Merge branch 'vlan_get_protocol'

Toshiaki Makita says:

====================
Fix checksum error when using stacked vlan

When I was testing 802.1ad, I found several drivers don't take into
account 802.1ad or multiple vlans when retrieving L3 (IP/IPv6) or
L4 (TCP/UDP) protocol for checksum offload.

It is mainly due to vlan_get_protocol(), which extracts ether type only
when it is tagged with single 802.1Q. When 802.1ad is used or there are
multiple vlans, it extracts vlan protocol and drivers cannot determine
which L3/L4 protocol is used.

Those drivers, most of which have IP_CSUM/IPV6_CSUM features, get L3/L4
header-offset by software, so it seems that their checksum offload works
with multiple vlans if we can parse protocols correctly.
(They know mac header length, and probably don't care about what is in it.)

And another thing, some of Intel's drivers seem to use skb->protocol where
vlan_get_protocol() is more suitable.

I tested that at least igb/igbvf on I350 works with this patch set.

Note:
We can hand a double tagged packet with CHECKSUM_PARTIAL to a HW driver
by creating a vlan device on a bridge device and enabling vlan_filtering
of the bridge with 802.1ad protocol.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 46 insertions, 14 deletions

diff --git a/include/linux/if_vlan.h b/include/linux/if_vlan.h
index 515a35e2a48a..960e666c51e4 100644
--- a/include/linux/if_vlan.h
+++ b/include/linux/if_vlan.h
@@ -472,27 +472,59 @@ static inline int vlan_get_tag(const struct sk_buff *skb, u16 *vlan_tci)
 /**
  * vlan_get_protocol - get protocol EtherType.
  * @skb: skbuff to query
+ * @type: first vlan protocol
+ * @depth: buffer to store length of eth and vlan tags in bytes
  *
  * Returns the EtherType of the packet, regardless of whether it is
  * vlan encapsulated (normal or hardware accelerated) or not.
  */
-static inline __be16 vlan_get_protocol(const struct sk_buff *skb)
+static inline __be16 __vlan_get_protocol(struct sk_buff *skb, __be16 type,
+                                         int *depth)
 {
-        __be16 protocol = 0;
-
-        if (vlan_tx_tag_present(skb) ||
-             skb->protocol != cpu_to_be16(ETH_P_8021Q))
-                protocol = skb->protocol;
-        else {
-                __be16 proto, *protop;
-                protop = skb_header_pointer(skb, offsetof(struct vlan_ethhdr,
-                                                h_vlan_encapsulated_proto),
-                                                sizeof(proto), &proto);
-                if (likely(protop))
-                        protocol = *protop;
+        unsigned int vlan_depth = skb->mac_len;
+
+        /* if type is 802.1Q/AD then the header should already be
+         * present at mac_len - VLAN_HLEN (if mac_len > 0), or at
+         * ETH_HLEN otherwise
+         */
+        if (type == htons(ETH_P_8021Q) || type == htons(ETH_P_8021AD)) {
+                if (vlan_depth) {
+                        if (WARN_ON(vlan_depth < VLAN_HLEN))
+                                return 0;
+                        vlan_depth -= VLAN_HLEN;
+                } else {
+                        vlan_depth = ETH_HLEN;
+                }
+                do {
+                        struct vlan_hdr *vh;
+
+                        if (unlikely(!pskb_may_pull(skb,
+                                                    vlan_depth + VLAN_HLEN)))
+                                return 0;
+
+                        vh = (struct vlan_hdr *)(skb->data + vlan_depth);
+                        type = vh->h_vlan_encapsulated_proto;
+                        vlan_depth += VLAN_HLEN;
+                } while (type == htons(ETH_P_8021Q) ||
+                         type == htons(ETH_P_8021AD));
         }
 
-        return protocol;
+        if (depth)
+                *depth = vlan_depth;
+
+        return type;
+}
+
+/**
+ * vlan_get_protocol - get protocol EtherType.
+ * @skb: skbuff to query
+ *
+ * Returns the EtherType of the packet, regardless of whether it is
+ * vlan encapsulated (normal or hardware accelerated) or not.
+ */
+static inline __be16 vlan_get_protocol(struct sk_buff *skb)
+{
+        return __vlan_get_protocol(skb, skb->protocol, NULL);
 }
 
 static inline void vlan_set_encap_proto(struct sk_buff *skb,