net: flow_dissector: Add IPSEC dissector

Support for dissecting IPSEC field SPI (which is
32bits in size) for ESP and AH packets.
Signed-off-by: Ratheesh Kannoth <rkannoth@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/flow_dissector.h

@@ -301,6 +301,14 @@ struct flow_dissector_key_l2tpv3 {
 	__be32 session_id;
 };
 
+/**
+ * struct flow_dissector_key_ipsec:
+ * @spi: identifier for a ipsec connection
+ */
+struct flow_dissector_key_ipsec {
+	__be32 spi;
+};
+
 /**
  * struct flow_dissector_key_cfm
  * @mdl_ver: maintenance domain level (mdl) and cfm protocol version
@@ -354,6 +362,7 @@ enum flow_dissector_key_id {
 	FLOW_DISSECTOR_KEY_PPPOE, /* struct flow_dissector_key_pppoe */
 	FLOW_DISSECTOR_KEY_L2TPV3, /* struct flow_dissector_key_l2tpv3 */
 	FLOW_DISSECTOR_KEY_CFM, /* struct flow_dissector_key_cfm */
+	FLOW_DISSECTOR_KEY_IPSEC, /* struct flow_dissector_key_ipsec */
 
 	FLOW_DISSECTOR_KEY_MAX,
 };

net/core/flow_dissector.c

@@ -205,6 +205,50 @@ static void __skb_flow_dissect_icmp(const struct sk_buff *skb,
 	skb_flow_get_icmp_tci(skb, key_icmp, data, thoff, hlen);
 }
 
+static void __skb_flow_dissect_ah(const struct sk_buff *skb,
+				  struct flow_dissector *flow_dissector,
+				  void *target_container, const void *data,
+				  int nhoff, int hlen)
+{
+	struct flow_dissector_key_ipsec *key_ah;
+	struct ip_auth_hdr _hdr, *hdr;
+
+	if (!dissector_uses_key(flow_dissector, FLOW_DISSECTOR_KEY_IPSEC))
+		return;
+
+	hdr = __skb_header_pointer(skb, nhoff, sizeof(_hdr), data, hlen, &_hdr);
+	if (!hdr)
+		return;
+
+	key_ah = skb_flow_dissector_target(flow_dissector,
+					   FLOW_DISSECTOR_KEY_IPSEC,
+					   target_container);
+
+	key_ah->spi = hdr->spi;
+}
+
+static void __skb_flow_dissect_esp(const struct sk_buff *skb,
+				   struct flow_dissector *flow_dissector,
+				   void *target_container, const void *data,
+				   int nhoff, int hlen)
+{
+	struct flow_dissector_key_ipsec *key_esp;
+	struct ip_esp_hdr _hdr, *hdr;
+
+	if (!dissector_uses_key(flow_dissector, FLOW_DISSECTOR_KEY_IPSEC))
+		return;
+
+	hdr = __skb_header_pointer(skb, nhoff, sizeof(_hdr), data, hlen, &_hdr);
+	if (!hdr)
+		return;
+
+	key_esp = skb_flow_dissector_target(flow_dissector,
+					    FLOW_DISSECTOR_KEY_IPSEC,
+					    target_container);
+
+	key_esp->spi = hdr->spi;
+}
+
 static void __skb_flow_dissect_l2tpv3(const struct sk_buff *skb,
 				      struct flow_dissector *flow_dissector,
 				      void *target_container, const void *data,
@@ -1571,7 +1615,14 @@ bool __skb_flow_dissect(const struct net *net,
 		__skb_flow_dissect_l2tpv3(skb, flow_dissector, target_container,
 					  data, nhoff, hlen);
 		break;
-
+	case IPPROTO_ESP:
+		__skb_flow_dissect_esp(skb, flow_dissector, target_container,
+				       data, nhoff, hlen);
+		break;
+	case IPPROTO_AH:
+		__skb_flow_dissect_ah(skb, flow_dissector, target_container,
+				      data, nhoff, hlen);
+		break;
 	default:
 		break;
 	}