[PATCH 0/5] Extract SYNPROXY infrastructure

[PATCH 0/5] Extract SYNPROXY infrastructure

[Fernando Fernandez Mancera]

The patch series have been tested by enabling iptables and ip6tables SYNPROXY.
All the modules loaded as expected.

$ lsmod | grep synproxy
Only IPv4:
nf_synproxy_ipv4       16384  1 ipt_SYNPROXY
nf_synproxy_core       16384  4 ipt_SYNPROXY,nf_synproxy_ipv4
nf_conntrack          159744  8 xt_conntrack,xt_state,ipt_SYNPROXY,nf_synproxy_ipv4,nf_synproxy_core,xt_CT

Only IPv6:
nf_synproxy_ipv6       16384  1 ip6t_SYNPROXY
nf_synproxy_core       16384  4 ip6t_SYNPROXY,nf_synproxy_ipv6
nf_conntrack          159744  8 ip6t_SYNPROXY,xt_conntrack,xt_state,nf_synproxy_ipv6,nf_synproxy_core,xt_CT

IPv4 and IPv6:
nf_synproxy_ipv6       16384  1 ip6t_SYNPROXY
nf_synproxy_ipv4       16384  1 ipt_SYNPROXY
nf_synproxy_core       16384  4 ip6t_SYNPROXY,nf_synproxy_ipv6,ipt_SYNPROXY,nf_synproxy_ipv4
nf_conntrack          159744  8 ip6t_SYNPROXY,xt_conntrack,xt_state,nf_synproxy_ipv6,ipt_SYNPROXY,nf_synproxy_ipv4,nf_synproxy_core,xt_CT

Fernando Fernandez Mancera (5):
  netfilter: synproxy: add common uapi for SYNPROXY infrastructure
  netfilter: synproxy: extract IPv4 SYNPROXY infrastructure from
    ipt_SYNPROXY
  netfilter: add NF_SYNPROXY_IPV4 symbol
  netfilter: synproxy: extract IPv6 SYNPROXY infrastructure from
    ip6t_SYNPROXY
  netfilter: add NF_SYNPROXY_IPV6 symbol

 include/net/netfilter/ipv4/nf_synproxy_ipv4.h |  42 ++
 include/net/netfilter/ipv6/nf_synproxy_ipv6.h |  43 ++
 include/uapi/linux/netfilter/nf_SYNPROXY.h    |  19 +
 include/uapi/linux/netfilter/xt_SYNPROXY.h    |  18 +-
 net/ipv4/netfilter/Kconfig                    |   4 +
 net/ipv4/netfilter/Makefile                   |   3 +
 net/ipv4/netfilter/ipt_SYNPROXY.c             | 394 +---------------
 net/ipv4/netfilter/nf_synproxy_ipv4.c         | 393 ++++++++++++++++
 net/ipv6/netfilter/Kconfig                    |   4 +
 net/ipv6/netfilter/Makefile                   |   3 +
 net/ipv6/netfilter/ip6t_SYNPROXY.c            | 420 +-----------------
 net/ipv6/netfilter/nf_synproxy_ipv6.c         | 414 +++++++++++++++++
 12 files changed, 947 insertions(+), 810 deletions(-)
 create mode 100644 include/net/netfilter/ipv4/nf_synproxy_ipv4.h
 create mode 100644 include/net/netfilter/ipv6/nf_synproxy_ipv6.h
 create mode 100644 include/uapi/linux/netfilter/nf_SYNPROXY.h
 create mode 100644 net/ipv4/netfilter/nf_synproxy_ipv4.c
 create mode 100644 net/ipv6/netfilter/nf_synproxy_ipv6.c

-- 
2.20.1

[PATCH 1/5 nf-next] netfilter: synproxy: add common uapi for SYNPROXY infrastructure

[Fernando Fernandez Mancera]

This new UAPI file is going to be used by the xt and nft common SYNPROXY
infrastructure. It is needed to avoid duplicated code.

Signed-off-by: Fernando Fernandez Mancera <ffmancera@riseup.net>
---
 include/uapi/linux/netfilter/nf_SYNPROXY.h | 19 +++++++++++++++++++
 include/uapi/linux/netfilter/xt_SYNPROXY.h | 18 +++++++-----------
 2 files changed, 26 insertions(+), 11 deletions(-)
 create mode 100644 include/uapi/linux/netfilter/nf_SYNPROXY.h

diff --git a/include/uapi/linux/netfilter/nf_SYNPROXY.h b/include/uapi/linux/netfilter/nf_SYNPROXY.h
new file mode 100644
index 000000000000..068d1b3a6f06
--- /dev/null
+++ b/include/uapi/linux/netfilter/nf_SYNPROXY.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _NF_SYNPROXY_H
+#define _NF_SYNPROXY_H
+
+#include <linux/types.h>
+
+#define NF_SYNPROXY_OPT_MSS		0x01
+#define NF_SYNPROXY_OPT_WSCALE		0x02
+#define NF_SYNPROXY_OPT_SACK_PERM	0x04
+#define NF_SYNPROXY_OPT_TIMESTAMP	0x08
+#define NF_SYNPROXY_OPT_ECN		0x10
+
+struct nf_synproxy_info {
+	__u8	options;
+	__u8	wscale;
+	__u16	mss;
+};
+
+#endif /* _NF_SYNPROXY_H */
diff --git a/include/uapi/linux/netfilter/xt_SYNPROXY.h b/include/uapi/linux/netfilter/xt_SYNPROXY.h
index ea5eba15d4c1..4d5611d647df 100644
--- a/include/uapi/linux/netfilter/xt_SYNPROXY.h
+++ b/include/uapi/linux/netfilter/xt_SYNPROXY.h
@@ -2,18 +2,14 @@
 #ifndef _XT_SYNPROXY_H
 #define _XT_SYNPROXY_H
 
-#include <linux/types.h>
+#include <linux/netfilter/nf_SYNPROXY.h>
 
-#define XT_SYNPROXY_OPT_MSS		0x01
-#define XT_SYNPROXY_OPT_WSCALE		0x02
-#define XT_SYNPROXY_OPT_SACK_PERM	0x04
-#define XT_SYNPROXY_OPT_TIMESTAMP	0x08
-#define XT_SYNPROXY_OPT_ECN		0x10
+#define XT_SYNPROXY_OPT_MSS		NF_SYNPROXY_OPT_MSS
+#define XT_SYNPROXY_OPT_WSCALE		NF_SYNPROXY_OPT_WSCALE
+#define XT_SYNPROXY_OPT_SACK_PERM	NF_SYNPROXY_OPT_SACK_PERM
+#define XT_SYNPROXY_OPT_TIMESTAMP	NF_SYNPROXY_OPT_TIMESTAMP
+#define XT_SYNPROXY_OPT_ECN		NF_SYNPROXY_OPT_ECN
 
-struct xt_synproxy_info {
-	__u8	options;
-	__u8	wscale;
-	__u16	mss;
-};
+#define xt_synproxy_info		nf_synproxy_info
 
 #endif /* _XT_SYNPROXY_H */
-- 
2.20.1

[PATCH 2/5 nf-next] netfilter: synproxy: extract IPv4 SYNPROXY infrastructure from ipt_SYNPROXY

[Fernando Fernandez Mancera]

Add common functions into nf_synproxy_ipv4.c to prepare for nftables support.

Signed-off-by: Fernando Fernandez Mancera <ffmancera@riseup.net>
---
 include/net/netfilter/ipv4/nf_synproxy_ipv4.h |  42 ++
 net/ipv4/netfilter/ipt_SYNPROXY.c             | 394 +-----------------
 net/ipv4/netfilter/nf_synproxy_ipv4.c         | 393 +++++++++++++++++
 3 files changed, 441 insertions(+), 388 deletions(-)
 create mode 100644 include/net/netfilter/ipv4/nf_synproxy_ipv4.h
 create mode 100644 net/ipv4/netfilter/nf_synproxy_ipv4.c

diff --git a/include/net/netfilter/ipv4/nf_synproxy_ipv4.h b/include/net/netfilter/ipv4/nf_synproxy_ipv4.h
new file mode 100644
index 000000000000..3a8dff2e58e7
--- /dev/null
+++ b/include/net/netfilter/ipv4/nf_synproxy_ipv4.h
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _NF_SYNPROXY_IPV4_H
+#define _NF_SYNPROXY_IPV4_H
+
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <net/tcp.h>
+
+#include <net/netfilter/nf_conntrack_seqadj.h>
+#include <net/netfilter/nf_conntrack_synproxy.h>
+
+void synproxy_send_client_synack(struct net *net, const struct sk_buff *skb,
+				 const struct tcphdr *th,
+				 const struct synproxy_options *opts);
+
+bool synproxy_recv_client_ack(struct net *net,
+			      const struct sk_buff *skb,
+			      const struct tcphdr *th,
+			      struct synproxy_options *opts, u32 recv_seq);
+
+unsigned int ipv4_synproxy_hook(void *priv, struct sk_buff *skb,
+				const struct nf_hook_state *nhs);
+int nf_synproxy_ipv4_init(struct synproxy_net *snet, struct net *net);
+void nf_synproxy_ipv4_fini(struct synproxy_net *snet, struct net *net);
+
+/* Hook operations used by {ip,nf}tables SYNPROXY support */
+const struct nf_hook_ops ipv4_synproxy_ops[] = {
+	{
+		.hook		= ipv4_synproxy_hook,
+		.pf		= NFPROTO_IPV4,
+		.hooknum	= NF_INET_LOCAL_IN,
+		.priority	= NF_IP_PRI_CONNTRACK_CONFIRM - 1,
+	},
+	{
+		.hook		= ipv4_synproxy_hook,
+		.pf		= NFPROTO_IPV4,
+		.hooknum	= NF_INET_POST_ROUTING,
+		.priority	= NF_IP_PRI_CONNTRACK_CONFIRM - 1,
+	},
+};
+
+#endif /* _NF_SYNPROXY_IPV4_H */
diff --git a/net/ipv4/netfilter/ipt_SYNPROXY.c b/net/ipv4/netfilter/ipt_SYNPROXY.c
index 690b17ef6a44..eb14c3bcbc15 100644
--- a/net/ipv4/netfilter/ipt_SYNPROXY.c
+++ b/net/ipv4/netfilter/ipt_SYNPROXY.c
@@ -6,258 +6,11 @@
  * published by the Free Software Foundation.
  */
 
