Re: [PATCH net-next] net: ip6_gre: Give ERSPAN a fill_info link op of its own

[Lorenzo Bianconi <lorenzo.bianconi@redhat.com>]

> In commit c706863bc890 ("net: ip6_gre: always reports o_key to
> userspace"), ip6gre and ip6gretap tunnels started reporting a TUNNEL_KEY
> output flag even if one was not configured at the device.
> 
> When an okey-less ip6gre or ip6gretap netdevice is created, it initially
> encapsulates the packets without okey. But any configuration change
> (even a non-change such as setting TOS to an already-configured value)
> then causes the okey flag from the reported configuration to be
> circulated back to actual configuration. From that point on, the device
> encapsulates packets with output key of 0.
> 
> The intention was to implement this behavior for ERSPAN devices, not for
> all ip6gre devices. The ERSPAN netdevice should really have its own
> fill_info callback. Add one.

Hi Petr,

I was assuming erspan_ver is set just for erspan tunnels. In particular I guess
the issue is due to the default erspan_ver configuration done in
ip6gre_netlink_parms (commit 84581bdae9587).
What about adding a routine to set erspan_ver and moving it in
ip6erspan_newlink/ip6erspan_changelink? In this way erspan_ver will be
defined just for erspan tunnels.
Moreover do we have a similar issue for IFLA_GRE_ERSPAN_INDEX in
ip6gre_fill_info?

Something like:

diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index 65a4f96dc462..bb525abd860e 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -1719,6 +1719,24 @@ static int ip6erspan_tap_validate(struct nlattr *tb[], struct nlattr *data[],
 	return 0;
 }
 
+static void ip6erspan_set_version(struct nlattr *data[],
+				  struct __ip6_tnl_parm *parms)
+{
+	parms->erspan_ver = 1;
+	if (data[IFLA_GRE_ERSPAN_VER])
+		parms->erspan_ver = nla_get_u8(data[IFLA_GRE_ERSPAN_VER]);
+
+	if (parms->erspan_ver == 1) {
+		if (data[IFLA_GRE_ERSPAN_INDEX])
+			parms->index = nla_get_u32(data[IFLA_GRE_ERSPAN_INDEX]);
+	} else if (parms->erspan_ver == 2) {
+		if (data[IFLA_GRE_ERSPAN_DIR])
+			parms->dir = nla_get_u8(data[IFLA_GRE_ERSPAN_DIR]);
+		if (data[IFLA_GRE_ERSPAN_HWID])
+			parms->hwid = nla_get_u16(data[IFLA_GRE_ERSPAN_HWID]);
+	}
+}
+
 static void ip6gre_netlink_parms(struct nlattr *data[],
 				struct __ip6_tnl_parm *parms)
 {
@@ -1767,20 +1785,6 @@ static void ip6gre_netlink_parms(struct nlattr *data[],
 
 	if (data[IFLA_GRE_COLLECT_METADATA])
 		parms->collect_md = true;
-
-	parms->erspan_ver = 1;
-	if (data[IFLA_GRE_ERSPAN_VER])
-		parms->erspan_ver = nla_get_u8(data[IFLA_GRE_ERSPAN_VER]);
-
-	if (parms->erspan_ver == 1) {
-		if (data[IFLA_GRE_ERSPAN_INDEX])
-			parms->index = nla_get_u32(data[IFLA_GRE_ERSPAN_INDEX]);
-	} else if (parms->erspan_ver == 2) {
-		if (data[IFLA_GRE_ERSPAN_DIR])
-			parms->dir = nla_get_u8(data[IFLA_GRE_ERSPAN_DIR]);
-		if (data[IFLA_GRE_ERSPAN_HWID])
-			parms->hwid = nla_get_u16(data[IFLA_GRE_ERSPAN_HWID]);
-	}
 }
 
 static int ip6gre_tap_init(struct net_device *dev)
@@ -2203,6 +2207,7 @@ static int ip6erspan_newlink(struct net *src_net, struct net_device *dev,
 	int err;
 
 	ip6gre_netlink_parms(data, &nt->parms);
+	ip6erspan_set_version(data, &nt->parms);
 	ign = net_generic(net, ip6gre_net_id);
 
 	if (nt->parms.collect_md) {
@@ -2248,6 +2253,7 @@ static int ip6erspan_changelink(struct net_device *dev, struct nlattr *tb[],
 	if (IS_ERR(t))
 		return PTR_ERR(t);
 
+	ip6erspan_set_version(data, &p);
 	ip6gre_tunnel_unlink_md(ign, t);
 	ip6gre_tunnel_unlink(ign, t);
 	ip6erspan_tnl_change(t, &p, !tb[IFLA_MTU]);

Does it fix reported issue?

