From: Ian Lance Taylor <iant@golang.org>
Date: Thu, 9 Jan 2025 21:04:51 +0000 (-0800)
Subject: net: permit Interface with no Name
X-Git-Tag: go1.25rc1~1185
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=4160ebf28f69a738203571bba6abab6ec0913080;p=gostls13.git

net: permit Interface with no Name

On darwin the utun interface sometimes has no name.

Fixes #71064

Change-Id: Iec51641880515f8bd3f97bd892c26f68fd588fa3
Reviewed-on: https://go-review.googlesource.com/c/go/+/641855
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Commit-Queue: Ian Lance Taylor <iant@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Damien Neil <dneil@google.com>
---

diff --git a/src/internal/routebsd/interface_classic.go b/src/internal/routebsd/interface_classic.go
index 7b26c7eb2a..af9531c0df 100644
--- a/src/internal/routebsd/interface_classic.go
+++ b/src/internal/routebsd/interface_classic.go
@@ -20,9 +20,7 @@ func (w *wireFormat) parseInterfaceMessage(b []byte) (Message, error) {
 		return nil, errInvalidMessage
 	}
 	attrs := uint(nativeEndian.Uint32(b[4:8]))
-	if attrs&syscall.RTA_IFP == 0 {
-		return nil, nil
-	}
+
 	m := &InterfaceMessage{
 		Version: int(b[2]),
 		Type:    int(b[3]),
@@ -32,12 +30,19 @@ func (w *wireFormat) parseInterfaceMessage(b []byte) (Message, error) {
 		extOff:  w.extOff,
 		raw:     b[:l],
 	}
-	a, err := parseLinkAddr(b[w.bodyOff:])
-	if err != nil {
-		return nil, err
+
+	// We used to require that RTA_IFP always be set.
+	// It turns out that on darwin messages about the
+	// utun interface may not include a name. Issue #71064.
+	if attrs&syscall.RTA_IFP != 0 {
+		a, err := parseLinkAddr(b[w.bodyOff:])
+		if err != nil {
+			return nil, err
+		}
+		m.Addrs[syscall.RTAX_IFP] = a
+		m.Name = a.(*LinkAddr).Name
 	}
-	m.Addrs[syscall.RTAX_IFP] = a
-	m.Name = a.(*LinkAddr).Name
+
 	return m, nil
 }
 
diff --git a/src/net/interface.go b/src/net/interface.go
index 74bb4f0e1c..b6057780c4 100644
--- a/src/net/interface.go
+++ b/src/net/interface.go
@@ -42,7 +42,7 @@ var (
 type Interface struct {
 	Index        int          // positive integer that starts at one, zero is never used
 	MTU          int          // maximum transmission unit
-	Name         string       // e.g., "en0", "lo0", "eth0.100"
+	Name         string       // e.g., "en0", "lo0", "eth0.100"; may be the empty string
 	HardwareAddr HardwareAddr // IEEE MAC-48, EUI-48 and EUI-64 form
 	Flags        Flags        // e.g., FlagUp, FlagLoopback, FlagMulticast
 }
@@ -221,9 +221,11 @@ func (zc *ipv6ZoneCache) update(ift []Interface, force bool) (updated bool) {
 	zc.toIndex = make(map[string]int, len(ift))
 	zc.toName = make(map[int]string, len(ift))
 	for _, ifi := range ift {
-		zc.toIndex[ifi.Name] = ifi.Index
-		if _, ok := zc.toName[ifi.Index]; !ok {
-			zc.toName[ifi.Index] = ifi.Name
+		if ifi.Name != "" {
+			zc.toIndex[ifi.Name] = ifi.Index
+			if _, ok := zc.toName[ifi.Index]; !ok {
+				zc.toName[ifi.Index] = ifi.Name
+			}
 		}
 	}
 	return true
diff --git a/src/net/interface_test.go b/src/net/interface_test.go
index a97d675e7e..72befca0d8 100644
--- a/src/net/interface_test.go
+++ b/src/net/interface_test.go
@@ -68,12 +68,14 @@ func TestInterfaces(t *testing.T) {
 				t.Errorf("got %v; want %v", ifxi, ifi)
 			}
 		}
-		ifxn, err := InterfaceByName(ifi.Name)
-		if err != nil {
-			t.Fatal(err)
-		}
-		if !reflect.DeepEqual(ifxn, &ifi) {
-			t.Errorf("got %v; want %v", ifxn, ifi)
+		if ifi.Name != "" {
+			ifxn, err := InterfaceByName(ifi.Name)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if !reflect.DeepEqual(ifxn, &ifi) {
+				t.Errorf("got %v; want %v", ifxn, ifi)
+			}
 		}
 		t.Logf("%s: flags=%v index=%d mtu=%d hwaddr=%v", ifi.Name, ifi.Flags, ifi.Index, ifi.MTU, ifi.HardwareAddr)
 	}