conn: inch BatchSize toward being non-dynamic

There's not really a use at the moment for making this configurable, and
once bind_windows.go behaves like bind_std.go, we'll be able to use
constants everywhere. So begin that simplification now.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

conn/bind_std.go

@@ -31,21 +31,13 @@ type StdNetBind struct {
 	blackhole6   bool
 	ipv4PC       *ipv4.PacketConn
 	ipv6PC       *ipv6.PacketConn
-	batchSize    int
 	udpAddrPool  sync.Pool
 	ipv4MsgsPool sync.Pool
 	ipv6MsgsPool sync.Pool
 }
 
-func NewStdNetBind() Bind { return NewStdNetBindBatch(DefaultBatchSize) }
-
-func NewStdNetBindBatch(maxBatchSize int) Bind {
-	if maxBatchSize == 0 {
-		maxBatchSize = DefaultBatchSize
-	}
+func NewStdNetBind() Bind {
 	return &StdNetBind{
-		batchSize: maxBatchSize,
-
 		udpAddrPool: sync.Pool{
 			New: func() any {
 				return &net.UDPAddr{
@@ -56,7 +48,7 @@ func NewStdNetBindBatch(maxBatchSize int) Bind {
 
 		ipv4MsgsPool: sync.Pool{
 			New: func() any {
-				msgs := make([]ipv4.Message, maxBatchSize)
+				msgs := make([]ipv4.Message, IdealBatchSize)
 				for i := range msgs {
 					msgs[i].Buffers = make(net.Buffers, 1)
 					msgs[i].OOB = make([]byte, srcControlSize)
@@ -67,7 +59,7 @@ func NewStdNetBindBatch(maxBatchSize int) Bind {
 
 		ipv6MsgsPool: sync.Pool{
 			New: func() any {
-				msgs := make([]ipv6.Message, maxBatchSize)
+				msgs := make([]ipv6.Message, IdealBatchSize)
 				for i := range msgs {
 					msgs[i].Buffers = make(net.Buffers, 1)
 					msgs[i].OOB = make([]byte, srcControlSize)
@@ -240,8 +232,10 @@ func (s *StdNetBind) receiveIPv6(buffs [][]byte, sizes []int, eps []Endpoint) (n
 	return numMsgs, nil
 }
 
+// TODO: When all Binds handle IdealBatchSize, remove this dynamic function and
+// rename the IdealBatchSize constant to BatchSize.
 func (s *StdNetBind) BatchSize() int {
-	return s.batchSize
+	return IdealBatchSize
 }
 
 func (s *StdNetBind) Close() error {

conn/bind_windows.go

@@ -321,6 +321,8 @@ func (bind *WinRingBind) Close() error {
 	return nil
 }
 
+// TODO: When all Binds handle IdealBatchSize, remove this dynamic function and
+// rename the IdealBatchSize constant to BatchSize.
 func (bind *WinRingBind) BatchSize() int {
 	// TODO: implement batching in and out of the ring
 	return 1

conn/conn.go

@@ -16,7 +16,7 @@ import (
 )
 
 const (
-	DefaultBatchSize = 128 // maximum number of packets handled per read and write
+	IdealBatchSize = 128 // maximum number of packets handled per read and write
 )
 
 // A ReceiveFunc receives at least one packet from the network and writes them