From d1e684a60b0dd89bde1db6f9c622168460888761 Mon Sep 17 00:00:00 2001
From: dennisafa <dennis.afa@gmail.com>
Date: Thu, 20 May 2021 11:31:37 -0600
Subject: [PATCH] Ability to set multicast attribute on a link

---
 link.go       |  1 +
 link_linux.go | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 link_test.go  | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 100 insertions(+)

diff --git a/link.go b/link.go
index 2e002d69..ca47d05a 100644
--- a/link.go
+++ b/link.go
@@ -36,6 +36,7 @@ type LinkAttrs struct {
 	Statistics   *LinkStatistics
 	Promisc      int
 	Allmulti     int
+	Multi        int
 	Xdp          *LinkXdp
 	EncapType    string
 	Protinfo     *Protinfo
diff --git a/link_linux.go b/link_linux.go
index caf30c05..916e7a8b 100644
--- a/link_linux.go
+++ b/link_linux.go
@@ -182,6 +182,51 @@ func (h *Handle) LinkSetAllmulticastOff(link Link) error {
 	return err
 }
 
+// LinkSetMulticastOn enables the reception of multicast packets for the link device.
+// Equivalent to: `ip link set $link multicast on`
+func LinkSetMulticastOn(link Link) error {
+	return pkgHandle.LinkSetMulticastOn(link)
+}
+
+// LinkSetMulticastOn enables the reception of multicast packets for the link device.
+// Equivalent to: `ip link set $link multicast on`
+func (h *Handle) LinkSetMulticastOn(link Link) error {
+	base := link.Attrs()
+	h.ensureIndex(base)
+	req := h.newNetlinkRequest(unix.RTM_NEWLINK, unix.NLM_F_ACK)
+
+	msg := nl.NewIfInfomsg(unix.AF_UNSPEC)
+	msg.Change = unix.IFF_MULTICAST
+	msg.Flags = unix.IFF_MULTICAST
+	msg.Index = int32(base.Index)
+	req.AddData(msg)
+
+	_, err := req.Execute(unix.NETLINK_ROUTE, 0)
+	return err
+}
+
+// LinkSetAllmulticastOff disables the reception of multicast packets for the link device.
+// Equivalent to: `ip link set $link multicast off`
+func LinkSetMulticastOff(link Link) error {
+	return pkgHandle.LinkSetMulticastOff(link)
+}
+
+// LinkSetAllmulticastOff disables the reception of multicast packets for the link device.
+// Equivalent to: `ip link set $link multicast off`
+func (h *Handle) LinkSetMulticastOff(link Link) error {
+	base := link.Attrs()
+	h.ensureIndex(base)
+	req := h.newNetlinkRequest(unix.RTM_NEWLINK, unix.NLM_F_ACK)
+
+	msg := nl.NewIfInfomsg(unix.AF_UNSPEC)
+	msg.Change = unix.IFF_MULTICAST
+	msg.Index = int32(base.Index)
+	req.AddData(msg)
+
+	_, err := req.Execute(unix.NETLINK_ROUTE, 0)
+	return err
+}
+
 func MacvlanMACAddrAdd(link Link, addr net.HardwareAddr) error {
 	return pkgHandle.MacvlanMACAddrAdd(link, addr)
 }
@@ -1648,6 +1693,10 @@ func LinkDeserialize(hdr *unix.NlMsghdr, m []byte) (Link, error) {
 	if msg.Flags&unix.IFF_ALLMULTI != 0 {
 		base.Allmulti = 1
 	}
+	if msg.Flags&unix.IFF_MULTICAST != 0 {
+		base.Multi = 1
+	}
+
 	var (
 		link      Link
 		stats32   *LinkStatistics32
diff --git a/link_test.go b/link_test.go
index 1c9c163b..5c02e107 100644
--- a/link_test.go
+++ b/link_test.go
@@ -2663,6 +2663,56 @@ func TestLinkSetAllmulticast(t *testing.T) {
 	}
 }
 
+func TestLinkSetMulticast(t *testing.T) {
+	tearDown := setUpNetlinkTest(t)
+	defer tearDown()
+
+	iface := &Veth{LinkAttrs: LinkAttrs{Name: "foo"}, PeerName: "bar"}
+	if err := LinkAdd(iface); err != nil {
+		t.Fatal(err)
+	}
+
+	link, err := LinkByName("foo")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err := LinkSetUp(link); err != nil {
+		t.Fatal(err)
+	}
+
+	link, err = LinkByName("foo")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err := LinkSetMulticastOn(link); err != nil {
+		t.Fatal(err)
+	}
+
+	link, err = LinkByName("foo")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if link.Attrs().Multi != 1 {
+		t.Fatal("IFF_MULTICAST was not set")
+	}
+
+	if err := LinkSetMulticastOff(link); err != nil {
+		t.Fatal(err)
+	}
+
+	link, err = LinkByName("foo")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if link.Attrs().Multi != 0 {
+		t.Fatal("IFF_MULTICAST is still set")
+	}
+}
+
 func TestLinkSetMacvlanMode(t *testing.T) {
 	tearDown := setUpNetlinkTest(t)
 	defer tearDown()