// -=-=- StartHere -=-=-
//
// # Chapter VI: Getting a webpage from an HTTP/HTTPS/HTTP3 endpoint.
//
// This chapter describes measuring the retrieval of a webpage from an
// HTTPS endpoint. We have seen how to TCP connect, we have
// seen how to TLS handshake, now it's time to see how we can
// combine these operations with that of fetching a webpage from a
// given TCP endpoint speaking HTTP and TLS. (As well as
// providing you with information on how to otherwise fetch
// from HTTP and HTTP/3 endpoints.)
//
// The program we're going to write, `main.go`, will use a
// high-level operation to perform this measurement in a
// single API call. The code implementing this API call will
// combine the operations we have seen in previous chapter
// with the "give me the webpage" operation. We are still
// quite far away from the ability of "measuring a URL" but
// we are increasingly moving towards more complex operations.
//
// (This file is auto-generated. Do not edit it directly! To apply
// changes you need to modify `./internal/tutorial/measurex/chapter06/main.go`.)
//
// ## main.go
//
// We have package declaration and imports as usual.
//
// ```Go
package main
import (
"context"
"encoding/json"
"flag"
"fmt"
"net/url"
"time"
"github.com/ooni/probe-cli/v3/internal/measurex"
"github.com/ooni/probe-cli/v3/internal/runtimex"
)
// ```
//
// We have factored the three lines to print a measurement
// into the following utility function called `print`.
//
// ```Go
func print(v interface{}) {
data, err := json.Marshal(v)
runtimex.PanicOnError(err, "json.Marshal failed")
fmt.Printf("%s\n", string(data))
}
// ```
//
// The initial part of the program is pretty much the same as the one
// used in previous chapters, expect that we have a few more command line
// flags now, so I will not add further comments.
//
// ```Go
func main() {
sni := flag.String("sni", "dns.google", "value for SNI extension")
address := flag.String("address", "8.8.4.4:443", "remote endpoint address")
timeout := flag.Duration("timeout", 60*time.Second, "timeout to use")
flag.Parse()
ctx, cancel := context.WithTimeout(context.Background(), *timeout)
defer cancel()
mx := measurex.NewMeasurerWithDefaultSettings()
// ```
//
// ### HTTPEndpoint: a description of what to measure
//
// First of all, let us create a description of the endpoint
// for `measurex`. Up to this point we have used endpoint
// to describe a level-4-like address. Therefore, we have seen
// TCP endpoints being used for the TCP connect and the TLS
// handshake, and we have seen QUIC endpoints being used
// for the QUIC handshake. Now, however, we are going
// to need more information to characterize the endpoint.
//
// ```Go
epnt := &measurex.HTTPEndpoint{
Domain: *sni,
Network: "tcp",
Address: *address,
SNI: *sni,
ALPN: []string{"h2", "http/1.1"},
URL: &url.URL{
Scheme: "https",
Host: *sni,
Path: "/",
},
Header: measurex.NewHTTPRequestHeaderForMeasuring(),
}
// ```
//
// In fact, in the above definition we recognize fields
// we have already discussed, such as:
//
// - `Network`, describing whether to use "tcp" or "quic";
//
// - `Address`, which is the endpoint address.
//
// But we also need to combine into this view of the
// endpoint additional fields for TLS:
//
// - `SNI`, to set the SNI;
//
// - `ALPN`, to set the ALPN;
//
// But then we also need to specify:
//
// - the URL to use;
//
// - the headers to use (for which we're using a handy
// factory for creating reasonable defaults for measuring).
//
// This API is not the highest level API with which to do
// the job, but it's still handy to introduce the
// `measurex.HTTPEndpoint` data structure since it's
// used by higher level APIs.
//
// (You may also be wondering about the CA pool. It turns
// out that for APIs such as this one and for higher
// level APIs, the default is to always use the bundled
// Mozilla CA pool, because this is what we use in
// most cases for performing measurements.)
//
// ### HTTPEndpointGetWithoutCookies
//
// When used with an HTTP URL, the `HTTPEndpointGetWithoutCookies`
// method combines two operations:
//
// - TCP connect
//
// - HTTP GET
//
// When the URL is HTTPS, we do:
//
// - TCP connect
//
// - TLS handshake
//
// - HTTP GET (or HTTP/2 GET depending on the ALPN)
//
// When the `HTTPEndpoint.Network` field value
// is QUIC, instead we do:
//
// - QUIC handshake
//
// - HTTP/3 GET
//
// ```Go
m := mx.HTTPEndpointGetWithoutCookies(ctx, epnt)
// ```
//
// The arguments for `HTTPEndpointGetWithDBWithoutCookies` are:
//
// - the context for deadline/timeout
//
// - the HTTPEndpoint descriptor
//
// The result is an `HTTPEndpointMeasurement` which
// you can inspect with
//
// ```
// go doc ./internal/measurex.HTTPEndpointMeasurement
// ```
//
// ### Printing the measurement
//
// Let us now print the resulting measurement.
