network: add protocol version field (breaks backward compatibility)

This patch adds the version field (8-bits long) to the nethdr
structure. This fields can be used to indicate the protocol version
in case that we detect an incompatibility between two conntrackd
daemons working with different protocol versions.

Unfortunately, this patch breaks backward compatibility, ie.
conntrackd <= 0.9.8 protocol is not compatible with the upcoming
conntrackd >= 0.9.9. Better do this now than later.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

4 files changed, 19 insertions, 14 deletions

diff --git a/include/network.h b/include/network.h
index d2e4edd..d2431f9 100644
--- a/include/network.h
+++ b/include/network.h
@@ -4,10 +4,13 @@
 #include <stdint.h>
 #include <sys/types.h>
 
+#define CONNTRACKD_PROTOCOL_VERSION	0
+
 struct nf_conntrack;
 
 struct nethdr {
-	uint16_t flags;
+	uint8_t version;
+	uint8_t flags;
 	uint16_t len;
 	uint32_t seq;
 };
@@ -17,7 +20,8 @@ struct nethdr {
 	(struct netpld *)(((char *)x) + sizeof(struct nethdr))
 
 struct nethdr_ack {
-	uint16_t flags; 
+	uint8_t version;
+	uint8_t flags; 
 	uint16_t len;
 	uint32_t seq;
 	uint32_t from;
@@ -87,7 +91,6 @@ ssize_t mcast_buffered_pending_netmsg(struct mcast_sock *m);
 
 #define HDR_NETWORK2HOST(x)						\
 ({									\
-	x->flags = ntohs(x->flags);					\
 	x->len   = ntohs(x->len);					\
 	x->seq   = ntohl(x->seq);					\
 	if (IS_CTL(x)) {						\
@@ -104,7 +107,6 @@ ssize_t mcast_buffered_pending_netmsg(struct mcast_sock *m);
 		__ack->from = htonl(__ack->from);			\
 		__ack->to = htonl(__ack->to);				\
 	}								\
-	x->flags = htons(x->flags);					\
 	x->len   = htons(x->len);					\
 	x->seq   = htonl(x->seq);					\
 })
diff --git a/src/network.c b/src/network.c
index 7d1d9fa..04c9d39 100644
--- a/src/network.c
+++ b/src/network.c
@@ -32,8 +32,7 @@ static size_t __do_send(struct mcast_sock *m, void *data, size_t len)
 	struct nethdr *net = data;
 
 	debug("send sq: %u fl:%u len:%u\n",
-		ntohl(net->seq), ntohs(net->flags),
-		ntohs(net->len));
+		ntohl(net->seq), net->flags, ntohs(net->len));
 
 	return mcast_send(m, net, len);
 }
@@ -46,6 +45,7 @@ static size_t __do_prepare(struct mcast_sock *m, void *data, size_t len)
 		seq_set = 1;
 		cur_seq = time(NULL);
 	}
+	net->version = CONNTRACKD_PROTOCOL_VERSION;
 	net->len = len;
 	net->seq = cur_seq++;
 	HDR_HOST2NETWORK(net);
diff --git a/src/sync-ftfw.c b/src/sync-ftfw.c
index ed97ceb..598945f 100644
--- a/src/sync-ftfw.c
+++ b/src/sync-ftfw.c
@@ -477,14 +477,12 @@ static void ftfw_send(struct nethdr *net, struct us_conntrack *u)
 			hello_state = HELLO_SAY;
 			/* fall through */
 		case HELLO_SAY:
-			net->flags = ntohs(net->flags) | NET_F_HELLO;
-			net->flags = htons(net->flags);
+			net->flags |= NET_F_HELLO;
 			break;
 		}
 
 		if (say_hello_back) {
-			net->flags = ntohs(net->flags) | NET_F_HELLO_BACK;
-			net->flags = htons(net->flags);
+			net->flags |= NET_F_HELLO_BACK;
 			say_hello_back = 0;
 		}
 
@@ -501,7 +499,7 @@ static int tx_queue_xmit(void *data1, const void *data2)
 	size_t len = prepare_send_netmsg(STATE_SYNC(mcast_client), net);
 
 	dp("tx_queue sq: %u fl:%u len:%u\n",
-               ntohl(net->seq), ntohs(net->flags), ntohs(net->len));
+               ntohl(net->seq), net->flags, ntohs(net->len));
 
 	mcast_buffered_send_netmsg(STATE_SYNC(mcast_client), net, len);
 	HDR_NETWORK2HOST(net);
@@ -521,8 +519,7 @@ static int tx_list_xmit(struct list_head *i, struct us_conntrack *u, int type)
 	size_t len = prepare_send_netmsg(STATE_SYNC(mcast_client), net);
 
 	dp("tx_list sq: %u fl:%u len:%u\n",
-                ntohl(net->seq), ntohs(net->flags),
-                ntohs(net->len));
+                ntohl(net->seq), net->flags, ntohs(net->len));
 
 	list_del_init(i);
 	tx_list_len--;
diff --git a/src/sync-mode.c b/src/sync-mode.c
index 4c22745..152a8e2 100644
--- a/src/sync-mode.c
+++ b/src/sync-mode.c
@@ -41,6 +41,12 @@ static void do_mcast_handler_step(struct nethdr *net, size_t remain)
 	struct nf_conntrack *ct = (struct nf_conntrack *)(void*) __ct;
 	struct us_conntrack *u;
 
+	if (net->version != CONNTRACKD_PROTOCOL_VERSION) {
+		STATE(malformed)++;
+		dlog(LOG_WARNING, "wrong protocol version `%u'", net->version);
+		return;
+	}
+
 	switch (STATE_SYNC(sync)->recv(net)) {
 		case MSG_DATA:
 			break;
@@ -144,7 +150,7 @@ static void mcast_handler(void)
 		}
 
 		debug("recv sq: %u fl:%u len:%u (rem:%d)\n", 
-			ntohl(net->seq), ntohs(net->flags),
+			ntohl(net->seq), net->flags,
 			ntohs(net->len), remain);
 
 		HDR_NETWORK2HOST(net);