net: sched: add mpls manipulation actions to TC

Currently, TC offers the ability to match on the MPLS fields of a packet
through the use of the flow_dissector_key_mpls struct. However, as yet, TC
actions do not allow the modification or manipulation of such fields.

Add a new module that registers TC action ops to allow manipulation of
MPLS. This includes the ability to push and pop headers as well as modify
the contents of new or existing headers. A further action to decrement the
TTL field of an MPLS header is also provided with a new helper added to
support this.

Examples of the usage of the new action with flower rules to push and pop
MPLS labels are:

tc filter add dev eth0 protocol ip parent ffff: flower \
    action mpls push protocol mpls_uc label 123  \
    action mirred egress redirect dev eth1

tc filter add dev eth0 protocol mpls_uc parent ffff: flower \
    action mpls pop protocol ipv4  \
    action mirred egress redirect dev eth1

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, 30 insertions, 0 deletions

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 93443a01ab39..6f1e31f674a3 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -59,6 +59,7 @@
 #include <linux/errqueue.h>
 #include <linux/prefetch.h>
 #include <linux/if_vlan.h>
+#include <linux/mpls.h>
 
 #include <net/protocol.h>
 #include <net/dst.h>
@@ -5565,6 +5566,35 @@ int skb_mpls_update_lse(struct sk_buff *skb, __be32 mpls_lse)
 EXPORT_SYMBOL_GPL(skb_mpls_update_lse);
 
 /**
+ * skb_mpls_dec_ttl() - decrement the TTL of the outermost MPLS header
+ *
+ * @skb: buffer
+ *
+ * Expects skb->data at mac header.
+ *
+ * Returns 0 on success, -errno otherwise.
+ */
+int skb_mpls_dec_ttl(struct sk_buff *skb)
+{
+	u32 lse;
+	u8 ttl;
+
+	if (unlikely(!eth_p_mpls(skb->protocol)))
+		return -EINVAL;
+
+	lse = be32_to_cpu(mpls_hdr(skb)->label_stack_entry);
+	ttl = (lse & MPLS_LS_TTL_MASK) >> MPLS_LS_TTL_SHIFT;
+	if (!--ttl)
+		return -EINVAL;
+
+	lse &= ~MPLS_LS_TTL_MASK;
+	lse |= ttl << MPLS_LS_TTL_SHIFT;
+
+	return skb_mpls_update_lse(skb, cpu_to_be32(lse));
+}
+EXPORT_SYMBOL_GPL(skb_mpls_dec_ttl);
+
+/**
  * alloc_skb_with_frags - allocate skb with page frags
  *
  * @header_len: size of linear part