Pull request: all: imp cyclo in new code

Updates AdguardTeam#2646,

Squashed commit of the following:

commit af6a6fa
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Mon May 31 20:00:36 2021 +0300

    all: imp code, docs

commit 1cd4781
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Mon May 31 18:51:23 2021 +0300

    all: imp cyclo in new code

internal/aghnet/etchostscontainer.go

@@ -2,7 +2,6 @@ package aghnet
 
 import (
 	"bufio"
-	"io"
 	"net"
 	"os"
 	"path/filepath"
@@ -231,40 +230,53 @@ func (ehc *EtcHostsContainer) updateTableRev(tableRev map[string][]string, newHo
 	log.Debug("etchostscontainer: added reverse-address %s -> %s", ipStr, newHost)
 }
 
-// Read IP-hostname pairs from file
-// Multiple hostnames per line (per one IP) is supported.
-func (ehc *EtcHostsContainer) load(table map[string][]net.IP, tableRev map[string][]string, fn string) {
+// parseHostsLine parses hosts from the fields.
+func parseHostsLine(fields []string) (hosts []string) {
+	for _, f := range fields {
+		hashIdx := strings.IndexByte(f, '#')
+		if hashIdx == 0 {
+			// The rest of the fields are a part of the comment.
+			// Skip immediately.
+			return
+		} else if hashIdx > 0 {
+			// Only a part of the field is a comment.
+			hosts = append(hosts, f[:hashIdx])
+
+			return hosts
+		}
+
+		hosts = append(hosts, f)
+	}
+
+	return hosts
+}
+
+// load reads IP-hostname pairs from the hosts file.  Multiple hostnames per
+// line for one IP are supported.
+func (ehc *EtcHostsContainer) load(
+	table map[string][]net.IP,
+	tableRev map[string][]string,
+	fn string,
+) {
 	f, err := os.Open(fn)
 	if err != nil {
 		log.Error("etchostscontainer: %s", err)
+
 		return
 	}
+
 	defer func() {
 		derr := f.Close()
 		if derr != nil {
 			log.Error("etchostscontainer: closing file: %s", err)
 		}
 	}()
 
-	r := bufio.NewReader(f)
 	log.Debug("etchostscontainer: loading hosts from file %s", fn)
 
-	for done := false; !done; {
-		var line string
-		line, err = r.ReadString('\n')
-		if err == io.EOF {
-			done = true
-		} else if err != nil {
-			log.Error("etchostscontainer: %s", err)
-
-			return
-		}
-
-		line = strings.TrimSpace(line)
-		if len(line) == 0 || line[0] == '#' {
-			continue
-		}
-
+	s := bufio.NewScanner(f)
+	for s.Scan() {
+		line := strings.TrimSpace(s.Text())
 		fields := strings.Fields(line)
 		if len(fields) < 2 {
 			continue
@@ -275,28 +287,17 @@ func (ehc *EtcHostsContainer) load(table map[string][]net.IP, tableRev map[strin
 			continue
 		}
 
-		for i := 1; i != len(fields); i++ {
-			host := fields[i]
-			if len(host) == 0 {
-				break
-			}
-
-			sharp := strings.IndexByte(host, '#')
-			if sharp == 0 {
-				// Skip the comments.
-				break
-			} else if sharp > 0 {
-				host = host[:sharp]
-			}
-
+		hosts := parseHostsLine(fields[1:])
+		for _, host := range hosts {
 			ehc.updateTable(table, host, ip)
 			ehc.updateTableRev(tableRev, host, ip)
-			if sharp >= 0 {
-				// Skip the comments again.
-				break
-			}
 		}
 	}
+
+	err = s.Err()
+	if err != nil {
+		log.Error("etchostscontainer: %s", err)
+	}
 }
 
 // onlyWrites is a filter for (*fsnotify.Watcher).Events.

internal/aghnet/etshostscontainer_test.go → internal/aghnet/etchostscontainer_test.go

@@ -23,10 +23,11 @@ func prepareTestFile(t *testing.T) (f *os.File) {
 	dir := t.TempDir()
 
 	f, err := os.CreateTemp(dir, "")
-	require.Nil(t, err)
+	require.NoError(t, err)
 	require.NotNil(t, f)
+
 	t.Cleanup(func() {
-		assert.Nil(t, f.Close())
+		assert.NoError(t, f.Close())
 	})
 
 	return f
@@ -37,7 +38,7 @@ func assertWriting(t *testing.T, f *os.File, strs ...string) {
 
 	for _, str := range strs {
 		n, err := f.WriteString(str)
-		require.Nil(t, err)
+		require.NoError(t, err)
 		assert.Equal(t, n, len(str))
 	}
 }
@@ -77,16 +78,16 @@ func TestEtcHostsContainerResolution(t *testing.T) {
 	t.Run("ptr", func(t *testing.T) {
 		testCases := []struct {
 			wantIP   string
-			wantLen  int
 			wantHost string
+			wantLen  int
 		}{
-			{wantIP: "127.0.0.1", wantLen: 2, wantHost: "host"},
-			{wantIP: "::1", wantLen: 1, wantHost: "localhost"},
+			{wantIP: "127.0.0.1", wantHost: "host", wantLen: 2},
+			{wantIP: "::1", wantHost: "localhost", wantLen: 1},
 		}
 
