child) handleRecord(rec *record) error {
 	c.mu.Lock()
 	req, ok := c.requests[rec.h.Id]
 	c.mu.Unlock()
 	if !ok && rec.h.Type != typeBeginRequest && rec.h.Type != typeGetValues {
 		// The spec says to ignore unknown request IDs.
 		return nil
 	}

 	switch rec.h.Type {
 	case typeBeginRequest:
 		if req != nil {
 			// The server is trying to begin a request with the same ID
 			// as an in-progress request. This is an error.
 			return errors.New("fcgi: received ID that is already in-flight")
 		}

 		var br beginRequest
 		if err := br.read(rec.content()); err != nil {
 			return err
 		}
 		if br.role != roleResponder {
 			c.conn.writeEndRequest(rec.h.Id, 0, statusUnknownRole)
 			return nil
 		}
 		req = newRequest(rec.h.Id, br.flags)
 		c.mu.Lock()
 		c.requests[rec.h.Id] = req
 		c.mu.Unlock()
 		return nil
 	case typeParams:
 		// NOTE(eds): Technically a key-value pair can straddle the boundary
 		// between two packets. We buffer until we've received all parameters.
 		if len(rec.content()) > 0 {
 			req.rawParams = append(req.rawParams, rec.content()...)
 			return nil
 		}
 		req.parseParams()
 		return nil
 	case typeStdin:
 		content := rec.content()
 		if req.pw == nil {
 			var body io.ReadCloser
 			if len(content) > 0 {
 				// body could be an io.LimitReader, but it shouldn't matter
 				// as long as both sides are behaving.
 				body, req.pw = io.Pipe()
 			} else {
 				body = emptyBody
 			}
 			go c.serveRequest(req, body)
 		}
 		if len(content) > 0 {
 			// TODO(eds): This blocks until the handler reads from the pipe.
 			// If the handler takes a long time, it might be a problem.
 			req.pw.Write(content)
 		} else if req.pw != nil {
 			req.pw.Close()
 		}
 		return nil
 	case typeGetValues:
 		values := map[string]string{"FCGI_MPXS_CONNS": "1"}
 		c.conn.writePairs(typeGetValuesResult, 0, values)
 		return nil
 	case typeData:
 		// If the filter role is implemented, read the data stream here.
 		return nil
 	case typeAbortRequest:
 		c.mu.Lock()
 		delete(c.requests, rec.h.Id)
 		c.mu.Unlock()
 		c.conn.writeEndRequest(rec.h.Id, 0, statusRequestComplete)
 		if req.pw != nil {
 			req.pw.CloseWithError(ErrRequestAborted)
 		}
 		if !req.keepConn {
 			// connection will close upon return
 			return errCloseConn
 		}
 		return nil
 	default:
 		b := make([]byte, 8)
 		b[0] = byte(rec.h.Type)
 		c.conn.writeRecord(typeUnknownType, 0, b)
 		return nil
 	}
 }

 // filterOutUsedEnvVars returns a new map of env vars without the
 // variables in the given envVars map that are read for creating each http.Request
 func filterOutUsedEnvVars(envVars map[string]string) map[string]string {
 	withoutUsedEnvVars := make(map[string]string)
 	for k, v := range envVars {
 		if addFastCGIEnvToContext(k) {
 			withoutUsedEnvVars[k] = v
 		}
 	}
 	return withoutUsedEnvVars
 }

 func (c *child) serveRequest(req *request, body io.ReadCloser) {
 	r := newResponse(c, req)
 	httpReq, err := cgi.RequestFromMap(req.params)
 	if err != nil {
 		// there was an error reading the request
 		r.WriteHeader(http.StatusInternalServerError)
 		c.conn.writeRecord(typeStderr, req.reqId, []byte(err.Error()))
 	} else {
 		httpReq.Body = body
 		withoutUsedEnvVars := filterOutUsedEnvVars(req.params)
 		envVarCtx := context.WithValue(httpReq.Context(), envVarsContextKey{}, withoutUsedEnvVars)
 		httpReq = httpReq.WithContext(envVarCtx)
 		c.handler.ServeHTTP(r, httpReq)
 	}
 	// Make sure we serve something even if nothing was written to r
 	r.Write(nil)
 	r.Close()
 	c.mu.Lock()
 	delete(c.requests, req.reqId)
 	c.mu.Unlock()
 	c.conn.writeEndRequest(req.reqId, 0, statusRequestComplete)

