flow_dissector: extract more ICMP information

The ICMP flow dissector currently parses only the Type and Code fields.
Some ICMP packets (echo, timestamp) have a 16 bit Identifier field which
is used to correlate packets.
Add such field in flow_dissector_key_icmp and replace skb_flow_get_be16()
with a more complex function which populate this field.

Signed-off-by: Matteo Croce <mcroce@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 50 insertions, 24 deletions

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 0fb721976f3d..0807df0bde02 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -178,27 +178,6 @@ int skb_flow_dissector_bpf_prog_detach(const union bpf_attr *attr)
 	mutex_unlock(&flow_dissector_mutex);
 	return 0;
 }
-/**
- * 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
- */
-static __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
@@ -234,8 +213,54 @@ __be32 __skb_flow_get_ports(const struct sk_buff *skb, int thoff, u8 ip_proto,
 }
 EXPORT_SYMBOL(__skb_flow_get_ports);
 
-/* If FLOW_DISSECTOR_KEY_ICMP is set, get the Type and Code from an ICMP packet
- * using skb_flow_get_be16().
+static bool icmp_has_id(u8 type)
+{
+	switch (type) {
+	case ICMP_ECHO:
+	case ICMP_ECHOREPLY:
+	case ICMP_TIMESTAMP:
+	case ICMP_TIMESTAMPREPLY:
+	case ICMPV6_ECHO_REQUEST:
+	case ICMPV6_ECHO_REPLY:
+		return true;
+	}
+
+	return false;
+}
+
+/**
+ * skb_flow_get_icmp_tci - extract ICMP(6) Type, Code and Identifier fields
+ * @skb: sk_buff to extract from
+ * @key_icmp: struct flow_dissector_key_icmp to fill
+ * @data: raw buffer pointer to the packet
+ * @toff: offset to extract at
+ * @hlen: packet header length
+ */
+void skb_flow_get_icmp_tci(const struct sk_buff *skb,
+			   struct flow_dissector_key_icmp *key_icmp,
+			   void *data, int thoff, int hlen)
+{
+	struct icmphdr *ih, _ih;
+
+	ih = __skb_header_pointer(skb, thoff, sizeof(_ih), data, hlen, &_ih);
+	if (!ih)
+		return;
+
+	key_icmp->type = ih->type;
+	key_icmp->code = ih->code;
+
+	/* As we use 0 to signal that the Id field is not present,
+	 * avoid confusion with packets without such field
+	 */
+	if (icmp_has_id(ih->type))
+		key_icmp->id = ih->un.echo.id ? : 1;
+	else
+		key_icmp->id = 0;
+}
+EXPORT_SYMBOL(skb_flow_get_icmp_tci);
+
+/* If FLOW_DISSECTOR_KEY_ICMP is set, dissect an ICMP packet
+ * using skb_flow_get_icmp_tci().
  */
 static void __skb_flow_dissect_icmp(const struct sk_buff *skb,
 				    struct flow_dissector *flow_dissector,
@@ -250,7 +275,8 @@ static void __skb_flow_dissect_icmp(const struct sk_buff *skb,
 	key_icmp = skb_flow_dissector_target(flow_dissector,
 					     FLOW_DISSECTOR_KEY_ICMP,
 					     target_container);
-	key_icmp->icmp = skb_flow_get_be16(skb, thoff, data, hlen);
+
+	skb_flow_get_icmp_tci(skb, key_icmp, data, thoff, hlen);
 }
 
 void skb_flow_dissect_meta(const struct sk_buff *skb,