feat(webconnectivity): long-term-evolution prototype (#882)

See https://github.com/ooni/probe/issues/2237

internal/experiment/webconnectivity/analysistcpip.go

@@ -0,0 +1,82 @@
+package webconnectivity
+
+//
+// TCP/IP analysis
+//
+
+import (
+	"fmt"
+	"net"
+
+	"github.com/ooni/probe-cli/v3/internal/model"
+	"github.com/ooni/probe-cli/v3/internal/netxlite"
+)
+
+// analysisTCPIPToplevel is the toplevel analysis function for TCP/IP results.
+//
+// This algorithm has two objectives:
+//
+// 1. walk the list of TCP connect attempts and mark each of them as
+// Status.Blocked = true | false | null depending on what the TH observed
+// for the same set of IP addresses (it's ugly to modify a data struct
+// in place, but this algorithm is defined by the spec);
+//
+// 2. assign the analysisFlagTCPIPBlocking flag to XBlockingFlags if
+// we see any TCP endpoint for which Status.Blocked is true.
+func (tk *TestKeys) analysisTCPIPToplevel(logger model.Logger) {
+	// if we don't have a control result, do nothing.
+	if tk.Control == nil || len(tk.Control.TCPConnect) <= 0 {
+		return
+	}
+	var (
+		istrue  = true
+		isfalse = false
+	)
+
+	// TODO(bassosimone): the TH should measure also some of the IP addrs it discovered
+	// and the probe did not discover to improve the analysis. Otherwise, the probe
+	// is fooled by the TH also failing for countries that return random IP addresses
+	// that are actually not working. Yet, ooni/data would definitely see this.
+
+	// walk the list of probe results and compare with TH results
+	for _, entry := range tk.TCPConnect {
+		// skip successful entries
+		failure := entry.Status.Failure
+		if failure == nil {
+			entry.Status.Blocked = &isfalse
+			continue // did not fail
+		}
+
+		// make sure we exclude the IPv6 failures caused by lack of
+		// proper IPv6 support by the probe
+		ipv6, err := netxlite.IsIPv6(entry.IP)
+		if err != nil {
+			continue // looks like a bug
+		}
+		if ipv6 {
+			ignore := (*failure == netxlite.FailureNetworkUnreachable ||
+				*failure == netxlite.FailureHostUnreachable)
+			if ignore {
+				// this occurs when we don't have IPv6 on the probe
+				continue
+			}
+		}
+
+		// obtain the corresponding endpoint
+		epnt := net.JoinHostPort(entry.IP, fmt.Sprintf("%d", entry.Port))
+		ctrl, found := tk.Control.TCPConnect[epnt]
+		if !found {
+			continue // only the probe tested this, so hard to say anything...
+		}
+		if ctrl.Failure != nil {
+			// If the TH failed as well, don't set XBlockingFlags and
+			// also don't bother with setting .Status.Blocked thus leaving
+			// it null. Performing precise error mapping should be a job
+			// for the pipeline rather than for the probe.
+			continue
+		}
+		logger.Warnf("TCP/IP: endpoint %s is blocked (see #%d)", epnt, entry.TransactionID)
+		entry.Status.Blocked = &istrue
+		tk.BlockingFlags |= analysisFlagTCPIPBlocking
+	}
+}