 	// Consume the entire body, so the host isn't still writing to
 	// us when we close the socket below in the !keepConn case,
 	// otherwise we'd send a RST. (golang.org/issue/4183)
 	// TODO(bradfitz): also bound this copy in time. Or send
 	// some sort of abort request to the host, so the host
 	// can properly cut off the client sending all the data.
 	// For now just bound it a little and
 	io.CopyN(io.Discard, body, 100<<20)
 	body.Close()

 	if !req.keepConn {
 		c.conn.Close()
 	}
 }

 func (c *child) cleanUp() {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 	for _, req := range c.requests {
 		if req.pw != nil {
 			// race with call to Close in c.serveRequest doesn't matter because
 			// Pipe(Reader|Writer).Close are idempotent
 			req.pw.CloseWithError(ErrConnClosed)
 		}
 	}
 }

 // Serve accepts incoming FastCGI connections on the listener l, creating a new
 // goroutine for each. The goroutine reads requests and then calls handler
 // to reply to them.
 // If l is nil, Serve accepts connections from os.Stdin.
 // If handler is nil, http.DefaultServeMux is used.
 func Serve(l net.Listener, handler http.Handler) error {
 	if l == nil {
 		var err error
 		l, err = net.FileListener(os.Stdin)
 		if err != nil {
 			return err
 		}
 		defer l.Close()
 	}
 	if handler == nil {
 		handler = http.DefaultServeMux
 	}
 	for {
 		rw, err := l.Accept()
 		if err != nil {
 			return err
 		}
 		c := newChild(rw, handler)
 		go c.serve()
 	}
 }

 // ProcessEnv returns FastCGI environment variables associated with the request r
 // for which no effort was made to be included in the request itself - the data
 // is hidden in the request's context. As an example, if REMOTE_USER is set for a
 // request, it will not be found anywhere in r, but it will be included in
 // ProcessEnv's response (via r's context).
 func ProcessEnv(r *http.Request) map[string]string {
 	env, _ := r.Context().Value(envVarsContextKey{}).(map[string]string)
 	return env
 }

 // addFastCGIEnvToContext reports whether to include the FastCGI environment variable s
 // in the http.Request.Context, accessible via ProcessEnv.
 func addFastCGIEnvToContext(s string) bool {
 	// Exclude things supported by net/http natively:
 	switch s {
 	case "CONTENT_LENGTH", "CONTENT_TYPE", "HTTPS",
 		"PATH_INFO", "QUERY_STRING", "REMOTE_ADDR",
 		"REMOTE_HOST", "REMOTE_PORT", "REQUEST_METHOD",
 		"REQUEST_URI", "SCRIPT_NAME", "SERVER_PROTOCOL":
 		return false
 	}
 	if strings.HasPrefix(s, "HTTP_") {
 		return false
 	}
 	// Explicitly include FastCGI-specific things.
 	// This list is redundant with the default "return true" below.
 	// Consider this documentation of the sorts of things we expect
 	// to maybe see.
 	switch s {
 	case "REMOTE_USER":
 		return true
 	}
 	// Unknown, so include it to be safe.
 	return true
 }
	// Copyright 2011 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	package fcgi

	// This file implements FastCGI from the perspective of a child process.

	import (
	"context"
	"errors"
	"fmt"
	"io"
	"net"
	"net/http"
	"net/http/cgi"
	"os"
	"strings"
	"sync"
	"time"
	)

