[PATCH RFC v4 2/9] virtio_net: Add functions for hashing

[Akihiko Odaki <akihiko.odaki@daynix.com>]

They are useful to implement VIRTIO_NET_F_RSS and
VIRTIO_NET_F_HASH_REPORT.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
---
 include/linux/virtio_net.h | 174 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 174 insertions(+)

diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
index 276ca543ef44..f7a4149efb3e 100644
--- a/include/linux/virtio_net.h
+++ b/include/linux/virtio_net.h
@@ -9,6 +9,180 @@
 #include <uapi/linux/tcp.h>
 #include <uapi/linux/virtio_net.h>
 
+struct virtio_net_hash {
+	u32 value;
+	u16 report;
+};
+
+struct virtio_net_toeplitz_state {
+	u32 hash;
+	u32 key_buffer;
+	const __be32 *key;
+};
+
+#define VIRTIO_NET_SUPPORTED_HASH_TYPES (VIRTIO_NET_RSS_HASH_TYPE_IPv4 | \
+					 VIRTIO_NET_RSS_HASH_TYPE_TCPv4 | \
+					 VIRTIO_NET_RSS_HASH_TYPE_UDPv4 | \
+					 VIRTIO_NET_RSS_HASH_TYPE_IPv6 | \
+					 VIRTIO_NET_RSS_HASH_TYPE_TCPv6 | \
+					 VIRTIO_NET_RSS_HASH_TYPE_UDPv6)
+
+#define VIRTIO_NET_RSS_MAX_KEY_SIZE 40
+
+static inline void virtio_net_toeplitz_calc(struct virtio_net_toeplitz_state *state,
+					    const __be32 *input, size_t len)
+{
+	u32 key;
+
+	while (len) {
+		state->key++;
+		key = be32_to_cpu(*state->key);
+
+		for (u32 bit = BIT(31); bit; bit >>= 1) {
+			if (be32_to_cpu(*input) & bit)
+				state->hash ^= state->key_buffer;
+
+			state->key_buffer =
+				(state->key_buffer << 1) | !!(key & bit);
+		}
+
+		input++;
+		len--;
+	}
+}
+
+static inline u8 virtio_net_hash_key_length(u32 types)
+{
+	size_t len = 0;
+
+	if (types & VIRTIO_NET_HASH_REPORT_IPv4)
+		len = max(len,
+			  sizeof(struct flow_dissector_key_ipv4_addrs));
+
+	if (types &
+	    (VIRTIO_NET_HASH_REPORT_TCPv4 | VIRTIO_NET_HASH_REPORT_UDPv4))
+		len = max(len,
+			  sizeof(struct flow_dissector_key_ipv4_addrs) +
+			  sizeof(struct flow_dissector_key_ports));
+
+	if (types & VIRTIO_NET_HASH_REPORT_IPv6)
+		len = max(len,
+			  sizeof(struct flow_dissector_key_ipv6_addrs));
+
+	if (types &
+	    (VIRTIO_NET_HASH_REPORT_TCPv6 | VIRTIO_NET_HASH_REPORT_UDPv6))
+		len = max(len,
+			  sizeof(struct flow_dissector_key_ipv6_addrs) +
+			  sizeof(struct flow_dissector_key_ports));
+
+	return sizeof_field(struct virtio_net_toeplitz_state, key_buffer) + len;
+}
+
+static inline u32 virtio_net_hash_report(u32 types,
+					 struct flow_dissector_key_basic key)
+{
+	switch (key.n_proto) {
+	case cpu_to_be16(ETH_P_IP):
+		if (key.ip_proto == IPPROTO_TCP &&
+		    (types & VIRTIO_NET_RSS_HASH_TYPE_TCPv4))
+			return VIRTIO_NET_HASH_REPORT_TCPv4;
+
+		if (key.ip_proto == IPPROTO_UDP &&
+		    (types & VIRTIO_NET_RSS_HASH_TYPE_UDPv4))
+			return VIRTIO_NET_HASH_REPORT_UDPv4;
