netfilter: ctnetlink: add kernel side filtering for dump

Conntrack dump does not support kernel side filtering (only get exists,
but it returns only one entry. And user has to give a full valid tuple)

It means that userspace has to implement filtering after receiving many
irrelevant entries, consuming resources (conntrack table is sometimes
very huge, much more than a routing table for example).

This patch adds filtering in kernel side. To achieve this goal, we:

 * Add a new CTA_FILTER netlink attributes, actually a flag list to
   parametize filtering
 * Convert some *nlattr_to_tuple() functions, to allow a partial parsing
   of CTA_TUPLE_ORIG and CTA_TUPLE_REPLY (so nf_conntrack_tuple it not
   fully set)

Filtering is now possible on:
 * IP SRC/DST values
 * Ports for TCP and UDP flows
 * IMCP(v6) codes types and IDs

Filtering is done as an "AND" operator. For example, when flags
PROTO_SRC_PORT, PROTO_NUM and IP_SRC are sets, only entries matching all
values are dumped.

Changes since v1:
  Set NLM_F_DUMP_FILTERED in nlm flags if entries are filtered

Changes since v2:
  Move several constants to nf_internals.h
  Move a fix on netlink values check in a separate patch
  Add a check on not-supported flags
  Return EOPNOTSUPP if CDA_FILTER is set in ctnetlink_flush_conntrack
  (not yet implemented)
  Code style issues

Changes since v3:
  Fix compilation warning reported by kbuild test robot

Changes since v4:
  Fix a regression introduced in v3 (returned EINVAL for valid netlink
  messages without CTA_MARK)

Changes since v5:
  Change definition of CTA_FILTER_F_ALL
  Fix a regression when CTA_TUPLE_ZONE is not set

Signed-off-by: Romain Bellan <romain.bellan@wifirst.fr>
Signed-off-by: Florent Fourcot <florent.fourcot@wifirst.fr>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netfilter/nf_conntrack_l4proto.h

@@ -42,7 +42,8 @@ struct nf_conntrack_l4proto {
 	/* Calculate tuple nlattr size */
 	unsigned int (*nlattr_tuple_size)(void);
 	int (*nlattr_to_tuple)(struct nlattr *tb[],
-			       struct nf_conntrack_tuple *t);
+			       struct nf_conntrack_tuple *t,
+			       u_int32_t flags);
 	const struct nla_policy *nla_policy;
 
 	struct {
@@ -152,7 +153,8 @@ const struct nf_conntrack_l4proto *nf_ct_l4proto_find(u8 l4proto);
 int nf_ct_port_tuple_to_nlattr(struct sk_buff *skb,
 			       const struct nf_conntrack_tuple *tuple);
 int nf_ct_port_nlattr_to_tuple(struct nlattr *tb[],
-			       struct nf_conntrack_tuple *t);
+			       struct nf_conntrack_tuple *t,
+			       u_int32_t flags);
 unsigned int nf_ct_port_nlattr_tuple_size(void);
 extern const struct nla_policy nf_ct_port_nla_policy[];
 

include/uapi/linux/netfilter/nfnetlink_conntrack.h

@@ -55,6 +55,7 @@ enum ctattr_type {
 	CTA_LABELS,
 	CTA_LABELS_MASK,
 	CTA_SYNPROXY,
+	CTA_FILTER,
 	__CTA_MAX
 };
 #define CTA_MAX (__CTA_MAX - 1)
@@ -276,4 +277,12 @@ enum ctattr_expect_stats {
 };
 #define CTA_STATS_EXP_MAX (__CTA_STATS_EXP_MAX - 1)
 