	// request holds the state for an in-progress request. As soon as it's complete,
	// it's converted to an http.Request.
	type request struct {
	pw *io.PipeWriter
	reqId uint16
	params map[string]string
	buf [1024]byte
	rawParams []byte
	keepConn bool
	}

	// envVarsContextKey uniquely identifies a mapping of CGI
	// environment variables to their values in a request context
	type envVarsContextKey struct{}

	func newRequest(reqId uint16, flags uint8) *request {
	r := &request{
	reqId: reqId,
	params: map[string]string{},
	keepConn: flags&flagKeepConn != 0,
	}
	r.rawParams = r.buf[:0]
	return r
	}

	// parseParams reads an encoded []byte into Params.
	func (r *request) parseParams() {
	text := r.rawParams
	r.rawParams = nil
	for len(text) > 0 {
	keyLen, n := readSize(text)
	if n == 0 {
	return
	}
	text = text[n:]
	valLen, n := readSize(text)
	if n == 0 {
	return
	}
	text = text[n:]
	if int(keyLen)+int(valLen) > len(text) {
	return
	}
	key := readString(text, keyLen)
	text = text[keyLen:]
	val := readString(text, valLen)
	text = text[valLen:]
	r.params[key] = val
	}
	}

	// response implements http.ResponseWriter.
	type response struct {
	req *request
	header http.Header
	code int
	wroteHeader bool
	wroteCGIHeader bool
	w *bufWriter
	}

	func newResponse(c child, req request) *response {
	return &response{
	req: req,
	header: http.Header{},
	w: newWriter(c.conn, typeStdout, req.reqId),
	}
	}

	func (r *response) Header() http.Header {
	return r.header
	}

	func (r *response) Write(p []byte) (n int, err error) {
	if !r.wroteHeader {
	r.WriteHeader(http.StatusOK)
	}
	if !r.wroteCGIHeader {
	r.writeCGIHeader(p)
	}
	return r.w.Write(p)
	}

	func (r *response) WriteHeader(code int) {
	if r.wroteHeader {
	return
	}
	r.wroteHeader = true
	r.code = code
	if code == http.StatusNotModified {
	// Must not have body.
	r.header.Del("Content-Type")
	r.header.Del("Content-Length")
	r.header.Del("Transfer-Encoding")
	}
	if r.header.Get("Date") == "" {
	r.header.Set("Date", time.Now().UTC().Format(http.TimeFormat))
	}
	}

	// writeCGIHeader finalizes the header sent to the client and writes it to the output.
	// p is not written by writeHeader, but is the first chunk of the body
	// that will be written. It is sniffed for a Content-Type if none is
	// set explicitly.
	func (r *response) writeCGIHeader(p []byte) {
	if r.wroteCGIHeader {
	return
	}
	r.wroteCGIHeader = true
	fmt.Fprintf(r.w, "Status: %d %s\r\n", r.code, http.StatusText(r.code))
	if _, hasType := r.header["Content-Type"]; r.code != http.StatusNotModified && !hasType {
	r.header.Set("Content-Type", http.DetectContentType(p))
	}
	r.header.Write(r.w)
	r.w.WriteString("\r\n")
	r.w.Flush()
	}

	func (r *response) Flush() {
	if !r.wroteHeader {
	r.WriteHeader(http.StatusOK)
	}
	r.w.Flush()
	}

	func (r *response) Close() error {
	r.Flush()
	return r.w.Close()
	}

	type child struct {
	conn *conn
	handler http.Handler

	mu sync.Mutex // protects requests:
	requests map[uint16]*request // keyed by request ID
	}

	func newChild(rwc io.ReadWriteCloser, handler http.Handler) *child {
	return &child{
	conn: newConn(rwc),
	handler: handler,
	requests: make(map[uint16]*request),
	}
	}

	func (c *child) serve() {
	defer c.conn.Close()
	defer c.cleanUp()
	var rec record
	for {
	if err := rec.read(c.conn.rwc); err != nil {
	return
	}
	if err := c.handleRecord(&rec); err != nil {
	return
	}
	}
	}

	var errCloseConn = errors.New("fcgi: connection should be closed")

	var emptyBody = io.NopCloser(strings.NewReader(""))