//
// ```Go
print(measurex.NewArchivalHTTPEndpointMeasurement(m))
}
// ```
//
// ## Running the example program
//
// Let us perform a vanilla run first:
//
// ```bash
// go run -race ./internal/tutorial/measurex/chapter06 | jq
// ```
//
// This is the JSON output. Let us comment it in detail:
//
// ```Javascript
// {
// // The returned type is called HTTPEndpointMeasurement
// // and you see that here on top we indeed have the
// // information on the endpoint and the URL.
// "url": "https://dns.google/",
// "network": "tcp",
// "address": "8.8.4.4:443",
//
// // These are the I/O operations we have already seen
// // in previous chapters
// "network_events": [
// {
// "address": "8.8.4.4:443",
// "failure": null,
// "num_bytes": 280,
// "operation": "write",
// "proto": "tcp",
// "t": 0.045800292,
// "started": 0.045782167,
// "oddity": ""
// },
// {
// "address": "8.8.4.4:443",
// "failure": null,
// "num_bytes": 517,
// "operation": "read",
// "proto": "tcp",
// "t": 0.082571,
// "started": 0.045805458,
// "oddity": ""
// },
// {
// "address": "8.8.4.4:443",
// "failure": null,
// "num_bytes": 4303,
// "operation": "read",
// "proto": "tcp",
// "t": 0.084400542,
// "started": 0.084372667,
// "oddity": ""
// },
// {
// "address": "8.8.4.4:443",
// "failure": null,
// "num_bytes": 64,
// "operation": "write",
// "proto": "tcp",
// "t": 0.086762625,
// "started": 0.086748292,
// "oddity": ""
// },
// {
// "address": "8.8.4.4:443",
// "failure": null,
// "num_bytes": 86,
// "operation": "write",
// "proto": "tcp",
// "t": 0.087851,
// "started": 0.087837625,
// "oddity": ""
// },
// {
// "address": "8.8.4.4:443",
// "failure": null,
// "num_bytes": 201,
// "operation": "write",
// "proto": "tcp",
// "t": 0.089527292,
// "started": 0.089507958,
// "oddity": ""
// },
// {
// "address": "8.8.4.4:443",
// "failure": null,
// "num_bytes": 93,
// "operation": "read",
// "proto": "tcp",
// "t": 0.168585625,
// "started": 0.088068375,
// "oddity": ""
// },
// {
// "address": "8.8.4.4:443",
// "failure": null,
// "num_bytes": 31,
// "operation": "write",
// "proto": "tcp",
// "t": 0.168713542,
// "started": 0.168671417,
// "oddity": ""
// },
// {
// "address": "8.8.4.4:443",
// "failure": null,
// "num_bytes": 2000,
// "operation": "read",
// "proto": "tcp",
// "t": 0.468671417,
// "started": 0.168759333,
// "oddity": ""
// },
// {
// "address": "8.8.4.4:443",
// "failure": null,
// "num_bytes": 39,
// "operation": "read",
// "proto": "tcp",
// "t": 0.47118175,
// "started": 0.471169667,
// "oddity": ""
// },
// {
// "address": "8.8.4.4:443",
// "failure": null,
// "num_bytes": 39,
// "operation": "write",
// "proto": "tcp",
// "t": 0.471335458,
// "started": 0.471268583,
// "oddity": ""
// },
// {
// "address": "8.8.4.4:443",
// "failure": null,
// "num_bytes": 24,
// "operation": "write",
// "proto": "tcp",
// "t": 0.471865,
// "started": 0.471836292,
// "oddity": ""
// }
// ],
//
// // Internally, HTTPEndpointGetWithoutCookies calls
// // TCPConnect and here we see the corresponding event
// "tcp_connect": [
// {
// "ip": "8.8.4.4",
// "port": 443,
// "t": 0.043644958,
// "status": {
// "blocked": false,
// "failure": null,
// "success": true
// },
// "started": 0.022849458,
// "oddity": ""
// }
// ],
//
// // Internally, HTTPEndpointGetWithoutCookies calls TLSConnectAndHandshake,
// // and here's the resulting handshake event. Of course, if we
// // specified a QUIC endpoint we would instead see here a
// // QUIC handshake event. And, we would not see any handshake
// // if the URL was instead an HTTP URL.
