nghttp2 - HTTP/2.0 C Library¶

nghttp - client¶

nghttp is a HTTP/2.0 client. It can connect to the HTTP/2.0 server with prior knowledge, HTTP Upgrade and NPN/ALPN TLS extension.

It has verbose output mode for framing information. Here is sample output from nghttp client:

$ src/nghttp -vn https://localhost:8443
[  0.003] NPN select next protocol: the remote server offers:
          * HTTP-draft-09/2.0
          * spdy/3
          * spdy/2
          * http/1.1
          NPN selected the protocol: HTTP-draft-09/2.0
[  0.005] send SETTINGS frame <length=16, flags=0x00, stream_id=0>
          (niv=2)
          [SETTINGS_MAX_CONCURRENT_STREAMS(4):100]
          [SETTINGS_INITIAL_WINDOW_SIZE(7):65535]
[  0.006] send HEADERS frame <length=47, flags=0x05, stream_id=1>
          ; END_STREAM | END_HEADERS
          ; Open new stream
          :authority: localhost:8443
          :method: GET
          :path: /
          :scheme: https
          accept: */*
          accept-encoding: gzip, deflate
          user-agent: nghttp2/0.1.0-DEV
[  0.006] recv SETTINGS frame <length=16, flags=0x00, stream_id=0>
          (niv=2)
          [SETTINGS_MAX_CONCURRENT_STREAMS(4):100]
          [SETTINGS_INITIAL_WINDOW_SIZE(7):65535]
[  0.006] send SETTINGS frame <length=0, flags=0x01, stream_id=0>
          ; ACK
          (niv=0)
[  0.006] recv WINDOW_UPDATE frame <length=4, flags=0x00, stream_id=0>
          (window_size_increment=1000000007)
[  0.006] recv SETTINGS frame <length=0, flags=0x01, stream_id=0>
          ; ACK
          (niv=0)
[  0.006] recv HEADERS frame <length=132, flags=0x04, stream_id=1>
          ; END_HEADERS
          ; First response header
          :status: 200
          accept-ranges: bytes
          content-encoding: gzip
          content-length: 146
          content-type: text/html
          date: Sun, 27 Oct 2013 14:23:54 GMT
          etag: "b1-4e5535a027780-gzip"
          last-modified: Sun, 01 Sep 2013 14:34:22 GMT
          server: Apache/2.4.6 (Debian)
          vary: Accept-Encoding
          via: 1.1 nghttpx
[  0.006] recv DATA frame <length=146, flags=0x00, stream_id=1>
[  0.006] recv DATA frame <length=0, flags=0x01, stream_id=1>
          ; END_STREAM
[  0.007] send GOAWAY frame <length=8, flags=0x00, stream_id=0>
          (last_stream_id=0, error_code=NO_ERROR(0), opaque_data(0)=[])

The HTTP Upgrade is performed like this:

$ src/nghttp -vnu http://localhost:8080
[  0.000] HTTP Upgrade request
GET / HTTP/1.1
Host: localhost:8080
Connection: Upgrade, HTTP2-Settings
Upgrade: HTTP-draft-09/2.0
HTTP2-Settings: AAAABAAAAGQAAAAHAAD__w
Accept: */*
User-Agent: nghttp2/0.1.0-DEV


[  0.000] HTTP Upgrade response
HTTP/1.1 101 Switching Protocols
Connection: Upgrade
Upgrade: HTTP-draft-09/2.0


