openvswitch: Add eventmask support to CT action.

Add a new optional conntrack action attribute OVS_CT_ATTR_EVENTMASK,
which can be used in conjunction with the commit flag
(OVS_CT_ATTR_COMMIT) to set the mask of bits specifying which
conntrack events (IPCT_*) should be delivered via the Netfilter
netlink multicast groups.  Default behavior depends on the system
configuration, but typically a lot of events are delivered.  This can be
very chatty for the NFNLGRP_CONNTRACK_UPDATE group, even if only some
types of events are of interest.

Netfilter core init_conntrack() adds the event cache extension, so we
only need to set the ctmask value.  However, if the system is
configured without support for events, the setting will be skipped due
to extension not being found.
Signed-off-by: Jarno Rajahalme <jarno@ovn.org>
Reviewed-by: Greg Rose <gvrose8192@gmail.com>
Acked-by: Joe Stringer <joe@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/uapi/linux/openvswitch.h

@@ -693,6 +693,17 @@ struct ovs_action_hash {
  * nothing if the connection is already committed will check that the current
  * packet is in conntrack entry's original direction.  If directionality does
  * not match, will delete the existing conntrack entry and commit a new one.
+ * @OVS_CT_ATTR_EVENTMASK: Mask of bits indicating which conntrack event types
+ * (enum ip_conntrack_events IPCT_*) should be reported.  For any bit set to
+ * zero, the corresponding event type is not generated.  Default behavior
+ * depends on system configuration, but typically all event types are
+ * generated, hence listening on NFNLGRP_CONNTRACK_UPDATE events may get a lot
+ * of events.  Explicitly passing this attribute allows limiting the updates
+ * received to the events of interest.  The bit 1 << IPCT_NEW, 1 <<
+ * IPCT_RELATED, and 1 << IPCT_DESTROY must be set to ones for those events to
+ * be received on NFNLGRP_CONNTRACK_NEW and NFNLGRP_CONNTRACK_DESTROY groups,
+ * respectively.  Remaining bits control the changes for which an event is
+ * delivered on the NFNLGRP_CONNTRACK_UPDATE group.
  */
 enum ovs_ct_attr {
 	OVS_CT_ATTR_UNSPEC,
@@ -704,6 +715,7 @@ enum ovs_ct_attr {
 				   related connections. */
 	OVS_CT_ATTR_NAT,        /* Nested OVS_NAT_ATTR_* */
 	OVS_CT_ATTR_FORCE_COMMIT,  /* No argument */
+	OVS_CT_ATTR_EVENTMASK,  /* u32 mask of IPCT_* events. */
 	__OVS_CT_ATTR_MAX
 };
 

net/openvswitch/conntrack.c

@@ -66,7 +66,9 @@ struct ovs_conntrack_info {
 	u8 commit : 1;
 	u8 nat : 3;                 /* enum ovs_ct_nat */
 	u8 force : 1;
+	u8 have_eventmask : 1;
 	u16 family;
+	u32 eventmask;              /* Mask of 1 << IPCT_*. */
 	struct md_mark mark;
 	struct md_labels labels;
 #ifdef CONFIG_NF_NAT_NEEDED
@@ -1007,6 +1009,20 @@ static int ovs_ct_commit(struct net *net, struct sw_flow_key *key,
 	if (!ct)
 		return 0;
 
+	/* Set the conntrack event mask if given.  NEW and DELETE events have
+	 * their own groups, but the NFNLGRP_CONNTRACK_UPDATE group listener
+	 * typically would receive many kinds of updates.  Setting the event
+	 * mask allows those events to be filtered.  The set event mask will
+	 * remain in effect for the lifetime of the connection unless changed
+	 * by a further CT action with both the commit flag and the eventmask
+	 * option. */
+	if (info->have_eventmask) {
+		struct nf_conntrack_ecache *cache = nf_ct_ecache_find(ct);
+
+		if (cache)
+			cache->ctmask = info->eventmask;
+	}
+
 	/* Apply changes before confirming the connection so that the initial
 	 * conntrack NEW netlink event carries the values given in the CT
 	 * action.
@@ -1238,6 +1254,8 @@ static const struct ovs_ct_len_tbl ovs_ct_attr_lens[OVS_CT_ATTR_MAX + 1] = {
 	/* NAT length is checked when parsing the nested attributes. */
 	[OVS_CT_ATTR_NAT]	= { .minlen = 0, .maxlen = INT_MAX },
 #endif
+	[OVS_CT_ATTR_EVENTMASK]	= { .minlen = sizeof(u32),
+				    .maxlen = sizeof(u32) },
 };
 
 static int parse_ct(const struct nlattr *attr, struct ovs_conntrack_info *info,
@@ -1316,6 +1334,11 @@ static int parse_ct(const struct nlattr *attr, struct ovs_conntrack_info *info,
 			break;
 		}
 #endif
+		case OVS_CT_ATTR_EVENTMASK:
+			info->have_eventmask = true;
+			info->eventmask = nla_get_u32(a);
+			break;
+
 		default:
 			OVS_NLERR(log, "Unknown conntrack attr (%d)",
 				  type);
@@ -1515,6 +1538,10 @@ int ovs_ct_action_to_attr(const struct ovs_conntrack_info *ct_info,
 				   ct_info->helper->name))
 			return -EMSGSIZE;
 	}
+	if (ct_info->have_eventmask &&
+	    nla_put_u32(skb, OVS_CT_ATTR_EVENTMASK, ct_info->eventmask))
+		return -EMSGSIZE;
+
 #ifdef CONFIG_NF_NAT_NEEDED
 	if (ct_info->nat && !ovs_ct_nat_to_attr(ct_info, skb))
 		return -EMSGSIZE;