// "tls_handshakes": [
// {
// "cipher_suite": "TLS_AES_128_GCM_SHA256",
// "failure": null,
// "negotiated_proto": "h2",
// "tls_version": "TLSv1.3",
// "peer_certificates": [
// {
// "data": "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",
// "format": "base64"
// },
// {
// "data": "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",
// "format": "base64"
// },
// {
// "data": "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",
// "format": "base64"
// }
// ],
// "t": 0.086816667,
// "address": "8.8.4.4:443",
// "server_name": "dns.google",
// "alpn": [
// "h2",
// "http/1.1"
// ],
// "no_tls_verify": false,
// "oddity": "",
// "proto": "tcp",
// "started": 0.043971083
// }
// ],
//
// // Finally here we see information about the round trip, which
// // is formatted according to https://github.com/ooni/spec/blob/master/data-formats/df-001-httpt.md:
// "requests": [
// {
//
// // This field indicates whether there was an error during
// // the HTTP round trip:
// "failure": null,
//
// // This field contains the request method, URL, and HTTP headers
// "request": {
// "method": "GET",
// "url": "https://dns.google/",
// "headers": {
// "accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",
// "accept-language": "en-US;q=0.8,en;q=0.5",
// "user-agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/94.0.4606.81 Safari/537.36"
// }
// },
//
// // This field contains the response status code, body, and headers.
// "response": {
// "code": 200,
// "headers": {
// "accept-ranges": "none",
// "alt-svc": "h3=\":443\"; ma=2592000,h3-29=\":443\"; ma=2592000,h3-Q050=\":443\"; ma=2592000,h3-Q046=\":443\"; ma=2592000,h3-Q043=\":443\"; ma=2592000,quic=\":443\"; ma=2592000; v=\"46,43\"",
// "cache-control": "private",
// "content-security-policy": "object-src 'none';base-uri 'self';script-src 'nonce-y/OGliLR2gbEfTG2i4MAaw==' 'strict-dynamic' 'report-sample' 'unsafe-eval' 'unsafe-inline' https: http:;report-uri https://csp.withgoogle.com/csp/honest_dns/1_0;frame-ancestors 'none'",
// "content-type": "text/html; charset=UTF-8",
// "date": "Fri, 05 Nov 2021 08:59:37 GMT",
// "server": "scaffolding on HTTPServer2",
// "strict-transport-security": "max-age=31536000; includeSubDomains; preload",
// "vary": "Accept-Encoding",
// "x-content-type-options": "nosniff",
// "x-frame-options": "SAMEORIGIN",
// "x-xss-protection": "0"
// },
//
// // The body in particular is a snapshot of the response
// // body: we don't want to read and submit to the OONI
// // collector large bodies.
// "body": {
// "data": "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",
// "format": "base64"
// },
//
// // This field tells us whether the size of the read
// // snapshot was smaller than the snapshot size. If
// // not, then the body has been truncated.
// "body_is_truncated": false,
//
// // These extra fields are not part of the spec and
// // hence we prefix them with `x_`. They tell us
// // the length of the body and whether the content
// // of the body is valid UTF8.
// "x_body_length": 1383,
// "x_body_is_utf8": true
// },
//
// // The t field is the moment where we finished the
// // round trip and saved the event. The started field
// // is instead when we started the round trip.
// //
// // You may notice that the start of the round trip
// // if after the `t` of the handshake. This tells us
// // that the code first connects, then handshakes, and
// // finally creates HTTP code for performing the
// // round trip.
// "t": 0.471535167,
// "started": 0.087176458,
//
// // As usual we also compute an oddity value related
// // in this case to the HTTP round trip.
// "oddity": ""
// }
// ]
// }
// ```
//
// Here are some suggestions for follow up measurements:
//
// 1. provoke a connect error by using:
//
// ```
// go run -race ./internal/tutorial/measurex/chapter06 -address 127.0.0.1:1 | jq
// ```
//
// 2. provoke a TLS handshake error by using:
//
// ```
// go run -race ./internal/tutorial/measurex/chapter06 -sni example.com | jq
// ```
//
// 3. provoke an HTTP round trip error by using:
//
// ```
// go run -race ./internal/tutorial/measurex/chapter06 -address 8.8.8.8:853 | jq
// ```
//
// 4. modify the code to fetch an HTTP endpoint instead (hint: you
// need to change the HTTPEndpoint's URL scheme);
//
// 5. modify the code to use QUIC and HTTP/3 instead (hint: you need to
// change the HTTPEndpoint's network and... is this enough?).
//
// ## Conclusion
//
// We have seen how to measure the flow of fetching a
// specific webpage from an HTTPEndpoint.
//
// -=-=- StopHere -=-=-