	// ErrRequestAborted is returned by Read when a handler attempts to read the
	// body of a request that has been aborted by the web server.
	var ErrRequestAborted = errors.New("fcgi: request aborted by web server")

	// ErrConnClosed is returned by Read when a handler attempts to read the body of
	// a request after the connection to the web server has been closed.
	var ErrConnClosed = errors.New("fcgi: connection to web server closed")

	func (c child) handleRecord(rec record) error {
	c.mu.Lock()
	req, ok := c.requests[rec.h.Id]
	c.mu.Unlock()
	if !ok && rec.h.Type != typeBeginRequest && rec.h.Type != typeGetValues {
	// The spec says to ignore unknown request IDs.
	return nil
	}

	switch rec.h.Type {
	case typeBeginRequest:
	if req != nil {
	// The server is trying to begin a request with the same ID
	// as an in-progress request. This is an error.
	return errors.New("fcgi: received ID that is already in-flight")
	}

	var br beginRequest
	if err := br.read(rec.content()); err != nil {
	return err
	}
	if br.role != roleResponder {
	c.conn.writeEndRequest(rec.h.Id, 0, statusUnknownRole)
	return nil
	}
	req = newRequest(rec.h.Id, br.flags)
	c.mu.Lock()
	c.requests[rec.h.Id] = req
	c.mu.Unlock()
	return nil
	case typeParams:
	// NOTE(eds): Technically a key-value pair can straddle the boundary
	// between two packets. We buffer until we've received all parameters.
	if len(rec.content()) > 0 {
	req.rawParams = append(req.rawParams, rec.content()...)
	return nil
	}
	req.parseParams()
	return nil
	case typeStdin:
	content := rec.content()
	if req.pw == nil {
	var body io.ReadCloser
	if len(content) > 0 {
	// body could be an io.LimitReader, but it shouldn't matter
	// as long as both sides are behaving.
	body, req.pw = io.Pipe()
	} else {
	body = emptyBody
	}
	go c.serveRequest(req, body)
	}
	if len(content) > 0 {
	// TODO(eds): This blocks until the handler reads from the pipe.
	// If the handler takes a long time, it might be a problem.
	req.pw.Write(content)
	} else if req.pw != nil {
	req.pw.Close()
	}
	return nil
	case typeGetValues:
	values := map[string]string{"FCGI_MPXS_CONNS": "1"}
	c.conn.writePairs(typeGetValuesResult, 0, values)
	return nil
	case typeData:
	// If the filter role is implemented, read the data stream here.
	return nil
	case typeAbortRequest:
	c.mu.Lock()
	delete(c.requests, rec.h.Id)
	c.mu.Unlock()
	c.conn.writeEndRequest(rec.h.Id, 0, statusRequestComplete)
	if req.pw != nil {
	req.pw.CloseWithError(ErrRequestAborted)
	}
	if !req.keepConn {
	// connection will close upon return
	return errCloseConn
	}
	return nil
	default:
	b := make([]byte, 8)
	b[0] = byte(rec.h.Type)
	c.conn.writeRecord(typeUnknownType, 0, b)
	return nil
	}
	}