[  0.001] HTTP Upgrade success
[  0.001] send SETTINGS frame <length=16, flags=0x00, stream_id=0>
          (niv=2)
          [SETTINGS_MAX_CONCURRENT_STREAMS(4):100]
          [SETTINGS_INITIAL_WINDOW_SIZE(7):65535]
[  0.001] recv SETTINGS frame <length=16, flags=0x00, stream_id=0>
          (niv=2)
          [SETTINGS_MAX_CONCURRENT_STREAMS(4):100]
          [SETTINGS_INITIAL_WINDOW_SIZE(7):65535]
[  0.001] recv WINDOW_UPDATE frame <length=4, flags=0x00, stream_id=0>
          (window_size_increment=1000000007)
[  0.001] recv HEADERS frame <length=121, flags=0x04, stream_id=1>
          ; END_HEADERS
          ; First response header
          :status: 200
          accept-ranges: bytes
          content-length: 177
          content-type: text/html
          date: Sun, 27 Oct 2013 14:26:04 GMT
          etag: "b1-4e5535a027780"
          last-modified: Sun, 01 Sep 2013 14:34:22 GMT
          server: Apache/2.4.6 (Debian)
          vary: Accept-Encoding
          via: 1.1 nghttpx
[  0.001] recv DATA frame <length=177, flags=0x00, stream_id=1>
[  0.001] recv DATA frame <length=0, flags=0x01, stream_id=1>
          ; END_STREAM
[  0.001] send SETTINGS frame <length=0, flags=0x01, stream_id=0>
          ; ACK
          (niv=0)
[  0.001] send GOAWAY frame <length=8, flags=0x00, stream_id=0>
          (last_stream_id=0, error_code=NO_ERROR(0), opaque_data(0)=[])
[  0.001] recv SETTINGS frame <length=0, flags=0x01, stream_id=0>
          ; ACK
          (niv=0)

nghttpd - server¶

nghttpd is static web server. It is single threaded and multiplexes connections using non-blocking socket.

By default, it uses SSL/TLS connection. Use --no-tls option to disable it.

nghttpd only accept the HTTP/2.0 connection via NPN/ALPN or direct HTTP/2.0 connection. No HTTP Upgrade is supported.

-p option allows users to configure server push.

Just like nghttp, it has verbose output mode for framing information. Here is sample output from nghttpd server:

$ src/nghttpd --no-tls -v 8080
IPv4: listen on port 8080
IPv6: listen on port 8080
[id=1] [  1.189] send SETTINGS frame <length=8, flags=0x00, stream_id=0>
          (niv=1)
          [SETTINGS_MAX_CONCURRENT_STREAMS(4):100]
[id=1] [  1.191] recv SETTINGS frame <length=16, flags=0x00, stream_id=0>
          (niv=2)
          [SETTINGS_MAX_CONCURRENT_STREAMS(4):100]
          [SETTINGS_INITIAL_WINDOW_SIZE(7):65535]
[id=1] [  1.191] recv HEADERS frame <length=47, flags=0x05, stream_id=1>
          ; END_STREAM | END_HEADERS
          ; Open new stream
          :authority: localhost:8080
          :method: GET
          :path: /
          :scheme: http
          accept: */*
          accept-encoding: gzip, deflate
          user-agent: nghttp2/0.1.0-DEV
[id=1] [  1.192] send SETTINGS frame <length=0, flags=0x01, stream_id=0>
          ; ACK
          (niv=0)
[id=1] [  1.192] send HEADERS frame <length=70, flags=0x04, stream_id=1>
          ; END_HEADERS
          ; First response header
          :status: 404
          content-encoding: gzip
          content-type: text/html; charset=UTF-8
          date: Sun, 27 Oct 2013 14:27:53 GMT
          server: nghttpd nghttp2/0.1.0-DEV
[id=1] [  1.192] send DATA frame <length=117, flags=0x00, stream_id=1>
[id=1] [  1.192] send DATA frame <length=0, flags=0x01, stream_id=1>
          ; END_STREAM
[id=1] [  1.192] stream_id=1 closed
[id=1] [  1.192] recv SETTINGS frame <length=0, flags=0x01, stream_id=0>
          ; ACK
          (niv=0)
[id=1] [  1.192] recv GOAWAY frame <length=8, flags=0x00, stream_id=0>
          (last_stream_id=0, error_code=NO_ERROR(0), opaque_data(0)=[])
[id=1] [  1.192] closed

nghttpx - proxy¶

The nghttpx is a multi-threaded reverse proxy for HTTP-draft-09/2.0, SPDY and HTTP/1.1. It has several operation modes:

The interesting mode at the moment is the default mode. It works like a reverse proxy and listens HTTP-draft-09/2.0, SPDY and HTTP/1.1 and can be deployed SSL/TLS terminator for existing web server.

