doctor/ethtool, ipn/ipnlocal: add ethtool bugreport check

Updates #11137

Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: Idbe862d80e428adb044249c47d9096b87f29d5d8

cmd/tailscaled/depaware.txt

@@ -138,7 +138,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
    L    github.com/pierrec/lz4/v4/internal/xxh32                     from github.com/pierrec/lz4/v4/internal/lz4stream
   LD    github.com/pkg/sftp                                          from tailscale.com/ssh/tailssh
   LD    github.com/pkg/sftp/internal/encoding/ssh/filexfer           from github.com/pkg/sftp
-   L 💣 github.com/safchain/ethtool                                  from tailscale.com/net/netkernelconf
+   L 💣 github.com/safchain/ethtool                                  from tailscale.com/net/netkernelconf+
    W 💣 github.com/tailscale/certstore                               from tailscale.com/control/controlclient
    W 💣 github.com/tailscale/go-winio                                from tailscale.com/safesocket
    W 💣 github.com/tailscale/go-winio/internal/fs                    from github.com/tailscale/go-winio
@@ -247,6 +247,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/derp/derphttp                                  from tailscale.com/cmd/tailscaled+
         tailscale.com/disco                                          from tailscale.com/derp+
         tailscale.com/doctor                                         from tailscale.com/ipn/ipnlocal
+        tailscale.com/doctor/ethtool                                 from tailscale.com/ipn/ipnlocal
      💣 tailscale.com/doctor/permissions                             from tailscale.com/ipn/ipnlocal
         tailscale.com/doctor/routetable                              from tailscale.com/ipn/ipnlocal
         tailscale.com/envknob                                        from tailscale.com/client/tailscale+

doctor/ethtool/ethtool.go

@@ -0,0 +1,23 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Package ethtool provides a doctor.Check that prints diagnostic information
+// obtained from the 'ethtool' utility on the current system.
+package ethtool
+
+import (
+	"context"
+
+	"tailscale.com/types/logger"
+)
+
+// Check implements the doctor.Check interface.
+type Check struct{}
+
+func (Check) Name() string {
+	return "ethtool"
+}
+
+func (Check) Run(_ context.Context, logf logger.Logf) error {
+	return ethtoolImpl(logf)
+}

doctor/ethtool/ethtool_linux.go

@@ -0,0 +1,78 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package ethtool
+
+import (
+	"net/netip"
+	"sort"
+
+	"github.com/safchain/ethtool"
+	"tailscale.com/net/interfaces"
+	"tailscale.com/types/logger"
+	"tailscale.com/util/set"
+)
+
+func ethtoolImpl(logf logger.Logf) error {
+	et, err := ethtool.NewEthtool()
+	if err != nil {
+		logf("could not create ethtool: %v", err)
+		return nil
+	}
+	defer et.Close()
+
+	interfaces.ForeachInterface(func(iface interfaces.Interface, _ []netip.Prefix) {
+		ilogf := logger.WithPrefix(logf, iface.Name+": ")
+		features, err := et.Features(iface.Name)
+		if err == nil {
+			enabled := []string{}
+			for feature, value := range features {
+				if value {
+					enabled = append(enabled, feature)
+				}
+			}
+			sort.Strings(enabled)
+			ilogf("features: %v", enabled)
+		} else {
+			ilogf("features: error: %v", err)
+		}
+
+		stats, err := et.Stats(iface.Name)
+		if err == nil {
+			printStats(ilogf, stats)
+		} else {
+			ilogf("stats: error: %v", err)
+		}
+	})
+
+	return nil
+}
+
+// Stats that should be printed if non-zero
+var nonzeroStats = set.SetOf([]string{
+	// AWS ENA driver statistics; see:
+	//    https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/monitoring-network-performance-ena.html
+	"bw_in_allowance_exceeded",
+	"bw_out_allowance_exceeded",
+	"conntrack_allowance_exceeded",
+	"linklocal_allowance_exceeded",
+	"pps_allowance_exceeded",
+})
+
+// Stats that should be printed if zero
+var zeroStats = set.SetOf([]string{
+	// AWS ENA driver statistics; see:
+	//    https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/monitoring-network-performance-ena.html
+	"conntrack_allowance_available",
+})
+
+func printStats(logf logger.Logf, stats map[string]uint64) {
+	for name, value := range stats {
+		if value != 0 && nonzeroStats.Contains(name) {
+			logf("stats: warning: %s = %d > 0", name, value)
+		}
+		if value == 0 && zeroStats.Contains(name) {
+			logf("stats: warning: %s = %d == 0", name, value)
+		}
+	}
+}

doctor/ethtool/ethtool_other.go

@@ -0,0 +1,17 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build !linux
+
+package ethtool
+
+import (
+	"runtime"
+
+	"tailscale.com/types/logger"
+)
+
+func ethtoolImpl(logf logger.Logf) error {
+	logf("unsupported on %s/%s", runtime.GOOS, runtime.GOARCH)
+	return nil
+}

ipn/ipnlocal/local.go

@@ -39,6 +39,7 @@ import (
 	"tailscale.com/control/controlclient"
 	"tailscale.com/control/controlknobs"
 	"tailscale.com/doctor"
+	"tailscale.com/doctor/ethtool"
 	"tailscale.com/doctor/permissions"
 	"tailscale.com/doctor/routetable"
 	"tailscale.com/envknob"
@@ -5511,6 +5512,7 @@ func (b *LocalBackend) Doctor(ctx context.Context, logf logger.Logf) {
 	checks = append(checks,
 		permissions.Check{},
 		routetable.Check{},
+		ethtool.Check{},
 	)
 
 	// Print a log message if any of the global DNS resolvers are Tailscale