net: Add functions to get skb->hash based on flow structures

Add skb_get_hash_flowi6 and skb_get_hash_flowi4 which derive an sk_buff
hash from flowi6 and flowi4 structures respectively. These functions
can be called when creating a packet in the output path where the new
sk_buff does not yet contain a fully formed packet that is parsable by
flow dissector.

Signed-off-by: Tom Herbert <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/linux/skbuff.h

···
 #include <net/flow_dissector.h>
 #include <linux/splice.h>
 #include <linux/in6.h>
+#include <net/flow.h>
 
 /* A. Checksumming of received packets by device.
  *
···
 {
 	if (!skb->l4_hash && !skb->sw_hash)
 		__skb_get_hash(skb);
+
+	return skb->hash;
+}
+
+__u32 __skb_get_hash_flowi6(struct sk_buff *skb, struct flowi6 *fl6);
+
+static inline __u32 skb_get_hash_flowi6(struct sk_buff *skb, struct flowi6 *fl6)
+{
+	if (!skb->l4_hash && !skb->sw_hash)
+		__skb_get_hash_flowi6(skb, fl6);
+
+	return skb->hash;
+}
+
+__u32 __skb_get_hash_flowi4(struct sk_buff *skb, struct flowi4 *fl);
+
+static inline __u32 skb_get_hash_flowi4(struct sk_buff *skb, struct flowi4 *fl4)
+{
+	if (!skb->l4_hash && !skb->sw_hash)
+		__skb_get_hash_flowi4(skb, fl4);
 
 	return skb->hash;
 }

net/core/flow_dissector.c

···
 }
 EXPORT_SYMBOL(make_flow_keys_digest);
 
+static inline void __skb_set_sw_hash(struct sk_buff *skb, u32 hash,
+				     struct flow_keys *keys)
+{
+	if (keys->ports.ports)
+		skb->l4_hash = 1;
+	skb->sw_hash = 1;
+	skb->hash = hash;
+}
+
 /**
  * __skb_get_hash: calculate a flow hash
  * @skb: sk_buff to calculate flow hash from
···
 	hash = ___skb_get_hash(skb, &keys, hashrnd);
 	if (!hash)
 		return;
-	if (keys.ports.ports)
-		skb->l4_hash = 1;
-	skb->sw_hash = 1;
-	skb->hash = hash;
+
+	__skb_set_sw_hash(skb, hash, &keys);
 }
 EXPORT_SYMBOL(__skb_get_hash);
 
···
 	return ___skb_get_hash(skb, &keys, perturb);
 }
 EXPORT_SYMBOL(skb_get_hash_perturb);
+
+__u32 __skb_get_hash_flowi6(struct sk_buff *skb, struct flowi6 *fl6)
+{
+	struct flow_keys keys;
+
+	memset(&keys, 0, sizeof(keys));
+
+	memcpy(&keys.addrs.v6addrs.src, &fl6->saddr,
+	       sizeof(keys.addrs.v6addrs.src));
+	memcpy(&keys.addrs.v6addrs.dst, &fl6->daddr,
+	       sizeof(keys.addrs.v6addrs.dst));
+	keys.control.addr_type = FLOW_DISSECTOR_KEY_IPV6_ADDRS;
+	keys.ports.src = fl6->fl6_sport;
+	keys.ports.dst = fl6->fl6_dport;
+	keys.keyid.keyid = fl6->fl6_gre_key;
+	keys.tags.flow_label = (__force u32)fl6->flowlabel;
+	keys.basic.ip_proto = fl6->flowi6_proto;
+
+	__skb_set_sw_hash(skb, flow_hash_from_keys(&keys), &keys);
+
+	return skb->hash;
+}
+EXPORT_SYMBOL(__skb_get_hash_flowi6);
+
+__u32 __skb_get_hash_flowi4(struct sk_buff *skb, struct flowi4 *fl4)
+{
+	struct flow_keys keys;
+
+	memset(&keys, 0, sizeof(keys));
+
+	keys.addrs.v4addrs.src = fl4->saddr;
+	keys.addrs.v4addrs.dst = fl4->daddr;
+	keys.control.addr_type = FLOW_DISSECTOR_KEY_IPV4_ADDRS;
+	keys.ports.src = fl4->fl4_sport;
+	keys.ports.dst = fl4->fl4_dport;
+	keys.keyid.keyid = fl4->fl4_gre_key;
+	keys.basic.ip_proto = fl4->flowi4_proto;
+
+	__skb_set_sw_hash(skb, flow_hash_from_keys(&keys), &keys);
+
+	return skb->hash;
+}
+EXPORT_SYMBOL(__skb_get_hash_flowi4);
 
 u32 __skb_get_poff(const struct sk_buff *skb, void *data,
 		   const struct flow_keys *keys, int hlen)