Implement IPv4 RSS software hash functions to use during packet ingress

and egress.

* rss_mbuf_software_hash_v4 - look at the IPv4 mbuf to fetch the IPv4 details
  + direction to calculate a hash.
* rss_proto_software_hash_v4 - hash the given source/destination IPv4 address,
  port and direction.
* rss_soft_m2cpuid - map the given mbuf to an RSS CPU ("bucket" for now)

These functions are intended to be used by the stack to support
the following:

* Not all NICs do RSS hashing, so we should support some way of doing
  a hash in software;
* The NIC / driver may not hash frames the way we want (eg UDP 4-tuple
  hashing when the stack is only doing 2-tuple hashing for UDP); so we
  may need to re-hash frames;
* .. same with IPv4 fragments - they will need to be re-hashed after
  reassembly;
* .. and same with things like IP tunneling and such;
* The transmit path for things like UDP, RAW and ICMP don't currently
  have any RSS information attached to them - so they'll need an
  RSS calculation performed before transmit.

TODO:

* Counters! Everywhere!
* Add a debug mode that software hashes received frames and compares them
  to the hardware hash provided by the hardware to ensure they match.

The IPv6 part of this is missing - I'm going to do some re-juggling of
where various parts of the RSS framework live before I add the IPv6
code (read: the IPv6 code is going to go into netinet6/in6_rss.[ch],
rather than living here.)

Note: This API is still fluid.  Please keep that in mind.

Differential Revision:	https://reviews.freebsd.org/D527
Reviewed by:	grehan

1 files changed, 23 insertions, 0 deletions

diff --git a/sys/netinet/in_rss.h b/sys/netinet/in_rss.h
index a911e3c..66fb611 100644
--- a/sys/netinet/in_rss.h
+++ b/sys/netinet/in_rss.h
@@ -83,6 +83,16 @@
 #define	RSS_KEYSIZE	40
 
 /*
+ * For RSS hash methods that do a software hash on an mbuf, the packet
+ * direction (ingress / egress) is required.
+ *
+ * The default direction (INGRESS) is the "receive into the NIC" - ie,
+ * what the hardware is hashing on.
+ */
+#define	RSS_HASH_PKT_INGRESS	0
+#define	RSS_HASH_PKT_EGRESS	1
+
+/*
  * Device driver interfaces to query RSS properties that must be programmed
  * into hardware.
  */
@@ -116,4 +126,17 @@ int		rss_hash2bucket(uint32_t hash_val, uint32_t hash_type,
 		uint32_t *bucket_id);
 int		rss_m2bucket(struct mbuf *m, uint32_t *bucket_id);
 
+/*
+ * Functions to calculate a software RSS hash for a given mbuf or
+ * packet detail.
+ */
+int		rss_mbuf_software_hash_v4(const struct mbuf *m, int dir,
+		    uint32_t *hashval, uint32_t *hashtype);
+int		rss_proto_software_hash_v4(struct in_addr src,
+		    struct in_addr dst, u_short src_port, u_short dst_port,
+		    int proto, uint32_t *hashval,
+		    uint32_t *hashtype);
+struct mbuf *	rss_soft_m2cpuid(struct mbuf *m, uintptr_t source,
+		    u_int *cpuid);
+
 #endif /* !_NETINET_IN_RSS_H_ */