-#include <linux/module.h>
-#include <linux/skbuff.h>
-#include <net/tcp.h>
-
 #include <linux/netfilter_ipv4/ip_tables.h>
 #include <linux/netfilter/x_tables.h>
 #include <linux/netfilter/xt_SYNPROXY.h>
-#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,
-		  __be32 daddr)
-{
-	struct iphdr *iph;
-
-	skb_reset_network_header(skb);
-	iph = skb_put(skb, sizeof(*iph));
-	iph->version	= 4;
-	iph->ihl	= sizeof(*iph) / 4;
-	iph->tos	= 0;
-	iph->id		= 0;
-	iph->frag_off	= htons(IP_DF);
-	iph->ttl	= net->ipv4.sysctl_ip_default_ttl;
-	iph->protocol	= IPPROTO_TCP;
-	iph->check	= 0;
-	iph->saddr	= saddr;
-	iph->daddr	= daddr;
-
-	return iph;
-}
-
-static void
-synproxy_send_tcp(struct net *net,
-		  const struct sk_buff *skb, struct sk_buff *nskb,
-		  struct nf_conntrack *nfct, enum ip_conntrack_info ctinfo,
-		  struct iphdr *niph, struct tcphdr *nth,
-		  unsigned int tcp_hdr_size)
-{
-	nth->check = ~tcp_v4_check(tcp_hdr_size, niph->saddr, niph->daddr, 0);
-	nskb->ip_summed   = CHECKSUM_PARTIAL;
-	nskb->csum_start  = (unsigned char *)nth - nskb->head;
-	nskb->csum_offset = offsetof(struct tcphdr, check);
-
-	skb_dst_set_noref(nskb, skb_dst(skb));
-	nskb->protocol = htons(ETH_P_IP);
-	if (ip_route_me_harder(net, nskb, RTN_UNSPEC))
-		goto free_nskb;
-
-	if (nfct) {
-		nf_ct_set(nskb, (struct nf_conn *)nfct, ctinfo);
-		nf_conntrack_get(nfct);
-	}
-
-	ip_local_out(net, nskb->sk, nskb);
-	return;
-
-free_nskb:
-	kfree_skb(nskb);
-}
-
-static void
-synproxy_send_client_synack(struct net *net,
-			    const struct sk_buff *skb, const struct tcphdr *th,
-			    const struct synproxy_options *opts)
-{
-	struct sk_buff *nskb;
-	struct iphdr *iph, *niph;
-	struct tcphdr *nth;
-	unsigned int tcp_hdr_size;
-	u16 mss = opts->mss;
-
-	iph = ip_hdr(skb);
-
-	tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
-	nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
-			 GFP_ATOMIC);
-	if (nskb == NULL)
-		return;
-	skb_reserve(nskb, MAX_TCP_HEADER);
-
-	niph = synproxy_build_ip(net, nskb, iph->daddr, iph->saddr);
-
-	skb_reset_transport_header(nskb);
-	nth = skb_put(nskb, tcp_hdr_size);
-	nth->source	= th->dest;
-	nth->dest	= th->source;
-	nth->seq	= htonl(__cookie_v4_init_sequence(iph, th, &mss));
-	nth->ack_seq	= htonl(ntohl(th->seq) + 1);
-	tcp_flag_word(nth) = TCP_FLAG_SYN | TCP_FLAG_ACK;
-	if (opts->options & XT_SYNPROXY_OPT_ECN)
-		tcp_flag_word(nth) |= TCP_FLAG_ECE;
-	nth->doff	= tcp_hdr_size / 4;
-	nth->window	= 0;
-	nth->check	= 0;
-	nth->urg_ptr	= 0;
-
-	synproxy_build_options(nth, opts);
-
-	synproxy_send_tcp(net, skb, nskb, skb_nfct(skb),
-			  IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size);
-}
-
-static void
-synproxy_send_server_syn(struct net *net,
-			 const struct sk_buff *skb, const struct tcphdr *th,
-			 const struct synproxy_options *opts, u32 recv_seq)
-{
-	struct synproxy_net *snet = synproxy_pernet(net);
-	struct sk_buff *nskb;
-	struct iphdr *iph, *niph;
-	struct tcphdr *nth;
-	unsigned int tcp_hdr_size;
-
-	iph = ip_hdr(skb);
-
-	tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
-	nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
-			 GFP_ATOMIC);
-	if (nskb == NULL)
-		return;
-	skb_reserve(nskb, MAX_TCP_HEADER);
-
-	niph = synproxy_build_ip(net, nskb, iph->saddr, iph->daddr);
-
-	skb_reset_transport_header(nskb);
-	nth = skb_put(nskb, tcp_hdr_size);
-	nth->source	= th->source;
-	nth->dest	= th->dest;
-	nth->seq	= htonl(recv_seq - 1);
-	/* ack_seq is used to relay our ISN to the synproxy hook to initialize
-	 * sequence number translation once a connection tracking entry exists.
-	 */
-	nth->ack_seq	= htonl(ntohl(th->ack_seq) - 1);
-	tcp_flag_word(nth) = TCP_FLAG_SYN;
-	if (opts->options & XT_SYNPROXY_OPT_ECN)
-		tcp_flag_word(nth) |= TCP_FLAG_ECE | TCP_FLAG_CWR;
-	nth->doff	= tcp_hdr_size / 4;
-	nth->window	= th->window;
-	nth->check	= 0;
-	nth->urg_ptr	= 0;
-
-	synproxy_build_options(nth, opts);
-
-	synproxy_send_tcp(net, skb, nskb, &snet->tmpl->ct_general, IP_CT_NEW,
-			  niph, nth, tcp_hdr_size);
-}
-
-static void
-synproxy_send_server_ack(struct net *net,
-			 const struct ip_ct_tcp *state,
-			 const struct sk_buff *skb, const struct tcphdr *th,
-			 const struct synproxy_options *opts)
-{
-	struct sk_buff *nskb;
-	struct iphdr *iph, *niph;
-	struct tcphdr *nth;
-	unsigned int tcp_hdr_size;
-
-	iph = ip_hdr(skb);
-
-	tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
-	nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
-			 GFP_ATOMIC);
-	if (nskb == NULL)
-		return;
-	skb_reserve(nskb, MAX_TCP_HEADER);
-
-	niph = synproxy_build_ip(net, nskb, iph->daddr, iph->saddr);
 
-	skb_reset_transport_header(nskb);
-	nth = skb_put(nskb, tcp_hdr_size);
-	nth->source	= th->dest;
-	nth->dest	= th->source;
-	nth->seq	= htonl(ntohl(th->ack_seq));
-	nth->ack_seq	= htonl(ntohl(th->seq) + 1);
-	tcp_flag_word(nth) = TCP_FLAG_ACK;
-	nth->doff	= tcp_hdr_size / 4;
-	nth->window	= htons(state->seen[IP_CT_DIR_ORIGINAL].td_maxwin);
-	nth->check	= 0;
-	nth->urg_ptr	= 0;
-
-	synproxy_build_options(nth, opts);
-
-	synproxy_send_tcp(net, skb, nskb, NULL, 0, niph, nth, tcp_hdr_size);
-}
-
-static void
-synproxy_send_client_ack(struct net *net,
-			 const struct sk_buff *skb, const struct tcphdr *th,
-			 const struct synproxy_options *opts)
-{
-	struct sk_buff *nskb;
-	struct iphdr *iph, *niph;
-	struct tcphdr *nth;
-	unsigned int tcp_hdr_size;
-
-	iph = ip_hdr(skb);
-
-	tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
-	nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
-			 GFP_ATOMIC);
-	if (nskb == NULL)
-		return;
-	skb_reserve(nskb, MAX_TCP_HEADER);
-
-	niph = synproxy_build_ip(net, nskb, iph->saddr, iph->daddr);
-
-	skb_reset_transport_header(nskb);
-	nth = skb_put(nskb, tcp_hdr_size);
-	nth->source	= th->source;
-	nth->dest	= th->dest;
-	nth->seq	= htonl(ntohl(th->seq) + 1);
-	nth->ack_seq	= th->ack_seq;
-	tcp_flag_word(nth) = TCP_FLAG_ACK;
-	nth->doff	= tcp_hdr_size / 4;
-	nth->window	= htons(ntohs(th->window) >> opts->wscale);
-	nth->check	= 0;
-	nth->urg_ptr	= 0;
-
-	synproxy_build_options(nth, opts);
-
-	synproxy_send_tcp(net, skb, nskb, skb_nfct(skb),
-			  IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size);
-}
-
-static bool
-synproxy_recv_client_ack(struct net *net,
-			 const struct sk_buff *skb, const struct tcphdr *th,
-			 struct synproxy_options *opts, u32 recv_seq)
-{
-	struct synproxy_net *snet = synproxy_pernet(net);
-	int mss;
-
-	mss = __cookie_v4_check(ip_hdr(skb), th, ntohl(th->ack_seq) - 1);
-	if (mss == 0) {
-		this_cpu_inc(snet->stats->cookie_invalid);
-		return false;
-	}
-
-	this_cpu_inc(snet->stats->cookie_valid);
-	opts->mss = mss;
-	opts->options |= XT_SYNPROXY_OPT_MSS;
-
-	if (opts->options & XT_SYNPROXY_OPT_TIMESTAMP)
-		synproxy_check_timestamp_cookie(opts);
-
-	synproxy_send_server_syn(net, skb, th, opts, recv_seq);
-	return true;
-}
+#include <net/netfilter/ipv4/nf_synproxy_ipv4.h>
 
 static unsigned int
 synproxy_tg4(struct sk_buff *skb, const struct xt_action_param *par)
@@ -309,135 +62,6 @@ synproxy_tg4(struct sk_buff *skb, const struct xt_action_param *par)
 	return XT_CONTINUE;
 }
 
-static unsigned int ipv4_synproxy_hook(void *priv,
-				       struct sk_buff *skb,
-				       const struct nf_hook_state *nhs)
-{
-	struct net *net = nhs->net;
-	struct synproxy_net *snet = synproxy_pernet(net);
-	enum ip_conntrack_info ctinfo;
-	struct nf_conn *ct;
-	struct nf_conn_synproxy *synproxy;
-	struct synproxy_options opts = {};
-	const struct ip_ct_tcp *state;
-	struct tcphdr *th, _th;
-	unsigned int thoff;
-
-	ct = nf_ct_get(skb, &ctinfo);
-	if (ct == NULL)
-		return NF_ACCEPT;
-
-	synproxy = nfct_synproxy(ct);
-	if (synproxy == NULL)
-		return NF_ACCEPT;
-
-	if (nf_is_loopback_packet(skb) ||
-	    ip_hdr(skb)->protocol != IPPROTO_TCP)
-		return NF_ACCEPT;
-
-	thoff = ip_hdrlen(skb);
-	th = skb_header_pointer(skb, thoff, sizeof(_th), &_th);
-	if (th == NULL)
-		return NF_DROP;
-
-	state = &ct->proto.tcp;
-	switch (state->state) {
-	case TCP_CONNTRACK_CLOSE:
-		if (th->rst && !test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
-			nf_ct_seqadj_init(ct, ctinfo, synproxy->isn -
-						      ntohl(th->seq) + 1);
-			break;
-		}
-
-		if (!th->syn || th->ack ||
-		    CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
-			break;
-
-		/* Reopened connection - reset the sequence number and timestamp
-		 * adjustments, they will get initialized once the connection is
-		 * reestablished.
-		 */
-		nf_ct_seqadj_init(ct, ctinfo, 0);
-		synproxy->tsoff = 0;
-		this_cpu_inc(snet->stats->conn_reopened);
-
-		/* fall through */
-	case TCP_CONNTRACK_SYN_SENT:
-		if (!synproxy_parse_options(skb, thoff, th, &opts))
-			return NF_DROP;
-
-		if (!th->syn && th->ack &&
-		    CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) {
-			/* Keep-Alives are sent with SEG.SEQ = SND.NXT-1,
-			 * therefore we need to add 1 to make the SYN sequence
-			 * number match the one of first SYN.
-			 */
-			if (synproxy_recv_client_ack(net, skb, th, &opts,
-						     ntohl(th->seq) + 1)) {
-				this_cpu_inc(snet->stats->cookie_retrans);
-				consume_skb(skb);
-				return NF_STOLEN;
-			} else {
-				return NF_DROP;
-			}
-		}
-
-		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)
-			break;
-
-		if (!synproxy_parse_options(skb, thoff, th, &opts))
-			return NF_DROP;
-
-		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 |
-				  XT_SYNPROXY_OPT_SACK_PERM);
-
-		swap(opts.tsval, opts.tsecr);
-		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);
-
-		consume_skb(skb);
-		return NF_STOLEN;
-	default:
-		break;
-	}
-
-	synproxy_tstamp_adjust(skb, thoff, th, ct, ctinfo, synproxy);
-	return NF_ACCEPT;
-}
-
-static const struct nf_hook_ops ipv4_synproxy_ops[] = {
-	{
-		.hook		= ipv4_synproxy_hook,
-		.pf		= NFPROTO_IPV4,
-		.hooknum	= NF_INET_LOCAL_IN,
-		.priority	= NF_IP_PRI_CONNTRACK_CONFIRM - 1,
-	},
-	{
-		.hook		= ipv4_synproxy_hook,
-		.pf		= NFPROTO_IPV4,
-		.hooknum	= NF_INET_POST_ROUTING,
-		.priority	= NF_IP_PRI_CONNTRACK_CONFIRM - 1,
-	},
-};
-
 static int synproxy_tg4_check(const struct xt_tgchk_param *par)
 {
 	struct synproxy_net *snet = synproxy_pernet(par->net);
@@ -452,13 +76,10 @@ static int synproxy_tg4_check(const struct xt_tgchk_param *par)
 	if (err)
 		return err;
 
-	if (snet->hook_ref4 == 0) {
-		err = nf_register_net_hooks(par->net, ipv4_synproxy_ops,
-					    ARRAY_SIZE(ipv4_synproxy_ops));
-		if (err) {
-			nf_ct_netns_put(par->net, par->family);
-			return err;
-		}
+	err = nf_synproxy_ipv4_init(snet, par->net);
+	if (err) {
+		nf_ct_netns_put(par->net, par->family);
+		return err;
 	}
 
 	snet->hook_ref4++;
@@ -469,10 +90,7 @@ static void synproxy_tg4_destroy(const struct xt_tgdtor_param *par)
 {
 	struct synproxy_net *snet = synproxy_pernet(par->net);
 
-	snet->hook_ref4--;
-	if (snet->hook_ref4 == 0)
-		nf_unregister_net_hooks(par->net, ipv4_synproxy_ops,
-					ARRAY_SIZE(ipv4_synproxy_ops));
+	nf_synproxy_ipv4_fini(snet, par->net);
 	nf_ct_netns_put(par->net, par->family);
 }
 
