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// Copyright 2014 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 http2
import (
"bytes"
"fmt"
"log"
"net/http"
"net/url"
"golang.org/x/net/http/httpguts"
"golang.org/x/net/http2/hpack"
)
// writeFramer is implemented by any type that is used to write frames.
type writeFramer interface {
writeFrame(writeContext) error
// staysWithinBuffer reports whether this writer promises that
// it will only write less than or equal to size bytes, and it
// won't Flush the write context.
staysWithinBuffer(size int) bool
}
// writeContext is the interface needed by the various frame writer
// types below. All the writeFrame methods below are scheduled via the
// frame writing scheduler (see writeScheduler in writesched.go).
//
// This interface is implemented by *serverConn.
//
// TODO: decide whether to a) use this in the client code (which didn't
// end up using this yet, because it has a simpler design, not
// currently implementing priorities), or b) delete this and
// make the server code a bit more concrete.
type writeContext interface {
Framer() *Framer
Flush() error
CloseConn() error
// HeaderEncoder returns an HPACK encoder that writes to the
// returned buffer.
HeaderEncoder() (*hpack.Encoder, *bytes.Buffer)
}
// writeEndsStream reports whether w writes a frame that will transition
// the stream to a half-closed local state. This returns false for RST_STREAM,
// which closes the entire stream (not just the local half).
func writeEndsStream(w writeFramer) bool {
switch v := w.(type) {
case *writeData:
return v.endStream
case *writeResHeaders:
return v.endStream
case nil:
// This can only happen if the caller reuses w after it's
// been intentionally nil'ed out to prevent use. Keep this
// here to catch future refactoring breaking it.
panic("writeEndsStream called on nil writeFramer")
}
return false
}
type flushFrameWriter struct{}
func (flushFrameWriter) writeFrame(ctx writeContext) error {
return ctx.Flush()
}
func (flushFrameWriter) staysWithinBuffer(max int) bool { return false }
type writeSettings []Setting
func (s writeSettings) staysWithinBuffer(max int) bool {
const settingSize = 6 // uint16 + uint32
return frameHeaderLen+settingSize*len(s) <= max
}
func (s writeSettings) writeFrame(ctx writeContext) error {
return ctx.Framer().WriteSettings([]Setting(s)...)
}
type writeGoAway struct {
maxStreamID uint32
code ErrCode
}
func (p *writeGoAway) writeFrame(ctx writeContext) error {
err := ctx.Framer().WriteGoAway(p.maxStreamID, p.code, nil)
ctx.Flush() // ignore error: we're hanging up on them anyway
return err
}
func (*writeGoAway) staysWithinBuffer(max int) bool { return false } // flushes
type writeData struct {
streamID uint32
p []byte
endStream bool
}
func (w *writeData) String() string {
return fmt.Sprintf("writeData(stream=%d, p=%d, endStream=%v)", w.streamID, len(w.p), w.endStream)
}
func (w *writeData) writeFrame(ctx writeContext) error {
return ctx.Framer().WriteData(w.streamID, w.endStream, w.p)
}
func (w *writeData) staysWithinBuffer(max int) bool {
return frameHeaderLen+len(w.p) <= max
}
// handlerPanicRST is the message sent from handler goroutines when
// the handler panics.
