openvswitch: Relax set header validation.

When installing a flow with an action to set a particular field we
need to validate that the packets that are part of the flow actually
contain that header.  With IP we use zeroed addresses and with TCP/UDP
the check is for zeroed ports.  This check is overly broad and can catch
packets like DHCP requests that have a zero source address in a
legitimate header.  This changes the check to look for a zeroed protocol
number for IP or for both ports be zero for TCP/UDP before considering
the header to not exist.
Reported-by: NEthan Jackson <ethan@nicira.com>
Signed-off-by: NJesse Gross <jesse@nicira.com>

net/openvswitch/datapath.c

@@ -425,10 +425,10 @@ static int validate_sample(const struct nlattr *attr,
 static int validate_tp_port(const struct sw_flow_key *flow_key)
 {
 	if (flow_key->eth.type == htons(ETH_P_IP)) {
-		if (flow_key->ipv4.tp.src && flow_key->ipv4.tp.dst)
+		if (flow_key->ipv4.tp.src || flow_key->ipv4.tp.dst)
 			return 0;
 	} else if (flow_key->eth.type == htons(ETH_P_IPV6)) {
-		if (flow_key->ipv6.tp.src && flow_key->ipv6.tp.dst)
+		if (flow_key->ipv6.tp.src || flow_key->ipv6.tp.dst)
 			return 0;
 	}
 
@@ -460,7 +460,7 @@ static int validate_set(const struct nlattr *a,
 		if (flow_key->eth.type != htons(ETH_P_IP))
 			return -EINVAL;
 
-		if (!flow_key->ipv4.addr.src || !flow_key->ipv4.addr.dst)
+		if (!flow_key->ip.proto)
 			return -EINVAL;
 
 		ipv4_key = nla_data(ovs_key);