[NETFILTER]: Add support for permanent expectations

A permanent expectation exists until timeing out and can expect
multiple related connections.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netfilter_ipv4/ip_conntrack.h

@@ -263,6 +263,9 @@ struct ip_conntrack_expect
 	/* Unique ID */
 	unsigned int id;
 
+	/* Flags */
+	unsigned int flags;
+
 #ifdef CONFIG_IP_NF_NAT_NEEDED
 	/* This is the original per-proto part, used to map the
 	 * expected connection the way the recipient expects. */
@@ -272,6 +275,8 @@ struct ip_conntrack_expect
 #endif
 };
 
+#define IP_CT_EXPECT_PERMANENT	0x1
+
 static inline struct ip_conntrack *
 tuplehash_to_ctrack(const struct ip_conntrack_tuple_hash *hash)
 {

net/ipv4/netfilter/ip_conntrack_amanda.c

@@ -108,6 +108,7 @@ static int help(struct sk_buff **pskb,
 		}
 
 		exp->expectfn = NULL;
+		exp->flags = 0;
 
 		exp->tuple.src.ip = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip;
 		exp->tuple.src.u.tcp.port = 0;

net/ipv4/netfilter/ip_conntrack_core.c

@@ -264,10 +264,14 @@ find_expectation(const struct ip_conntrack_tuple *tuple)
 		   master ct never got confirmed, we'd hold a reference to it
 		   and weird things would happen to future packets). */
 		if (ip_ct_tuple_mask_cmp(tuple, &i->tuple, &i->mask)
-		    && is_confirmed(i->master)
-		    && del_timer(&i->timeout)) {
-			unlink_expect(i);
-			return i;
+		    && is_confirmed(i->master)) {
+			if (i->flags & IP_CT_EXPECT_PERMANENT) {
+				atomic_inc(&i->use);
+				return i;
+			} else if (del_timer(&i->timeout)) {
+				unlink_expect(i);
+				return i;
+			}
 		}
 	}
 	return NULL;

net/ipv4/netfilter/ip_conntrack_ftp.c

@@ -421,6 +421,7 @@ static int help(struct sk_buff **pskb,
 		  { 0xFFFFFFFF, { .tcp = { 0xFFFF } }, 0xFF }});
 
 	exp->expectfn = NULL;
+	exp->flags = 0;
 
 	/* Now, NAT might want to mangle the packet, and register the
 	 * (possibly changed) expectation itself. */

net/ipv4/netfilter/ip_conntrack_irc.c

@@ -221,6 +221,7 @@ static int help(struct sk_buff **pskb,
 				{ { 0, { 0 } },
 				  { 0xFFFFFFFF, { .tcp = { 0xFFFF } }, 0xFF }});
 			exp->expectfn = NULL;
+			exp->flags = 0;
 			if (ip_nat_irc_hook)
 				ret = ip_nat_irc_hook(pskb, ctinfo, 
 						      addr_beg_p - ib_ptr,

net/ipv4/netfilter/ip_conntrack_netlink.c

@@ -1413,6 +1413,7 @@ ctnetlink_create_expect(struct nfattr *cda[])
 	}
 
 	exp->expectfn = NULL;
+	exp->flags = 0;
 	exp->master = ct;
 	memcpy(&exp->tuple, &tuple, sizeof(struct ip_conntrack_tuple));
 	memcpy(&exp->mask, &mask, sizeof(struct ip_conntrack_tuple));

net/ipv4/netfilter/ip_conntrack_tftp.c

@@ -75,6 +75,7 @@ static int tftp_help(struct sk_buff **pskb,
 		exp->mask.dst.u.udp.port = 0xffff;
 		exp->mask.dst.protonum = 0xff;
 		exp->expectfn = NULL;
+		exp->flags = 0;
 
 		DEBUGP("expect: ");
 		DUMP_TUPLE(&exp->tuple);