type handlerPanicRST struct {
StreamID uint32
}
func (hp handlerPanicRST) writeFrame(ctx writeContext) error {
return ctx.Framer().WriteRSTStream(hp.StreamID, ErrCodeInternal)
}
func (hp handlerPanicRST) staysWithinBuffer(max int) bool { return frameHeaderLen+4 <= max }
func (se StreamError) writeFrame(ctx writeContext) error {
return ctx.Framer().WriteRSTStream(se.StreamID, se.Code)
}
func (se StreamError) staysWithinBuffer(max int) bool { return frameHeaderLen+4 <= max }
type writePingAck struct{ pf *PingFrame }
func (w writePingAck) writeFrame(ctx writeContext) error {
return ctx.Framer().WritePing(true, w.pf.Data)
}
func (w writePingAck) staysWithinBuffer(max int) bool { return frameHeaderLen+len(w.pf.Data) <= max }
type writeSettingsAck struct{}
func (writeSettingsAck) writeFrame(ctx writeContext) error {
return ctx.Framer().WriteSettingsAck()
}
func (writeSettingsAck) staysWithinBuffer(max int) bool { return frameHeaderLen <= max }
// splitHeaderBlock splits headerBlock into fragments so that each fragment fits
// in a single frame, then calls fn for each fragment. firstFrag/lastFrag are true
// for the first/last fragment, respectively.
func splitHeaderBlock(ctx writeContext, headerBlock []byte, fn func(ctx writeContext, frag []byte, firstFrag, lastFrag bool) error) error {
// For now we're lazy and just pick the minimum MAX_FRAME_SIZE
// that all peers must support (16KB). Later we could care
// more and send larger frames if the peer advertised it, but
// there's little point. Most headers are small anyway (so we
// generally won't have CONTINUATION frames), and extra frames
// only waste 9 bytes anyway.
const maxFrameSize = 16384
first := true
for len(headerBlock) > 0 {
frag := headerBlock
if len(frag) > maxFrameSize {
frag = frag[:maxFrameSize]
}
headerBlock = headerBlock[len(frag):]
if err := fn(ctx, frag, first, len(headerBlock) == 0); err != nil {
return err
}
first = false
}
return nil
}
// writeResHeaders is a request to write a HEADERS and 0+ CONTINUATION frames
// for HTTP response headers or trailers from a server handler.
type writeResHeaders struct {
streamID uint32
httpResCode int // 0 means no ":status" line
h http.Header // may be nil
trailers []string // if non-nil, which keys of h to write. nil means all.
endStream bool
date string
contentType string
contentLength string
}
func encKV(enc *hpack.Encoder, k, v string) {
if VerboseLogs {
log.Printf("http2: server encoding header %q = %q", k, v)
}
enc.WriteField(hpack.HeaderField{Name: k, Value: v})
}
func (w *writeResHeaders) staysWithinBuffer(max int) bool {
// TODO: this is a common one. It'd be nice to return true
// here and get into the fast path if we could be clever and
// calculate the size fast enough, or at least a conservative
// upper bound that usually fires. (Maybe if w.h and
// w.trailers are nil, so we don't need to enumerate it.)
// Otherwise I'm afraid that just calculating the length to
// answer this question would be slower than the ~2µs benefit.
return false
}
func (w *writeResHeaders) writeFrame(ctx writeContext) error {
enc, buf := ctx.HeaderEncoder()
buf.Reset()
if w.httpResCode != 0 {
encKV(enc, ":status", httpCodeString(w.httpResCode))
}
encodeHeaders(enc, w.h, w.trailers)
if w.contentType != "" {
encKV(enc, "content-type", w.contentType)
}
if w.contentLength != "" {
encKV(enc, "content-length", w.contentLength)
}
if w.date != "" {
encKV(enc, "date", w.date)
}
headerBlock := buf.Bytes()
if len(headerBlock) == 0 && w.trailers == nil {
panic("unexpected empty hpack")
}
return splitHeaderBlock(ctx, headerBlock, w.writeHeaderBlock)
}
func (w *writeResHeaders) writeHeaderBlock(ctx writeContext, frag []byte, firstFrag, lastFrag bool) error {
if firstFrag {
return ctx.Framer().WriteHeaders(HeadersFrameParam{
StreamID: w.streamID,
BlockFragment: frag,
EndStream: w.endStream,
EndHeaders: lastFrag,
})
} else {
return ctx.Framer().WriteContinuation(w.streamID, lastFrag, frag)
}
}
// writePushPromise is a request to write a PUSH_PROMISE and 0+ CONTINUATION frames.
