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Message-ID: <83ffac16-f03a-acd7-815a-0b952c0ef951@6wind.com> Date: Mon, 13 May 2019 17:18:28 +0200 From: Nicolas Dichtel <nicolas.dichtel@...nd.com> To: David Ahern <dsahern@...il.com>, Sabrina Dubroca <sd@...asysnail.net>, netdev@...r.kernel.org Cc: Dan Winship <danw@...hat.com> Subject: Re: [PATCH net v2] rtnetlink: always put ILFA_LINK for links with a link-netnsid Le 13/05/2019 à 17:07, David Ahern a écrit : > 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? > Adding this attribute may change the output of 'ip link'. See this patch for example: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=95ec655bc465 Nicolas
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