prealloc them buffers

inside.go

@@ -18,14 +18,16 @@ import (
 // outs: slice of output buffers (one per packet) with virtio headroom
 // q: queue index
 // localCache: firewall conntrack cache
-func (f *Interface) consumeInsidePackets(packets [][]byte, sizes []int, count int, outs [][]byte, q int, localCache firewall.ConntrackCache) {
+// batchPackets: pre-allocated slice for accumulating encrypted packets
+// batchAddrs: pre-allocated slice for accumulating destination addresses
+func (f *Interface) consumeInsidePackets(packets [][]byte, sizes []int, count int, outs [][]byte, q int, localCache firewall.ConntrackCache, batchPackets *[][]byte, batchAddrs *[]netip.AddrPort) {
 	// Reusable per-packet state
 	fwPacket := &firewall.Packet{}
 	nb := make([]byte, 12, 12)
 
-	// Accumulate encrypted packets for batch sending
-	batchPackets := make([][]byte, 0, count)
-	batchAddrs := make([]netip.AddrPort, 0, count)
+	// Reset batch accumulation slices (reuse capacity)
+	*batchPackets = (*batchPackets)[:0]
+	*batchAddrs = (*batchAddrs)[:0]
 
 	// Process each packet in the batch
 	for i := 0; i < count; i++ {
@@ -137,15 +139,15 @@ func (f *Interface) consumeInsidePackets(packets [][]byte, sizes []int, count in
 		}
 
 		// Add to batch
-		batchPackets = append(batchPackets, out)
-		batchAddrs = append(batchAddrs, hostinfo.remote)
+		*batchPackets = append(*batchPackets, out)
+		*batchAddrs = append(*batchAddrs, hostinfo.remote)
 	}
 
 	// Send all accumulated packets in one batch
-	if len(batchPackets) > 0 {
-		n, err := f.writers[q].WriteMulti(batchPackets, batchAddrs)
+	if len(*batchPackets) > 0 {
+		n, err := f.writers[q].WriteMulti(*batchPackets, *batchAddrs)
 		if err != nil {
-			f.l.WithError(err).WithField("sent", n).WithField("total", len(batchPackets)).Error("Failed to send batch")
+			f.l.WithError(err).WithField("sent", n).WithField("total", len(*batchPackets)).Error("Failed to send batch")
 		}
 	}
 }

interface.go

@@ -341,6 +341,10 @@ func (f *Interface) listenInBatch(reader io.ReadWriteCloser, batchReader BatchRe
 		outs[idx] = outBuf[virtioNetHdrLen:] // Slice starting after headroom
 	}
 
+	// Pre-allocate batch accumulation buffers for sending
+	batchPackets := make([][]byte, 0, batchSize)
+	batchAddrs := make([]netip.AddrPort, 0, batchSize)
+
 	conntrackCache := firewall.NewConntrackCacheTicker(f.conntrackCacheTimeout)
 
 	for {
@@ -356,7 +360,7 @@ func (f *Interface) listenInBatch(reader io.ReadWriteCloser, batchReader BatchRe
 		}
 
 		// Process all packets in the batch at once
-		f.consumeInsidePackets(bufs, sizes, n, outs, i, conntrackCache.Get(f.l))
+		f.consumeInsidePackets(bufs, sizes, n, outs, i, conntrackCache.Get(f.l), &batchPackets, &batchAddrs)
 	}
 }
 

udp/udp_linux.go

@@ -22,6 +22,11 @@ type StdConn struct {
 	isV4  bool
 	l     *logrus.Logger
 	batch int
+
+	// Pre-allocated buffers for batch writes (sized for IPv6, works for both)
+	writeMsgs   []rawMessage
+	writeIovecs []iovec
+	writeNames  [][]byte
 }
 
 func maybeIPV4(ip net.IP) (net.IP, bool) {
@@ -69,7 +74,26 @@ func NewListener(l *logrus.Logger, ip netip.Addr, port int, multi bool, batch in
 		return nil, fmt.Errorf("unable to bind to socket: %s", err)
 	}
 
