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net/http: document that Handlers shouldn't mutate Request

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Also, don't read from the Request.Headers in the http Server code once
ServeHTTP has started. This is partially redundant with documenting
that handlers shouldn't mutate request, but: the space is free due to
bool packing, it's faster to do the checks once instead of N times in
writeChunk, and it's a little nicer to code which previously didn't
play by the unwritten rules. But I'm not going to fix all the cases.

Fixes #14940

Change-Id: I612a8826b41c8682b59515081c590c512ee6949e
Reviewed-on: https://go-review.googlesource.com/21530
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Andrew Gerrand <adg@golang.org>
This commit is contained in:
Brad Fitzpatrick 2016-04-05 15:59:55 +00:00
parent 8556c76f88
commit e0307c25be
1 changed files with 19 additions and 8 deletions
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27
src/net/http/server.go
View file

@ -50,6 +50,9 @@ var (
// ResponseWriter. Cautious handlers should read the Request.Body
// first, and then reply.
//
// Except for reading the body, handlers should not modify the
// provided Request.
//
// If ServeHTTP panics, the server (the caller of ServeHTTP) assumes
// that the effect of the panic was isolated to the active request.
// It recovers the panic, logs a stack trace to the server error log,
@ -306,11 +309,13 @@ func (cw *chunkWriter) close() {
// A response represents the server side of an HTTP response.
type response struct {
conn *conn
req *Request // request for this response
reqBody io.ReadCloser
wroteHeader bool // reply header has been (logically) written
wroteContinue bool // 100 Continue response was written
conn *conn
req *Request // request for this response
reqBody io.ReadCloser
wroteHeader bool // reply header has been (logically) written
wroteContinue bool // 100 Continue response was written
wants10KeepAlive bool // HTTP/1.0 w/ Connection "keep-alive"
wantsClose bool // HTTP request has Connection "close"
w *bufio.Writer // buffers output in chunks to chunkWriter
cw chunkWriter
@ -748,6 +753,12 @@ func (c *conn) readRequest() (w *response, err error) {
reqBody: req.Body,
handlerHeader: make(Header),
contentLength: -1,
// We populate these ahead of time so we're not
// reading from req.Header after their Handler starts
// and maybe mutates it (Issue 14940)
wants10KeepAlive: req.wantsHttp10KeepAlive(),
wantsClose: req.wantsClose(),
}
if isH2Upgrade {
w.closeAfterReply = true
@ -929,7 +940,7 @@ func (cw *chunkWriter) writeHeader(p []byte) {
// If this was an HTTP/1.0 request with keep-alive and we sent a
// Content-Length back, we can make this a keep-alive response ...
if w.req.wantsHttp10KeepAlive() && keepAlivesEnabled {
if w.wants10KeepAlive && keepAlivesEnabled {
sentLength := header.get("Content-Length") != ""
if sentLength && header.get("Connection") == "keep-alive" {
w.closeAfterReply = false
@ -939,12 +950,12 @@ func (cw *chunkWriter) writeHeader(p []byte) {
// Check for a explicit (and valid) Content-Length header.
hasCL := w.contentLength != -1
if w.req.wantsHttp10KeepAlive() && (isHEAD || hasCL) {
if w.wants10KeepAlive && (isHEAD || hasCL) {
_, connectionHeaderSet := header["Connection"]
if !connectionHeaderSet {
setHeader.connection = "keep-alive"
}
} else if !w.req.ProtoAtLeast(1, 1) || w.req.wantsClose() {
} else if !w.req.ProtoAtLeast(1, 1) || w.wantsClose {
w.closeAfterReply = true
}