 		for _, tc := range testCases {
 			a, err := dns.ReverseAddr(tc.wantIP)
-			require.Nil(t, err)
+			require.NoError(t, err)
 
 			a = strings.TrimSuffix(a, ".")
 			hosts := ehc.ProcessReverse(a, dns.TypePTR)
@@ -114,7 +115,7 @@ func TestEtcHostsContainerFSNotify(t *testing.T) {
 	t.Cleanup(ehc.Close)
 
 	assertWriting(t, f, "127.0.0.2   newhost\n")
-	require.Nil(t, f.Sync())
+	require.NoError(t, f.Sync())
 
 	// Wait until fsnotify has triggerred and processed the
 	// file-modification event.

internal/aghnet/net_linux.go

@@ -68,40 +68,41 @@ func ifaceHasStaticIP(ifaceName string) (has bool, err error) {
 	return false, ErrNoStaticIPInfo
 }
 
+// findIfaceLine scans s until it finds the line that declares an interface with
+// the given name.  If findIfaceLine can't find the line, it returns false.
+func findIfaceLine(s *bufio.Scanner, name string) (ok bool) {
+	for s.Scan() {
+		line := strings.TrimSpace(s.Text())
+		fields := strings.Fields(line)
+		if len(fields) == 2 && fields[0] == "interface" && fields[1] == name {
+			return true
+		}
+	}
+
+	return false
+}
+
 // dhcpcdStaticConfig checks if interface is configured by /etc/dhcpcd.conf to
 // have a static IP.
 func dhcpcdStaticConfig(r io.Reader, ifaceName string) (has bool, err error) {
 	s := bufio.NewScanner(r)
-	var withinInterfaceCtx bool
+	ifaceFound := findIfaceLine(s, ifaceName)
+	if !ifaceFound {
+		return false, s.Err()
+	}
 
 	for s.Scan() {
 		line := strings.TrimSpace(s.Text())
-
-		if withinInterfaceCtx && len(line) == 0 {
-			// An empty line resets our state.
-			withinInterfaceCtx = false
-		}
-
-		if len(line) == 0 || line[0] == '#' {
-			continue
-		}
-
 		fields := strings.Fields(line)
-
-		if withinInterfaceCtx {
-			if len(fields) >= 2 && fields[0] == "static" && strings.HasPrefix(fields[1], "ip_address=") {
-				return true, nil
-			}
-			if len(fields) > 0 && fields[0] == "interface" {
-				// Another interface found.
-				withinInterfaceCtx = false
-			}
-			continue
+		if len(fields) >= 2 &&
+			fields[0] == "static" &&
+			strings.HasPrefix(fields[1], "ip_address=") {
+			return true, s.Err()
 		}
 
-		if len(fields) == 2 && fields[0] == "interface" && fields[1] == ifaceName {
-			// The interface found.
-			withinInterfaceCtx = true
+		if len(fields) > 0 && fields[0] == "interface" {
+			// Another interface found.
+			break
 		}
 	}
 

internal/aghnet/systemresolvers.go

@@ -3,7 +3,6 @@ package aghnet
 import (
 	"time"
 
-	"github.com/AdguardTeam/golibs/errors"
 	"github.com/AdguardTeam/golibs/log"
 )
 
@@ -25,18 +24,6 @@ type SystemResolvers interface {
 	refresh() (err error)
 }
 
-const (
-	// errBadAddrPassed is returned when dialFunc can't parse an IP address.
-	errBadAddrPassed errors.Error = "the passed string is not a valid IP address"
-
-	// errFakeDial is an error which dialFunc is expected to return.
-	errFakeDial errors.Error = "this error signals the successful dialFunc work"
-
-	// errUnexpectedHostFormat is returned by validateDialedHost when the host has
-	// more than one percent sign.
-	errUnexpectedHostFormat errors.Error = "unexpected host format"
-)
-
 // refreshWithTicker refreshes the cache of sr after each tick form tickCh.
 func refreshWithTicker(sr SystemResolvers, tickCh <-chan time.Time) {
 	defer log.OnPanic("systemResolvers")

internal/aghnet/systemresolvers_others.go

@@ -32,6 +32,18 @@ type systemResolvers struct {
 	addrsLock sync.RWMutex
 }
 
+const (
+	// errBadAddrPassed is returned when dialFunc can't parse an IP address.
+	errBadAddrPassed errors.Error = "the passed string is not a valid IP address"
+
+	// errFakeDial is an error which dialFunc is expected to return.
+	errFakeDial errors.Error = "this error signals the successful dialFunc work"
+
+	// errUnexpectedHostFormat is returned by validateDialedHost when the host has
+	// more than one percent sign.
+	errUnexpectedHostFormat errors.Error = "unexpected host format"
+)
+
 func (sr *systemResolvers) refresh() (err error) {
 	defer func() { err = errors.Annotate(err, "systemResolvers: %w") }()