flow disector: ARP support

Allow dissection of (R)ARP operation hardware and protocol addresses
for Ethernet hardware and IPv4 protocol addresses.

There are currently no users of FLOW_DISSECTOR_KEY_ARP.
A follow-up patch will allow FLOW_DISSECTOR_KEY_ARP to be used by the
flower classifier.

Signed-off-by: Simon Horman <simon.horman@netronome.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/flow_dissector.h

@@ -88,6 +88,24 @@ struct flow_dissector_key_addrs {
 	};
 };
 
+/**
+ * flow_dissector_key_arp:
+ *	@ports: Operation, source and target addresses for an ARP header
+ *              for Ethernet hardware addresses and IPv4 protocol addresses
+ *		sip: Sender IP address
+ *		tip: Target IP address
+ *		op:  Operation
+ *		sha: Sender hardware address
+ *		tpa: Target hardware address
+ */
+struct flow_dissector_key_arp {
+	__u32 sip;
+	__u32 tip;
+	__u8 op;
+	unsigned char sha[ETH_ALEN];
+	unsigned char tha[ETH_ALEN];
+};
+
 /**
  * flow_dissector_key_tp_ports:
  *	@ports: port numbers of Transport header
@@ -141,6 +159,7 @@ enum flow_dissector_key_id {
 	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_ARP, /* struct flow_dissector_key_arp */
 	FLOW_DISSECTOR_KEY_VLAN, /* struct flow_dissector_key_flow_vlan */
 	FLOW_DISSECTOR_KEY_FLOW_LABEL, /* struct flow_dissector_key_flow_tags */
 	FLOW_DISSECTOR_KEY_GRE_KEYID, /* struct flow_dissector_key_keyid */

net/core/flow_dissector.c

@@ -138,6 +138,7 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
 	struct flow_dissector_key_control *key_control;
 	struct flow_dissector_key_basic *key_basic;
 	struct flow_dissector_key_addrs *key_addrs;
+	struct flow_dissector_key_arp *key_arp;
 	struct flow_dissector_key_ports *key_ports;
 	struct flow_dissector_key_icmp *key_icmp;
 	struct flow_dissector_key_tags *key_tags;
@@ -379,6 +380,62 @@ mpls:
 
 		nhoff += FCOE_HEADER_LEN;
 		goto out_good;
+
+	case htons(ETH_P_ARP):
+	case htons(ETH_P_RARP): {
+		struct {
+			unsigned char ar_sha[ETH_ALEN];
+			unsigned char ar_sip[4];
+			unsigned char ar_tha[ETH_ALEN];
+			unsigned char ar_tip[4];
+		} *arp_eth, _arp_eth;
+		const struct arphdr *arp;
+		struct arphdr *_arp;
+
+		arp = __skb_header_pointer(skb, nhoff, sizeof(_arp), data,
+					   hlen, &_arp);
+		if (!arp)
+			goto out_bad;
+
+		if (arp->ar_hrd != htons(ARPHRD_ETHER) ||
+		    arp->ar_pro != htons(ETH_P_IP) ||
+		    arp->ar_hln != ETH_ALEN ||
+		    arp->ar_pln != 4 ||
+		    (arp->ar_op != htons(ARPOP_REPLY) &&
+		     arp->ar_op != htons(ARPOP_REQUEST)))
+			goto out_bad;
+
+		arp_eth = __skb_header_pointer(skb, nhoff + sizeof(_arp),
+					       sizeof(_arp_eth), data,
+					       hlen - sizeof(_arp),
+					       &_arp_eth);
+		if (!arp)
+			goto out_bad;
+
+		if (dissector_uses_key(flow_dissector,
+				       FLOW_DISSECTOR_KEY_ARP)) {
+
+			key_arp = skb_flow_dissector_target(flow_dissector,
+							    FLOW_DISSECTOR_KEY_ARP,
+							    target_container);
+
+			memcpy(&key_arp->sip, arp_eth->ar_sip,
+			       sizeof(key_arp->sip));
+			memcpy(&key_arp->tip, arp_eth->ar_tip,
+			       sizeof(key_arp->tip));
+
+			/* Only store the lower byte of the opcode;
+			 * this covers ARPOP_REPLY and ARPOP_REQUEST.
+			 */
+			key_arp->op = ntohs(arp->ar_op) & 0xff;
+
+			ether_addr_copy(key_arp->sha, arp_eth->ar_sha);
+			ether_addr_copy(key_arp->tha, arp_eth->ar_tha);
+		}
+
+		goto out_good;
+	}
+
 	default:
 		goto out_bad;
 	}