Introduce the pickup facilities to take over TCP connections

PATCH Applied Pablo Neira Ayuso 2 participants 2 messages Jul 25, 2006 – Aug 8, 2006

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Networking netfilter

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Pablo Neira Ayuso

author maintainer

2006-07-25 13:25 UTC #0 lore raw

PATCH 5/8 Introduce the pickup facilities to take over TCP connections

This patch introduces a new flag called IPS_PICKUP that forces the protocol handler to pick up the required information in order to ensure that the connection will reach a successful state.

Two new ctnetlink attributes are also introduced to inject the window scale factor since TCP window tracking could need it to take over the connection properly.

Signed-off-by Pablo Neira Ayuso <[email protected]>

Signature · 1 line

The dawn of the fourth age of Linux firewalling is coming; a time of great struggle and heroic deeds -- J.Kadlecsik got inspired by J.Morris

[CONNTRACK] Introduce the pickup facilities to take over TCP connections

This patch introduces a new flag called IPS_PICKUP that forces the protocol handler to pick up the required information in order to ensure that the connection will reach a successful state.

Two new ctnetlink attributes are also introduced to inject the window scale factor since TCP window tracking could need it to take over the connection properly.

Signed-off-by Pablo Neira Ayuso <[email protected]>

net/ipv4/netfilter/ip_conntrack_proto_tcp.c +62 ~~-21~~

Index: net-2.6/net/ipv4/netfilter/ip_conntrack_proto_tcp.c
===================================================================
@@ -346,6 +346,12 @@ static int tcp_to_nfattr(struct sk_buff 
 	nest_parms = NFA_NEST(skb, CTA_PROTOINFO_TCP);
 	NFA_PUT(skb, CTA_PROTOINFO_TCP_STATE, sizeof(u_int8_t),
 		&ct->proto.tcp.state);
+	/* window scale factor: original direction (SYN) */
+	NFA_PUT(skb, CTA_PROTOINFO_TCP_WSCALE_ORIGINAL, sizeof(u_int8_t),
+		&ct->proto.tcp.seen[0].td_scale);
+	/* window scale factor: reply direction (SYN+ACK) */
+	NFA_PUT(skb, CTA_PROTOINFO_TCP_WSCALE_REPLY, sizeof(u_int8_t),
+		&ct->proto.tcp.seen[1].td_scale);
 	read_unlock_bh(&tcp_lock);
 
 	NFA_NEST_END(skb, nest_parms);

@@ -358,7 +364,9 @@ nfattr_failure:
 }
 
 static const size_t cta_min_tcp[CTA_PROTOINFO_TCP_MAX] = {
-	[CTA_PROTOINFO_TCP_STATE-1]	= sizeof(u_int8_t),
+	[CTA_PROTOINFO_TCP_STATE-1]		= sizeof(u_int8_t),
+	[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL-1]	= sizeof(u_int8_t),
+	[CTA_PROTOINFO_TCP_WSCALE_REPLY-1]	= sizeof(u_int8_t),
 };
 
 static int nfattr_to_tcp(struct nfattr *cda[], struct ip_conntrack *ct)

@@ -382,6 +390,24 @@ static int nfattr_to_tcp(struct nfattr *
 	write_lock_bh(&tcp_lock);
 	ct->proto.tcp.state = 
 		*(u_int8_t *)NFA_DATA(tb[CTA_PROTOINFO_TCP_STATE-1]);
+	/* window scale factor: original direction (SYN) */
+	if (tb[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL-1])
+		ct->proto.tcp.seen[0].td_scale = 
+		*(u_int8_t *)NFA_DATA(tb[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL-1]);
+	/* window scale factor: reply direction (SYN+ACK) */
+	if (tb[CTA_PROTOINFO_TCP_WSCALE_REPLY-1])
+		ct->proto.tcp.seen[1].td_scale = 
+		*(u_int8_t *)NFA_DATA(tb[CTA_PROTOINFO_TCP_WSCALE_REPLY-1]);
+	/* set WINDOW_SCALE flag */
+	if (tb[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL-1] ||
+	    tb[CTA_PROTOINFO_TCP_WSCALE_REPLY-1]) {
+		/*
+		 * we have to assume that both sides have
+		 * sent Window Scale options (RFC 1323)
+		 */
+		ct->proto.tcp.seen[0].flags |=
+		ct->proto.tcp.seen[1].flags |= IP_CT_TCP_FLAG_WINDOW_SCALE;
+	}
 	write_unlock_bh(&tcp_lock);
 
 	return 0;

@@ -425,10 +451,10 @@ static unsigned int get_conntrack_index(
    we doesn't have to deal with fragments. 
 */
 
-static inline __u32 segment_seq_plus_len(__u32 seq,
-					 size_t len,
-					 struct iphdr *iph,
-					 struct tcphdr *tcph)
+static inline __u32 segment_seq_plus_len(const __u32 seq,
+					 const size_t len,
+					 const struct iphdr *iph,
+					 const struct tcphdr *tcph)
 {
 	return (seq + len - (iph->ihl + tcph->doff)*4
 		+ (tcph->syn ? 1 : 0) + (tcph->fin ? 1 : 0));

