net: core: move pop MPLS functionality from OvS to core helper

Open vSwitch provides code to pop an MPLS header to a packet. In
preparation for supporting this in TC, move the pop code to an skb helper
that can be reused.

Remove the, now unused, update_ethertype static function from OvS.

Signed-off-by: John Hurley <john.hurley@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 42 insertions, 0 deletions

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 495fd743a935..8c00be4d8919 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -5490,6 +5490,48 @@ int skb_mpls_push(struct sk_buff *skb, __be32 mpls_lse, __be16 mpls_proto)
 EXPORT_SYMBOL_GPL(skb_mpls_push);
 
 /**
+ * skb_mpls_pop() - pop the outermost MPLS header
+ *
+ * @skb: buffer
+ * @next_proto: ethertype of header after popped MPLS header
+ *
+ * Expects skb->data at mac header.
+ *
+ * Returns 0 on success, -errno otherwise.
+ */
+int skb_mpls_pop(struct sk_buff *skb, __be16 next_proto)
+{
+	int err;
+
+	if (unlikely(!eth_p_mpls(skb->protocol)))
+		return -EINVAL;
+
+	err = skb_ensure_writable(skb, skb->mac_len + MPLS_HLEN);
+	if (unlikely(err))
+		return err;
+
+	skb_postpull_rcsum(skb, mpls_hdr(skb), MPLS_HLEN);
+	memmove(skb_mac_header(skb) + MPLS_HLEN, skb_mac_header(skb),
+		skb->mac_len);
+
+	__skb_pull(skb, MPLS_HLEN);
+	skb_reset_mac_header(skb);
+	skb_set_network_header(skb, skb->mac_len);
+
+	if (skb->dev && skb->dev->type == ARPHRD_ETHER) {
+		struct ethhdr *hdr;
+
+		/* use mpls_hdr() to get ethertype to account for VLANs. */
+		hdr = (struct ethhdr *)((void *)mpls_hdr(skb) - ETH_HLEN);
+		skb_mod_eth_type(skb, hdr, next_proto);
+	}
+	skb->protocol = next_proto;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(skb_mpls_pop);
+
+/**
  * alloc_skb_with_frags - allocate skb with page frags
  *
  * @header_len: size of linear part