diff --git a/net/ipv4/netfilter/nf_synproxy_ipv4.c b/net/ipv4/netfilter/nf_synproxy_ipv4.c
new file mode 100644
index 000000000000..40c7d7f92ab1
--- /dev/null
+++ b/net/ipv4/netfilter/nf_synproxy_ipv4.c
@@ -0,0 +1,393 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <net/netfilter/nf_conntrack.h>
+#include <net/netfilter/nf_conntrack_ecache.h>
+#include <net/netfilter/ipv4/nf_synproxy_ipv4.h>
+
+#include <linux/netfilter/nf_SYNPROXY.h>
+
+static struct iphdr *
+synproxy_build_ip(struct net *net, struct sk_buff *skb, __be32 saddr,
+		  __be32 daddr)
+{
+	struct iphdr *iph;
+
+	skb_reset_network_header(skb);
+	iph = skb_put(skb, sizeof(*iph));
+	iph->version	= 4;
+	iph->ihl	= sizeof(*iph) / 4;
+	iph->tos	= 0;
+	iph->id		= 0;
+	iph->frag_off	= htons(IP_DF);
+	iph->ttl	= net->ipv4.sysctl_ip_default_ttl;
+	iph->protocol	= IPPROTO_TCP;
+	iph->check	= 0;
+	iph->saddr	= saddr;
+	iph->daddr	= daddr;
+
+	return iph;
+}
+
+static void
+synproxy_send_tcp(struct net *net,
+		  const struct sk_buff *skb, struct sk_buff *nskb,
+		  struct nf_conntrack *nfct, enum ip_conntrack_info ctinfo,
+		  struct iphdr *niph, struct tcphdr *nth,
+		  unsigned int tcp_hdr_size)
+{
+	nth->check = ~tcp_v4_check(tcp_hdr_size, niph->saddr, niph->daddr, 0);
+	nskb->ip_summed   = CHECKSUM_PARTIAL;
+	nskb->csum_start  = (unsigned char *)nth - nskb->head;
+	nskb->csum_offset = offsetof(struct tcphdr, check);
+
+	skb_dst_set_noref(nskb, skb_dst(skb));
+	nskb->protocol = htons(ETH_P_IP);
+	if (ip_route_me_harder(net, nskb, RTN_UNSPEC))
+		goto free_nskb;
+
+	if (nfct) {
+		nf_ct_set(nskb, (struct nf_conn *)nfct, ctinfo);
+		nf_conntrack_get(nfct);
+	}
+
+	ip_local_out(net, nskb->sk, nskb);
+	return;
+
+free_nskb:
+	kfree_skb(nskb);
+}
+
+void
+synproxy_send_client_synack(struct net *net,
+			    const struct sk_buff *skb, const struct tcphdr *th,
+			    const struct synproxy_options *opts)
+{
+	struct sk_buff *nskb;
+	struct iphdr *iph, *niph;
+	struct tcphdr *nth;
+	unsigned int tcp_hdr_size;
+	u16 mss = opts->mss;
+
+	iph = ip_hdr(skb);
+
+	tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
+	nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
+			 GFP_ATOMIC);
+	if (nskb == NULL)
+		return;
+	skb_reserve(nskb, MAX_TCP_HEADER);
+
+	niph = synproxy_build_ip(net, nskb, iph->daddr, iph->saddr);
+
+	skb_reset_transport_header(nskb);
+	nth = skb_put(nskb, tcp_hdr_size);
+	nth->source	= th->dest;
+	nth->dest	= th->source;
+	nth->seq	= htonl(__cookie_v4_init_sequence(iph, th, &mss));
+	nth->ack_seq	= htonl(ntohl(th->seq) + 1);
+	tcp_flag_word(nth) = TCP_FLAG_SYN | TCP_FLAG_ACK;
+	if (opts->options & NF_SYNPROXY_OPT_ECN)
+		tcp_flag_word(nth) |= TCP_FLAG_ECE;
+	nth->doff	= tcp_hdr_size / 4;
+	nth->window	= 0;
+	nth->check	= 0;
+	nth->urg_ptr	= 0;
+
+	synproxy_build_options(nth, opts);
+
+	synproxy_send_tcp(net, skb, nskb, skb_nfct(skb),
+			  IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size);
+}
+EXPORT_SYMBOL_GPL(synproxy_send_client_synack);
+
+static void
+synproxy_send_server_syn(struct net *net,
+			 const struct sk_buff *skb, const struct tcphdr *th,
+			 const struct synproxy_options *opts, u32 recv_seq)
+{
+	struct synproxy_net *snet = synproxy_pernet(net);
+	struct sk_buff *nskb;
+	struct iphdr *iph, *niph;
+	struct tcphdr *nth;
+	unsigned int tcp_hdr_size;
+
+	iph = ip_hdr(skb);
+
+	tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
+	nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
+			 GFP_ATOMIC);
+	if (nskb == NULL)
+		return;
+	skb_reserve(nskb, MAX_TCP_HEADER);
+
+	niph = synproxy_build_ip(net, nskb, iph->saddr, iph->daddr);
+
+	skb_reset_transport_header(nskb);
+	nth = skb_put(nskb, tcp_hdr_size);
+	nth->source	= th->source;
+	nth->dest	= th->dest;
+	nth->seq	= htonl(recv_seq - 1);
+	/* ack_seq is used to relay our ISN to the synproxy hook to initialize
+	 * sequence number translation once a connection tracking entry exists.
+	 */
+	nth->ack_seq	= htonl(ntohl(th->ack_seq) - 1);
+	tcp_flag_word(nth) = TCP_FLAG_SYN;
+	if (opts->options & NF_SYNPROXY_OPT_ECN)
+		tcp_flag_word(nth) |= TCP_FLAG_ECE | TCP_FLAG_CWR;
+	nth->doff	= tcp_hdr_size / 4;
+	nth->window	= th->window;
+	nth->check	= 0;
+	nth->urg_ptr	= 0;
+
+	synproxy_build_options(nth, opts);
+
+	synproxy_send_tcp(net, skb, nskb, &snet->tmpl->ct_general, IP_CT_NEW,
+			  niph, nth, tcp_hdr_size);
+}
+
+static void
+synproxy_send_server_ack(struct net *net,
+			 const struct ip_ct_tcp *state,
+			 const struct sk_buff *skb, const struct tcphdr *th,
+			 const struct synproxy_options *opts)
+{
+	struct sk_buff *nskb;
+	struct iphdr *iph, *niph;
+	struct tcphdr *nth;
+	unsigned int tcp_hdr_size;
+
+	iph = ip_hdr(skb);
+
+	tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
+	nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
+			 GFP_ATOMIC);
+	if (nskb == NULL)
+		return;
+	skb_reserve(nskb, MAX_TCP_HEADER);
+
+	niph = synproxy_build_ip(net, nskb, iph->daddr, iph->saddr);
+
+	skb_reset_transport_header(nskb);
+	nth = skb_put(nskb, tcp_hdr_size);
+	nth->source	= th->dest;
+	nth->dest	= th->source;
+	nth->seq	= htonl(ntohl(th->ack_seq));
+	nth->ack_seq	= htonl(ntohl(th->seq) + 1);
+	tcp_flag_word(nth) = TCP_FLAG_ACK;
+	nth->doff	= tcp_hdr_size / 4;
+	nth->window	= htons(state->seen[IP_CT_DIR_ORIGINAL].td_maxwin);
+	nth->check	= 0;
+	nth->urg_ptr	= 0;
+
+	synproxy_build_options(nth, opts);
+
+	synproxy_send_tcp(net, skb, nskb, NULL, 0, niph, nth, tcp_hdr_size);
+}
+
+static void
+synproxy_send_client_ack(struct net *net,
+			 const struct sk_buff *skb, const struct tcphdr *th,
+			 const struct synproxy_options *opts)
+{
+	struct sk_buff *nskb;
+	struct iphdr *iph, *niph;
+	struct tcphdr *nth;
+	unsigned int tcp_hdr_size;
+
+	iph = ip_hdr(skb);
+
+	tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
+	nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
+			 GFP_ATOMIC);
+	if (nskb == NULL)
+		return;
+	skb_reserve(nskb, MAX_TCP_HEADER);
+
+	niph = synproxy_build_ip(net, nskb, iph->saddr, iph->daddr);
+
+	skb_reset_transport_header(nskb);
+	nth = skb_put(nskb, tcp_hdr_size);
+	nth->source	= th->source;
+	nth->dest	= th->dest;
+	nth->seq	= htonl(ntohl(th->seq) + 1);
+	nth->ack_seq	= th->ack_seq;
+	tcp_flag_word(nth) = TCP_FLAG_ACK;
+	nth->doff	= tcp_hdr_size / 4;
+	nth->window	= htons(ntohs(th->window) >> opts->wscale);
+	nth->check	= 0;
+	nth->urg_ptr	= 0;
+
+	synproxy_build_options(nth, opts);
+
+	synproxy_send_tcp(net, skb, nskb, skb_nfct(skb),
+			  IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size);
+}
+
+bool
+synproxy_recv_client_ack(struct net *net,
+			 const struct sk_buff *skb, const struct tcphdr *th,
+			 struct synproxy_options *opts, u32 recv_seq)
+{
+	struct synproxy_net *snet = synproxy_pernet(net);
+	int mss;
+
+	mss = __cookie_v4_check(ip_hdr(skb), th, ntohl(th->ack_seq) - 1);
+	if (mss == 0) {
+		this_cpu_inc(snet->stats->cookie_invalid);
+		return false;
+	}
+
+	this_cpu_inc(snet->stats->cookie_valid);
+	opts->mss = mss;
+	opts->options |= NF_SYNPROXY_OPT_MSS;
+
+	if (opts->options & NF_SYNPROXY_OPT_TIMESTAMP)
+		synproxy_check_timestamp_cookie(opts);
+
+	synproxy_send_server_syn(net, skb, th, opts, recv_seq);
+	return true;
+}
+EXPORT_SYMBOL_GPL(synproxy_recv_client_ack);
+
+unsigned int
+ipv4_synproxy_hook(void *priv, struct sk_buff *skb,
+		   const struct nf_hook_state *nhs)
+{
+	struct net *net = nhs->net;
+	struct synproxy_net *snet = synproxy_pernet(net);
+	enum ip_conntrack_info ctinfo;
+	struct nf_conn *ct;
+	struct nf_conn_synproxy *synproxy;
+	struct synproxy_options opts = {};
+	const struct ip_ct_tcp *state;
+	struct tcphdr *th, _th;
+	unsigned int thoff;
+
+	ct = nf_ct_get(skb, &ctinfo);
+	if (ct == NULL)
+		return NF_ACCEPT;
+
+	synproxy = nfct_synproxy(ct);
+	if (synproxy == NULL)
+		return NF_ACCEPT;
+
+	if (nf_is_loopback_packet(skb) ||
+	    ip_hdr(skb)->protocol != IPPROTO_TCP)
+		return NF_ACCEPT;
+
+	thoff = ip_hdrlen(skb);
+	th = skb_header_pointer(skb, thoff, sizeof(_th), &_th);
+	if (th == NULL)
+		return NF_DROP;
+
+	state = &ct->proto.tcp;
+	switch (state->state) {
+	case TCP_CONNTRACK_CLOSE:
+		if (th->rst && !test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
+			nf_ct_seqadj_init(ct, ctinfo, synproxy->isn -
+						      ntohl(th->seq) + 1);
+			break;
+		}
+
+		if (!th->syn || th->ack ||
+		    CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
+			break;
+
+		/* Reopened connection - reset the sequence number and timestamp
+		 * adjustments, they will get initialized once the connection is
+		 * reestablished.
+		 */
+		nf_ct_seqadj_init(ct, ctinfo, 0);
+		synproxy->tsoff = 0;
+		this_cpu_inc(snet->stats->conn_reopened);
+
+		/* fall through */
+	case TCP_CONNTRACK_SYN_SENT:
+		if (!synproxy_parse_options(skb, thoff, th, &opts))
+			return NF_DROP;
+
+		if (!th->syn && th->ack &&
+		    CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) {
+			/* Keep-Alives are sent with SEG.SEQ = SND.NXT-1,
+			 * therefore we need to add 1 to make the SYN sequence
+			 * number match the one of first SYN.
+			 */
+			if (synproxy_recv_client_ack(net, skb, th, &opts,
+						     ntohl(th->seq) + 1)) {
+				this_cpu_inc(snet->stats->cookie_retrans);
+				consume_skb(skb);
+				return NF_STOLEN;
+			} else {
+				return NF_DROP;
+			}
+		}
+
+		synproxy->isn = ntohl(th->ack_seq);
+		if (opts.options & NF_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)
+			break;
+
+		if (!synproxy_parse_options(skb, thoff, th, &opts))
+			return NF_DROP;
+
+		if (opts.options & NF_SYNPROXY_OPT_TIMESTAMP) {
+			synproxy->tsoff = opts.tsval - synproxy->its;
+			nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
+		}
+
+		opts.options &= ~(NF_SYNPROXY_OPT_MSS |
+				  NF_SYNPROXY_OPT_WSCALE |
+				  NF_SYNPROXY_OPT_SACK_PERM);
+
+		swap(opts.tsval, opts.tsecr);
+		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);
+
+		consume_skb(skb);
+		return NF_STOLEN;
+	default:
+		break;
+	}
+
+	synproxy_tstamp_adjust(skb, thoff, th, ct, ctinfo, synproxy);
+	return NF_ACCEPT;
+}
+EXPORT_SYMBOL_GPL(ipv4_synproxy_hook);
+
+int nf_synproxy_ipv4_init(struct synproxy_net *snet, struct net *net)
+{
+	int err;
+
+        if (snet->hook_ref4 == 0) {
+                err = nf_register_net_hooks(net, ipv4_synproxy_ops,
+                                            ARRAY_SIZE(ipv4_synproxy_ops));
+                if (err)
+                        return err;
+        }
+
+        snet->hook_ref4++;
+	return err;
+}
+EXPORT_SYMBOL_GPL(nf_synproxy_ipv4_init);
+
+void nf_synproxy_ipv4_fini(struct synproxy_net *snet, struct net *net)
+{
+        snet->hook_ref4--;
+        if (snet->hook_ref4 == 0)
+                nf_unregister_net_hooks(net, ipv4_synproxy_ops,
+                                        ARRAY_SIZE(ipv4_synproxy_ops));
+}
+EXPORT_SYMBOL_GPL(nf_synproxy_ipv4_fini);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Fernando Fernandez <ffmancera@riseup.net>");
-- 
2.20.1

[PATCH 3/5 nf-next] netfilter: add NF_SYNPROXY_IPV4 symbol

[Fernando Fernandez Mancera]

Signed-off-by: Fernando Fernandez Mancera <ffmancera@riseup.net>
---
 net/ipv4/netfilter/Kconfig  | 4 ++++
 net/ipv4/netfilter/Makefile | 3 +++
 2 files changed, 7 insertions(+)

diff --git a/net/ipv4/netfilter/Kconfig b/net/ipv4/netfilter/Kconfig
index 1412b029f37f..5038bb95dbf2 100644
--- a/net/ipv4/netfilter/Kconfig
+++ b/net/ipv4/netfilter/Kconfig
@@ -18,6 +18,9 @@ config NF_SOCKET_IPV4
 config NF_TPROXY_IPV4
 	tristate "IPv4 tproxy support"
 
+config NF_SYNPROXY_IPV4
+	tristate
+
 if NF_TABLES
 
 config NF_TABLES_IPV4
@@ -196,6 +199,7 @@ config IP_NF_TARGET_REJECT
 config IP_NF_TARGET_SYNPROXY
 	tristate "SYNPROXY target support"
 	depends on NF_CONNTRACK && NETFILTER_ADVANCED
+	select NF_SYNPROXY_IPV4
 	select NETFILTER_SYNPROXY
 	select SYN_COOKIES
 	help
diff --git a/net/ipv4/netfilter/Makefile b/net/ipv4/netfilter/Makefile
index c50e0ec095d2..01267eea7c4e 100644
--- a/net/ipv4/netfilter/Makefile
+++ b/net/ipv4/netfilter/Makefile
@@ -6,6 +6,9 @@
 # defrag
 obj-$(CONFIG_NF_DEFRAG_IPV4) += nf_defrag_ipv4.o
 
+#synproxy
+obj-$(CONFIG_NF_SYNPROXY_IPV4) += nf_synproxy_ipv4.o
+
 obj-$(CONFIG_NF_SOCKET_IPV4) += nf_socket_ipv4.o
 obj-$(CONFIG_NF_TPROXY_IPV4) += nf_tproxy_ipv4.o
 
-- 
2.20.1

[PATCH 4/5 nf-next] netfilter: synproxy: extract IPv6 SYNPROXY infrastructure from ip6t_SYNPROXY

[Fernando Fernandez Mancera]

Add common functions into nf_synproxy_ipv6.c to prepare for nftables support.

