1 files changed, 59 insertions, 4 deletions
diff --git a/src/net/sock_linux.go b/src/net/sock_linux.go
index 7bca37605e..9f62ed3dee 100644
--- a/src/net/sock_linux.go
+++ b/src/net/sock_linux.go
@@ -6,6 +6,63 @@ package net
 
 import "syscall"
 
+func kernelVersion() (major int, minor int) {
+	var uname syscall.Utsname
+	if err := syscall.Uname(&uname); err != nil {
+		return
+	}
+
+	rl := uname.Release
+	var values [2]int
+	vi := 0
+	value := 0
+	for _, c := range rl {
+		if c >= '0' && c <= '9' {
+			value = (value * 10) + int(c-'0')
+		} else {
+			// Note that we're assuming N.N.N here.  If we see anything else we are likely to
+			// mis-parse it.
+			values[vi] = value
+			vi++
+			if vi >= len(values) {
+				break
+			}
+			value = 0
+		}
+	}
+	switch vi {
+	case 0:
+		return 0, 0
+	case 1:
+		return values[0], 0
+	case 2:
+		return values[0], values[1]
+	}
+	return
+}
+
+// Linux stores the backlog as:
+//
+//  - uint16 in kernel version < 4.1,
+//  - uint32 in kernel version >= 4.1
+//
+// Truncate number to avoid wrapping.
+//
+// See issue 5030 and 41470.
+func maxAckBacklog(n int) int {
+	major, minor := kernelVersion()
+	size := 16
+	if major > 4 || (major == 4 && minor >= 1) {
+		size = 32
+	}
+
+	var max uint = 1<<size - 1
+	if uint(n) > max {
+		n = int(max)
+	}
+	return n
+}
+
 func maxListenerBacklog() int {
 	fd, err := open("/proc/sys/net/core/somaxconn")
 	if err != nil {
@@ -21,11 +78,9 @@ func maxListenerBacklog() int {
 	if n == 0 || !ok {
 		return syscall.SOMAXCONN
 	}
-	// Linux stores the backlog in a uint16.
-	// Truncate number to avoid wrapping.
-	// See issue 5030.
+
 	if n > 1<<16-1 {
-		n = 1<<16 - 1
+		return maxAckBacklog(n)
 	}
 	return n
 }