container: use new netlink implementation

This is adapted from the container netlink implementation and is much more reusable.

Signed-off-by: Ophestra <cat@gensokyo.uk>

container/dispatcher.go

@@ -3,6 +3,8 @@ package container
 import (
 	"io"
 	"io/fs"
+	"log"
+	"net"
 	"os"
 	"os/exec"
 	"os/signal"
@@ -12,6 +14,7 @@ import (
 
 	"hakurei.app/container/seccomp"
 	"hakurei.app/container/std"
+	"hakurei.app/internal/netlink"
 	"hakurei.app/message"
 )
 
@@ -167,7 +170,47 @@ func (k direct) mountTmpfs(fsname, target string, flags uintptr, size int, perm
 func (direct) ensureFile(name string, perm, pperm os.FileMode) error {
 	return ensureFile(name, perm, pperm)
 }
-func (direct) mustLoopback(msg message.Msg) { mustLoopback(msg) }
+func (direct) mustLoopback(msg message.Msg) {
+	var lo int
+	if ifi, err := net.InterfaceByName("lo"); err != nil {
+		log.Fatalln(err)
+	} else {
+		lo = ifi.Index
+	}
+
+	c, err := netlink.DialRoute()
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	must := func(err error) {
+		if err == nil {
+			return
+		}
+		if closeErr := c.Close(); closeErr != nil {
+			msg.Verbosef("cannot close RTNETLINK: %v", closeErr)
+		}
+
+		switch err.(type) {
+		case *os.SyscallError:
+			msg.GetLogger().Fatalf("cannot %v", err)
+
+		case syscall.Errno:
+			msg.GetLogger().Fatalf("RTNETLINK answers: %v", err)
+
+		default:
+			msg.GetLogger().Fatalf("RTNETLINK answers with malformed message")
+		}
+	}
+	must(c.SendNewaddrLo(uint32(lo)))
+	must(c.SendIfInfomsg(syscall.RTM_NEWLINK, 0, &syscall.IfInfomsg{
+		Family: syscall.AF_UNSPEC,
+		Index:  int32(lo),
+		Flags:  syscall.IFF_UP,
+		Change: syscall.IFF_UP,
+	}))
+	must(c.Close())
+}
 
 func (direct) seccompLoad(rules []std.NativeRule, flags seccomp.ExportFlag) error {
 	return seccomp.Load(rules, flags)