	// filterOutUsedEnvVars returns a new map of env vars without the
	// variables in the given envVars map that are read for creating each http.Request
	func filterOutUsedEnvVars(envVars map[string]string) map[string]string {
	withoutUsedEnvVars := make(map[string]string)
	for k, v := range envVars {
	if addFastCGIEnvToContext(k) {
	withoutUsedEnvVars[k] = v
	}
	}
	return withoutUsedEnvVars
	}

	func (c child) serveRequest(req request, body io.ReadCloser) {
	r := newResponse(c, req)
	httpReq, err := cgi.RequestFromMap(req.params)
	if err != nil {
	// there was an error reading the request
	r.WriteHeader(http.StatusInternalServerError)
	c.conn.writeRecord(typeStderr, req.reqId, []byte(err.Error()))
	} else {
	httpReq.Body = body
	withoutUsedEnvVars := filterOutUsedEnvVars(req.params)
	envVarCtx := context.WithValue(httpReq.Context(), envVarsContextKey{}, withoutUsedEnvVars)
	httpReq = httpReq.WithContext(envVarCtx)
	c.handler.ServeHTTP(r, httpReq)
	}
	// Make sure we serve something even if nothing was written to r
	r.Write(nil)
	r.Close()
	c.mu.Lock()
	delete(c.requests, req.reqId)
	c.mu.Unlock()
	c.conn.writeEndRequest(req.reqId, 0, statusRequestComplete)

	// Consume the entire body, so the host isn't still writing to
	// us when we close the socket below in the !keepConn case,
	// otherwise we'd send a RST. (golang.org/issue/4183)
	// TODO(bradfitz): also bound this copy in time. Or send
	// some sort of abort request to the host, so the host
	// can properly cut off the client sending all the data.
	// For now just bound it a little and
	io.CopyN(io.Discard, body, 100<<20)
	body.Close()

	if !req.keepConn {
	c.conn.Close()
	}
	}

	func (c *child) cleanUp() {
	c.mu.Lock()
	defer c.mu.Unlock()
	for _, req := range c.requests {
	if req.pw != nil {
	// race with call to Close in c.serveRequest doesn't matter because
	// Pipe(Reader\|Writer).Close are idempotent
	req.pw.CloseWithError(ErrConnClosed)
	}
	}
	}

	// Serve accepts incoming FastCGI connections on the listener l, creating a new
	// goroutine for each. The goroutine reads requests and then calls handler
	// to reply to them.
	// If l is nil, Serve accepts connections from os.Stdin.
	// If handler is nil, http.DefaultServeMux is used.
	func Serve(l net.Listener, handler http.Handler) error {
	if l == nil {
	var err error
	l, err = net.FileListener(os.Stdin)
	if err != nil {
	return err
	}
	defer l.Close()
	}
	if handler == nil {
	handler = http.DefaultServeMux
	}
	for {
	rw, err := l.Accept()
	if err != nil {
	return err
	}
	c := newChild(rw, handler)
	go c.serve()
	}
	}

	// ProcessEnv returns FastCGI environment variables associated with the request r
	// for which no effort was made to be included in the request itself - the data
	// is hidden in the request's context. As an example, if REMOTE_USER is set for a
	// request, it will not be found anywhere in r, but it will be included in
	// ProcessEnv's response (via r's context).
	func ProcessEnv(r *http.Request) map[string]string {
	env, _ := r.Context().Value(envVarsContextKey{}).(map[string]string)
	return env
	}

	// addFastCGIEnvToContext reports whether to include the FastCGI environment variable s
	// in the http.Request.Context, accessible via ProcessEnv.
	func addFastCGIEnvToContext(s string) bool {
	// Exclude things supported by net/http natively:
	switch s {
	case "CONTENT_LENGTH", "CONTENT_TYPE", "HTTPS",
	"PATH_INFO", "QUERY_STRING", "REMOTE_ADDR",
	"REMOTE_HOST", "REMOTE_PORT", "REQUEST_METHOD",
	"REQUEST_URI", "SCRIPT_NAME", "SERVER_PROTOCOL":
	return false
	}
	if strings.HasPrefix(s, "HTTP_") {
	return false
	}
	// Explicitly include FastCGI-specific things.
	// This list is redundant with the default "return true" below.
	// Consider this documentation of the sorts of things we expect
	// to maybe see.
	switch s {
	case "REMOTE_USER":
	return true
	}
	// Unknown, so include it to be safe.
	return true
	}