Re: [PATCH net,v2] vrf: check forwarding on the original netdevice when generating ICMP dest unreachable

The concern only applies when the skb->dev is an l3mdev master, right?
After I sent v2, I'm worried that rt shouldn't be derefrenced if
in_dev is NULL. Even though I think it should be ok, it's better to
keep the original execution order. So, how about this before I put
another patch? The net for the iif is derived from skb->dev.

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index a4f44d8..9a29225 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c

@@ -930,14 +930,23 @@ void ip_rt_send_redirect(struct sk_buff *skb)

 static int ip_error(struct sk_buff *skb)
 {
-       struct in_device *in_dev = __in_dev_get_rcu(skb->dev);
        struct rtable *rt = skb_rtable(skb);
+       struct net_device *dev = skb->dev;
+       struct in_device *in_dev;
        struct inet_peer *peer;
        unsigned long now;
        struct net *net;
        bool send;
        int code;

+       if (netif_is_l3_master(skb->dev)) {
+               dev = __dev_get_by_index(dev_net(skb->dev), IPCB(skb)->iif);
+               if (!dev)
+                       goto out;
+       }
+
+       in_dev = __in_dev_get_rcu(dev);
+
        /* IP on this device is disabled. */
        if (!in_dev)
                goto out;

On Wed, Feb 28, 2018 at 10:49 AM, David Ahern [off-list ref] wrote:

On 2/28/18 7:46 AM, Stephen Suryaputra wrote:

quoted

When ip_error() is called the device is the l3mdev master instead of the
original device. So the forwarding check should be on the original one.

Changes from v1:
- Only need to reset the device on which __in_dev_get_rcu() is done (per
  David Ahern).

Signed-off-by: Stephen Suryaputra <redacted>
---
 net/ipv4/route.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index a4f44d8..89c020f 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c

@@ -930,19 +930,26 @@ void ip_rt_send_redirect(struct sk_buff *skb)

 static int ip_error(struct sk_buff *skb)
 {
-     struct in_device *in_dev = __in_dev_get_rcu(skb->dev);
      struct rtable *rt = skb_rtable(skb);
+     struct net_device *dev = skb->dev;
+     struct in_device *in_dev;
      struct inet_peer *peer;
      unsigned long now;
      struct net *net;
      bool send;
      int code;

+     net = dev_net(rt->dst.dev);
+
+     if (netif_is_l3_master(skb->dev))
+             dev = __dev_get_by_index(net, IPCB(skb)->iif);

Do need to handle the device disappearing.
if (!dev)
        goto out;

quoted

+
+     in_dev = __in_dev_get_rcu(dev);
+
      /* IP on this device is disabled. */
      if (!in_dev)
              goto out;

-     net = dev_net(rt->dst.dev);
      if (!IN_DEV_FORWARD(in_dev)) {
              switch (rt->dst.error) {
              case EHOSTUNREACH: