[PATCH net-next v5 1/2] flow dissector: ICMP support

[Simon Horman <simon.horman@netronome.com>]

Allow dissection of ICMP(V6) type and code. This should only occur
if a packet is ICMP(V6) and the dissector has FLOW_DISSECTOR_KEY_ICMP set.

There are currently no users of FLOW_DISSECTOR_KEY_ICMP.
A follow-up patch will allow FLOW_DISSECTOR_KEY_ICMP to be used by
the flower classifier.
---
v5
* Drop remaining helpers

v4
* Do not add icmp to struct flow_keys, it is not needed
* Do not test for ICMP protocols in packet in __skb_flow_dissect,
  this is also not needed
* Drop now unnecessary helpers

v3
* Add FLOW_DISSECTOR_KEY_ICMP and use separate structure for ICMP, struct
  flow_dissector_key_icmp, which is a union with struct
  flow_dissector_key_ports in struct flow_keys.
* Drop checks for !ICMP before accessing port field

v2
* Include all helpers in this patch
---
 include/net/flow_dissector.h | 17 +++++++++++++++++
 net/core/flow_dissector.c    | 31 +++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/include/net/flow_dissector.h b/include/net/flow_dissector.h
index c4f31666afd2..d896a33e00d4 100644
--- a/include/net/flow_dissector.h
+++ b/include/net/flow_dissector.h
@@ -104,6 +104,22 @@ struct flow_dissector_key_ports {
 	};
 };
 
+/**
+ * flow_dissector_key_icmp:
+ *	@ports: type and code of ICMP header
+ *		icmp: ICMP type (high) and code (low)
+ *		type: ICMP type
+ *		code: ICMP code
+ */
+struct flow_dissector_key_icmp {
+	union {
+		__be16 icmp;
+		struct {
+			u8 type;
+			u8 code;
+		};
+	};
+};
 
 /**
  * struct flow_dissector_key_eth_addrs:
@@ -122,6 +138,7 @@ enum flow_dissector_key_id {
 	FLOW_DISSECTOR_KEY_IPV4_ADDRS, /* struct flow_dissector_key_ipv4_addrs */
 	FLOW_DISSECTOR_KEY_IPV6_ADDRS, /* struct flow_dissector_key_ipv6_addrs */
 	FLOW_DISSECTOR_KEY_PORTS, /* struct flow_dissector_key_ports */
+	FLOW_DISSECTOR_KEY_ICMP, /* struct flow_dissector_key_icmp */
 	FLOW_DISSECTOR_KEY_ETH_ADDRS, /* struct flow_dissector_key_eth_addrs */
 	FLOW_DISSECTOR_KEY_TIPC_ADDRS, /* struct flow_dissector_key_tipc_addrs */
 	FLOW_DISSECTOR_KEY_VLAN, /* struct flow_dissector_key_flow_vlan */
diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 1eb6f949e5b2..d6447dc10371 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -58,6 +58,28 @@ void skb_flow_dissector_init(struct flow_dissector *flow_dissector,
 EXPORT_SYMBOL(skb_flow_dissector_init);
 
 /**
+ * skb_flow_get_be16 - extract be16 entity
+ * @skb: sk_buff to extract from
+ * @poff: offset to extract at
+ * @data: raw buffer pointer to the packet
+ * @hlen: packet header length
+ *
+ * The function will try to retrieve a be32 entity at
+ * offset poff
+ */
+__be16 skb_flow_get_be16(const struct sk_buff *skb, int poff, void *data,
+			 int hlen)
+{
+	__be16 *u, _u;
+
+	u = __skb_header_pointer(skb, poff, sizeof(_u), data, hlen, &_u);
+	if (u)
+		return *u;
+
+	return 0;
+}
+
+/**
  * __skb_flow_get_ports - extract the upper layer ports and return them
  * @skb: sk_buff to extract the ports from
  * @thoff: transport header offset
@@ -117,6 +139,7 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
 	struct flow_dissector_key_basic *key_basic;
 	struct flow_dissector_key_addrs *key_addrs;
 	struct flow_dissector_key_ports *key_ports;
+	struct flow_dissector_key_icmp *key_icmp;
 	struct flow_dissector_key_tags *key_tags;
 	struct flow_dissector_key_vlan *key_vlan;
 	struct flow_dissector_key_keyid *key_keyid;
@@ -546,6 +569,14 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
 							data, hlen);
 	}
 
+	if (dissector_uses_key(flow_dissector,
+			       FLOW_DISSECTOR_KEY_ICMP)) {
+		key_icmp = skb_flow_dissector_target(flow_dissector,
+						     FLOW_DISSECTOR_KEY_ICMP,
+						     target_container);
+		key_icmp->icmp = skb_flow_get_be16(skb, nhoff, data, hlen);
+	}
+
 out_good:
 	ret = true;
 
-- 
2.7.0.rc3.207.g0ac5344