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Message-ID: <9974090c-5124-b3a1-1290-ac9efc4569c4@gmail.com> Date: Mon, 13 May 2019 09:07:48 -0600 From: David Ahern <dsahern@...il.com> To: Sabrina Dubroca <sd@...asysnail.net>, netdev@...r.kernel.org Cc: Dan Winship <danw@...hat.com>, Nicolas Dichtel <nicolas.dichtel@...nd.com> Subject: Re: [PATCH net v2] rtnetlink: always put ILFA_LINK for links with a link-netnsid On 5/13/19 7:47 AM, Sabrina Dubroca wrote: > 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. > > Analyzed-by: Dan Winship <danw@...hat.com> > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Signed-off-by: Sabrina Dubroca <sd@...asysnail.net> > Acked-by: Nicolas Dichtel <nicolas.dichtel@...nd.com> > --- > v2: change Fixes tag, it's been here forever as Nicolas said, and add his Ack > > net/core/rtnetlink.c | 16 ++++++++++------ > 1 file changed, 10 insertions(+), 6 deletions(-) > > diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c > index 2bd12afb9297..adcc045952c2 100644 > --- a/net/core/rtnetlink.c > +++ b/net/core/rtnetlink.c > @@ -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 nla_put_u32(skb, IFLA_LINK, ifindex); > + return 0; > } > > static noinline_for_stack int nla_put_ifalias(struct sk_buff *skb, why not always adding the attribute?
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