netfilter: ctnetlink: synproxy support

This patch exposes synproxy information per-conntrack. Moreover, send
sequence adjustment events once server sends us the SYN,ACK packet, so
we can synchronize the sequence adjustment too for packets going as
reply from the server, as part of the synproxy logic.

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

3 files changed, 98 insertions, 5 deletions

diff --git a/net/ipv4/netfilter/ipt_SYNPROXY.c b/net/ipv4/netfilter/ipt_SYNPROXY.c
index f75fc6b53115..690b17ef6a44 100644
--- a/net/ipv4/netfilter/ipt_SYNPROXY.c
+++ b/net/ipv4/netfilter/ipt_SYNPROXY.c
@@ -16,6 +16,7 @@
 #include <net/netfilter/nf_conntrack.h>
 #include <net/netfilter/nf_conntrack_seqadj.h>
 #include <net/netfilter/nf_conntrack_synproxy.h>
+#include <net/netfilter/nf_conntrack_ecache.h>
 
 static struct iphdr *
 synproxy_build_ip(struct net *net, struct sk_buff *skb, __be32 saddr,
@@ -384,6 +385,8 @@ static unsigned int ipv4_synproxy_hook(void *priv,
 		synproxy->isn = ntohl(th->ack_seq);
 		if (opts.options & XT_SYNPROXY_OPT_TIMESTAMP)
 			synproxy->its = opts.tsecr;
+
+		nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
 		break;
 	case TCP_CONNTRACK_SYN_RECV:
 		if (!th->syn || !th->ack)
@@ -392,8 +395,10 @@ static unsigned int ipv4_synproxy_hook(void *priv,
 		if (!synproxy_parse_options(skb, thoff, th, &opts))
 			return NF_DROP;
 
-		if (opts.options & XT_SYNPROXY_OPT_TIMESTAMP)
+		if (opts.options & XT_SYNPROXY_OPT_TIMESTAMP) {
 			synproxy->tsoff = opts.tsval - synproxy->its;
+			nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
+		}
 
 		opts.options &= ~(XT_SYNPROXY_OPT_MSS |
 				  XT_SYNPROXY_OPT_WSCALE |
@@ -403,6 +408,7 @@ static unsigned int ipv4_synproxy_hook(void *priv,
 		synproxy_send_server_ack(net, state, skb, th, &opts);
 
 		nf_ct_seqadj_init(ct, ctinfo, synproxy->isn - ntohl(th->seq));
+		nf_conntrack_event_cache(IPCT_SEQADJ, ct);
 
 		swap(opts.tsval, opts.tsecr);
 		synproxy_send_client_ack(net, skb, th, &opts);
diff --git a/net/ipv6/netfilter/ip6t_SYNPROXY.c b/net/ipv6/netfilter/ip6t_SYNPROXY.c
index 437af8c95277..cb6d42b03cb5 100644
--- a/net/ipv6/netfilter/ip6t_SYNPROXY.c
+++ b/net/ipv6/netfilter/ip6t_SYNPROXY.c
@@ -18,6 +18,7 @@
 #include <net/netfilter/nf_conntrack.h>
 #include <net/netfilter/nf_conntrack_seqadj.h>
 #include <net/netfilter/nf_conntrack_synproxy.h>
+#include <net/netfilter/nf_conntrack_ecache.h>
 
 static struct ipv6hdr *
 synproxy_build_ip(struct net *net, struct sk_buff *skb,
@@ -405,6 +406,8 @@ static unsigned int ipv6_synproxy_hook(void *priv,
 		synproxy->isn = ntohl(th->ack_seq);
 		if (opts.options & XT_SYNPROXY_OPT_TIMESTAMP)
 			synproxy->its = opts.tsecr;
+
+		nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
 		break;
 	case TCP_CONNTRACK_SYN_RECV:
 		if (!th->syn || !th->ack)
@@ -413,8 +416,10 @@ static unsigned int ipv6_synproxy_hook(void *priv,
 		if (!synproxy_parse_options(skb, thoff, th, &opts))
 			return NF_DROP;
 
-		if (opts.options & XT_SYNPROXY_OPT_TIMESTAMP)
+		if (opts.options & XT_SYNPROXY_OPT_TIMESTAMP) {
 			synproxy->tsoff = opts.tsval - synproxy->its;
+			nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
+		}
 
 		opts.options &= ~(XT_SYNPROXY_OPT_MSS |
 				  XT_SYNPROXY_OPT_WSCALE |
@@ -424,6 +429,7 @@ static unsigned int ipv6_synproxy_hook(void *priv,
 		synproxy_send_server_ack(net, state, skb, th, &opts);
 
 		nf_ct_seqadj_init(ct, ctinfo, synproxy->isn - ntohl(th->seq));
+		nf_conntrack_event_cache(IPCT_SEQADJ, ct);
 
 		swap(opts.tsval, opts.tsecr);
 		synproxy_send_client_ack(net, skb, th, &opts);
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 8884d302d33a..11ef85a57244 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -440,6 +440,31 @@ err:
 	return -1;
 }
 
+static int ctnetlink_dump_ct_synproxy(struct sk_buff *skb, struct nf_conn *ct)
+{
+	struct nf_conn_synproxy *synproxy = nfct_synproxy(ct);
+	struct nlattr *nest_parms;
+
+	if (!synproxy)
+		return 0;
+
+	nest_parms = nla_nest_start(skb, CTA_SYNPROXY | NLA_F_NESTED);
+	if (!nest_parms)
+		goto nla_put_failure;
+
+	if (nla_put_be32(skb, CTA_SYNPROXY_ISN, htonl(synproxy->isn)) ||
+	    nla_put_be32(skb, CTA_SYNPROXY_ITS, htonl(synproxy->its)) ||
+	    nla_put_be32(skb, CTA_SYNPROXY_TSOFF, htonl(synproxy->tsoff)))
+		goto nla_put_failure;
+
+	nla_nest_end(skb, nest_parms);
+
+	return 0;
+
+nla_put_failure:
+	return -1;
+}
+
 static int ctnetlink_dump_id(struct sk_buff *skb, const struct nf_conn *ct)
 {
 	if (nla_put_be32(skb, CTA_ID, htonl((unsigned long)ct)))
@@ -518,7 +543,8 @@ ctnetlink_fill_info(struct sk_buff *skb, u32 portid, u32 seq, u32 type,
 	    ctnetlink_dump_id(skb, ct) < 0 ||
 	    ctnetlink_dump_use(skb, ct) < 0 ||
 	    ctnetlink_dump_master(skb, ct) < 0 ||
-	    ctnetlink_dump_ct_seq_adj(skb, ct) < 0)
+	    ctnetlink_dump_ct_seq_adj(skb, ct) < 0 ||
+	    ctnetlink_dump_ct_synproxy(skb, ct) < 0)
 		goto nla_put_failure;
 
 	nlmsg_end(skb, nlh);
@@ -730,6 +756,10 @@ ctnetlink_conntrack_event(unsigned int events, struct nf_ct_event *item)
 		if (events & (1 << IPCT_SEQADJ) &&
 		    ctnetlink_dump_ct_seq_adj(skb, ct) < 0)
 			goto nla_put_failure;
+
+		if (events & (1 << IPCT_SYNPROXY) &&
+		    ctnetlink_dump_ct_synproxy(skb, ct) < 0)
+			goto nla_put_failure;
 	}
 
 #ifdef CONFIG_NF_CONNTRACK_MARK
@@ -1689,6 +1719,39 @@ err:
 	return ret;
 }
 
+static const struct nla_policy synproxy_policy[CTA_SYNPROXY_MAX + 1] = {
+	[CTA_SYNPROXY_ISN]	= { .type = NLA_U32 },
+	[CTA_SYNPROXY_ITS]	= { .type = NLA_U32 },
+	[CTA_SYNPROXY_TSOFF]	= { .type = NLA_U32 },
+};
+
+static int ctnetlink_change_synproxy(struct nf_conn *ct,
+				     const struct nlattr * const cda[])
+{
+	struct nf_conn_synproxy *synproxy = nfct_synproxy(ct);
+	struct nlattr *tb[CTA_SYNPROXY_MAX + 1];
+	int err;
+
+	if (!synproxy)
+		return 0;
+
+	err = nla_parse_nested(tb, CTA_SYNPROXY_MAX, cda[CTA_SYNPROXY],
+			       synproxy_policy, NULL);
+	if (err < 0)
+		return err;
+
+	if (!tb[CTA_SYNPROXY_ISN] ||
+	    !tb[CTA_SYNPROXY_ITS] ||
+	    !tb[CTA_SYNPROXY_TSOFF])
+		return -EINVAL;
+
+	synproxy->isn = ntohl(nla_get_be32(tb[CTA_SYNPROXY_ISN]));
+	synproxy->its = ntohl(nla_get_be32(tb[CTA_SYNPROXY_ITS]));
+	synproxy->tsoff = ntohl(nla_get_be32(tb[CTA_SYNPROXY_TSOFF]));
+
+	return 0;
+}
+
 static int
 ctnetlink_attach_labels(struct nf_conn *ct, const struct nlattr * const cda[])
 {
@@ -1759,6 +1822,12 @@ ctnetlink_change_conntrack(struct nf_conn *ct,
 			return err;
 	}
 
+	if (cda[CTA_SYNPROXY]) {
+		err = ctnetlink_change_synproxy(ct, cda);
+		if (err < 0)
+			return err;
+	}
+
 	if (cda[CTA_LABELS]) {
 		err = ctnetlink_attach_labels(ct, cda);
 		if (err < 0)
@@ -1880,6 +1949,12 @@ ctnetlink_create_conntrack(struct net *net,
 			goto err2;
 	}
 
+	if (cda[CTA_SYNPROXY]) {
+		err = ctnetlink_change_synproxy(ct, cda);
+		if (err < 0)
+			goto err2;
+	}
+
 #if defined(CONFIG_NF_CONNTRACK_MARK)
 	if (cda[CTA_MARK])
 		ct->mark = ntohl(nla_get_be32(cda[CTA_MARK]));
@@ -1991,7 +2066,9 @@ static int ctnetlink_new_conntrack(struct net *net, struct sock *ctnl,
 						      (1 << IPCT_HELPER) |
 						      (1 << IPCT_PROTOINFO) |
 						      (1 << IPCT_SEQADJ) |
-						      (1 << IPCT_MARK) | events,
+						      (1 << IPCT_MARK) |
+						      (1 << IPCT_SYNPROXY) |
+						      events,
 						      ct, NETLINK_CB(skb).portid,
 						      nlmsg_report(nlh));
 			nf_ct_put(ct);
@@ -2012,7 +2089,8 @@ static int ctnetlink_new_conntrack(struct net *net, struct sock *ctnl,
 						      (1 << IPCT_LABEL) |
 						      (1 << IPCT_PROTOINFO) |
 						      (1 << IPCT_SEQADJ) |
-						      (1 << IPCT_MARK),
+						      (1 << IPCT_MARK) |
+						      (1 << IPCT_SYNPROXY),
 						      ct, NETLINK_CB(skb).portid,
 						      nlmsg_report(nlh));
 		}
@@ -2282,6 +2360,9 @@ static int __ctnetlink_glue_build(struct sk_buff *skb, struct nf_conn *ct)
 	    ctnetlink_dump_ct_seq_adj(skb, ct) < 0)
 		goto nla_put_failure;
 
+	if (ctnetlink_dump_ct_synproxy(skb, ct) < 0)
+		goto nla_put_failure;
+
 #ifdef CONFIG_NF_CONNTRACK_MARK
 	if (ct->mark && ctnetlink_dump_mark(skb, ct) < 0)
 		goto nla_put_failure;