From 68913c5fc8a6df4f8ca4b28a621163f190388e96 Mon Sep 17 00:00:00 2001
From: Albert Sundjaja <albertsundjaja@gmail.com>
Date: Fri, 21 Feb 2025 23:34:09 +1100
Subject: [PATCH] remove redundant defer and improved comments and code in
 sockaddr

---
 src/net/unixsock_linux_test.go   |  4 ++--
 src/net/unixsock_windows_test.go |  4 ++--
 src/syscall/syscall_linux.go     | 20 +++++++++++++-------
 src/syscall/syscall_windows.go   | 20 +++++++++++++-------
 4 files changed, 30 insertions(+), 18 deletions(-)

diff --git a/src/net/unixsock_linux_test.go b/src/net/unixsock_linux_test.go
index 3c8fd85a9f..fa50ba7bd5 100644
--- a/src/net/unixsock_linux_test.go
+++ b/src/net/unixsock_linux_test.go
@@ -49,7 +49,7 @@ func TestUnixAutobindClose(t *testing.T) {
 	ln.Close()
 }
 
-func TestUnixAbstractLongNameNullStart(t *testing.T) {
+func TestUnixAbstractLongNameNulStart(t *testing.T) {
 	// Create an abstract socket name that starts with a null byte ("\x00")
 	// whose length is the maximum of RawSockaddrUnix Path len
 	paddedAddr := make([]byte, len(syscall.RawSockaddrUnix{}.Path))
@@ -63,7 +63,7 @@ func TestUnixAbstractLongNameNullStart(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	defer c.Close()
+	c.Close()
 }
 
 func TestUnixgramLinuxAbstractLongName(t *testing.T) {
diff --git a/src/net/unixsock_windows_test.go b/src/net/unixsock_windows_test.go
index c30916c838..4c1a8d7e7e 100644
--- a/src/net/unixsock_windows_test.go
+++ b/src/net/unixsock_windows_test.go
@@ -70,7 +70,7 @@ func TestUnixConnLocalWindows(t *testing.T) {
 	}
 }
 
-func TestUnixAbstractLongNameNullStart(t *testing.T) {
+func TestUnixAbstractLongNameNulStart(t *testing.T) {
 	if !windows.SupportUnixSocket() {
 		t.Skip("unix test")
 	}
@@ -88,7 +88,7 @@ func TestUnixAbstractLongNameNullStart(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	defer c.Close()
+	c.Close()
 }
 
 func TestModeSocket(t *testing.T) {
diff --git a/src/syscall/syscall_linux.go b/src/syscall/syscall_linux.go
index 7e3443e106..3c73a09ff2 100644
--- a/src/syscall/syscall_linux.go
+++ b/src/syscall/syscall_linux.go
@@ -550,7 +550,12 @@ func (sa *SockaddrUnix) sockaddr() (unsafe.Pointer, _Socklen, error) {
 	if n > len(sa.raw.Path) {
 		return nil, 0, EINVAL
 	}
+	// Abstract addresses start with NUL.
+	// '@' is also a valid way to specify abstract addresses.
 	isAbstract := n > 0 && (name[0] == '@' || name[0] == '\x00')
+
+	// Non-abstract addresses is NUL terminated.
+	// The length can't use the full capacity as we need to add NUL.
 	if n == len(sa.raw.Path) && !isAbstract {
 		return nil, 0, EINVAL
 	}
@@ -558,15 +563,16 @@ func (sa *SockaddrUnix) sockaddr() (unsafe.Pointer, _Socklen, error) {
 	for i := 0; i < n; i++ {
 		sa.raw.Path[i] = int8(name[i])
 	}
-	// length is family (uint16), name, NUL.
-	sl := _Socklen(2)
-	if n > 0 {
-		sl += _Socklen(n) + 1
-	}
+	// Length is family + name (+ NUL if non-abstract).
+	// Family is of type uint16 (2 bytes).
+	sl := _Socklen(2 + n)
 	if isAbstract {
+		// Abstract addresses are not NUL terminated.
+		// We rewrite '@' prefix to NUL here.
 		sa.raw.Path[0] = 0
-		// Don't count trailing NUL for abstract address.
-		sl--
+	} else {
+		// Add NUL for non-abstract addresses.
+		sl++
 	}
 
 	return unsafe.Pointer(&sa.raw), sl, nil
diff --git a/src/syscall/syscall_windows.go b/src/syscall/syscall_windows.go
index 6bc2c5a6bb..da72c72e3b 100644
--- a/src/syscall/syscall_windows.go
+++ b/src/syscall/syscall_windows.go
@@ -858,7 +858,12 @@ func (sa *SockaddrUnix) sockaddr() (unsafe.Pointer, int32, error) {
 	if n > len(sa.raw.Path) {
 		return nil, 0, EINVAL
 	}
+	// Abstract addresses start with NUL.
+	// '@' is also a valid way to specify abstract addresses.
 	isAbstract := n > 0 && (name[0] == '@' || name[0] == '\x00')
+
+	// Non-abstract addresses is NUL terminated.
+	// The length can't use the full capacity as we need to add NUL.
 	if n == len(sa.raw.Path) && !isAbstract {
 		return nil, 0, EINVAL
 	}
@@ -866,15 +871,16 @@ func (sa *SockaddrUnix) sockaddr() (unsafe.Pointer, int32, error) {
 	for i := 0; i < n; i++ {
 		sa.raw.Path[i] = int8(name[i])
 	}
-	// length is family (uint16), name, NUL.
-	sl := int32(2)
-	if n > 0 {
-		sl += int32(n) + 1
-	}
+	// Length is family + name (+ NUL if non-abstract).
+	// Family is of type uint16 (2 bytes).
+	sl := _Socklen(2 + n)
 	if isAbstract {
+		// Abstract addresses are not NUL terminated.
+		// We rewrite '@' prefix to NUL here.
 		sa.raw.Path[0] = 0
-		// Don't count trailing NUL for abstract address.
-		sl--
+	} else {
+		// Add NUL for non-abstract addresses.
+		sl++
 	}
 
 	return unsafe.Pointer(&sa.raw), sl, nil