Add brutal infra

transport/internet/brutal/brutal.go

@@ -0,0 +1,53 @@
+//go:build linux
+
+package brutal
+
+import (
+	"os"
+	"unsafe"
+
+	"github.com/xtls/xray-core/common/net"
+	"golang.org/x/sys/unix"
+)
+
+//go:linkname setsockopt syscall.setsockopt
+func setsockopt(s int, level int, name int, val unsafe.Pointer, vallen uintptr) (err error)
+
+const (
+	TCP_BRUTAL_PARAMS = 23301
+)
+
+type TCPBrutalParams struct {
+	Rate     uint64
+	CwndGain uint32
+}
+
+func setBrutalFD(fd uintptr, sendBPS uint64) error {
+	err := unix.SetsockoptString(int(fd), unix.IPPROTO_TCP, unix.TCP_CONGESTION, "brutal")
+	if err != nil {
+		return err
+	}
+	params := TCPBrutalParams{
+		Rate:     sendBPS,
+		CwndGain: 20, // hysteria2 default
+	}
+	err = setsockopt(int(fd), unix.IPPROTO_TCP, TCP_BRUTAL_PARAMS, unsafe.Pointer(&params), unsafe.Sizeof(params))
+	if err != nil {
+		return os.NewSyscallError("setsockopt IPPROTO_TCP TCP_BRUTAL_PARAMS", err)
+	}
+	return nil
+}
+
+func SetBrutal(conn *net.TCPConn, sendBPS uint64) error {
+	syscallConn, err := conn.SyscallConn()
+	if err != nil {
+		return err
+	}
+	syscallConn.Control(func(fd uintptr) {
+		err = setBrutalFD(fd, sendBPS)
+	})
+	if err != nil {
+		return err
+	}
+	return nil
+}

transport/internet/brutal/brutal_others.go

@@ -0,0 +1,12 @@
+//go:build !linux
+
+package brutal
+
+import (
+	"github.com/xtls/xray-core/common/errors"
+	"github.com/xtls/xray-core/common/net"
+)
+
+func SetBrutal(conn *net.TCPConn, sendBPS uint64) error {
+	return errors.New("brutal not available on this platform")
+}