Add common functions into nf_synproxy_ipv4.c to prepare for nftables support.
Signed-off-by: Fernando Fernandez Mancera <ffmancera@xxxxxxxxxx>
---
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@xxxxxxxxxx>");
--
2.20.1