-	return &StdConn{sysFd: fd, isV4: ip.Is4(), l: l, batch: batch}, err
+	c := &StdConn{sysFd: fd, isV4: ip.Is4(), l: l, batch: batch}
+
+	// Pre-allocate write message structures for batching (sized for IPv6, works for both)
+	c.writeMsgs = make([]rawMessage, batch)
+	c.writeIovecs = make([]iovec, batch)
+	c.writeNames = make([][]byte, batch)
+
+	for i := range c.writeMsgs {
+		// Allocate for IPv6 size (larger than IPv4, works for both)
+		c.writeNames[i] = make([]byte, unix.SizeofSockaddrInet6)
+
+		// Point to the iovec in the slice
+		c.writeMsgs[i].Hdr.Iov = &c.writeIovecs[i]
+		c.writeMsgs[i].Hdr.Iovlen = 1
+
+		c.writeMsgs[i].Hdr.Name = &c.writeNames[i][0]
+		// Namelen will be set appropriately in writeMulti4/writeMulti6
+	}
+
+	return c, err
 }
 
 func (u *StdConn) Rebind() error {
@@ -262,75 +286,120 @@ func (u *StdConn) writeTo4(b []byte, ip netip.AddrPort) error {
 }
 
 func (u *StdConn) writeMulti4(packets [][]byte, addrs []netip.AddrPort) (int, error) {
-	msgs, iovecs, names := u.PrepareWriteMessages4(len(packets))
-
-	for i := range packets {
-		if !addrs[i].Addr().Is4() {
-			return i, ErrInvalidIPv6RemoteForSocket
+	sent := 0
+	for sent < len(packets) {
+		// Determine batch size based on remaining packets and buffer capacity
+		batchSize := len(packets) - sent
+		if batchSize > len(u.writeMsgs) {
+			batchSize = len(u.writeMsgs)
 		}
 
-		// Setup the packet buffer
-		iovecs[i].Base = &packets[i][0]
-		iovecs[i].Len = uint64(len(packets[i]))
+		// Use pre-allocated buffers
+		msgs := u.writeMsgs[:batchSize]
+		iovecs := u.writeIovecs[:batchSize]
+		names := u.writeNames[:batchSize]
 
-		// Setup the destination address
-		rsa := (*unix.RawSockaddrInet4)(unsafe.Pointer(&names[i][0]))
-		rsa.Family = unix.AF_INET
-		rsa.Addr = addrs[i].Addr().As4()
-		binary.BigEndian.PutUint16((*[2]byte)(unsafe.Pointer(&rsa.Port))[:], addrs[i].Port())
-	}
+		// Setup message structures for this batch
+		for i := 0; i < batchSize; i++ {
+			pktIdx := sent + i
+			if !addrs[pktIdx].Addr().Is4() {
+				return sent + i, ErrInvalidIPv6RemoteForSocket
+			}
 
-	for {
-		n, _, err := unix.Syscall6(
+			// Setup the packet buffer
+			iovecs[i].Base = &packets[pktIdx][0]
+			iovecs[i].Len = uint64(len(packets[pktIdx]))
+
+			// Setup the destination address
+			rsa := (*unix.RawSockaddrInet4)(unsafe.Pointer(&names[i][0]))
+			rsa.Family = unix.AF_INET
+			rsa.Addr = addrs[pktIdx].Addr().As4()
+			binary.BigEndian.PutUint16((*[2]byte)(unsafe.Pointer(&rsa.Port))[:], addrs[pktIdx].Port())
+
+			// Set the appropriate address length for IPv4
+			msgs[i].Hdr.Namelen = unix.SizeofSockaddrInet4
+		}
+
+		// Send this batch
+		nsent, _, err := unix.Syscall6(
 			unix.SYS_SENDMMSG,
 			uintptr(u.sysFd),
 			uintptr(unsafe.Pointer(&msgs[0])),
-			uintptr(len(msgs)),
+			uintptr(batchSize),
 			0,
 			0,
 			0,
 		)
 
 		if err != 0 {
-			return int(n), &net.OpError{Op: "sendmmsg", Err: err}
+			return sent + int(nsent), &net.OpError{Op: "sendmmsg", Err: err}
 		}
 
