[PATCH net-next v7 3/5] net: core: add MPLS update core helper and use in OvS

[John Hurley]

Open vSwitch allows the updating of an existing MPLS header on a packet.
In preparation for supporting similar functionality in TC, move this to a
common skb helper function.

Signed-off-by: John Hurley <john.hur...@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicin...@netronome.com>
Reviewed-by: Simon Horman <simon.hor...@netronome.com>
Reviewed-by: Willem de Bruijn <will...@google.com>
Acked-by: Cong Wang <xiyou.wangc...@gmail.com>
---
 include/linux/skbuff.h    |  1 +
 net/core/skbuff.c         | 33 +++++++++++++++++++++++++++++++++
 net/openvswitch/actions.c | 13 +++----------
 3 files changed, 37 insertions(+), 10 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 88b34fe..dc07f00 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -3448,6 +3448,7 @@ int skb_vlan_pop(struct sk_buff *skb);
 int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci);
 int skb_mpls_push(struct sk_buff *skb, __be32 mpls_lse, __be16 mpls_proto);
 int skb_mpls_pop(struct sk_buff *skb, __be16 next_proto);
+int skb_mpls_update_lse(struct sk_buff *skb, __be32 mpls_lse);
 struct sk_buff *pskb_extract(struct sk_buff *skb, int off, int to_copy,
                             gfp_t gfp);
 
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index ce30989..46da15c 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -5433,6 +5433,39 @@ int skb_mpls_pop(struct sk_buff *skb, __be16 next_proto)
 EXPORT_SYMBOL_GPL(skb_mpls_pop);
 
 /**
+ * skb_mpls_update_lse() - modify outermost MPLS header and update csum
+ *
+ * @skb: buffer
+ * @mpls_lse: new MPLS label stack entry to update to
+ *
+ * Expects skb->data at mac header.
+ *
+ * Returns 0 on success, -errno otherwise.
+ */
+int skb_mpls_update_lse(struct sk_buff *skb, __be32 mpls_lse)
+{
+       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;
+
+       if (skb->ip_summed == CHECKSUM_COMPLETE) {
+               __be32 diff[] = { ~mpls_hdr(skb)->label_stack_entry, mpls_lse };
+
+               skb->csum = csum_partial((char *)diff, sizeof(diff), skb->csum);
+       }
+
+       mpls_hdr(skb)->label_stack_entry = mpls_lse;
+
+       return 0;
+}
+EXPORT_SYMBOL_GPL(skb_mpls_update_lse);
+
+/**
  * alloc_skb_with_frags - allocate skb with page frags
  *
  * @header_len: size of linear part
diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
index 62715bb..3572e11 100644
--- a/net/openvswitch/actions.c
+++ b/net/openvswitch/actions.c
@@ -193,19 +193,12 @@ static int set_mpls(struct sk_buff *skb, struct 
sw_flow_key *flow_key,
        __be32 lse;
        int err;
 
-       err = skb_ensure_writable(skb, skb->mac_len + MPLS_HLEN);
-       if (unlikely(err))
-               return err;
-
        stack = mpls_hdr(skb);
        lse = OVS_MASKED(stack->label_stack_entry, *mpls_lse, *mask);
-       if (skb->ip_summed == CHECKSUM_COMPLETE) {
-               __be32 diff[] = { ~(stack->label_stack_entry), lse };
-
-               skb->csum = csum_partial((char *)diff, sizeof(diff), skb->csum);
-       }
+       err = skb_mpls_update_lse(skb, lse);
+       if (err)
+               return err;
 
-       stack->label_stack_entry = lse;
        flow_key->mpls.top_lse = lse;
        return 0;
 }
-- 
2.7.4