+enum ctattr_filter {
+	CTA_FILTER_UNSPEC,
+	CTA_FILTER_ORIG_FLAGS,
+	CTA_FILTER_REPLY_FLAGS,
+	__CTA_FILTER_MAX
+};
+#define CTA_FILTER_MAX (__CTA_FILTER_MAX - 1)
+
 #endif /* _IPCONNTRACK_NETLINK_H */

net/netfilter/nf_conntrack_core.c

@@ -1974,13 +1974,22 @@ const struct nla_policy nf_ct_port_nla_policy[CTA_PROTO_MAX+1] = {
 EXPORT_SYMBOL_GPL(nf_ct_port_nla_policy);
 
 int nf_ct_port_nlattr_to_tuple(struct nlattr *tb[],
-			       struct nf_conntrack_tuple *t)
+			       struct nf_conntrack_tuple *t,
+			       u_int32_t flags)
 {
-	if (!tb[CTA_PROTO_SRC_PORT] || !tb[CTA_PROTO_DST_PORT])
-		return -EINVAL;
+	if (flags & CTA_FILTER_FLAG(CTA_PROTO_SRC_PORT)) {
+		if (!tb[CTA_PROTO_SRC_PORT])
+			return -EINVAL;
 
-	t->src.u.tcp.port = nla_get_be16(tb[CTA_PROTO_SRC_PORT]);
-	t->dst.u.tcp.port = nla_get_be16(tb[CTA_PROTO_DST_PORT]);
+		t->src.u.tcp.port = nla_get_be16(tb[CTA_PROTO_SRC_PORT]);
+	}
+
+	if (flags & CTA_FILTER_FLAG(CTA_PROTO_DST_PORT)) {
+		if (!tb[CTA_PROTO_DST_PORT])
+			return -EINVAL;
+
+		t->dst.u.tcp.port = nla_get_be16(tb[CTA_PROTO_DST_PORT]);
+	}
 
 	return 0;
 }

net/netfilter/nf_conntrack_proto_icmp.c

@@ -20,6 +20,8 @@
 #include <net/netfilter/nf_conntrack_zones.h>
 #include <net/netfilter/nf_log.h>
 
+#include "nf_internals.h"
+
 static const unsigned int nf_ct_icmp_timeout = 30*HZ;
 
 bool icmp_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
@@ -271,20 +273,32 @@ static const struct nla_policy icmp_nla_policy[CTA_PROTO_MAX+1] = {
 };
 
 static int icmp_nlattr_to_tuple(struct nlattr *tb[],
-				struct nf_conntrack_tuple *tuple)
+				struct nf_conntrack_tuple *tuple,
+				u_int32_t flags)
 {
-	if (!tb[CTA_PROTO_ICMP_TYPE] ||
-	    !tb[CTA_PROTO_ICMP_CODE] ||
-	    !tb[CTA_PROTO_ICMP_ID])
-		return -EINVAL;
+	if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMP_TYPE)) {
+		if (!tb[CTA_PROTO_ICMP_TYPE])
+			return -EINVAL;
 
-	tuple->dst.u.icmp.type = nla_get_u8(tb[CTA_PROTO_ICMP_TYPE]);
-	tuple->dst.u.icmp.code = nla_get_u8(tb[CTA_PROTO_ICMP_CODE]);
-	tuple->src.u.icmp.id = nla_get_be16(tb[CTA_PROTO_ICMP_ID]);
+		tuple->dst.u.icmp.type = nla_get_u8(tb[CTA_PROTO_ICMP_TYPE]);
+		if (tuple->dst.u.icmp.type >= sizeof(invmap) ||
+		    !invmap[tuple->dst.u.icmp.type])
+			return -EINVAL;
+	}
 
-	if (tuple->dst.u.icmp.type >= sizeof(invmap) ||
-	    !invmap[tuple->dst.u.icmp.type])
-		return -EINVAL;
+	if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMP_CODE)) {
+		if (!tb[CTA_PROTO_ICMP_CODE])
+			return -EINVAL;
+
+		tuple->dst.u.icmp.code = nla_get_u8(tb[CTA_PROTO_ICMP_CODE]);
+	}
+
+	if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMP_ID)) {
+		if (!tb[CTA_PROTO_ICMP_ID])
+			return -EINVAL;
+
+		tuple->src.u.icmp.id = nla_get_be16(tb[CTA_PROTO_ICMP_ID]);
+	}
 
 	return 0;
 }

net/netfilter/nf_conntrack_proto_icmpv6.c

@@ -24,6 +24,8 @@
 #include <net/netfilter/nf_conntrack_zones.h>
 #include <net/netfilter/nf_log.h>
 
