Add support for IFLA_MIN_MTU and IFLA_MAX_MTU in LinkAttrs

[AlekseyMamedoff]

Added attributes MinMTU, MaxMTU to LinkAttrs struct
Added cases for IFLA_MIN_MTU, IFLA_MAX_MTU
Signed-off-by: Aleksey Mamedov [email protected]

[lazysegtree]

@AlekseyMamedoff , Fix for TestXfrmStateWithPcpunumWithoutSADir, the test which is failing in your PR, was recently merged in main. Please rebase with main.

[AlekseyMamedoff]

@lazysegtree Done. Test passed. Thx.

[lazysegtree]

@AlekseyMamedoff
Shouldn't you also add a corresponding method LinkSetMinMTU

If you are adding functionality to parse this attribute via netlink, we should also be able to add it to Links

[lazysegtree]

Also a unit test would be great. Something like

func TestLinkMinMaxMTU(t *testing.T) {
	tearDown := setUpNetlinkTest(t)
	defer tearDown()

	iface := &Dummy{LinkAttrs{
		Name: "foo",
	}}
	if err := LinkAdd(iface); err != nil {
		t.Fatal(err)
	}

	link, err := LinkByName("foo")
	err = LinkSetMinMTU(link, 1000)
	if link.Attrs().MinMTU != 1000 {
		t.Fatal("MinMTU not correct")
	}
}

[aboch]

@AlekseyMamedoff ping