-		return int(n), nil
+		sent += int(nsent)
+		if int(nsent) < batchSize {
+			// Couldn't send all packets in batch, return what we sent
+			return sent, nil
+		}
 	}
+
+	return sent, nil
 }
 
 func (u *StdConn) writeMulti6(packets [][]byte, addrs []netip.AddrPort) (int, error) {
-	msgs, iovecs, names := u.PrepareWriteMessages6(len(packets))
-
-	for i := range packets {
-		// Setup the packet buffer
-		iovecs[i].Base = &packets[i][0]
-		iovecs[i].Len = uint64(len(packets[i]))
-
-		// Setup the destination address
-		rsa := (*unix.RawSockaddrInet6)(unsafe.Pointer(&names[i][0]))
-		rsa.Family = unix.AF_INET6
-		rsa.Addr = addrs[i].Addr().As16()
-		binary.BigEndian.PutUint16((*[2]byte)(unsafe.Pointer(&rsa.Port))[:], addrs[i].Port())
-	}
+	sent := 0
+	for sent < len(packets) {
+		// Determine batch size based on remaining packets and buffer capacity
+		batchSize := len(packets) - sent
+		if batchSize > len(u.writeMsgs) {
+			batchSize = len(u.writeMsgs)
+		}
 
-	for {
-		n, _, err := unix.Syscall6(
+		// Use pre-allocated buffers
+		msgs := u.writeMsgs[:batchSize]
+		iovecs := u.writeIovecs[:batchSize]
+		names := u.writeNames[:batchSize]
+
+		// Setup message structures for this batch
+		for i := 0; i < batchSize; i++ {
+			pktIdx := sent + i
+
+			// Setup the packet buffer
+			iovecs[i].Base = &packets[pktIdx][0]
+			iovecs[i].Len = uint64(len(packets[pktIdx]))
+
+			// Setup the destination address
+			rsa := (*unix.RawSockaddrInet6)(unsafe.Pointer(&names[i][0]))
+			rsa.Family = unix.AF_INET6
+			rsa.Addr = addrs[pktIdx].Addr().As16()
+			binary.BigEndian.PutUint16((*[2]byte)(unsafe.Pointer(&rsa.Port))[:], addrs[pktIdx].Port())
+
+			// Set the appropriate address length for IPv6
+			msgs[i].Hdr.Namelen = unix.SizeofSockaddrInet6
+		}
+
+		// Send this batch
+		nsent, _, err := unix.Syscall6(
 			unix.SYS_SENDMMSG,
 			uintptr(u.sysFd),
 			uintptr(unsafe.Pointer(&msgs[0])),
-			uintptr(len(msgs)),
+			uintptr(batchSize),
 			0,
 			0,
 			0,
 		)
 
 		if err != 0 {
-			return int(n), &net.OpError{Op: "sendmmsg", Err: err}
+			return sent + int(nsent), &net.OpError{Op: "sendmmsg", Err: err}
 		}
 
-		return int(n), nil
+		sent += int(nsent)
+		if int(nsent) < batchSize {
+			// Couldn't send all packets in batch, return what we sent
+			return sent, nil
+		}
 	}
+
+	return sent, nil
 }
 
 func (u *StdConn) ReloadConfig(c *config.C) {

udp/udp_linux_64.go

@@ -55,41 +55,3 @@ func (u *StdConn) PrepareRawMessages(n int) ([]rawMessage, [][]byte, [][]byte) {
 
 	return msgs, buffers, names
 }
-
-func (u *StdConn) PrepareWriteMessages4(n int) ([]rawMessage, []iovec, [][]byte) {
-	msgs := make([]rawMessage, n)
-	iovecs := make([]iovec, n)
-	names := make([][]byte, n)
-
-	for i := range msgs {
-		names[i] = make([]byte, unix.SizeofSockaddrInet4)
-
-		// Point to the iovec in the slice
-		msgs[i].Hdr.Iov = &iovecs[i]
-		msgs[i].Hdr.Iovlen = 1
-
-		msgs[i].Hdr.Name = &names[i][0]
-		msgs[i].Hdr.Namelen = unix.SizeofSockaddrInet4
-	}
-
-	return msgs, iovecs, names
-}
-
-func (u *StdConn) PrepareWriteMessages6(n int) ([]rawMessage, []iovec, [][]byte) {
-	msgs := make([]rawMessage, n)
-	iovecs := make([]iovec, n)
-	names := make([][]byte, n)
-
-	for i := range msgs {
-		names[i] = make([]byte, unix.SizeofSockaddrInet6)
-
-		// Point to the iovec in the slice
-		msgs[i].Hdr.Iov = &iovecs[i]
-		msgs[i].Hdr.Iovlen = 1
-
-		msgs[i].Hdr.Name = &names[i][0]
-		msgs[i].Hdr.Namelen = unix.SizeofSockaddrInet6
-	}
-
-	return msgs, iovecs, names
-}