Add link netkit

This commit introduces the LinkNetkit type into LinkAttributes,
facilitating Netkit data's encoding to and decoding from the LinkInfo.Data field.

This addition prioritizes backward compatibility and introduces necessary condition checks.
For decoding, if the LinkInfo kind is netkit, the data within LinkInfo.Data is decoded to the Netkit field.
During encoding, Netkit data is encoded into LinkInfo.Data with LinkInfo.Kind set as netkit.
Concurrent settings of LinkInfo and Netkit during encoding trigger an error to maintain integrity.

Signed-off-by: Birol Bilgin <[email protected]>

internal/unix/types_linux.go

@@ -71,6 +71,12 @@ const (
 	IFLA_INFO_SLAVE_KIND        = linux.IFLA_INFO_SLAVE_KIND
 	IFLA_INFO_DATA              = linux.IFLA_INFO_DATA
 	IFLA_INFO_SLAVE_DATA        = linux.IFLA_INFO_SLAVE_DATA
+	IFLA_NETKIT_UNSPEC          = linux.IFLA_NETKIT_UNSPEC
+	IFLA_NETKIT_PEER_INFO       = linux.IFLA_NETKIT_PEER_INFO
+	IFLA_NETKIT_PRIMARY         = linux.IFLA_NETKIT_PRIMARY
+	IFLA_NETKIT_POLICY          = linux.IFLA_NETKIT_POLICY
+	IFLA_NETKIT_PEER_POLICY     = linux.IFLA_NETKIT_PEER_POLICY
+	IFLA_NETKIT_MODE            = linux.IFLA_NETKIT_MODE
 	IFLA_XDP                    = linux.IFLA_XDP
 	IFLA_XDP_FD                 = linux.IFLA_XDP_FD
 	IFLA_XDP_ATTACHED           = linux.IFLA_XDP_ATTACHED
@@ -147,4 +153,10 @@ const (
 	FRA_IP_PROTO                = linux.FRA_IP_PROTO
 	FRA_SPORT_RANGE             = linux.FRA_SPORT_RANGE
 	FRA_DPORT_RANGE             = linux.FRA_DPORT_RANGE
+	NETKIT_NEXT                 = linux.NETKIT_NEXT
+	NETKIT_PASS                 = linux.NETKIT_PASS
+	NETKIT_DROP                 = linux.NETKIT_DROP
+	NETKIT_REDIRECT             = linux.NETKIT_REDIRECT
+	NETKIT_L2                   = linux.NETKIT_L2
+	NETKIT_L3                   = linux.NETKIT_L3
 )

internal/unix/types_other.go

@@ -67,6 +67,12 @@ const (
 	IFLA_INFO_SLAVE_KIND        = 0x4
 	IFLA_INFO_DATA              = 0x2
 	IFLA_INFO_SLAVE_DATA        = 0x5
+	IFLA_NETKIT_UNSPEC          = 0x0
+	IFLA_NETKIT_PEER_INFO       = 0x1
+	IFLA_NETKIT_PRIMARY         = 0x2
+	IFLA_NETKIT_POLICY          = 0x3
+	IFLA_NETKIT_PEER_POLICY     = 0x4
+	IFLA_NETKIT_MODE            = 0x5
 	IFLA_XDP                    = 0x2b
 	IFLA_XDP_FD                 = 0x1
 	IFLA_XDP_ATTACHED           = 0x2
@@ -143,4 +149,10 @@ const (
 	FRA_IP_PROTO                = 0x16
 	FRA_SPORT_RANGE             = 0x17
 	FRA_DPORT_RANGE             = 0x18
+	NETKIT_NEXT                 = -0x1
+	NETKIT_PASS                 = 0x0
+	NETKIT_DROP                 = 0x2
+	NETKIT_REDIRECT             = 0x7
+	NETKIT_L2                   = 0x0
+	NETKIT_L3                   = 0x1
 )

link.go

@@ -222,6 +222,7 @@ type LinkAttributes struct {
 	TxQueueLen       *uint32          // Interface transmit queue len in number of packets
 	Type             uint32           // Link type
 	XDP              *LinkXDP         // Express Data Patch Information
+	Netkit           *LinkNetkit      // Netkit link Information
 }
 
