package nftables

import (
	"os"
	"strconv"
	"strings"
	"testing"

	"github.com/mdlayher/netlink"
	"golang.org/x/sys/unix"
)

func TestLargeBuffersRaisesSocketBuffers(t *testing.T) {
	c, err := netlink.Dial(unix.NETLINK_NETFILTER, nil)
	if err != nil {
		t.Skipf("netlink unavailable: %v", err)
	}
	defer c.Close()
	if err := largeBuffers(c); err != nil {
		t.Fatal(err)
	}
	// Without CAP_NET_ADMIN the kernel caps at the sysctl max; it doubles either way.
	for opt, sysctl := range map[int]string{unix.SO_RCVBUF: "rmem_max", unix.SO_SNDBUF: "wmem_max"} {
		want := 2 * min(batchBufSize, procInt(t, "/proc/sys/net/core/"+sysctl))
		if got := sockBuf(t, c, opt); got < want {
			t.Errorf("%s-bounded buffer = %d, want >= %d", sysctl, got, want)
		}
	}
}

func procInt(t *testing.T, path string) int {
	t.Helper()
	b, err := os.ReadFile(path)
	if err != nil {
		t.Skipf("reading %s: %v", path, err)
	}
	v, err := strconv.Atoi(strings.TrimSpace(string(b)))
	if err != nil {
		t.Fatal(err)
	}
	return v
}

func sockBuf(t *testing.T, c *netlink.Conn, opt int) int {
	t.Helper()
	rc, err := c.SyscallConn()
	if err != nil {
		t.Fatal(err)
	}
	var v int
	var serr error
	if err := rc.Control(func(fd uintptr) { v, serr = unix.GetsockoptInt(int(fd), unix.SOL_SOCKET, opt) }); err != nil {
		t.Fatal(err)
	}
	if serr != nil {
		t.Fatal(serr)
	}
	return v
}