Signed-off-by: Fernando Fernandez Mancera <ffmancera@riseup.net>
---
 include/net/netfilter/ipv6/nf_synproxy_ipv6.h |  43 ++
 net/ipv6/netfilter/ip6t_SYNPROXY.c            | 420 +-----------------
 net/ipv6/netfilter/nf_synproxy_ipv6.c         | 414 +++++++++++++++++
 3 files changed, 466 insertions(+), 411 deletions(-)
 create mode 100644 include/net/netfilter/ipv6/nf_synproxy_ipv6.h
 create mode 100644 net/ipv6/netfilter/nf_synproxy_ipv6.c

diff --git a/include/net/netfilter/ipv6/nf_synproxy_ipv6.h b/include/net/netfilter/ipv6/nf_synproxy_ipv6.h
new file mode 100644
index 000000000000..afcbbfa5bc17
--- /dev/null
+++ b/include/net/netfilter/ipv6/nf_synproxy_ipv6.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _NF_SYNPROXY_IPV6_H
+#define _NF_SYNPROXY_IPV6_H
+
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <net/ip6_checksum.h>
+#include <net/ip6_route.h>
+#include <net/tcp.h>
+
+#include <net/netfilter/nf_conntrack_seqadj.h>
+#include <net/netfilter/nf_conntrack_synproxy.h>
+
+void synproxy_send_client_synack_ipv6(struct net *net, const struct sk_buff *skb,
+				      const struct tcphdr *th,
+				      const struct synproxy_options *opts);
+
+bool synproxy_recv_client_ack_ipv6(struct net *net, const struct sk_buff *skb,
+				   const struct tcphdr *th,
+				   struct synproxy_options *opts, u32 recv_seq);
+
+unsigned int ipv6_synproxy_hook(void *priv, struct sk_buff *skb,
+				const struct nf_hook_state *nhs);
+
+int nf_synproxy_ipv6_init(struct synproxy_net *snet, struct net *net);
+void nf_synproxy_ipv6_fini(struct synproxy_net *snet, struct net *net);
+
+static const struct nf_hook_ops ipv6_synproxy_ops[] = {
+	{
+		.hook		= ipv6_synproxy_hook,
+		.pf		= NFPROTO_IPV6,
+		.hooknum	= NF_INET_LOCAL_IN,
+		.priority	= NF_IP_PRI_CONNTRACK_CONFIRM - 1,
+	},
+	{
+		.hook		= ipv6_synproxy_hook,
+		.pf		= NFPROTO_IPV6,
+		.hooknum	= NF_INET_POST_ROUTING,
+		.priority	= NF_IP_PRI_CONNTRACK_CONFIRM - 1,
+	},
+};
+
+#endif /* _NF_SYNPROXY_IPV6_H */
diff --git a/net/ipv6/netfilter/ip6t_SYNPROXY.c b/net/ipv6/netfilter/ip6t_SYNPROXY.c
index cb6d42b03cb5..e53eb76a2bad 100644
--- a/net/ipv6/netfilter/ip6t_SYNPROXY.c
+++ b/net/ipv6/netfilter/ip6t_SYNPROXY.c
@@ -6,272 +6,11 @@
  * published by the Free Software Foundation.
  */
 
-#include <linux/module.h>
-#include <linux/skbuff.h>
-#include <net/ip6_checksum.h>
-#include <net/ip6_route.h>
-#include <net/tcp.h>
-
 #include <linux/netfilter_ipv6/ip6_tables.h>
 #include <linux/netfilter/x_tables.h>
 #include <linux/netfilter/xt_SYNPROXY.h>
-#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,
-		  const struct in6_addr *saddr,
-		  const struct in6_addr *daddr)
-{
-	struct ipv6hdr *iph;
-
-	skb_reset_network_header(skb);
-	iph = skb_put(skb, sizeof(*iph));
-	ip6_flow_hdr(iph, 0, 0);
-	iph->hop_limit	= net->ipv6.devconf_all->hop_limit;
-	iph->nexthdr	= IPPROTO_TCP;
-	iph->saddr	= *saddr;
-	iph->daddr	= *daddr;
-
-	return iph;
-}
-
-static void
-synproxy_send_tcp(struct net *net,
-		  const struct sk_buff *skb, struct sk_buff *nskb,
-		  struct nf_conntrack *nfct, enum ip_conntrack_info ctinfo,
-		  struct ipv6hdr *niph, struct tcphdr *nth,
-		  unsigned int tcp_hdr_size)
-{
-	struct dst_entry *dst;
-	struct flowi6 fl6;
-
-	nth->check = ~tcp_v6_check(tcp_hdr_size, &niph->saddr, &niph->daddr, 0);
-	nskb->ip_summed   = CHECKSUM_PARTIAL;
-	nskb->csum_start  = (unsigned char *)nth - nskb->head;
-	nskb->csum_offset = offsetof(struct tcphdr, check);
-
-	memset(&fl6, 0, sizeof(fl6));
-	fl6.flowi6_proto = IPPROTO_TCP;
-	fl6.saddr = niph->saddr;
-	fl6.daddr = niph->daddr;
-	fl6.fl6_sport = nth->source;
-	fl6.fl6_dport = nth->dest;
-	security_skb_classify_flow((struct sk_buff *)skb, flowi6_to_flowi(&fl6));
-	dst = ip6_route_output(net, NULL, &fl6);
-	if (dst->error) {
-		dst_release(dst);
-		goto free_nskb;
-	}
-	dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), NULL, 0);
-	if (IS_ERR(dst))
-		goto free_nskb;
-
-	skb_dst_set(nskb, dst);
-
-	if (nfct) {
-		nf_ct_set(nskb, (struct nf_conn *)nfct, ctinfo);
-		nf_conntrack_get(nfct);
-	}
-
-	ip6_local_out(net, nskb->sk, nskb);
-	return;
-
-free_nskb:
-	kfree_skb(nskb);
-}
-
-static void
-synproxy_send_client_synack(struct net *net,
-			    const struct sk_buff *skb, const struct tcphdr *th,
-			    const struct synproxy_options *opts)
-{
-	struct sk_buff *nskb;
-	struct ipv6hdr *iph, *niph;
-	struct tcphdr *nth;
-	unsigned int tcp_hdr_size;
-	u16 mss = opts->mss;
-
-	iph = ipv6_hdr(skb);
-
-	tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
-	nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
-			 GFP_ATOMIC);
-	if (nskb == NULL)
-		return;
-	skb_reserve(nskb, MAX_TCP_HEADER);
-
-	niph = synproxy_build_ip(net, nskb, &iph->daddr, &iph->saddr);
-
-	skb_reset_transport_header(nskb);
-	nth = skb_put(nskb, tcp_hdr_size);
-	nth->source	= th->dest;
-	nth->dest	= th->source;
-	nth->seq	= htonl(__cookie_v6_init_sequence(iph, th, &mss));
-	nth->ack_seq	= htonl(ntohl(th->seq) + 1);
-	tcp_flag_word(nth) = TCP_FLAG_SYN | TCP_FLAG_ACK;
-	if (opts->options & XT_SYNPROXY_OPT_ECN)
-		tcp_flag_word(nth) |= TCP_FLAG_ECE;
-	nth->doff	= tcp_hdr_size / 4;
-	nth->window	= 0;
-	nth->check	= 0;
-	nth->urg_ptr	= 0;
-
-	synproxy_build_options(nth, opts);
-
-	synproxy_send_tcp(net, skb, nskb, skb_nfct(skb),
-			  IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size);
-}
 
-static void
-synproxy_send_server_syn(struct net *net,
-			 const struct sk_buff *skb, const struct tcphdr *th,
-			 const struct synproxy_options *opts, u32 recv_seq)
-{
-	struct synproxy_net *snet = synproxy_pernet(net);
-	struct sk_buff *nskb;
-	struct ipv6hdr *iph, *niph;
-	struct tcphdr *nth;
-	unsigned int tcp_hdr_size;
-
-	iph = ipv6_hdr(skb);
-
-	tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
-	nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
-			 GFP_ATOMIC);
-	if (nskb == NULL)
-		return;
-	skb_reserve(nskb, MAX_TCP_HEADER);
-
-	niph = synproxy_build_ip(net, nskb, &iph->saddr, &iph->daddr);
-
-	skb_reset_transport_header(nskb);
-	nth = skb_put(nskb, tcp_hdr_size);
-	nth->source	= th->source;
-	nth->dest	= th->dest;
-	nth->seq	= htonl(recv_seq - 1);
-	/* ack_seq is used to relay our ISN to the synproxy hook to initialize
-	 * sequence number translation once a connection tracking entry exists.
-	 */
-	nth->ack_seq	= htonl(ntohl(th->ack_seq) - 1);
-	tcp_flag_word(nth) = TCP_FLAG_SYN;
-	if (opts->options & XT_SYNPROXY_OPT_ECN)
-		tcp_flag_word(nth) |= TCP_FLAG_ECE | TCP_FLAG_CWR;
-	nth->doff	= tcp_hdr_size / 4;
-	nth->window	= th->window;
-	nth->check	= 0;
-	nth->urg_ptr	= 0;
-
-	synproxy_build_options(nth, opts);
-
-	synproxy_send_tcp(net, skb, nskb, &snet->tmpl->ct_general, IP_CT_NEW,
-			  niph, nth, tcp_hdr_size);
-}
-
-static void
-synproxy_send_server_ack(struct net *net,
-			 const struct ip_ct_tcp *state,
-			 const struct sk_buff *skb, const struct tcphdr *th,
-			 const struct synproxy_options *opts)
-{
-	struct sk_buff *nskb;
-	struct ipv6hdr *iph, *niph;
-	struct tcphdr *nth;
-	unsigned int tcp_hdr_size;
-
-	iph = ipv6_hdr(skb);
-
-	tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
-	nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
-			 GFP_ATOMIC);
-	if (nskb == NULL)
-		return;
-	skb_reserve(nskb, MAX_TCP_HEADER);
-
-	niph = synproxy_build_ip(net, nskb, &iph->daddr, &iph->saddr);
-
-	skb_reset_transport_header(nskb);
-	nth = skb_put(nskb, tcp_hdr_size);
-	nth->source	= th->dest;
-	nth->dest	= th->source;
-	nth->seq	= htonl(ntohl(th->ack_seq));
-	nth->ack_seq	= htonl(ntohl(th->seq) + 1);
-	tcp_flag_word(nth) = TCP_FLAG_ACK;
-	nth->doff	= tcp_hdr_size / 4;
-	nth->window	= htons(state->seen[IP_CT_DIR_ORIGINAL].td_maxwin);
-	nth->check	= 0;
-	nth->urg_ptr	= 0;
-
-	synproxy_build_options(nth, opts);
-
-	synproxy_send_tcp(net, skb, nskb, NULL, 0, niph, nth, tcp_hdr_size);
-}
-
-static void
-synproxy_send_client_ack(struct net *net,
-			 const struct sk_buff *skb, const struct tcphdr *th,
-			 const struct synproxy_options *opts)
-{
-	struct sk_buff *nskb;
-	struct ipv6hdr *iph, *niph;
-	struct tcphdr *nth;
-	unsigned int tcp_hdr_size;
-
-	iph = ipv6_hdr(skb);
-
-	tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
-	nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
-			 GFP_ATOMIC);
-	if (nskb == NULL)
-		return;
-	skb_reserve(nskb, MAX_TCP_HEADER);
-
-	niph = synproxy_build_ip(net, nskb, &iph->saddr, &iph->daddr);
-
-	skb_reset_transport_header(nskb);
-	nth = skb_put(nskb, tcp_hdr_size);
-	nth->source	= th->source;
-	nth->dest	= th->dest;
-	nth->seq	= htonl(ntohl(th->seq) + 1);
-	nth->ack_seq	= th->ack_seq;
-	tcp_flag_word(nth) = TCP_FLAG_ACK;
-	nth->doff	= tcp_hdr_size / 4;
-	nth->window	= htons(ntohs(th->window) >> opts->wscale);
-	nth->check	= 0;
-	nth->urg_ptr	= 0;
-
-	synproxy_build_options(nth, opts);
-
-	synproxy_send_tcp(net, skb, nskb, skb_nfct(skb),
-			  IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size);
-}
-
-static bool
-synproxy_recv_client_ack(struct net *net,
-			 const struct sk_buff *skb, const struct tcphdr *th,
-			 struct synproxy_options *opts, u32 recv_seq)
-{
-	struct synproxy_net *snet = synproxy_pernet(net);
-	int mss;
-
-	mss = __cookie_v6_check(ipv6_hdr(skb), th, ntohl(th->ack_seq) - 1);
-	if (mss == 0) {
-		this_cpu_inc(snet->stats->cookie_invalid);
-		return false;
-	}
-
-	this_cpu_inc(snet->stats->cookie_valid);
-	opts->mss = mss;
-	opts->options |= XT_SYNPROXY_OPT_MSS;
-
-	if (opts->options & XT_SYNPROXY_OPT_TIMESTAMP)
-		synproxy_check_timestamp_cookie(opts);
-
-	synproxy_send_server_syn(net, skb, th, opts, recv_seq);
-	return true;
-}
+#include <net/netfilter/ipv6/nf_synproxy_ipv6.h>
 
 static unsigned int
 synproxy_tg6(struct sk_buff *skb, const struct xt_action_param *par)
@@ -307,13 +46,14 @@ synproxy_tg6(struct sk_buff *skb, const struct xt_action_param *par)
 					  XT_SYNPROXY_OPT_SACK_PERM |
 					  XT_SYNPROXY_OPT_ECN);
 
-		synproxy_send_client_synack(net, skb, th, &opts);
+		synproxy_send_client_synack_ipv6(net, skb, th, &opts);
 		consume_skb(skb);
 		return NF_STOLEN;
 
 	} else if (th->ack && !(th->fin || th->rst || th->syn)) {
 		/* ACK from client */
-		if (synproxy_recv_client_ack(net, skb, th, &opts, ntohl(th->seq))) {
+		if (synproxy_recv_client_ack_ipv6(net, skb, th, &opts,
+						  ntohl(th->seq))) {
 			consume_skb(skb);
 			return NF_STOLEN;
 		} else {
@@ -324,141 +64,6 @@ synproxy_tg6(struct sk_buff *skb, const struct xt_action_param *par)
 	return XT_CONTINUE;
 }
 
-static unsigned int ipv6_synproxy_hook(void *priv,
-				       struct sk_buff *skb,
-				       const struct nf_hook_state *nhs)
-{
-	struct net *net = nhs->net;
-	struct synproxy_net *snet = synproxy_pernet(net);
-	enum ip_conntrack_info ctinfo;
-	struct nf_conn *ct;
-	struct nf_conn_synproxy *synproxy;
-	struct synproxy_options opts = {};
-	const struct ip_ct_tcp *state;
-	struct tcphdr *th, _th;
-	__be16 frag_off;
-	u8 nexthdr;
-	int thoff;
-
-	ct = nf_ct_get(skb, &ctinfo);
-	if (ct == NULL)
-		return NF_ACCEPT;
-
-	synproxy = nfct_synproxy(ct);
-	if (synproxy == NULL)
-		return NF_ACCEPT;
-
-	if (nf_is_loopback_packet(skb))
-		return NF_ACCEPT;
-
-	nexthdr = ipv6_hdr(skb)->nexthdr;
-	thoff = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &nexthdr,
-				 &frag_off);
-	if (thoff < 0 || nexthdr != IPPROTO_TCP)
-		return NF_ACCEPT;
-
-	th = skb_header_pointer(skb, thoff, sizeof(_th), &_th);
-	if (th == NULL)
-		return NF_DROP;
-
-	state = &ct->proto.tcp;
-	switch (state->state) {
-	case TCP_CONNTRACK_CLOSE:
-		if (th->rst && !test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
-			nf_ct_seqadj_init(ct, ctinfo, synproxy->isn -
-						      ntohl(th->seq) + 1);
-			break;
-		}
-
-		if (!th->syn || th->ack ||
-		    CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
-			break;
-
-		/* Reopened connection - reset the sequence number and timestamp
-		 * adjustments, they will get initialized once the connection is
-		 * reestablished.
-		 */
-		nf_ct_seqadj_init(ct, ctinfo, 0);
-		synproxy->tsoff = 0;
-		this_cpu_inc(snet->stats->conn_reopened);
-
-		/* fall through */
-	case TCP_CONNTRACK_SYN_SENT:
-		if (!synproxy_parse_options(skb, thoff, th, &opts))
-			return NF_DROP;
-
-		if (!th->syn && th->ack &&
-		    CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) {
-			/* Keep-Alives are sent with SEG.SEQ = SND.NXT-1,
-			 * therefore we need to add 1 to make the SYN sequence
-			 * number match the one of first SYN.
-			 */
-			if (synproxy_recv_client_ack(net, skb, th, &opts,
-						     ntohl(th->seq) + 1)) {
-				this_cpu_inc(snet->stats->cookie_retrans);
-				consume_skb(skb);
-				return NF_STOLEN;
-			} else {
-				return NF_DROP;
-			}
-		}
-
-		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)
-			break;
-
-		if (!synproxy_parse_options(skb, thoff, th, &opts))
-			return NF_DROP;
-
-		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 |
-				  XT_SYNPROXY_OPT_SACK_PERM);
-
-		swap(opts.tsval, opts.tsecr);
-		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);
-
-		consume_skb(skb);
-		return NF_STOLEN;
-	default:
-		break;
-	}
-
-	synproxy_tstamp_adjust(skb, thoff, th, ct, ctinfo, synproxy);
-	return NF_ACCEPT;
-}
-
-static const struct nf_hook_ops ipv6_synproxy_ops[] = {
-	{
-		.hook		= ipv6_synproxy_hook,
-		.pf		= NFPROTO_IPV6,
-		.hooknum	= NF_INET_LOCAL_IN,
-		.priority	= NF_IP_PRI_CONNTRACK_CONFIRM - 1,
-	},
-	{
-		.hook		= ipv6_synproxy_hook,
-		.pf		= NFPROTO_IPV6,
-		.hooknum	= NF_INET_POST_ROUTING,
-		.priority	= NF_IP_PRI_CONNTRACK_CONFIRM - 1,
-	},
-};
-
 static int synproxy_tg6_check(const struct xt_tgchk_param *par)
 {
 	struct synproxy_net *snet = synproxy_pernet(par->net);
@@ -474,16 +79,12 @@ static int synproxy_tg6_check(const struct xt_tgchk_param *par)
 	if (err)
 		return err;
 
-	if (snet->hook_ref6 == 0) {
-		err = nf_register_net_hooks(par->net, ipv6_synproxy_ops,
-					    ARRAY_SIZE(ipv6_synproxy_ops));
-		if (err) {
-			nf_ct_netns_put(par->net, par->family);
-			return err;
-		}
+	err = nf_synproxy_ipv6_init(snet, par->net);
+	if (err) {
+		nf_ct_netns_put(par->net, par->family);
+		return err;
 	}
 
-	snet->hook_ref6++;
 	return err;
 }
 
@@ -491,10 +92,7 @@ static void synproxy_tg6_destroy(const struct xt_tgdtor_param *par)
 {
 	struct synproxy_net *snet = synproxy_pernet(par->net);
 
-	snet->hook_ref6--;
-	if (snet->hook_ref6 == 0)
-		nf_unregister_net_hooks(par->net, ipv6_synproxy_ops,
-					ARRAY_SIZE(ipv6_synproxy_ops));
+	nf_synproxy_ipv6_fini(snet, par->net);
 	nf_ct_netns_put(par->net, par->family);
 }
 
diff --git a/net/ipv6/netfilter/nf_synproxy_ipv6.c b/net/ipv6/netfilter/nf_synproxy_ipv6.c
new file mode 100644
index 000000000000..31568ef65913
--- /dev/null
+++ b/net/ipv6/netfilter/nf_synproxy_ipv6.c
@@ -0,0 +1,414 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <net/netfilter/nf_conntrack.h>
+#include <net/netfilter/nf_conntrack_ecache.h>
+#include <net/netfilter/ipv6/nf_synproxy_ipv6.h>
+
+#include <linux/netfilter/nf_SYNPROXY.h>
+
+static struct ipv6hdr *
+synproxy_build_ip(struct net *net, struct sk_buff *skb,
+		  const struct in6_addr *saddr,
+		  const struct in6_addr *daddr)
+{
+	struct ipv6hdr *iph;
+
+	skb_reset_network_header(skb);
+	iph = skb_put(skb, sizeof(*iph));
+	ip6_flow_hdr(iph, 0, 0);
+	iph->hop_limit	= net->ipv6.devconf_all->hop_limit;
+	iph->nexthdr	= IPPROTO_TCP;
+	iph->saddr	= *saddr;
+	iph->daddr	= *daddr;
+
+	return iph;
+}
+
+static void
+synproxy_send_tcp(struct net *net,
+		  const struct sk_buff *skb, struct sk_buff *nskb,
+		  struct nf_conntrack *nfct, enum ip_conntrack_info ctinfo,
+		  struct ipv6hdr *niph, struct tcphdr *nth,
+		  unsigned int tcp_hdr_size)
+{
+	struct dst_entry *dst;
+	struct flowi6 fl6;
+
+	nth->check = ~tcp_v6_check(tcp_hdr_size, &niph->saddr, &niph->daddr, 0);
+	nskb->ip_summed   = CHECKSUM_PARTIAL;
+	nskb->csum_start  = (unsigned char *)nth - nskb->head;
+	nskb->csum_offset = offsetof(struct tcphdr, check);
+
+	memset(&fl6, 0, sizeof(fl6));
+	fl6.flowi6_proto = IPPROTO_TCP;
+	fl6.saddr = niph->saddr;
+	fl6.daddr = niph->daddr;
+	fl6.fl6_sport = nth->source;
+	fl6.fl6_dport = nth->dest;
+	security_skb_classify_flow((struct sk_buff *)skb, flowi6_to_flowi(&fl6));
+	dst = ip6_route_output(net, NULL, &fl6);
+	if (dst->error) {
+		dst_release(dst);
+		goto free_nskb;
+	}
+	dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), NULL, 0);
+	if (IS_ERR(dst))
+		goto free_nskb;
+
+	skb_dst_set(nskb, dst);
+
+	if (nfct) {
+		nf_ct_set(nskb, (struct nf_conn *)nfct, ctinfo);
+		nf_conntrack_get(nfct);
+	}
+
+	ip6_local_out(net, nskb->sk, nskb);
+	return;
+
+free_nskb:
+	kfree_skb(nskb);
+}
+
+void
+synproxy_send_client_synack_ipv6(struct net *net,
+				 const struct sk_buff *skb,
+				 const struct tcphdr *th,
+				 const struct synproxy_options *opts)
+{
+	struct sk_buff *nskb;
+	struct ipv6hdr *iph, *niph;
+	struct tcphdr *nth;
+	unsigned int tcp_hdr_size;
+	u16 mss = opts->mss;
+
+	iph = ipv6_hdr(skb);
+
+	tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
+	nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
+			 GFP_ATOMIC);
+	if (nskb == NULL)
+		return;
+	skb_reserve(nskb, MAX_TCP_HEADER);
+
+	niph = synproxy_build_ip(net, nskb, &iph->daddr, &iph->saddr);
+
+	skb_reset_transport_header(nskb);
+	nth = skb_put(nskb, tcp_hdr_size);
+	nth->source	= th->dest;
+	nth->dest	= th->source;
+	nth->seq	= htonl(__cookie_v6_init_sequence(iph, th, &mss));
+	nth->ack_seq	= htonl(ntohl(th->seq) + 1);
+	tcp_flag_word(nth) = TCP_FLAG_SYN | TCP_FLAG_ACK;
+	if (opts->options & NF_SYNPROXY_OPT_ECN)
+		tcp_flag_word(nth) |= TCP_FLAG_ECE;
+	nth->doff	= tcp_hdr_size / 4;
+	nth->window	= 0;
+	nth->check	= 0;
+	nth->urg_ptr	= 0;
+
+	synproxy_build_options(nth, opts);
+
+	synproxy_send_tcp(net, skb, nskb, skb_nfct(skb),
+			  IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size);
+}
+EXPORT_SYMBOL_GPL(synproxy_send_client_synack_ipv6);
+
+static void
+synproxy_send_server_syn(struct net *net,
+			 const struct sk_buff *skb, const struct tcphdr *th,
+			 const struct synproxy_options *opts, u32 recv_seq)
+{
+	struct synproxy_net *snet = synproxy_pernet(net);
+	struct sk_buff *nskb;
+	struct ipv6hdr *iph, *niph;
+	struct tcphdr *nth;
+	unsigned int tcp_hdr_size;
+
+	iph = ipv6_hdr(skb);
+
+	tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
+	nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
+			 GFP_ATOMIC);
+	if (nskb == NULL)
+		return;
+	skb_reserve(nskb, MAX_TCP_HEADER);
+
+	niph = synproxy_build_ip(net, nskb, &iph->saddr, &iph->daddr);
+
+	skb_reset_transport_header(nskb);
+	nth = skb_put(nskb, tcp_hdr_size);
+	nth->source	= th->source;
+	nth->dest	= th->dest;
+	nth->seq	= htonl(recv_seq - 1);
+	/* ack_seq is used to relay our ISN to the synproxy hook to initialize
+	 * sequence number translation once a connection tracking entry exists.
+	 */
+	nth->ack_seq	= htonl(ntohl(th->ack_seq) - 1);
+	tcp_flag_word(nth) = TCP_FLAG_SYN;
+	if (opts->options & NF_SYNPROXY_OPT_ECN)
+		tcp_flag_word(nth) |= TCP_FLAG_ECE | TCP_FLAG_CWR;
+	nth->doff	= tcp_hdr_size / 4;
+	nth->window	= th->window;
+	nth->check	= 0;
+	nth->urg_ptr	= 0;
+
+	synproxy_build_options(nth, opts);
+
+	synproxy_send_tcp(net, skb, nskb, &snet->tmpl->ct_general, IP_CT_NEW,
+			  niph, nth, tcp_hdr_size);
+}
+
+static void
+synproxy_send_server_ack(struct net *net,
+			 const struct ip_ct_tcp *state,
+			 const struct sk_buff *skb, const struct tcphdr *th,
+			 const struct synproxy_options *opts)
+{
+	struct sk_buff *nskb;
+	struct ipv6hdr *iph, *niph;
+	struct tcphdr *nth;
+	unsigned int tcp_hdr_size;
+
+	iph = ipv6_hdr(skb);
+
+	tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
+	nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
+			 GFP_ATOMIC);
+	if (nskb == NULL)
+		return;
+	skb_reserve(nskb, MAX_TCP_HEADER);
+
+	niph = synproxy_build_ip(net, nskb, &iph->daddr, &iph->saddr);
+
+	skb_reset_transport_header(nskb);
+	nth = skb_put(nskb, tcp_hdr_size);
+	nth->source	= th->dest;
+	nth->dest	= th->source;
+	nth->seq	= htonl(ntohl(th->ack_seq));
+	nth->ack_seq	= htonl(ntohl(th->seq) + 1);
+	tcp_flag_word(nth) = TCP_FLAG_ACK;
+	nth->doff	= tcp_hdr_size / 4;
+	nth->window	= htons(state->seen[IP_CT_DIR_ORIGINAL].td_maxwin);
+	nth->check	= 0;
+	nth->urg_ptr	= 0;
+
+	synproxy_build_options(nth, opts);
+
+	synproxy_send_tcp(net, skb, nskb, NULL, 0, niph, nth, tcp_hdr_size);
+}
+
+static void
+synproxy_send_client_ack(struct net *net,
+			 const struct sk_buff *skb, const struct tcphdr *th,
+			 const struct synproxy_options *opts)
+{
+	struct sk_buff *nskb;
+	struct ipv6hdr *iph, *niph;
+	struct tcphdr *nth;
+	unsigned int tcp_hdr_size;
+
+	iph = ipv6_hdr(skb);
+
+	tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
+	nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
+			 GFP_ATOMIC);
+	if (nskb == NULL)
+		return;
+	skb_reserve(nskb, MAX_TCP_HEADER);
+
+	niph = synproxy_build_ip(net, nskb, &iph->saddr, &iph->daddr);
+
+	skb_reset_transport_header(nskb);
+	nth = skb_put(nskb, tcp_hdr_size);
+	nth->source	= th->source;
+	nth->dest	= th->dest;
+	nth->seq	= htonl(ntohl(th->seq) + 1);
+	nth->ack_seq	= th->ack_seq;
+	tcp_flag_word(nth) = TCP_FLAG_ACK;
+	nth->doff	= tcp_hdr_size / 4;
+	nth->window	= htons(ntohs(th->window) >> opts->wscale);
+	nth->check	= 0;
+	nth->urg_ptr	= 0;
+
+	synproxy_build_options(nth, opts);
+
+	synproxy_send_tcp(net, skb, nskb, skb_nfct(skb),
+			  IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size);
+}
+
+bool
+synproxy_recv_client_ack_ipv6(struct net *net,
+			      const struct sk_buff *skb, const struct tcphdr *th,
+			      struct synproxy_options *opts, u32 recv_seq)
+{
+	struct synproxy_net *snet = synproxy_pernet(net);
+	int mss;
+
+	mss = __cookie_v6_check(ipv6_hdr(skb), th, ntohl(th->ack_seq) - 1);
+	if (mss == 0) {
+		this_cpu_inc(snet->stats->cookie_invalid);
+		return false;
+	}
+
+	this_cpu_inc(snet->stats->cookie_valid);
+	opts->mss = mss;
+	opts->options |= NF_SYNPROXY_OPT_MSS;
+
+	if (opts->options & NF_SYNPROXY_OPT_TIMESTAMP)
+		synproxy_check_timestamp_cookie(opts);
+
+	synproxy_send_server_syn(net, skb, th, opts, recv_seq);
+	return true;
+}
+EXPORT_SYMBOL_GPL(synproxy_recv_client_ack_ipv6);
+
+unsigned int
+ipv6_synproxy_hook(void *priv, struct sk_buff *skb,
+		   const struct nf_hook_state *nhs)
+{
+	struct net *net = nhs->net;
+	struct synproxy_net *snet = synproxy_pernet(net);
+	enum ip_conntrack_info ctinfo;
+	struct nf_conn *ct;
+	struct nf_conn_synproxy *synproxy;
+	struct synproxy_options opts = {};
+	const struct ip_ct_tcp *state;
+	struct tcphdr *th, _th;
+	__be16 frag_off;
+	u8 nexthdr;
+	int thoff;
+
+	ct = nf_ct_get(skb, &ctinfo);
+	if (ct == NULL)
+		return NF_ACCEPT;
+
+	synproxy = nfct_synproxy(ct);
+	if (synproxy == NULL)
+		return NF_ACCEPT;
+
+	if (nf_is_loopback_packet(skb))
+		return NF_ACCEPT;
+
+	nexthdr = ipv6_hdr(skb)->nexthdr;
+	thoff = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &nexthdr,
+				 &frag_off);
+	if (thoff < 0 || nexthdr != IPPROTO_TCP)
+		return NF_ACCEPT;
+
+	th = skb_header_pointer(skb, thoff, sizeof(_th), &_th);
+	if (th == NULL)
+		return NF_DROP;
+
+	state = &ct->proto.tcp;
+	switch (state->state) {
+	case TCP_CONNTRACK_CLOSE:
+		if (th->rst && !test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
+			nf_ct_seqadj_init(ct, ctinfo, synproxy->isn -
+						      ntohl(th->seq) + 1);
+			break;
+		}
+
+		if (!th->syn || th->ack ||
+		    CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
+			break;
+
+		/* Reopened connection - reset the sequence number and timestamp
+		 * adjustments, they will get initialized once the connection is
+		 * reestablished.
+		 */
+		nf_ct_seqadj_init(ct, ctinfo, 0);
+		synproxy->tsoff = 0;
+		this_cpu_inc(snet->stats->conn_reopened);
+
+		/* fall through */
+	case TCP_CONNTRACK_SYN_SENT:
+		if (!synproxy_parse_options(skb, thoff, th, &opts))
+			return NF_DROP;
+
+		if (!th->syn && th->ack &&
+		    CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) {
+			/* Keep-Alives are sent with SEG.SEQ = SND.NXT-1,
+			 * therefore we need to add 1 to make the SYN sequence
+			 * number match the one of first SYN.
+			 */
+			if (synproxy_recv_client_ack_ipv6(net, skb, th, &opts,
+							  ntohl(th->seq) + 1)) {
+				this_cpu_inc(snet->stats->cookie_retrans);
+				consume_skb(skb);
+				return NF_STOLEN;
+			} else {
+				return NF_DROP;
+			}
+		}
+
+		synproxy->isn = ntohl(th->ack_seq);
+		if (opts.options & NF_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)
+			break;
+
+		if (!synproxy_parse_options(skb, thoff, th, &opts))
+			return NF_DROP;
+
+		if (opts.options & NF_SYNPROXY_OPT_TIMESTAMP) {
+			synproxy->tsoff = opts.tsval - synproxy->its;
+			nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
+		}
+
+		opts.options &= ~(NF_SYNPROXY_OPT_MSS |
+				  NF_SYNPROXY_OPT_WSCALE |
+				  NF_SYNPROXY_OPT_SACK_PERM);
+
+		swap(opts.tsval, opts.tsecr);
+		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);
+
+		consume_skb(skb);
+		return NF_STOLEN;
+	default:
+		break;
+	}
+
+	synproxy_tstamp_adjust(skb, thoff, th, ct, ctinfo, synproxy);
+	return NF_ACCEPT;
+}
+EXPORT_SYMBOL_GPL(ipv6_synproxy_hook);
+
+int
+nf_synproxy_ipv6_init(struct synproxy_net *snet, struct net *net)
+{
+	int err;
+
+        if (snet->hook_ref6 == 0) {
+                err = nf_register_net_hooks(net, ipv6_synproxy_ops,
+                                            ARRAY_SIZE(ipv6_synproxy_ops));
+                if (err)
+                        return err;
+        }
+
+	snet->hook_ref6++;
+	return err;
+}
+EXPORT_SYMBOL_GPL(nf_synproxy_ipv6_init);
+
+void
+nf_synproxy_ipv6_fini(struct synproxy_net *snet, struct net *net)
+{
+        snet->hook_ref6--;
+        if (snet->hook_ref6 == 0)
+                nf_unregister_net_hooks(net, ipv6_synproxy_ops,
+					ARRAY_SIZE(ipv6_synproxy_ops));
+}
+EXPORT_SYMBOL_GPL(nf_synproxy_ipv6_fini);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Fernando Fernandez <ffmancera@riseup.net>");
-- 
2.20.1

[PATCH 5/5 nf-next] netfilter: add NF_SYNPROXY_IPV6 symbol

[Fernando Fernandez Mancera]

Signed-off-by: Fernando Fernandez Mancera <ffmancera@riseup.net>
---
 net/ipv6/netfilter/Kconfig  | 4 ++++
 net/ipv6/netfilter/Makefile | 3 +++
 2 files changed, 7 insertions(+)

diff --git a/net/ipv6/netfilter/Kconfig b/net/ipv6/netfilter/Kconfig
index 086fc669279e..60146a0d390d 100644
--- a/net/ipv6/netfilter/Kconfig
+++ b/net/ipv6/netfilter/Kconfig
@@ -5,6 +5,9 @@
 menu "IPv6: Netfilter Configuration"
 	depends on INET && IPV6 && NETFILTER
 
+config NF_SYNPROXY_IPV6
+	tristate
+
 config NF_SOCKET_IPV6
 	tristate "IPv6 socket lookup support"
 	help
@@ -212,6 +215,7 @@ config IP6_NF_TARGET_REJECT
 config IP6_NF_TARGET_SYNPROXY
 	tristate "SYNPROXY target support"
 	depends on NF_CONNTRACK && NETFILTER_ADVANCED
+	select NF_SYNPROXY_IPV6
 	select NETFILTER_SYNPROXY
 	select SYN_COOKIES
 	help
diff --git a/net/ipv6/netfilter/Makefile b/net/ipv6/netfilter/Makefile
index 731a74c60dca..d9ee2f8c9ae2 100644
--- a/net/ipv6/netfilter/Makefile
+++ b/net/ipv6/netfilter/Makefile
@@ -15,6 +15,9 @@ obj-$(CONFIG_IP6_NF_NAT) += ip6table_nat.o
 nf_defrag_ipv6-y := nf_defrag_ipv6_hooks.o nf_conntrack_reasm.o
 obj-$(CONFIG_NF_DEFRAG_IPV6) += nf_defrag_ipv6.o
 
+#synproxy
+obj-$(CONFIG_NF_SYNPROXY_IPV6) += nf_synproxy_ipv6.o
+
 obj-$(CONFIG_NF_SOCKET_IPV6) += nf_socket_ipv6.o
 obj-$(CONFIG_NF_TPROXY_IPV6) += nf_tproxy_ipv6.o
 
-- 
2.20.1

Re: [PATCH 0/5] Extract SYNPROXY infrastructure

[Jan Engelhardt]

On Saturday 2019-05-18 20:21, Fernando Fernandez Mancera wrote:

>The patch series have been tested by enabling iptables and ip6tables SYNPROXY.
>All the modules loaded as expected.

What is the subsequent plan? Making new modules brings the usual module 
overhead (16K it seems), and if there is just one user, that seems 
wasteful.

>$ lsmod | grep synproxy
>IPv4 and IPv6:
>nf_synproxy_ipv6       16384  1 ip6t_SYNPROXY
>nf_synproxy_ipv4       16384  1 ipt_SYNPROXY
>nf_synproxy_core       16384  4 ip6t_SYNPROXY,nf_synproxy_ipv6,ipt_SYNPROXY,nf_synproxy_ipv4
>nf_conntrack          159744  8 ip6t_SYNPROXY,xt_conntrack,xt_state,nf_synproxy_ipv6,ipt_SYNPROXY,nf_synproxy_ipv4,nf_synproxy_core,xt_CT

> net/ipv4/netfilter/nf_synproxy_ipv4.c         | 393 ++++++++++++++++
> net/ipv6/netfilter/nf_synproxy_ipv6.c         | 414 +++++++++++++++++

Re: [PATCH 4/5 nf-next] netfilter: synproxy: extract IPv6 SYNPROXY infrastructure from ip6t_SYNPROXY

[Florian Westphal]

Fernando Fernandez Mancera <ffmancera@riseup.net> wrote:

Hi Fernando

> +void
> +synproxy_send_client_synack_ipv6(struct net *net,
> +				 const struct sk_buff *skb,
> +				 const struct tcphdr *th,
> +				 const struct synproxy_options *opts)

[..]

> +	nth->seq	= htonl(__cookie_v6_init_sequence(iph, th, &mss));

It seems that __cookie_v6_init_sequence() is the only dependency of
this module on ipv6.

If we would make it accessible via nf_ipv6_ops struct, then the
dependency goes away and we could place ipv4 and ipv6 parts in a
single module.

Just saying, it would avoid adding extra modules.
We could then have

nf_synproxy.ko  # shared code
nft_synproxy.ko # nftables frontend
xt_SYNPROXY.ko	# ip(6)tables frontends

Re: [PATCH 4/5 nf-next] netfilter: synproxy: extract IPv6 SYNPROXY infrastructure from ip6t_SYNPROXY

[Fernando Fernandez Mancera]

Hi Florian,

El 18 de mayo de 2019 22:20:32 CEST, Florian Westphal <fw@strlen.de> escribió:
>Fernando Fernandez Mancera <ffmancera@riseup.net> wrote:
>
>Hi Fernando
>
>> +void
>> +synproxy_send_client_synack_ipv6(struct net *net,
>> +				 const struct sk_buff *skb,
>> +				 const struct tcphdr *th,
>> +				 const struct synproxy_options *opts)
>
>[..]
>
>> +	nth->seq	= htonl(__cookie_v6_init_sequence(iph, th, &mss));
>
>It seems that __cookie_v6_init_sequence() is the only dependency of
>this module on ipv6.
>
>If we would make it accessible via nf_ipv6_ops struct, then the
>dependency goes away and we could place ipv4 and ipv6 parts in a
>single module.
>
>Just saying, it would avoid adding extra modules.

This would be awesome but I am not sure if it is possible right now. I am going to try it and send a new patch series. Thank you  about this!

>We could then have
>
>nf_synproxy.ko  # shared code
>nft_synproxy.ko # nftables frontend
>xt_SYNPROXY.ko	# ip(6)tables frontends

In this case, ip6t_synproxy wouldn't need to select IPV6 Cookie module right? Thanks!

Re: [PATCH 4/5 nf-next] netfilter: synproxy: extract IPv6 SYNPROXY infrastructure from ip6t_SYNPROXY

[Florian Westphal]

Fernando Fernandez Mancera <ffmancera@riseup.net> wrote:
> >If we would make it accessible via nf_ipv6_ops struct, then the
> >dependency goes away and we could place ipv4 and ipv6 parts in a
> >single module.
> >
> >Just saying, it would avoid adding extra modules.
> 
> This would be awesome but I am not sure if it is possible right now. I am going to try it and send a new patch series. Thank you  about this!

You would need to make something similar as
commit 960587285a56ec3cafb4d1e6b25c19eced4d0bce first.

Let me know if you need help.

> >We could then have
> >
> >nf_synproxy.ko  # shared code
> >nft_synproxy.ko # nftables frontend
> >xt_SYNPROXY.ko	# ip(6)tables frontends
> 
> In this case, ip6t_synproxy wouldn't need to select IPV6 Cookie module right? Thanks!

No, it would not need to do this.

Basically all the .c code would have

#if IS_ENABLED(CONFIG_IPV6)
ipv6-code here
#endif

where needed, so in case the kernel is built with CONFIG_IPV6=m|y, the
functionality is available.

Re: [PATCH 0/5] Extract SYNPROXY infrastructure

[Fernando Fernandez Mancera]

Hi Jan,

On 5/18/19 9:29 PM, Jan Engelhardt wrote:
> On Saturday 2019-05-18 20:21, Fernando Fernandez Mancera wrote:
> 
>> The patch series have been tested by enabling iptables and ip6tables SYNPROXY.
>> All the modules loaded as expected.
> 
> What is the subsequent plan? Making new modules brings the usual module 
> overhead (16K it seems), and if there is just one user, that seems 
> wasteful.
>

The idea is to simplify these two modules in a single one (as Florian
suggested and it have be done in the v2). At this point, we only need to
implement the nft_synproxy module which is going to be the frontend
module for the nftables support.

In my opinion, SYNPROXY still being useful and it would be nice to
support it in nftables, furthermore there are some improvements planned
to do for the SYNPROXY nftables module. Thank you!

>> $ lsmod | grep synproxy
>> IPv4 and IPv6:
>> nf_synproxy_ipv6       16384  1 ip6t_SYNPROXY
>> nf_synproxy_ipv4       16384  1 ipt_SYNPROXY
>> nf_synproxy_core       16384  4 ip6t_SYNPROXY,nf_synproxy_ipv6,ipt_SYNPROXY,nf_synproxy_ipv4
>> nf_conntrack          159744  8 ip6t_SYNPROXY,xt_conntrack,xt_state,nf_synproxy_ipv6,ipt_SYNPROXY,nf_synproxy_ipv4,nf_synproxy_core,xt_CT
> 
>> net/ipv4/netfilter/nf_synproxy_ipv4.c         | 393 ++++++++++++++++
>> net/ipv6/netfilter/nf_synproxy_ipv6.c         | 414 +++++++++++++++++