net/flow_dissector: add support for dissection of misc ip header fields

Add support for dissection of ip tos and ttl and ipv6 traffic-class
and hoplimit. Both are dissected into the same struct.

Uses similar call to ip dissection function as with tcp, arp and others.
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/flow_dissector.h

@@ -165,6 +165,16 @@ struct flow_dissector_key_tcp {
 	__be16 flags;
 };
 
+/**
+ * struct flow_dissector_key_ip:
+ * @tos: tos
+ * @ttl: ttl
+ */
+struct flow_dissector_key_ip {
+	__u8	tos;
+	__u8	ttl;
+};
+
 enum flow_dissector_key_id {
 	FLOW_DISSECTOR_KEY_CONTROL, /* struct flow_dissector_key_control */
 	FLOW_DISSECTOR_KEY_BASIC, /* struct flow_dissector_key_basic */
@@ -186,6 +196,7 @@ enum flow_dissector_key_id {
 	FLOW_DISSECTOR_KEY_ENC_PORTS, /* struct flow_dissector_key_ports */
 	FLOW_DISSECTOR_KEY_MPLS, /* struct flow_dissector_key_mpls */
 	FLOW_DISSECTOR_KEY_TCP, /* struct flow_dissector_key_tcp */
+	FLOW_DISSECTOR_KEY_IP, /* struct flow_dissector_key_ip */
 
 	FLOW_DISSECTOR_KEY_MAX,
 };

net/core/flow_dissector.c

@@ -367,6 +367,40 @@ __skb_flow_dissect_tcp(const struct sk_buff *skb,
 	key_tcp->flags = (*(__be16 *) &tcp_flag_word(th) & htons(0x0FFF));
 }
 
+static void
+__skb_flow_dissect_ipv4(const struct sk_buff *skb,
+			struct flow_dissector *flow_dissector,
+			void *target_container, void *data, const struct iphdr *iph)
+{
+	struct flow_dissector_key_ip *key_ip;
+
+	if (!dissector_uses_key(flow_dissector, FLOW_DISSECTOR_KEY_IP))
+		return;
+
+	key_ip = skb_flow_dissector_target(flow_dissector,
+					   FLOW_DISSECTOR_KEY_IP,
+					   target_container);
+	key_ip->tos = iph->tos;
+	key_ip->ttl = iph->ttl;
+}
+
+static void
+__skb_flow_dissect_ipv6(const struct sk_buff *skb,
+			struct flow_dissector *flow_dissector,
+			void *target_container, void *data, const struct ipv6hdr *iph)
+{
+	struct flow_dissector_key_ip *key_ip;
+
+	if (!dissector_uses_key(flow_dissector, FLOW_DISSECTOR_KEY_IP))
+		return;
+
+	key_ip = skb_flow_dissector_target(flow_dissector,
+					   FLOW_DISSECTOR_KEY_IP,
+					   target_container);
+	key_ip->tos = ipv6_get_dsfield(iph);
+	key_ip->ttl = iph->hop_limit;
+}
+
 /**
  * __skb_flow_dissect - extract the flow_keys struct and return it
  * @skb: sk_buff to extract the flow from, can be NULL if the rest are specified
@@ -469,6 +503,9 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
 			}
 		}
 
+		__skb_flow_dissect_ipv4(skb, flow_dissector,
+					target_container, data, iph);
+
 		if (flags & FLOW_DISSECTOR_F_STOP_AT_L3)
 			goto out_good;
 
@@ -514,6 +551,9 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
 				goto out_good;
 		}
 
+		__skb_flow_dissect_ipv6(skb, flow_dissector,
+					target_container, data, iph);
+
 		if (flags & FLOW_DISSECTOR_F_STOP_AT_L3)
 			goto out_good;