+
+		if (types & VIRTIO_NET_RSS_HASH_TYPE_IPv4)
+			return VIRTIO_NET_HASH_REPORT_IPv4;
+
+		return VIRTIO_NET_HASH_REPORT_NONE;
+
+	case cpu_to_be16(ETH_P_IPV6):
+		if (key.ip_proto == IPPROTO_TCP &&
+		    (types & VIRTIO_NET_RSS_HASH_TYPE_TCPv6))
+			return VIRTIO_NET_HASH_REPORT_TCPv6;
+
+		if (key.ip_proto == IPPROTO_UDP &&
+		    (types & VIRTIO_NET_RSS_HASH_TYPE_UDPv6))
+			return VIRTIO_NET_HASH_REPORT_UDPv6;
+
+		if (types & VIRTIO_NET_RSS_HASH_TYPE_IPv6)
+			return VIRTIO_NET_HASH_REPORT_IPv6;
+
+		return VIRTIO_NET_HASH_REPORT_NONE;
+
+	default:
+		return VIRTIO_NET_HASH_REPORT_NONE;
+	}
+}
+
+static inline void virtio_net_hash_rss(const struct sk_buff *skb,
+				       u32 types, const __be32 *key,
+				       struct virtio_net_hash *hash)
+{
+	struct virtio_net_toeplitz_state toeplitz_state = {
+		.key_buffer = be32_to_cpu(*key),
+		.key = key
+	};
+	struct flow_keys flow;
+	u16 report;
+
+	if (!skb_flow_dissect_flow_keys(skb, &flow, 0)) {
+		hash->report = VIRTIO_NET_HASH_REPORT_NONE;
+		return;
+	}
+
+	report = virtio_net_hash_report(types, flow.basic);
+
+	switch (report) {
+	case VIRTIO_NET_HASH_REPORT_IPv4:
+		virtio_net_toeplitz_calc(&toeplitz_state,
+					 (__be32 *)&flow.addrs.v4addrs,
+					 sizeof(flow.addrs.v4addrs) / 4);
+		break;
+
+	case VIRTIO_NET_HASH_REPORT_TCPv4:
+		virtio_net_toeplitz_calc(&toeplitz_state,
+					 (__be32 *)&flow.addrs.v4addrs,
+					 sizeof(flow.addrs.v4addrs) / 4);
+		virtio_net_toeplitz_calc(&toeplitz_state, &flow.ports.ports, 1);
+		break;
+
+	case VIRTIO_NET_HASH_REPORT_UDPv4:
+		virtio_net_toeplitz_calc(&toeplitz_state,
+					 (__be32 *)&flow.addrs.v4addrs,
+					 sizeof(flow.addrs.v4addrs) / 4);
+		virtio_net_toeplitz_calc(&toeplitz_state, &flow.ports.ports, 1);
+		break;
+
+	case VIRTIO_NET_HASH_REPORT_IPv6:
+		virtio_net_toeplitz_calc(&toeplitz_state,
+					 (__be32 *)&flow.addrs.v6addrs,
+					 sizeof(flow.addrs.v6addrs) / 4);
+		break;
+
+	case VIRTIO_NET_HASH_REPORT_TCPv6:
+		virtio_net_toeplitz_calc(&toeplitz_state,
+					 (__be32 *)&flow.addrs.v6addrs,
+					 sizeof(flow.addrs.v6addrs) / 4);
+		virtio_net_toeplitz_calc(&toeplitz_state, &flow.ports.ports, 1);
+		break;
+
+	case VIRTIO_NET_HASH_REPORT_UDPv6:
+		virtio_net_toeplitz_calc(&toeplitz_state,
+					 (__be32 *)&flow.addrs.v6addrs,
+					 sizeof(flow.addrs.v6addrs) / 4);
+		virtio_net_toeplitz_calc(&toeplitz_state, &flow.ports.ports, 1);
+		break;
+
+	default:
+		hash->report = VIRTIO_NET_HASH_REPORT_NONE;
+		return;
+	}
+
+	hash->value = toeplitz_state.hash;
+	hash->report = report;
+}
+
 static inline bool virtio_net_hdr_match_proto(__be16 protocol, __u8 gso_type)
 {
 	switch (gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {

-- 
2.46.0