internal/netlink: generalise implementation from container

This is useful for uevent implementation.

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

internal/netlink/rtnl_test.go

@@ -0,0 +1,62 @@
+package netlink
+
+import (
+	"syscall"
+	"testing"
+)
+
+func TestPayloadRTNETLINK(t *testing.T) {
+	t.Parallel()
+
+	checkPayload(t, []payloadTestCase{
+		{"RTM_NEWADDR lo", func(c *conn) {
+			(&RouteConn{c}).writeNewaddrLo(1)
+		}, []byte{
+			/* Len   */ 0x28, 0, 0, 0,
+			/* Type  */ 0x14, 0,
+			/* Flags */ 5, 6,
+			/* Seq   */ 0, 0, 0, 0,
+			/* Pid   */ 1, 0, 0, 0,
+
+			/* Family    */ 2,
+			/* Prefixlen */ 8,
+			/* Flags     */ 0x80,
+			/* Scope     */ 0xfe,
+			/* Index     */ 1, 0, 0, 0,
+
+			/* Len     */ 8, 0,
+			/* Type    */ 2, 0,
+			/* in_addr */ 127, 0, 0, 1,
+
+			/* Len     */ 8, 0,
+			/* Type    */ 1, 0,
+			/* in_addr */ 127, 0, 0, 1,
+		}},
+
+		{"RTM_NEWLINK", func(c *conn) {
+			c.seq++
+			(&RouteConn{c}).writeIfInfomsg(
+				syscall.RTM_NEWLINK, 0,
+				&syscall.IfInfomsg{
+					Family: syscall.AF_UNSPEC,
+					Index:  1,
+					Flags:  syscall.IFF_UP,
+					Change: syscall.IFF_UP,
+				},
+			)
+		}, []byte{
+			/* Len   */ 0x20, 0, 0, 0,
+			/* Type  */ 0x10, 0,
+			/* Flags */ 5, 0,
+			/* Seq   */ 1, 0, 0, 0,
+			/* Pid   */ 1, 0, 0, 0,
+
+			/* Family */ 0,
+			/* pad    */ 0,
+			/* Type   */ 0, 0,
+			/* Index  */ 1, 0, 0, 0,
+			/* Flags  */ 1, 0, 0, 0,
+			/* Change */ 1, 0, 0, 0,
+		}},
+	})
+}