 // OperationalState represents an interface's operational state.
@@ -285,6 +286,18 @@ func (a *LinkAttributes) decode(ad *netlink.AttributeDecoder) error {
 		case unix.IFLA_LINKINFO:
 			a.Info = &LinkInfo{}
 			ad.Nested(a.Info.decode)
+			switch a.Info.Kind {
+			case "netkit":
+				a.Netkit = &LinkNetkit{}
+				dec, err := netlink.NewAttributeDecoder(a.Info.Data)
+				if err != nil {
+					return err
+				}
+				dec.ByteOrder = ad.ByteOrder
+				if err := a.Netkit.decode(dec); err != nil {
+					return err
+				}
+			}
 		case unix.IFLA_LINKMODE:
 			v := ad.Uint8()
 			a.LinkMode = &v
@@ -351,6 +364,33 @@ func (a *LinkAttributes) encode(ae *netlink.AttributeEncoder) error {
 		ae.Uint8(unix.IFLA_OPERSTATE, uint8(a.OperationalState))
 	}
 
+	if a.Netkit != nil {
+		if a.Info != nil {
+			return errors.New("fields Netkit and Info cannot be set at the same time")
+		}
+
+		if a.Address != nil || a.Netkit.PeerInfo.Attributes.Address != nil {
+			return errors.New("netkit does not support setting Ethernet address")
+		}
+
+		nae := netlink.NewAttributeEncoder()
+		nae.ByteOrder = ae.ByteOrder
+
+		err := a.Netkit.encode(nae)
+		if err != nil {
+			return err
+		}
+		b, err := nae.Encode()
+		if err != nil {
+			return err
+		}
+
+		a.Info = &LinkInfo{
+			Kind: "netkit",
+			Data: b,
+		}
+	}
+
 	if a.Info != nil {
 		nae := netlink.NewAttributeEncoder()
 		nae.ByteOrder = ae.ByteOrder
@@ -584,6 +624,48 @@ func (i *LinkInfo) encode(ae *netlink.AttributeEncoder) error {
 	return nil
 }
 
+// LinkNetkit holds netkit link specific information
+type LinkNetkit struct {
+	Mode       uint32
+	Policy     int32
+	PeerPolicy int32
+	Primary    bool
+	PeerInfo   *LinkMessage
+}
+
+func (n *LinkNetkit) decode(ad *netlink.AttributeDecoder) error {
+	for ad.Next() {
+		switch ad.Type() {
+		case unix.IFLA_NETKIT_MODE:
+			n.Mode = ad.Uint32()
+		case unix.IFLA_NETKIT_POLICY:
+			n.Policy = ad.Int32()
+		case unix.IFLA_NETKIT_PEER_POLICY:
+			n.PeerPolicy = ad.Int32()
+		case unix.IFLA_NETKIT_PRIMARY:
+			n.Primary = ad.Uint8() != 0
+		}
+	}
+	return nil
+}
+
+func (n *LinkNetkit) encode(ae *netlink.AttributeEncoder) error {
+	ae.Uint32(unix.IFLA_NETKIT_MODE, n.Mode)
+	ae.Int32(unix.IFLA_NETKIT_POLICY, n.Policy)
+	ae.Int32(unix.IFLA_NETKIT_PEER_POLICY, n.PeerPolicy)
+	if n.PeerInfo != nil {
+		n.PeerInfo.Family = unix.AF_UNSPEC
+		// we need to set the netkit.peerInfo.Flags and .Change according to primary link
+		// however we do not have this information here
+		b, err := n.PeerInfo.MarshalBinary()
+		if err != nil {
+			return err
+		}
+		ae.Bytes(unix.IFLA_NETKIT_PEER_INFO, b)
+	}
+	return nil
+}
+
 // LinkXDP holds Express Data Path specific information
 type LinkXDP struct {
 	FD         int32