The default mode, --http2-proxy and --http2-bridge modes use SSL/TLS in the frontend connection by default. To disable SSL/TLS, use --frontend-no-tls option. If that option is used, SPDY is disabled in the frontend and incoming HTTP/1.1 connection can be upgraded to HTTP/2.0 through HTTP Upgrade.

The --http2-bridge, --client and --client-proxy modes use SSL/TLS in the backend connection by deafult. To disable SSL/TLS, use --backend-no-tls option.

The nghttpx supports configuration file. See --conf option and sample configuration file nghttpx.conf.sample.

The nghttpx does not support server push.

In the default mode, (without any of --http2-proxy, --http2-bridge, --client-proxy and --client options), nghttpx works as reverse proxy to the backend server:

Client <-- (HTTP/2.0, SPDY, HTTP/1.1) --> nghttpx <-- (HTTP/1.1) --> Web Server
                                      [reverse proxy]

With --http2-proxy option, it works as so called secure proxy (aka SPDY proxy):

Client <-- (HTTP/2.0, SPDY, HTTP/1.1) --> nghttpx <-- (HTTP/1.1) --> Proxy
                                       [secure proxy]            (e.g., Squid)

The Client in the above is needs to be configured to use nghttpx as secure proxy.

At the time of this writing, Chrome is the only browser which supports secure proxy. The one way to configure Chrome to use secure proxy is create proxy.pac script like this:

function FindProxyForURL(url, host) {
    return "HTTPS SERVERADDR:PORT";
}

SERVERADDR and PORT is the hostname/address and port of the machine nghttpx is running. Please note that Chrome requires valid certificate for secure proxy.

Then run chrome with the following arguments:

$ google-chrome --proxy-pac-url=file:///path/to/proxy.pac --use-npn

With --http2-bridge, it accepts HTTP/2.0, SPDY and HTTP/1.1 connections and communicates with backend in HTTP/2.0:

Client <-- (HTTP/2.0, SPDY, HTTP/1.1) --> nghttpx <-- (HTTP/2.0) --> Web or HTTP/2.0 Proxy etc
                                                                     (e.g., nghttpx -s)

With --client-proxy option, it works as forward proxy and expects that the backend is HTTP/2.0 proxy:

Client <-- (HTTP/2.0, HTTP/1.1) --> nghttpx <-- (HTTP/2.0) --> HTTP/2.0 Proxy
                                 [forward proxy]               (e.g., nghttpx -s)

The Client is needs to be configured to use nghttpx as forward proxy. The frontend HTTP/1.1 connection can be upgraded to HTTP/2.0 through HTTP Upgrade. With the above configuration, one can use HTTP/1.1 client to access and test their HTTP/2.0 servers.

With --client option, it works as reverse proxy and expects that the backend is HTTP/2.0 Web server:

Client <-- (HTTP/2.0, HTTP/1.1) --> nghttpx <-- (HTTP/2.0) --> Web Server
                                [reverse proxy]

The frontend HTTP/1.1 connection can be upgraded to HTTP/2.0 through HTTP Upgrade.

For the operation modes which talk to the backend in HTTP/2.0 over SSL/TLS, the backend connections can be tunneled though HTTP proxy. The proxy is specified using --backend-http-proxy-uri option. The following figure illustrates the example of --http2-bridge and --backend-http-proxy-uri option to talk to the outside HTTP/2.0 proxy through HTTP proxy:

Client <-- (HTTP/2.0, SPDY, HTTP/1.1) --> nghttpx <-- (HTTP/2.0) --

        --===================---> HTTP/2.0 Proxy
          (HTTP proxy tunnel)     (e.g., nghttpx -s)

deflatehd - header compressor¶

The deflatehd reads JSON data or HTTP/1-style header fields from stdin and outputs compressed header block in JSON.

For the JSON input, the root JSON object must contain context key, which indicates which compression context is used. If it is request, request compression context is used. Otherwise, response compression context is used. The value of cases key contains the sequence of input header set. They share the same compression context and are processed in the order they appear. Each item in the sequence is a JSON object and it must have at least headers key. Its value is an array of a JSON object containing exactly one name/value pair.