type writePushPromise struct {
streamID uint32 // pusher stream
method string // for :method
url *url.URL // for :scheme, :authority, :path
h http.Header
// Creates an ID for a pushed stream. This runs on serveG just before
// the frame is written. The returned ID is copied to promisedID.
allocatePromisedID func() (uint32, error)
promisedID uint32
}
func (w *writePushPromise) staysWithinBuffer(max int) bool {
// TODO: see writeResHeaders.staysWithinBuffer
return false
}
func (w *writePushPromise) writeFrame(ctx writeContext) error {
enc, buf := ctx.HeaderEncoder()
buf.Reset()
encKV(enc, ":method", w.method)
encKV(enc, ":scheme", w.url.Scheme)
encKV(enc, ":authority", w.url.Host)
encKV(enc, ":path", w.url.RequestURI())
encodeHeaders(enc, w.h, nil)
headerBlock := buf.Bytes()
if len(headerBlock) == 0 {
panic("unexpected empty hpack")
}
return splitHeaderBlock(ctx, headerBlock, w.writeHeaderBlock)
}
func (w *writePushPromise) writeHeaderBlock(ctx writeContext, frag []byte, firstFrag, lastFrag bool) error {
if firstFrag {
return ctx.Framer().WritePushPromise(PushPromiseParam{
StreamID: w.streamID,
PromiseID: w.promisedID,
BlockFragment: frag,
EndHeaders: lastFrag,
})
} else {
return ctx.Framer().WriteContinuation(w.streamID, lastFrag, frag)
}
}
type write100ContinueHeadersFrame struct {
streamID uint32
}
func (w write100ContinueHeadersFrame) writeFrame(ctx writeContext) error {
enc, buf := ctx.HeaderEncoder()
buf.Reset()
encKV(enc, ":status", "100")
return ctx.Framer().WriteHeaders(HeadersFrameParam{
StreamID: w.streamID,
BlockFragment: buf.Bytes(),
EndStream: false,
EndHeaders: true,
})
}
func (w write100ContinueHeadersFrame) staysWithinBuffer(max int) bool {
// Sloppy but conservative:
return 9+2*(len(":status")+len("100")) <= max
}
type writeWindowUpdate struct {
streamID uint32 // or 0 for conn-level
n uint32
}
func (wu writeWindowUpdate) staysWithinBuffer(max int) bool { return frameHeaderLen+4 <= max }
func (wu writeWindowUpdate) writeFrame(ctx writeContext) error {
return ctx.Framer().WriteWindowUpdate(wu.streamID, wu.n)
}
// encodeHeaders encodes an http.Header. If keys is not nil, then (k, h[k])
// is encoded only if k is in keys.
func encodeHeaders(enc *hpack.Encoder, h http.Header, keys []string) {
if keys == nil {
sorter := sorterPool.Get().(*sorter)
// Using defer here, since the returned keys from the
// sorter.Keys method is only valid until the sorter
// is returned:
defer sorterPool.Put(sorter)
keys = sorter.Keys(h)
}
for _, k := range keys {
vv := h[k]
k, ascii := lowerHeader(k)
if !ascii {
// Skip writing invalid headers. Per RFC 7540, Section 8.1.2, header
// field names have to be ASCII characters (just as in HTTP/1.x).
continue
}
if !validWireHeaderFieldName(k) {
// Skip it as backup paranoia. Per
// golang.org/issue/14048, these should
// already be rejected at a higher level.
continue
}
isTE := k == "transfer-encoding"
for _, v := range vv {
if !httpguts.ValidHeaderFieldValue(v) {
// TODO: return an error? golang.org/issue/14048
// For now just omit it.
continue
}
// TODO: more of "8.1.2.2 Connection-Specific Header Fields"
if isTE && v != "trailers" {
continue
}
encKV(enc, k, v)
}
}
}
