// 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 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 = lowerHeader(k) 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) } } }