Subject: Re: [PATCH net] vxlan: Fix regression when dropping packets due to invalid src addresses

From: Ido Schimmel <[email-masked]>
Date: Sun, 2 Jun 2024 11:37:53 +0300

On Fri, May 31, 2024 at 05:41:37PM +0200, Daniel Borkmann wrote:
> diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c
> index f78dd0438843..7353f27b02dc 100644
> --- a/drivers/net/vxlan/vxlan_core.c
> +++ b/drivers/net/vxlan/vxlan_core.c
> @@ -1605,6 +1605,7 @@ static bool vxlan_set_mac(struct vxlan_dev *vxlan,
>  			  struct vxlan_sock *vs,
>  			  struct sk_buff *skb, __be32 vni)
>  {
> +	bool learning = vxlan->cfg.flags & VXLAN_F_LEARN;
>  	union vxlan_addr saddr;
>  	u32 ifindex = skb->dev->ifindex;
>  
> @@ -1616,8 +1617,11 @@ static bool vxlan_set_mac(struct vxlan_dev *vxlan,
>  	if (ether_addr_equal(eth_hdr(skb)->h_source, vxlan->dev->dev_addr))
>  		return false;
>  
> -	/* Ignore packets from invalid src-address */
> -	if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
> +	/* Ignore packets from invalid src-address when in learning mode,
> +	 * otherwise let them through e.g. when originating from NOARP
> +	 * devices with all-zero mac, etc.
> +	 */
> +	if (learning && !is_valid_ether_addr(eth_hdr(skb)->h_source))
>  		return false;
>  
>  	/* Get address from the outer IP header */
> @@ -1631,7 +1635,7 @@ static bool vxlan_set_mac(struct vxlan_dev *vxlan,
>  #endif
>  	}
>  
> -	if ((vxlan->cfg.flags & VXLAN_F_LEARN) &&
> +	if (learning &&
>  	    vxlan_snoop(skb->dev, &saddr, eth_hdr(skb)->h_source, ifindex, vni))
>  		return false;

Daniel, I think we can simply move this check out of the main path to
vxlan_snoop() which is only called when learning is enabled:

diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c
index 7496c14e8329..89f3945b448f 100644
--- a/drivers/net/vxlan/vxlan_core.c
+++ b/drivers/net/vxlan/vxlan_core.c
@@ -1446,6 +1446,10 @@ static bool vxlan_snoop(struct net_device *dev,
        struct vxlan_fdb *f;
        u32 ifindex = 0;
 
+       /* Ignore packets from invalid src-address */
+       if (!is_valid_ether_addr(src_mac))
+               return true;
+
 #if IS_ENABLED(CONFIG_IPV6)
        if (src_ip->sa.sa_family == AF_INET6 &&
            (ipv6_addr_type(&src_ip->sin6.sin6_addr) & IPV6_ADDR_LINKLOCAL))
@@ -1616,10 +1620,6 @@ static bool vxlan_set_mac(struct vxlan_dev *vxlan,
        if (ether_addr_equal(eth_hdr(skb)->h_source, vxlan->dev->dev_addr))
                return false;
 
-       /* Ignore packets from invalid src-address */
-       if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
-               return false;
-
        /* Get address from the outer IP header */
        if (vxlan_get_sk_family(vs) == AF_INET) {
                saddr.sin.sin_addr.s_addr = ip_hdr(skb)->saddr;

WDYT?