[PATCH net-next v2] ipv4: fix validate_source for VRF setup

[PATCH net-next v2] ipv4: fix validate_source for VRF setup

[Paolo Abeni]

David reported breakages of VRF scenarios due to the
commit 6e617de84e87 ("net: avoid a full fib lookup when rp_filter is
disabled."): the local addresses based test is too strict when VRFs
are in place.

With this change we fall-back to a full lookup when custom fib rules
are in place; so that we address the VRF use case and possibly other
similar issues in non trivial setups.

v1 -> v2:
 - fix build breakage when CONFIG_IP_MULTIPLE_TABLES is not defined,
   reported by the kbuild test robot

Reported-by: David Ahern <dsahern@gmail.com>
Fixes: 6e617de84e87 ("net: avoid a full fib lookup when rp_filter is disabled.")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 net/ipv4/fib_frontend.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index f02819134ba2..f52d27a422c3 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -73,6 +73,11 @@ static int __net_init fib4_rules_init(struct net *net)
 	fib_free_table(main_table);
 	return -ENOMEM;
 }
+
+static bool fib4_has_custom_rules(struct net *net)
+{
+	return false;
+}
 #else
 
 struct fib_table *fib_new_table(struct net *net, u32 id)
@@ -128,6 +133,11 @@ struct fib_table *fib_get_table(struct net *net, u32 id)
 	}
 	return NULL;
 }
+
+static bool fib4_has_custom_rules(struct net *net)
+{
+	return net->ipv4.fib_has_custom_rules;
+}
 #endif /* CONFIG_IP_MULTIPLE_TABLES */
 
 static void fib_replace_table(struct net *net, struct fib_table *old,
@@ -405,10 +415,12 @@ int fib_validate_source(struct sk_buff *skb, __be32 src, __be32 dst,
 	    (dev->ifindex != oif || !IN_DEV_TX_REDIRECTS(idev))) {
 		if (IN_DEV_ACCEPT_LOCAL(idev))
 			goto ok;
-		/* if no local routes are added from user space we can check
-		 * for local addresses looking-up the ifaddr table
+		/* with custom local routes in place, checking local addresses
+		 * only will be too optimistic, with custom rules, checking
+		 * local addresses only can be too strict, e.g. due to vrf
 		 */
-		if (net->ipv4.fib_has_custom_local_routes)
+		if (net->ipv4.fib_has_custom_local_routes ||
+		    fib4_has_custom_rules(net))
 			goto full_check;
 		if (inet_lookup_ifaddr_rcu(net, src))
 			return -EINVAL;
-- 
2.13.6

Re: [PATCH net-next v2] ipv4: fix validate_source for VRF setup

[David Ahern]

On 10/31/17 7:32 AM, Paolo Abeni wrote:
> David reported breakages of VRF scenarios due to the
> commit 6e617de84e87 ("net: avoid a full fib lookup when rp_filter is
> disabled."): the local addresses based test is too strict when VRFs
> are in place.
> 
> With this change we fall-back to a full lookup when custom fib rules
> are in place; so that we address the VRF use case and possibly other
> similar issues in non trivial setups.
> 
> v1 -> v2:
>  - fix build breakage when CONFIG_IP_MULTIPLE_TABLES is not defined,
>    reported by the kbuild test robot
> 
> Reported-by: David Ahern <dsahern@gmail.com>
> Fixes: 6e617de84e87 ("net: avoid a full fib lookup when rp_filter is disabled.")
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> ---
>  net/ipv4/fib_frontend.c | 18 +++++++++++++++---
>  1 file changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
> index f02819134ba2..f52d27a422c3 100644
> --- a/net/ipv4/fib_frontend.c
> +++ b/net/ipv4/fib_frontend.c
> @@ -73,6 +73,11 @@ static int __net_init fib4_rules_init(struct net *net)
>  	fib_free_table(main_table);
>  	return -ENOMEM;
>  }
> +
> +static bool fib4_has_custom_rules(struct net *net)
> +{
> +	return false;
> +}
>  #else
>  
>  struct fib_table *fib_new_table(struct net *net, u32 id)
> @@ -128,6 +133,11 @@ struct fib_table *fib_get_table(struct net *net, u32 id)
>  	}
>  	return NULL;
>  }
> +
> +static bool fib4_has_custom_rules(struct net *net)
> +{
> +	return net->ipv4.fib_has_custom_rules;
> +}
>  #endif /* CONFIG_IP_MULTIPLE_TABLES */
>  
>  static void fib_replace_table(struct net *net, struct fib_table *old,
> @@ -405,10 +415,12 @@ int fib_validate_source(struct sk_buff *skb, __be32 src, __be32 dst,
>  	    (dev->ifindex != oif || !IN_DEV_TX_REDIRECTS(idev))) {
>  		if (IN_DEV_ACCEPT_LOCAL(idev))
>  			goto ok;
> -		/* if no local routes are added from user space we can check
> -		 * for local addresses looking-up the ifaddr table
> +		/* with custom local routes in place, checking local addresses
> +		 * only will be too optimistic, with custom rules, checking
> +		 * local addresses only can be too strict, e.g. due to vrf
>  		 */
> -		if (net->ipv4.fib_has_custom_local_routes)
> +		if (net->ipv4.fib_has_custom_local_routes ||
> +		    fib4_has_custom_rules(net))
>  			goto full_check;
>  		if (inet_lookup_ifaddr_rcu(net, src))
>  			return -EINVAL;
> 

That seems specific to VRF, but I can't think of a better solution. so,
Acked-by: David Ahern <dsahern@gmail.com>

Re: [PATCH net-next v2] ipv4: fix validate_source for VRF setup

[David Miller]

From: Paolo Abeni <pabeni@redhat.com>
Date: Tue, 31 Oct 2017 14:32:38 +0100

> David reported breakages of VRF scenarios due to the
> commit 6e617de84e87 ("net: avoid a full fib lookup when rp_filter is
> disabled."): the local addresses based test is too strict when VRFs
> are in place.
> 
> With this change we fall-back to a full lookup when custom fib rules
> are in place; so that we address the VRF use case and possibly other
> similar issues in non trivial setups.
> 
> v1 -> v2:
>  - fix build breakage when CONFIG_IP_MULTIPLE_TABLES is not defined,
>    reported by the kbuild test robot
> 
> Reported-by: David Ahern <dsahern@gmail.com>
> Fixes: 6e617de84e87 ("net: avoid a full fib lookup when rp_filter is disabled.")
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Applied.