Re: VRF destination unreachable

On 2/23/18 10:49 AM, Stephen Suryaputra wrote:

Greetings,

We found that ICMP destination unreachable isn't sent if VRF
forwarding isn't configured, i.e.
/proc/sys/net/ipv4/conf/<vrf_net_device>/forwarding isn't set. The
relevant code is:

static int ip_error(struct sk_buff *skb)
{
...
        // in_dev is the vrf net_device
        if (!IN_DEV_FORWARD(in_dev)) {
                switch (rt->dst.error) {
                case EHOSTUNREACH:
                        __IP_INC_STATS(net, IPSTATS_MIB_INADDRERRORS);
                        break;

                case ENETUNREACH:
                        __IP_INC_STATS(net, IPSTATS_MIB_INNOROUTES);
                        break;
                }
                goto out;
        }
...
out:    kfree_skb(skb);
        return 0;
}

The question: is it intended to be set? The basic forwarding seems to
be working without. We do set it on the slave net devices.

Unintended side effect of VRF as a netdev. This should fix it:

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 5ca7415cd48c..d59d005fb7c5 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c

@@ -944,7 +944,7 @@ static int ip_error(struct sk_buff *skb)
                goto out;

        net = dev_net(rt->dst.dev);
-       if (!IN_DEV_FORWARD(in_dev)) {
+       if (!IN_DEV_FORWARD(in_dev) && !netif_is_l3_master(skb->dev)) {
                switch (rt->dst.error) {
                case EHOSTUNREACH:
                        __IP_INC_STATS(net, IPSTATS_MIB_INADDRERRORS);