@@ -890,6 +916,28 @@ static int tcp_error(struct sk_buff *skb
 	return NF_ACCEPT;
 }
 
+static void tcp_pickup_connection(struct ip_conntrack *conntrack,
+				  const struct sk_buff *skb,
+				  const struct iphdr *iph,
+				  const struct tcphdr *th)
+{
+	conntrack->proto.tcp.seen[0].td_end =
+		segment_seq_plus_len(ntohl(th->seq), skb->len, iph, th);
+	conntrack->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
+	if (conntrack->proto.tcp.seen[0].td_maxwin == 0)
+		conntrack->proto.tcp.seen[0].td_maxwin = 1;
+	conntrack->proto.tcp.seen[0].td_maxend =
+		conntrack->proto.tcp.seen[0].td_end + 
+		conntrack->proto.tcp.seen[0].td_maxwin;
+		conntrack->proto.tcp.seen[0].td_scale = 0;
+
+	/* We assume SACK. Should we assume window scaling too? */
+	conntrack->proto.tcp.seen[0].flags |=
+	conntrack->proto.tcp.seen[1].flags |= IP_CT_TCP_FLAG_SACK_PERM;
+	conntrack->proto.tcp.seen[0].loose = 
+	conntrack->proto.tcp.seen[1].loose = ip_ct_tcp_loose;
+}
+
 /* Returns verdict for packet, or -1 for invalid. */
 static int tcp_packet(struct ip_conntrack *conntrack,
 		      const struct sk_buff *skb,

@@ -907,6 +955,14 @@ static int tcp_packet(struct ip_conntrac
 	BUG_ON(th == NULL);
 	
 	write_lock_bh(&tcp_lock);
+
+	/*
+	 * This conntrack was added via ctnetlink or ct_sync and needs to
+	 * take over sequence tracking in order to work properly.
+	 */
+	if (test_and_clear_bit(IPS_PICKUP, &conntrack->status))
+		tcp_pickup_connection(conntrack, skb, iph, th);
+
 	old_state = conntrack->proto.tcp.state;
 	dir = CTINFO2DIR(ctinfo);
 	index = get_conntrack_index(th);

@@ -1116,22 +1172,7 @@ static int tcp_new(struct ip_conntrack *
 		 * its history is lost for us.
 		 * Let's try to use the data from the packet.
 		 */
-		conntrack->proto.tcp.seen[0].td_end =
-			segment_seq_plus_len(ntohl(th->seq), skb->len,
-					     iph, th);
-		conntrack->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
-		if (conntrack->proto.tcp.seen[0].td_maxwin == 0)
-			conntrack->proto.tcp.seen[0].td_maxwin = 1;
-		conntrack->proto.tcp.seen[0].td_maxend =
-			conntrack->proto.tcp.seen[0].td_end + 
-			conntrack->proto.tcp.seen[0].td_maxwin;
-		conntrack->proto.tcp.seen[0].td_scale = 0;
-
-		/* We assume SACK. Should we assume window scaling too? */
-		conntrack->proto.tcp.seen[0].flags =
-		conntrack->proto.tcp.seen[1].flags = IP_CT_TCP_FLAG_SACK_PERM;
-		conntrack->proto.tcp.seen[0].loose = 
-		conntrack->proto.tcp.seen[1].loose = ip_ct_tcp_loose;
+		tcp_pickup_connection(conntrack, skb, iph, th);
 	}
     
 	conntrack->proto.tcp.seen[1].td_end = 0;

include/linux/netfilter/nf_conntrack_common.h +4 -0

Index: net-2.6/include/linux/netfilter/nf_conntrack_common.h
===================================================================
@@ -73,6 +73,10 @@ enum ip_conntrack_status {
 	/* Connection has fixed timeout. */
 	IPS_FIXED_TIMEOUT_BIT = 10,
 	IPS_FIXED_TIMEOUT = (1 << IPS_FIXED_TIMEOUT_BIT),
+
+	/* Pick up connection information if required */
+	IPS_PICKUP_BIT = 11,
+	IPS_PICKUP = (1 << IPS_PICKUP_BIT),
 };
 
 /* Connection tracking event bits */

net/netfilter/nf_conntrack_proto_tcp.c +62 ~~-21~~

125 lines not on this page · raw message

include/linux/netfilter/nfnetlink_conntrack.h +2 -0

Index: net-2.6/include/linux/netfilter/nfnetlink_conntrack.h
===================================================================
@@ -83,6 +83,8 @@ enum ctattr_protoinfo {
 enum ctattr_protoinfo_tcp {
 	CTA_PROTOINFO_TCP_UNSPEC,
 	CTA_PROTOINFO_TCP_STATE,
+	CTA_PROTOINFO_TCP_WSCALE_ORIGINAL,
+	CTA_PROTOINFO_TCP_WSCALE_REPLY,
 	__CTA_PROTOINFO_TCP_MAX
 };
 #define CTA_PROTOINFO_TCP_MAX (__CTA_PROTOINFO_TCP_MAX - 1)

