Make sure we can build ndt-server on macOS

We don't support macOS officially. However it's useful to build on
a system that is different from the containers where we deploy.

As mentioned in #100, I am convinced that Travis is different enough
from the containers where we deploy to look like macOS.

bbr/bbr_stub.go

@@ -4,12 +4,14 @@ package bbr
 
 import (
 	"os"
+
+	"github.com/m-lab/ndt-server/ndt7/model"
 )
 
 func enableBBR(*os.File) error {
 	return ErrNoSupport
 }
 
-func getMaxBandwidthAndMinRTT(*os.File) (float64, float64, error) {
-	return 0.0, 0.0, ErrNoSupport
+func getMaxBandwidthAndMinRTT(*os.File) (model.BBRInfo, error) {
+	return model.BBRInfo{}, ErrNoSupport
 }

legacy/web100/web100.go

@@ -3,16 +3,6 @@
 // it only needs to measure once.
 package web100
 
-import (
-	"context"
-	"errors"
-	"log"
-	"os"
-	"time"
-
-	"golang.org/x/sys/unix"
-)
-
 // Metrics holds web100 data. According to the legacy NDT protocol, each of
 // these metrics is required. That does not mean each is required to be
 // non-zero, but it does mean that the field should be present in any response.
@@ -34,54 +24,3 @@ type Metrics struct {
 	// Useful metrics that are not part of the required set.
 	BytesPerSecond float64
 }
-
-func summarize(snaps []*unix.TCPInfo) (*Metrics, error) {
-	if len(snaps) == 0 {
-		return nil, errors.New("zero-length list of data collected")
-	}
-	minrtt := uint32(0)
-	for _, snap := range snaps {
-		if snap.Rtt < minrtt || minrtt == 0 {
-			minrtt = snap.Rtt
-		}
-	}
-	info := &Metrics{MinRTT: minrtt / 1000} // Convert microseconds to milliseconds.
-	log.Println("Summarized data:", info)
-	return info, nil
-}
-
-// MeasureViaPolling collects all required data by polling. It is required for
-// non-BBR connections because MinRTT is one of our critical metrics.
-func MeasureViaPolling(ctx context.Context, fp *os.File, c chan *Metrics) {
-	defer close(c)
-	ticker := time.NewTicker(100 * time.Millisecond)
-	defer ticker.Stop()
-	snaps := make([]*unix.TCPInfo, 0, 100)
-	// Poll until the context is canceled.
-	for {
-		// Get the tcp_cc metrics
-		info, err := unix.GetsockoptTCPInfo(int(fp.Fd()), unix.IPPROTO_TCP, unix.TCP_INFO)
-		if err == nil {
-			snaps = append(snaps, info)
-		} else {
-			log.Println("Getsockopt error:", err)
-		}
-		select {
-		case <-ticker.C:
-			continue
-		case <-ctx.Done():
-			info, err := summarize(snaps)
-			if err == nil {
-				c <- info
-			}
-			return
-		}
-	}
-}
-
-// TODO: Implement BBR support for legacy clients.
-/*
-func MeasureBBR(ctx context.Context, fp *os.File) (Metrics, error) {
-	return Metrics{}, errors.New("MeasureBBR is unimplemented")
-}
-*/

legacy/web100/web100_linux.go

@@ -0,0 +1,62 @@
+package web100
+
+import (
+	"context"
+	"errors"
+	"log"
+	"os"
+	"time"
+
+	"golang.org/x/sys/unix"
+)
+
+func summarize(snaps []*unix.TCPInfo) (*Metrics, error) {
+	if len(snaps) == 0 {
+		return nil, errors.New("zero-length list of data collected")
+	}
+	minrtt := uint32(0)
+	for _, snap := range snaps {
+		if snap.Rtt < minrtt || minrtt == 0 {
+			minrtt = snap.Rtt
+		}
+	}
+	info := &Metrics{MinRTT: minrtt / 1000} // Convert microseconds to milliseconds.
+	log.Println("Summarized data:", info)
+	return info, nil
+}
+
+// MeasureViaPolling collects all required data by polling. It is required for
+// non-BBR connections because MinRTT is one of our critical metrics.
+func MeasureViaPolling(ctx context.Context, fp *os.File, c chan *Metrics) {
+	defer close(c)
+	ticker := time.NewTicker(100 * time.Millisecond)
+	defer ticker.Stop()
+	snaps := make([]*unix.TCPInfo, 0, 100)
+	// Poll until the context is canceled.
+	for {
+		// Get the tcp_cc metrics
+		info, err := unix.GetsockoptTCPInfo(int(fp.Fd()), unix.IPPROTO_TCP, unix.TCP_INFO)
+		if err == nil {
+			snaps = append(snaps, info)
+		} else {
+			log.Println("Getsockopt error:", err)
+		}
+		select {
+		case <-ticker.C:
+			continue
+		case <-ctx.Done():
+			info, err := summarize(snaps)
+			if err == nil {
+				c <- info
+			}
+			return
+		}
+	}
+}
+
+// TODO: Implement BBR support for legacy clients.
+/*
+func MeasureBBR(ctx context.Context, fp *os.File) (Metrics, error) {
+	return Metrics{}, errors.New("MeasureBBR is unimplemented")
+}
+*/

legacy/web100/web100_stub.go

@@ -0,0 +1,14 @@
+// +build !linux
+
+package web100
+
+import (
+	"context"
+	"os"
+)
+
+// MeasureViaPolling collects all required data by polling. It is required for
+// non-BBR connections because MinRTT is one of our critical metrics.
+func MeasureViaPolling(ctx context.Context, fp *os.File, c chan *Metrics) {
+	// Just a stub.
+}