Regards,
Lorenzo

> 
> Fixes: c706863bc890 ("net: ip6_gre: always reports o_key to userspace")
> CC: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
> Signed-off-by: Petr Machata <petrm@mellanox.com>
> ---
>  net/ipv6/ip6_gre.c | 31 ++++++++++++++++++++++++-------
>  1 file changed, 24 insertions(+), 7 deletions(-)
> 
> diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
> index 65a4f96dc462..0a6087cffe54 100644
> --- a/net/ipv6/ip6_gre.c
> +++ b/net/ipv6/ip6_gre.c
> @@ -2094,15 +2094,13 @@ static size_t ip6gre_get_size(const struct net_device *dev)
>  		0;
>  }
>  
> -static int ip6gre_fill_info(struct sk_buff *skb, const struct net_device *dev)
> +static int __ip6gre_fill_info(struct sk_buff *skb,
> +			      const struct net_device *dev,
> +			      __be16 base_o_flags)
>  {
>  	struct ip6_tnl *t = netdev_priv(dev);
>  	struct __ip6_tnl_parm *p = &t->parms;
> -	__be16 o_flags = p->o_flags;
> -
> -	if ((p->erspan_ver == 1 || p->erspan_ver == 2) &&
> -	    !p->collect_md)
> -		o_flags |= TUNNEL_KEY;
> +	__be16 o_flags = p->o_flags | base_o_flags;
>  
>  	if (nla_put_u32(skb, IFLA_GRE_LINK, p->link) ||
>  	    nla_put_be16(skb, IFLA_GRE_IFLAGS,
> @@ -2155,6 +2153,11 @@ static int ip6gre_fill_info(struct sk_buff *skb, const struct net_device *dev)
>  	return -EMSGSIZE;
>  }
>  
> +static int ip6gre_fill_info(struct sk_buff *skb, const struct net_device *dev)
> +{
> +	return __ip6gre_fill_info(skb, dev, 0);
> +}
> +
>  static const struct nla_policy ip6gre_policy[IFLA_GRE_MAX + 1] = {
>  	[IFLA_GRE_LINK]        = { .type = NLA_U32 },
>  	[IFLA_GRE_IFLAGS]      = { .type = NLA_U16 },
> @@ -2256,6 +2259,20 @@ static int ip6erspan_changelink(struct net_device *dev, struct nlattr *tb[],
>  	return 0;
>  }
>  
> +static int ip6erspan_fill_info(struct sk_buff *skb,
> +			       const struct net_device *dev)
> +{
> +	struct ip6_tnl *t = netdev_priv(dev);
> +	struct __ip6_tnl_parm *p = &t->parms;
> +	__be16 base_o_flags = 0;
> +
> +	if ((p->erspan_ver == 1 || p->erspan_ver == 2) &&
> +	    !p->collect_md)
> +		base_o_flags |= TUNNEL_KEY;
> +
> +	return __ip6gre_fill_info(skb, dev, base_o_flags);
> +}
> +
>  static struct rtnl_link_ops ip6gre_link_ops __read_mostly = {
>  	.kind		= "ip6gre",
>  	.maxtype	= IFLA_GRE_MAX,
> @@ -2295,7 +2312,7 @@ static struct rtnl_link_ops ip6erspan_tap_ops __read_mostly = {
>  	.newlink	= ip6erspan_newlink,
>  	.changelink	= ip6erspan_changelink,
>  	.get_size	= ip6gre_get_size,
> -	.fill_info	= ip6gre_fill_info,
> +	.fill_info	= ip6erspan_fill_info,
>  	.get_link_net	= ip6_tnl_get_link_net,
>  };
>  
> -- 
> 2.4.11
>