I'm trying to set up a TCP server which accepts and decodes HTTP/2 data. The code to actually parse the frames can be found in this article:
Decoding http2 frame header/data in Go
I'm having issues, however, with setting up the server. The connection gets accepted, but it hangs on framer.ReadFrame(). Here is a code example:
// generate with: openssl req -x509 -newkey rsa:4096 -keyout server.key -out server.pem -days 365 -nodes
cert, err := tls.LoadX509KeyPair("server.pem", "server.key")
if err != nil {
log.Fatal(err)
}
tlsCfg := &tls.Config{
Certificates: []tls.Certificate{cert},
NextProtos: []string{"h2"},
}
l, err := tls.Listen("tcp", ":8787", tlsCfg)
if err != nil {
log.Fatal(err)
}
defer l.Close()
conn, err := l.Accept()
if err != nil {
log.Fatalln(err)
}
defer conn.Close()
framer := http2.NewFramer(conn, conn)
frame, _ := framer.ReadFrame() // Here it hangs
I request the server using curl
curl -v https://127.0.0.1:8787/ -k --http2
The conversation doesn't start with a frame. First the client sends the string
"PRI * HTTP/2.0
SM
"
You can tell by inspecting the bytes sent by the client:
framer := http2.NewFramer(conn, io.TeeReader(conn, hex.Dumper(os.Stdout)))
// 00000000 50 52 49 20 2a 20 48 54 54 50 2f 32 2e 30 0d 0a |PRI * HTTP/2.0..|
// 00000010 0d 0a 53 4d 0d 0a 0d 0a 00 00 12 04 00 00 00 00 |..SM............|
// 00000020 00 00 03 00 00 00 64 00 04 40 00 00 00 00 02 00 |......d..@......|
// 00000030 00 00 00 00 00 04 08 00 00 00 00 00 3f ff 00 01 |............?...|
// 00000040 00 00 1e 01 05 00 00 00 01 82 84 87 41 8a a0 e4 |............A...|
// 00000050 1d 13 9d 09 b8 f3 af 3b 7a 88 25 b6 50 c3 ab b6 |.......;z.%.P...|
// 00000060 fa e0 53 03 2a 2f 2a ^C
If you modify your code to read that string first it works as expected:
conn, err := l.Accept()
if err != nil {
log.Fatalln(err)
}
defer conn.Close()
const preface = "PRI * HTTP/2.0
SM
"
b := make([]byte, len(preface))
if _, err := io.ReadFull(conn, b); err != nil {
log.Fatalln(err)
}
if string(b) != preface {
log.Fatalln("invalid preface")
}
framer := http2.NewFramer(conn, conn)
frame, err := framer.ReadFrame()
fmt.Println(frame, err)
// Output:
// [FrameHeader SETTINGS len=18] <nil>
If found these articles useful when playing with HTTP2 myself: