Source file src/net/http/fcgi/child.go

Documentation: net/http/fcgi

  // 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"
  	"io/ioutil"
  	"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
  	w           *bufWriter
  	wroteHeader bool
  }
  
  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(data []byte) (int, error) {
  	if !r.wroteHeader {
  		r.WriteHeader(http.StatusOK)
  	}
  	return r.w.Write(data)
  }
  
  func (r *response) WriteHeader(code int) {
  	if r.wroteHeader {
  		return
  	}
  	r.wroteHeader = true
  	if code == http.StatusNotModified {
  		// Must not have body.
  		r.header.Del("Content-Type")
  		r.header.Del("Content-Length")
  		r.header.Del("Transfer-Encoding")
  	} else if r.header.Get("Content-Type") == "" {
  		r.header.Set("Content-Type", "text/html; charset=utf-8")
  	}
  
  	if r.header.Get("Date") == "" {
  		r.header.Set("Date", time.Now().UTC().Format(http.TimeFormat))
  	}
  
  	fmt.Fprintf(r.w, "Status: %d %s\r\n", code, http.StatusText(code))
  	r.header.Write(r.w)
  	r.w.WriteString("\r\n")
  }
  
  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 = ioutil.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)
  	}
  	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(ioutil.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
  }
  

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