Add socket receive buffer size configuration

README.md

@@ -72,3 +72,21 @@ For documentation and more examples please take a look at [![PkgGoDev](https://p
 ## Requirements
 
 * A version of Go that is [supported by upstream](https://golang.org/doc/devel/release.html#policy)
+
+## Advanced Configuration
+
+### Socket Buffer Size
+
+For high-throughput scenarios, you may need to increase the socket receive buffer size:
+
+```go
+config := nflog.Config{
+    Group:       100,
+    Copymode:    nflog.CopyPacket,
+    SockBufSize: 2097152, // 2MB socket buffer
+}
+
+nf, err := nflog.Open(&config)
+```
+
+Note: Setting a large socket buffer may require CAP_NET_ADMIN capability or increased system limits.

nflog.go

@@ -78,6 +78,36 @@
 	}
 	nflog.Con = con
 
+	// Set socket receive buffer size if specified
+	if config.SockBufSize > 0 {
+		// Linux doubles the buffer size, so request half of what user wants
+		requestSize := config.SockBufSize / 2
+
+		// Get the underlying file descriptor
+		rawConn, err := con.SyscallConn()
+		if err != nil {
+			con.Close()
+			return nil, fmt.Errorf("failed to get raw connection: %w", err)
+		}
+
+		var sockErr error
+		err = rawConn.Control(func(fd uintptr) {
+			// Try SO_RCVBUFFORCE first (bypasses limits with CAP_NET_ADMIN)
+			sockErr = unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_RCVBUFFORCE, int(requestSize))
+			if sockErr != nil {
+				// Fall back to SO_RCVBUF
+				sockErr = unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_RCVBUF, int(requestSize))
+				if sockErr != nil && config.Logger != nil {
+					config.Logger.Errorf("Failed to set socket buffer size to %d: %v", requestSize, sockErr)
+				}
+			}
+		})
+		if err != nil {
+			con.Close()
+			return nil, fmt.Errorf("failed to control socket: %w", err)
+		}
+	}
+
 	if config.Logger == nil {
 		nflog.logger = new(devNull)
 	} else {

nflog_test.go

@@ -4,7 +4,10 @@
 package nflog
 
 import (
+	"os"
 	"testing"
+
+	"golang.org/x/sys/unix"
 )
 
 func TestOpen(t *testing.T) {
@@ -33,3 +36,60 @@ func TestOpen(t *testing.T) {
 		})
 	}
 }
+
+func TestSockBufSize(t *testing.T) {
+	// Skip if not root
+	if os.Getuid() != 0 {
+		t.Skip("Test requires root privileges")
+	}
+
+	config := &Config{
+		Group:       1,
+		Copymode:    CopyPacket,
+		SockBufSize: 2097152, // 2MB
+	}
+
+	nf, err := Open(config)
+	if err != nil {
+		t.Fatalf("failed to open nflog: %v", err)
+	}
+	defer nf.Close()
+
+	// Verify buffer size was applied
+	rawConn, err := nf.Con.SyscallConn()
+	if err != nil {
+		t.Fatalf("failed to get raw connection: %v", err)
+	}
+
+	var bufsize int
+	var sockErr error
+	err = rawConn.Control(func(fd uintptr) {
+		bufsize, sockErr = unix.GetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_RCVBUF)
+	})
+	if err != nil {
+		t.Fatalf("failed to control socket: %v", err)
+	}
+	if sockErr != nil {
+		t.Fatalf("failed to get socket buffer size: %v", sockErr)
+	}
+
+	// Linux doubles the value internally, so we check if it's at least our requested size
+	if bufsize < int(config.SockBufSize) {
+		t.Errorf("socket buffer size not applied correctly: got %d, want at least %d",
+			bufsize, config.SockBufSize)
+	}
+}
+
+func TestSockBufSizeDefault(t *testing.T) {
+	config := &Config{
+		Group:       1,
+		Copymode:    CopyPacket,
+		SockBufSize: 0,
+	}
+
+	nf, err := Open(config)
+	if err != nil {
+		t.Fatalf("failed to open nflog with default socket buffer: %v", err)
+	}
+	defer nf.Close()
+}

types.go

@@ -153,6 +153,10 @@ type Config struct {
 	// that will be copied to userspace.
 	Bufsize uint32
 
+	// Size of the socket receive buffer (in bytes)
+	// If set to 0, the system default will be used
+	SockBufSize uint32
+
 	// Optional settings to enable/disable features
 	Settings uint16