Patrick McHardy

2006-08-08 10:33 UTC #1 lore raw

Quoted 64 lines · Pablo Neira Ayuso

This patch introduces a new flag called IPS_PICKUP that forces the protocol handler to pick up the required information in order to ensure that the connection will reach a successful state.
Two new ctnetlink attributes are also introduced to inject the window scale factor since TCP window tracking could need it to take over the connection properly.
Signed-off-by Pablo Neira Ayuso <[email protected]>
------------------------------------------------------------------------
[CONNTRACK] Introduce the pickup facilities to take over TCP connections
This patch introduces a new flag called IPS_PICKUP that forces the protocol handler to pick up the required information in order to ensure that the connection will reach a successful state.
Two new ctnetlink attributes are also introduced to inject the window scale factor since TCP window tracking could need it to take over the connection properly.
Signed-off-by Pablo Neira Ayuso <[email protected]>
Index: net-2.6/net/ipv4/netfilter/ip_conntrack_proto_tcp.c
===================================================================
net/ipv4/netfilter/ip_conntrack_proto_tcp.c +16 -1
@@ -346,6 +346,12 @@ static int tcp_to_nfattr(struct sk_buff 
 	nest_parms = NFA_NEST(skb, CTA_PROTOINFO_TCP);
 	NFA_PUT(skb, CTA_PROTOINFO_TCP_STATE, sizeof(u_int8_t),
 		&ct->proto.tcp.state);
+	/* window scale factor: original direction (SYN) */
+	NFA_PUT(skb, CTA_PROTOINFO_TCP_WSCALE_ORIGINAL, sizeof(u_int8_t),
+		&ct->proto.tcp.seen[0].td_scale);
+	/* window scale factor: reply direction (SYN+ACK) */
+	NFA_PUT(skb, CTA_PROTOINFO_TCP_WSCALE_REPLY, sizeof(u_int8_t),
+		&ct->proto.tcp.seen[1].td_scale);
 	read_unlock_bh(&tcp_lock);
 
 	NFA_NEST_END(skb, nest_parms);
@@ -358,7 +364,9 @@ nfattr_failure:
 }
 
 static const size_t cta_min_tcp[CTA_PROTOINFO_TCP_MAX] = {
-	[CTA_PROTOINFO_TCP_STATE-1]	= sizeof(u_int8_t),
+	[CTA_PROTOINFO_TCP_STATE-1]		= sizeof(u_int8_t),
+	[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL-1]	= sizeof(u_int8_t),
+	[CTA_PROTOINFO_TCP_WSCALE_REPLY-1]	= sizeof(u_int8_t),
 };
 
 static int nfattr_to_tcp(struct nfattr *cda[], struct ip_conntrack *ct)
@@ -382,6 +390,24 @@ static int nfattr_to_tcp(struct nfattr *
 	write_lock_bh(&tcp_lock);
 	ct->proto.tcp.state = 
 		*(u_int8_t *)NFA_DATA(tb[CTA_PROTOINFO_TCP_STATE-1]);
+	/* window scale factor: original direction (SYN) */
+	if (tb[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL-1])
+		ct->proto.tcp.seen[0].td_scale = 
+		*(u_int8_t *)NFA_DATA(tb[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL-1]);
+	/* window scale factor: reply direction (SYN+ACK) */
+	if (tb[CTA_PROTOINFO_TCP_WSCALE_REPLY-1])
+		ct->proto.tcp.seen[1].td_scale = 

net/ipv4/netfilter/ip_conntrack_proto_tcp.c static int nfattr_to_tcp(struct nfattr * · line 409

Quoted 10 lines

net/ipv4/netfilter/ip_conntrack_proto_tcp.c +10 -0

+		*(u_int8_t *)NFA_DATA(tb[CTA_PROTOINFO_TCP_WSCALE_REPLY-1]);
+	/* set WINDOW_SCALE flag */
+	if (tb[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL-1] ||
+	    tb[CTA_PROTOINFO_TCP_WSCALE_REPLY-1]) {
+		/*
+		 * we have to assume that both sides have
+		 * sent Window Scale options (RFC 1323)
+		 */
+		ct->proto.tcp.seen[0].flags |=
+		ct->proto.tcp.seen[1].flags |= IP_CT_TCP_FLAG_WINDOW_SCALE;

This will also set all other flags from seen[1] in seen[0]. RFC 1323 also says quite the opposite, both sides must send a wscale option to enable it. For unreplied connections this will do the wrong thing. And we should have an option to unset it, also for the case where we're synchronizing the state of an unreplied connection. I also think it would be better to add netlink attributes for the entire flags mask, for example IP_CT_TCP_FLAG_SACK_PERM also wants to be synchronized I guess.