Example:

{
  "context": "request",
  "cases":
  [
    {
      "headers": [
        { ":method": "GET" },
        { ":path": "/" }
      ]
    },
    {
      "headers": [
        { ":method": "POST" },
        { ":path": "/" }
      ]
    }
  ]
}

With -t option, the program can accept more familiar HTTP/1 style header field block. Each header set is delimited by empty line:

Example:

:method: GET
:scheme: https
:path: /

:method: POST
user-agent: nghttp2

The output is JSON object. It contains context key and its value is request if the compression context is request, otherwise response. The root JSON object also contains cases key and its value is an array of JSON object, which has at least following keys:

seq

The index of header set in the input.

input_length

The sum of length of name/value pair in the input.

output_length

The length of compressed header block.

percentage_of_original_size

input_length / output_length * 100

wire

The compressed header block in hex string.

headers

The input header set.

header_table_size

The header table size adjsuted before deflating header set.

Examples:

{
  "context": "request",
  "cases":
  [
    {
      "seq": 0,
      "input_length": 66,
      "output_length": 20,
      "percentage_of_original_size": 30.303030303030305,
      "wire": "01881f3468e5891afcbf83868a3d856659c62e3f",
      "headers": [
        {
          ":authority": "example.org"
        },
        {
          ":method": "GET"
        },
        {
          ":path": "/"
        },
        {
          ":scheme": "https"
        },
        {
          "user-agent": "nghttp2"
        }
      ],
      "header_table_size": 4096
    }
    ,
    {
      "seq": 1,
      "input_length": 74,
      "output_length": 10,
      "percentage_of_original_size": 13.513513513513514,
      "wire": "88448504252dd5918485",
      "headers": [
        {
          ":authority": "example.org"
        },
        {
          ":method": "POST"
        },
        {
          ":path": "/account"
        },
        {
          ":scheme": "https"
        },
        {
          "user-agent": "nghttp2"
        }
      ],
      "header_table_size": 4096
    }
  ]
}

The output can be used as the input for inflatehd and deflatehd.

With -d option, the extra header_table key is added and its associated value contains the state of dyanmic header table after the corresponding header set was processed. The value contains following keys:

entries

The entry in the header table. If referenced is true, it is in the reference set. The size includes the overhead (32 bytes). The index corresponds to the index of header table. The name is the header field name and the value is the header field value. They may be displayed as **DEALLOCATED**, which means that the memory for that string is freed and not available. This will happen when the specifying smaller value in -S than -s.

size

The sum of the spaces entries occupied, this includes the entry overhead.

max_size

The maximum header table size.

deflate_size

The sum of the spaces entries occupied within max_deflate_size.

max_deflate_size

The maximum header table size encoder uses. This can be smaller than max_size. In this case, encoder only uses up to first max_deflate_size buffer. Since the header table size is still max_size, the encoder has to keep track of entries ouside the max_deflate_size but inside the max_size and make sure that they are no longer referenced.

Example:

{
  "context": "request",
  "cases":
  [
    {
      "seq": 0,
      "input_length": 66,
      "output_length": 20,
      "percentage_of_original_size": 30.303030303030305,
      "wire": "01881f3468e5891afcbf83868a3d856659c62e3f",
      "headers": [
        {
          ":authority": "example.org"
        },
        {
          ":method": "GET"
        },
        {
          ":path": "/"
        },
        {
          ":scheme": "https"
        },
        {
          "user-agent": "nghttp2"
        }
      ],
      "header_table_size": 4096,
      "header_table": {
        "entries": [
          {
            "index": 1,
            "name": "user-agent",
            "value": "nghttp2",
            "referenced": true,
            "size": 49
          },
          {
            "index": 2,
            "name": ":scheme",
            "value": "https",
            "referenced": true,
            "size": 44
          },
          {
            "index": 3,
            "name": ":path",
            "value": "/",
            "referenced": true,
            "size": 38
          },
          {
            "index": 4,
            "name": ":method",
            "value": "GET",
            "referenced": true,
            "size": 42
          },
          {
            "index": 5,
            "name": ":authority",
            "value": "example.org",
            "referenced": true,
            "size": 53
          }
        ],
        "size": 226,
        "max_size": 4096,
        "deflate_size": 226,
        "max_deflate_size": 4096
      }
    }
    ,
    {
      "seq": 1,
      "input_length": 74,
      "output_length": 10,
      "percentage_of_original_size": 13.513513513513514,
      "wire": "88448504252dd5918485",
      "headers": [
        {
          ":authority": "example.org"
        },
        {
          ":method": "POST"
        },
        {
          ":path": "/account"
        },
        {
          ":scheme": "https"
        },
        {
          "user-agent": "nghttp2"
        }
      ],
      "header_table_size": 4096,
      "header_table": {
        "entries": [
          {
            "index": 1,
            "name": ":method",
            "value": "POST",
            "referenced": true,
            "size": 43
          },
          {
            "index": 2,
            "name": "user-agent",
            "value": "nghttp2",
            "referenced": true,
            "size": 49
          },
          {
            "index": 3,
            "name": ":scheme",
            "value": "https",
            "referenced": true,
            "size": 44
          },
          {
            "index": 4,
            "name": ":path",
            "value": "/",
            "referenced": false,
            "size": 38
          },
          {
            "index": 5,
            "name": ":method",
            "value": "GET",
            "referenced": false,
            "size": 42
          },
          {
            "index": 6,
            "name": ":authority",
            "value": "example.org",
            "referenced": true,
            "size": 53
          }
        ],
        "size": 269,
        "max_size": 4096,
        "deflate_size": 269,
        "max_deflate_size": 4096
      }
    }
  ]
}

inflatehd - header decompressor¶

The inflatehd reads JSON data from stdin and outputs decompressed name/value pairs in JSON.

The root JSON object must contain context key, which indicates which compression context is used. If it is request, request compression context is used. Otherwise, response compression context is used. The value of cases key contains the sequence of compressed header block. They share the same compression context and are processed in the order they appear. Each item in the sequence is a JSON object and it must have at least wire key. Its value is a string containing compressed header block in hex string.

Example:

{
  "context": "request",
  "cases":
  [
    { "wire": "8285" },
    { "wire": "8583" }
  ]
}

The output is JSON object. It contains context key and its value is request if the compression context is request, otherwise response. The root JSON object also contains cases key and its value is an array of JSON object, which has at least following keys:

seq

The index of header set in the input.

headers

The JSON array contains decompressed name/value pairs.

wire

The compressed header block in hex string.

header_table_size

The header table size adjsuted before inflating compressed header block.

Example:

{
  "context": "request",
  "cases":
  [
    {
      "seq": 0,
      "wire": "01881f3468e5891afcbf83868a3d856659c62e3f",
      "headers": [
        {
          ":authority": "example.org"
        },
        {
          ":method": "GET"
        },
        {
          ":path": "/"
        },
        {
          ":scheme": "https"
        },
        {
          "user-agent": "nghttp2"
        }
      ],
      "header_table_size": 4096
    }
    ,
    {
      "seq": 1,
      "wire": "88448504252dd5918485",
      "headers": [
        {
          ":method": "POST"
        },
        {
          ":path": "/account"
        },
        {
          "user-agent": "nghttp2"
        },
        {
          ":scheme": "https"
        },
        {
          ":authority": "example.org"
        }
      ],
      "header_table_size": 4096
    }
  ]
}

The output can be used as the input for deflatehd and inflatehd.

With -d option, the extra header_table key is added and its associated value contains the state of dyanmic header table after the corresponding header set was processed. The format is the same as deflatehd.

Example¶

The following example code illustrates basic usage of HPACK compressor and decompressor in Python:

import binascii
import nghttp2

deflater = nghttp2.HDDeflater(nghttp2.HD_SIDE_REQUEST)
inflater = nghttp2.HDInflater(nghttp2.HD_SIDE_REQUEST)

data = deflater.deflate([(b'foo', b'bar'),
                         (b'baz', b'buz')])
print(binascii.b2a_hex(data))

hdrs = inflater.inflate(data)
print(hdrs)