flow_dissector: introduce programable flow_dissector

Introduce dissector infrastructure which allows user to specify which
parts of skb he wants to dissect.

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 48 insertions, 0 deletions

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index d885e282908e..6883e22b8fc4 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -1,3 +1,4 @@
+#include <linux/kernel.h>
 #include <linux/skbuff.h>
 #include <linux/export.h>
 #include <linux/ip.h>
@@ -15,6 +16,53 @@
 #include <net/flow_dissector.h>
 #include <scsi/fc/fc_fcoe.h>
 
+static bool skb_flow_dissector_uses_key(struct flow_dissector *flow_dissector,
+					enum flow_dissector_key_id key_id)
+{
+	return flow_dissector->used_keys & (1 << key_id);
+}
+
+static void skb_flow_dissector_set_key(struct flow_dissector *flow_dissector,
+				       enum flow_dissector_key_id key_id)
+{
+	flow_dissector->used_keys |= (1 << key_id);
+}
+
+static void *skb_flow_dissector_target(struct flow_dissector *flow_dissector,
+				       enum flow_dissector_key_id key_id,
+				       void *target_container)
+{
+	return ((char *) target_container) + flow_dissector->offset[key_id];
+}
+
+void skb_flow_dissector_init(struct flow_dissector *flow_dissector,
+			     const struct flow_dissector_key *key,
+			     unsigned int key_count)
+{
+	unsigned int i;
+
+	memset(flow_dissector, 0, sizeof(*flow_dissector));
+
+	for (i = 0; i < key_count; i++, key++) {
+		/* User should make sure that every key target offset is withing
+		 * boundaries of unsigned short.
+		 */
+		BUG_ON(key->offset > USHRT_MAX);
+		BUG_ON(skb_flow_dissector_uses_key(flow_dissector,
+						   key->key_id));
+
+		skb_flow_dissector_set_key(flow_dissector, key->key_id);
+		flow_dissector->offset[key->key_id] = key->offset;
+	}
+
+	/* Ensure that the dissector always includes basic key. That way
+	 * we are able to avoid handling lack of it in fast path.
+	 */
+	BUG_ON(!skb_flow_dissector_uses_key(flow_dissector,
+					    FLOW_DISSECTOR_KEY_BASIC));
+}
+EXPORT_SYMBOL(skb_flow_dissector_init);
+
 /* copy saddr & daddr, possibly using 64bit load/store
  * Equivalent to :	flow->src = iph->saddr;
  *			flow->dst = iph->daddr;