+#include "nf_internals.h"
+
 static const unsigned int nf_ct_icmpv6_timeout = 30*HZ;
 
 bool icmpv6_pkt_to_tuple(const struct sk_buff *skb,
@@ -193,21 +195,33 @@ static const struct nla_policy icmpv6_nla_policy[CTA_PROTO_MAX+1] = {
 };
 
 static int icmpv6_nlattr_to_tuple(struct nlattr *tb[],
-				struct nf_conntrack_tuple *tuple)
+				struct nf_conntrack_tuple *tuple,
+				u_int32_t flags)
 {
-	if (!tb[CTA_PROTO_ICMPV6_TYPE] ||
-	    !tb[CTA_PROTO_ICMPV6_CODE] ||
-	    !tb[CTA_PROTO_ICMPV6_ID])
-		return -EINVAL;
+	if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMPV6_TYPE)) {
+		if (!tb[CTA_PROTO_ICMPV6_TYPE])
+			return -EINVAL;
 
-	tuple->dst.u.icmp.type = nla_get_u8(tb[CTA_PROTO_ICMPV6_TYPE]);
-	tuple->dst.u.icmp.code = nla_get_u8(tb[CTA_PROTO_ICMPV6_CODE]);
-	tuple->src.u.icmp.id = nla_get_be16(tb[CTA_PROTO_ICMPV6_ID]);
+		tuple->dst.u.icmp.type = nla_get_u8(tb[CTA_PROTO_ICMPV6_TYPE]);
+		if (tuple->dst.u.icmp.type < 128 ||
+		    tuple->dst.u.icmp.type - 128 >= sizeof(invmap) ||
+		    !invmap[tuple->dst.u.icmp.type - 128])
+			return -EINVAL;
+	}
 
-	if (tuple->dst.u.icmp.type < 128 ||
-	    tuple->dst.u.icmp.type - 128 >= sizeof(invmap) ||
-	    !invmap[tuple->dst.u.icmp.type - 128])
-		return -EINVAL;
+	if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMPV6_CODE)) {
+		if (!tb[CTA_PROTO_ICMPV6_CODE])
+			return -EINVAL;
+
+		tuple->dst.u.icmp.code = nla_get_u8(tb[CTA_PROTO_ICMPV6_CODE]);
+	}
+
+	if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMPV6_ID)) {
+		if (!tb[CTA_PROTO_ICMPV6_ID])
+			return -EINVAL;
+
+		tuple->src.u.icmp.id = nla_get_be16(tb[CTA_PROTO_ICMPV6_ID]);
+	}
 
 	return 0;
 }

net/netfilter/nf_internals.h

@@ -6,6 +6,23 @@
 #include <linux/skbuff.h>
 #include <linux/netdevice.h>
 
+/* nf_conntrack_netlink.c: applied on tuple filters */
+#define CTA_FILTER_F_CTA_IP_SRC			(1 << 0)
+#define CTA_FILTER_F_CTA_IP_DST			(1 << 1)
+#define CTA_FILTER_F_CTA_TUPLE_ZONE		(1 << 2)
+#define CTA_FILTER_F_CTA_PROTO_NUM		(1 << 3)
+#define CTA_FILTER_F_CTA_PROTO_SRC_PORT		(1 << 4)
+#define CTA_FILTER_F_CTA_PROTO_DST_PORT		(1 << 5)
+#define CTA_FILTER_F_CTA_PROTO_ICMP_TYPE	(1 << 6)
+#define CTA_FILTER_F_CTA_PROTO_ICMP_CODE	(1 << 7)
+#define CTA_FILTER_F_CTA_PROTO_ICMP_ID		(1 << 8)
+#define CTA_FILTER_F_CTA_PROTO_ICMPV6_TYPE	(1 << 9)
+#define CTA_FILTER_F_CTA_PROTO_ICMPV6_CODE	(1 << 10)
+#define CTA_FILTER_F_CTA_PROTO_ICMPV6_ID	(1 << 11)
+#define CTA_FILTER_F_MAX			(1 << 12)
+#define CTA_FILTER_F_ALL			(CTA_FILTER_F_MAX-1)
+#define CTA_FILTER_FLAG(ctattr) CTA_FILTER_F_ ## ctattr
+
 /* nf_queue.c */
 void nf_queue_nf_hook_drop(struct net *net);