parseIptunData caused index out of range panic

[AirbornWdd]

The ip link command dump:

13: tunl0@NONE: <NOARP> mtu 1480 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ipip 0.0.0.0 brd 0.0.0.0
14: ipip0@NONE: <NOARP,UP,LOWER_UP> mtu 1480 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/ipip 0.0.0.0 brd 0.0.0.0
15: ip6tnl0@NONE: <NOARP> mtu 1452 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/tunnel6 :: brd ::
16: ipip60@NONE: <NOARP,UP,LOWER_UP> mtu 1452 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/tunnel6 :: brd ::

The panic backtrace are:

panic: runtime error: index out of range

 github.com/vishvananda/netlink.parseIptunData(0xcc4b40, 0xc000214580, 0xc00028ee00, 0xd, 0x10)
         /go/src/github.com/vishvananda/netlink/link_linux.go:2580 +0x2c1
 github.com/vishvananda/netlink.LinkDeserialize(0x0, 0xc00028497c, 0x590, 0x113c, 0x9, 0xc00028c700, 0x8, 0x10)
         /go/src/github.com/vishvananda/netlink/link_linux.go:1608 +0x1482
 github.com/vishvananda/netlink.(*Handle).LinkList(0x1359fd0, 0xbff8b3, 0x9, 0x21a, 0xc000034f70, 0xc000034f00)
         /go/src/github.com/vishvananda/netlink/link_linux.go:1813 +0x2e6
 github.com/vishvananda/netlink.LinkList(...)
         /go/src/github.com/vishvananda/netlink/link_linux.go:1791

[AirbornWdd]

dlv dumps:

(dlv) bt
 0  0x00000000009772c3 in github.com/vishvananda/netlink.parseIptunData
    at /go/src/github.com/vishvananda/netlink/link_linux.go:2557
 1  0x000000000096b7e2 in github.com/vishvananda/netlink.LinkDeserialize
    at /go/src/github.com/vishvananda/netlink/link_linux.go:1608
 2  0x000000000096de96 in github.com/vishvananda/netlink.(*Handle).LinkList
    at /go/src/github.com/vishvananda/netlink/link_linux.go:1813
 3  0x00000000009b97e7 in github.com/vishvananda/netlink.LinkList
    at /go/src/github.com/vishvananda/netlink/link_linux.go:1791
…………
 8  0x00000000009da72b in main.main
    at /go/src/xlb/main.go:53
 9  0x00000000004fdb1c in runtime.main
    at /usr/local/go/src/runtime/proc.go:200
10  0x000000000052b3a1 in runtime.goexit
    at /usr/local/go/src/runtime/asm_amd64.s:1337
(dlv) locals
attrs = (unreadable read out of bounds)
(err) = (unreadable could not find loclist entry at 0x35ffdb for address 0x96b7e2)
base = github.com/vishvananda/netlink.LinkAttrs {Index: 14, MTU: 1480, TxQLen: 1000,...+22 more}
link = github.com/vishvananda/netlink.Link(*github.com/vishvananda/netlink.Iptun) 0xbeef0008
stats32 = (unreadable could not find loclist entry at 0x35fb09 for address 0x96b7e2)
stats64 = ("*github.com/vishvananda/netlink.LinkStatistics64")(0xc00026ed80)
linkType = "ipip"
linkSlave = github.com/vishvananda/netlink.LinkSlave nil
slaveType = ""
infos = (unreadable empty OP stack)
(err) = (unreadable could not find loclist entry at 0x36017b for address 0x96b7e2)
data = []syscall.NetlinkRouteAttr len: 13, cap: 16, [...]
err = (unreadable could not find loclist entry at 0x3602c3 for address 0x96b7e2)
(dlv) p data[12]
syscall.NetlinkRouteAttr {
        Attr: syscall.RtAttr {Len: 4, Type: 19},
        Value: []uint8 len: 0, cap: 3756, [],}
(dlv) p link
github.com/vishvananda/netlink.Link(*github.com/vishvananda/netlink.Iptun) *{
        LinkAttrs: github.com/vishvananda/netlink.LinkAttrs {
                Index: 0,
                MTU: 0,
                TxQLen: 0,
                Name: "",
                HardwareAddr: net.HardwareAddr len: 0, cap: 0, nil,
                Flags: 0,
                RawFlags: 0,
                ParentIndex: 0,
                MasterIndex: 0,
                Namespace: interface {} nil,
                Alias: "",
                Statistics: *github.com/vishvananda/netlink.LinkStatistics nil,
                Promisc: 0,
                Xdp: *github.com/vishvananda/netlink.LinkXdp nil,
                EncapType: "",
                Protinfo: *github.com/vishvananda/netlink.Protinfo nil,
                OperState: 0,
                NetNsID: 0,
                NumTxQueues: 0,
                NumRxQueues: 0,
                GSOMaxSize: 0,
                GSOMaxSegs: 0,
                Vfs: []github.com/vishvananda/netlink.VfInfo len: 0, cap: 0, nil,
                Group: 0,
                Slave: github.com/vishvananda/netlink.LinkSlave nil,},
        Ttl: 0,
        Tos: 0,
        PMtuDisc: 0,
        Link: 0,
        Local: net.IP len: 0, cap: 0, nil,
        Remote: net.IP len: 0, cap: 0, nil,
        EncapSport: 0,
        EncapDport: 0,
        EncapType: 0,
        EncapFlags: 0,
        FlowBased: false,}
(dlv)

[vishvananda]

Looks like

netlink/link_linux.go

Line 2580 in ec20eb4

iptun.FlowBased = int8(datum.Value[0]) != 0

can have an empty value. I guess that line should be wrapped in a:
if len(datum.Value) != 0

[AirbornWdd]

Looks like

netlink/link_linux.go

Line 2580 in ec20eb4

iptun.FlowBased = int8(datum.Value[0]) != 0

can have an empty value. I guess that line should be wrapped in a:
if len(datum.Value) != 0

Not only vxlan interface has the issue, all tunnel interface should be checked. Is this OK ?

diff --git a/link_linux.go b/link_linux.go
index 72eb13d..4dd4c0f 100644
--- a/link_linux.go
+++ b/link_linux.go
@@ -2561,6 +2561,9 @@ func addIptunAttrs(iptun *Iptun, linkInfo *nl.RtAttr) {
 func parseIptunData(link Link, data []syscall.NetlinkRouteAttr) {
        iptun := link.(*Iptun)
        for _, datum := range data {
+               if len(datum.Value) == 0 {
+                       continue
+               }
                switch datum.Attr.Type {
                case nl.IFLA_IPTUN_LOCAL:
                        iptun.Local = net.IP(datum.Value[0:4])

[vishvananda]

This looks fine. Did you want to propose a change? Or shall i do it

[AirbornWdd]

This looks fine. Did you want to propose a change? Or shall i do it

I think you can do it. ;-)