inlet/flow: avoid repeating common socket options for Linux and others

Also, fix the description for `SO_REUSEADDR`.

inlet/flow/input/udp/socket.go

@@ -14,6 +14,23 @@ import (
 	"golang.org/x/sys/unix"
 )
 
+// commonUDPSocketOptions are the options common to all OS.
+var commonUDPSocketOptions = []socketOption{
+	{
+		// Allow a listener to bind again to a socket that was just closed
+		Name:      "SO_REUSEADDR",
+		Level:     unix.SOL_SOCKET,
+		Option:    unix.SO_REUSEADDR,
+		Mandatory: true,
+	}, {
+		// Allow multiple listeners to bind to the same port
+		Name:      "SO_REUSEPORT",
+		Level:     unix.SOL_SOCKET,
+		Option:    unix.SO_REUSEPORT,
+		Mandatory: true,
+	},
+}
+
 type oobMessage struct {
 	Drops    uint32
 	Received time.Time

inlet/flow/input/udp/socket_linux.go

@@ -15,31 +15,17 @@ import (
 
 var (
 	oobLength        = syscall.CmsgLen(4) + syscall.CmsgLen(16) // uint32 + 2*int64
-	udpSocketOptions = []socketOption{
+	udpSocketOptions = append(commonUDPSocketOptions, socketOption{
-		{
-			// Allow multiple listeners to bind to the same IP
-			Name:      "SO_REUSEADDR",
-			Level:     unix.SOL_SOCKET,
-			Option:    unix.SO_REUSEADDR,
-			Mandatory: true,
-		}, {
-			// Allow multiple listeners to bind to the same port
-			Name:      "SO_REUSEPORT",
-			Level:     unix.SOL_SOCKET,
-			Option:    unix.SO_REUSEPORT,
-			Mandatory: true,
-		}, {
 		// Get the number of dropped packets
 		Name:   "SO_RXQ_OVFL",
 		Level:  unix.SOL_SOCKET,
 		Option: unix.SO_RXQ_OVFL,
-		}, {
+	}, socketOption{
 		// Ask the kernel to timestamp incoming packets
 		Name:   "SO_TIMESTAMP_NEW",
 		Level:  unix.SOL_SOCKET,
 		Option: unix.SO_TIMESTAMP_NEW | unix.SOF_TIMESTAMPING_RX_SOFTWARE,
-		},
+	})
-	}
 )
 
 // parseSocketControlMessage parses b and extract the number of drops

inlet/flow/input/udp/socket_others.go

@@ -7,27 +7,11 @@ package udp
 
 import (
 	"errors"
-
-	"golang.org/x/sys/unix"
 )
 
 var (
 	oobLength        = 0
-	udpSocketOptions = []socketOption{
+	udpSocketOptions = commonUDPSocketOptions
-		{
-			// Allow multiple listeners to bind to the same IP
-			Name:      "SO_REUSEADDR",
-			Level:     unix.SOL_SOCKET,
-			Option:    unix.SO_REUSEADDR,
-			Mandatory: true,
-		}, {
-			// Allow multiple listeners to bind to the same port
-			Name:      "SO_REUSEPORT",
-			Level:     unix.SOL_SOCKET,
-			Option:    unix.SO_REUSEPORT,
-			Mandatory: true,
-		},
-	}
 )
 
 // parseSocketControlMessage always returns 0.