Use h2c from x/net to handle h2c requests

Co-authored-by: Mathieu Lonjaret <mathieu.lonjaret@gmail.com>

vendor/golang.org/x/net/http2/hpack/hpack.go

@@ -92,6 +92,8 @@ type Decoder struct {
 	// saveBuf is previous data passed to Write which we weren't able
 	// to fully parse before. Unlike buf, we own this data.
 	saveBuf bytes.Buffer
+
+	firstField bool // processing the first field of the header block
 }
 
 // NewDecoder returns a new decoder with the provided maximum dynamic
@@ -101,6 +103,7 @@ func NewDecoder(maxDynamicTableSize uint32, emitFunc func(f HeaderField)) *Decod
 	d := &Decoder{
 		emit:        emitFunc,
 		emitEnabled: true,
+		firstField:  true,
 	}
 	d.dynTab.table.init()
 	d.dynTab.allowedMaxSize = maxDynamicTableSize
@@ -226,11 +229,15 @@ func (d *Decoder) DecodeFull(p []byte) ([]HeaderField, error) {
 	return hf, nil
 }
 
+// Close declares that the decoding is complete and resets the Decoder
+// to be reused again for a new header block. If there is any remaining
+// data in the decoder's buffer, Close returns an error.
 func (d *Decoder) Close() error {
 	if d.saveBuf.Len() > 0 {
 		d.saveBuf.Reset()
 		return DecodingError{errors.New("truncated headers")}
 	}
+	d.firstField = true
 	return nil
 }
 
@@ -266,6 +273,7 @@ func (d *Decoder) Write(p []byte) (n int, err error) {
 			d.saveBuf.Write(d.buf)
 			return len(p), nil
 		}
+		d.firstField = false
 		if err != nil {
 			break
 		}
@@ -391,7 +399,7 @@ func (d *Decoder) callEmit(hf HeaderField) error {
 func (d *Decoder) parseDynamicTableSizeUpdate() error {
 	// RFC 7541, sec 4.2: This dynamic table size update MUST occur at the
 	// beginning of the first header block following the change to the dynamic table size.
-	if d.dynTab.size > 0 {
+	if !d.firstField && d.dynTab.size > 0 {
 		return DecodingError{errors.New("dynamic table size update MUST occur at the beginning of a header block")}
 	}
 

vendor/golang.org/x/net/http2/hpack/huffman.go

@@ -47,6 +47,7 @@ var ErrInvalidHuffman = errors.New("hpack: invalid Huffman-encoded data")
 // If maxLen is greater than 0, attempts to write more to buf than
 // maxLen bytes will return ErrStringLength.
 func huffmanDecode(buf *bytes.Buffer, maxLen int, v []byte) error {
+	rootHuffmanNode := getRootHuffmanNode()
 	n := rootHuffmanNode
 	// cur is the bit buffer that has not been fed into n.
 	// cbits is the number of low order bits in cur that are valid.
@@ -106,7 +107,7 @@ func huffmanDecode(buf *bytes.Buffer, maxLen int, v []byte) error {
 
 type node struct {
 	// children is non-nil for internal nodes
-	children []*node
+	children *[256]*node
 
 	// The following are only valid if children is nil:
 	codeLen uint8 // number of bits that led to the output of sym
@@ -114,22 +115,31 @@ type node struct {
 }
 
 func newInternalNode() *node {
-	return &node{children: make([]*node, 256)}
+	return &node{children: new([256]*node)}
 }
 
-var rootHuffmanNode = newInternalNode()
+var (
+	buildRootOnce       sync.Once
+	lazyRootHuffmanNode *node
+)
 
-func init() {
+func getRootHuffmanNode() *node {
+	buildRootOnce.Do(buildRootHuffmanNode)
+	return lazyRootHuffmanNode
+}
+
+func buildRootHuffmanNode() {
 	if len(huffmanCodes) != 256 {
 		panic("unexpected size")
 	}
+	lazyRootHuffmanNode = newInternalNode()
 	for i, code := range huffmanCodes {
 		addDecoderNode(byte(i), code, huffmanCodeLen[i])
 	}
 }
 
 func addDecoderNode(sym byte, code uint32, codeLen uint8) {
-	cur := rootHuffmanNode
+	cur := lazyRootHuffmanNode
 	for codeLen > 8 {
 		codeLen -= 8
 		i := uint8(code >> codeLen)