Commit feadc4b6 authored by Sabrina Dubroca's avatar Sabrina Dubroca Committed by David S. Miller
Browse files

rtnetlink: always put IFLA_LINK for links with a link-netnsid 



Currently, nla_put_iflink() doesn't put the IFLA_LINK attribute when
iflink == ifindex.

In some cases, a device can be created in a different netns with the
same ifindex as its parent. That device will not dump its IFLA_LINK
attribute, which can confuse some userspace software that expects it.
For example, if the last ifindex created in init_net and foo are both
8, these commands will trigger the issue:

    ip link add parent type dummy                   # ifindex 9
    ip link add link parent netns foo type macvlan  # ifindex 9 in ns foo

So, in case a device puts the IFLA_LINK_NETNSID attribute in a dump,
always put the IFLA_LINK attribute as well.

Thanks to Dan Winship for analyzing the original OpenShift bug down to
the missing netlink attribute.

v2: change Fixes tag, it's been here forever, as Nicolas Dichtel said
    add Nicolas' ack
v3: change Fixes tag
    fix subject typo, spotted by Edward Cree

Analyzed-by: default avatarDan Winship <danw@redhat.com>
Fixes: d8a5ec67 ("[NET]: netlink support for moving devices between network namespaces.")
Signed-off-by: default avatarSabrina Dubroca <sd@queasysnail.net>
Acked-by: default avatarNicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 00f9fec4

net/core/rtnetlink.c

+10 −6
Original line number Diff line number Diff line
@@ -1496,14 +1496,15 @@ static int put_master_ifindex(struct sk_buff *skb, struct net_device *dev) 
	return ret;

}



static int nla_put_iflink(struct sk_buff *skb, const struct net_device *dev)

static int nla_put_iflink(struct sk_buff *skb, const struct net_device *dev,

			  bool force)

{

	int ifindex = dev_get_iflink(dev);



	if (dev->ifindex == ifindex)

		return 0;



	if (force || dev->ifindex != ifindex)

		return nla_put_u32(skb, IFLA_LINK, ifindex);



	return 0;

}



static noinline_for_stack int nla_put_ifalias(struct sk_buff *skb,
@@ -1520,6 +1521,8 @@ static int rtnl_fill_link_netnsid(struct sk_buff *skb, 
				  const struct net_device *dev,

				  struct net *src_net)

{

	bool put_iflink = false;



	if (dev->rtnl_link_ops && dev->rtnl_link_ops->get_link_net) {

		struct net *link_net = dev->rtnl_link_ops->get_link_net(dev);
@@ -1528,10 +1531,12 @@ static int rtnl_fill_link_netnsid(struct sk_buff *skb, 


			if (nla_put_s32(skb, IFLA_LINK_NETNSID, id))

				return -EMSGSIZE;



			put_iflink = true;

		}

	}



	return 0;

	return nla_put_iflink(skb, dev, put_iflink);

}



static int rtnl_fill_link_af(struct sk_buff *skb,
@@ -1617,7 +1622,6 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, 
#ifdef CONFIG_RPS

	    nla_put_u32(skb, IFLA_NUM_RX_QUEUES, dev->num_rx_queues) ||

#endif

	    nla_put_iflink(skb, dev) ||

	    put_master_ifindex(skb, dev) ||

	    nla_put_u8(skb, IFLA_CARRIER, netif_carrier_ok(dev)) ||

	    (dev->qdisc &&

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