netdev - Re: [PATCH net-next v2] bonding: Always assign be16 value to vlan

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Date: Thu, 11 May 2023 16:43:57 -0700
From: Jay Vosburgh <jay.vosburgh@...onical.com>
To: Simon Horman <horms@...nel.org>
cc: Jakub Kicinski <kuba@...nel.org>,
    "David S. Miller" <davem@...emloft.net>,
    Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
    Andy Gospodarek <andy@...yhouse.net>,
    Vladimir Oltean <olteanv@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v2] bonding: Always assign be16 value to vlan_proto

Simon Horman <horms@...nel.org> wrote:

>The type of the vlan_proto field is __be16.
>And most users of the field use it as such.
>
>In the case of setting or testing the field for the special VLAN_N_VID
>value, host byte order is used. Which seems incorrect.
>
>It also seems somewhat odd to store a VLAN ID value in a field that is
>otherwise used to store Ether types.
>
>Address this issue by defining BOND_VLAN_PROTO_NONE, a big endian value.
>0xffff was chosen somewhat arbitrarily. What is important is that it
>doesn't overlap with any valid VLAN Ether types.

As I think you mentioned, 0xffff is marked as a reserved ethertype.

>I don't believe the problems described above are a bug because
>VLAN_N_VID in both little-endian and big-endian byte order does not
>conflict with any supported VLAN Ether types in big-endian byte order.
>
>Reported by sparse as:
>
> .../bond_main.c:2857:26: warning: restricted __be16 degrades to integer
> .../bond_main.c:2863:20: warning: restricted __be16 degrades to integer
> .../bond_main.c:2939:40: warning: incorrect type in assignment (different base types)
> .../bond_main.c:2939:40:    expected restricted __be16 [usertype] vlan_proto
> .../bond_main.c:2939:40:    got int
>
>No functional changes intended.
>Compile tested only.
>
>Signed-off-by: Simon Horman <horms@...nel.org>

Acked-by: Jay Vosburgh <jay.vosburgh@...onical.com>

	-J

>---
>Changes in v2:
>- Decribe Ether Type aspect of problem in patch description
>- Use an Ether Type rather than VID valie as sential
>- Link to v1: https://lore.kernel.org/r/20230420-bonding-be-vlan-proto-v1-1-754399f51d01@kernel.org
>---
> drivers/net/bonding/bond_main.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
>diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>index 3fed888629f7..ebf61c19dcef 100644
>--- a/drivers/net/bonding/bond_main.c
>+++ b/drivers/net/bonding/bond_main.c
>@@ -2871,6 +2871,8 @@ static bool bond_has_this_ip(struct bonding *bond, __be32 ip)
> 	return ret;
> }
> 
>+#define BOND_VLAN_PROTO_NONE cpu_to_be16(0xffff)
>+
> static bool bond_handle_vlan(struct slave *slave, struct bond_vlan_tag *tags,
> 			     struct sk_buff *skb)
> {
>@@ -2878,13 +2880,13 @@ static bool bond_handle_vlan(struct slave *slave, struct bond_vlan_tag *tags,
> 	struct net_device *slave_dev = slave->dev;
> 	struct bond_vlan_tag *outer_tag = tags;
> 
>-	if (!tags || tags->vlan_proto == VLAN_N_VID)
>+	if (!tags || tags->vlan_proto == BOND_VLAN_PROTO_NONE)
> 		return true;
> 
> 	tags++;
> 
> 	/* Go through all the tags backwards and add them to the packet */
>-	while (tags->vlan_proto != VLAN_N_VID) {
>+	while (tags->vlan_proto != BOND_VLAN_PROTO_NONE) {
> 		if (!tags->vlan_id) {
> 			tags++;
> 			continue;
>@@ -2960,7 +2962,7 @@ struct bond_vlan_tag *bond_verify_device_path(struct net_device *start_dev,
> 		tags = kcalloc(level + 1, sizeof(*tags), GFP_ATOMIC);
> 		if (!tags)
> 			return ERR_PTR(-ENOMEM);
>-		tags[level].vlan_proto = VLAN_N_VID;
>+		tags[level].vlan_proto = BOND_VLAN_PROTO_NONE;
> 		return tags;
> 	}
> 
>
>

---
	-Jay Vosburgh, jay.vosburgh@...onical.com