netfilter: add SYNPROXY core/target
Add a SYNPROXY for netfilter. The code is split into two parts, the synproxy
core with common functions and an address family specific target.
The SYNPROXY receives the connection request from the client, responds with
a SYN/ACK containing a SYN cookie and announcing a zero window and checks
whether the final ACK from the client contains a valid cookie.
It then establishes a connection to the original destination and, if
successful, sends a window update to the client with the window size
announced by the server.
Support for timestamps, SACK, window scaling and MSS options can be
statically configured as target parameters if the features of the server
are known. If timestamps are used, the timestamp value sent back to
the client in the SYN/ACK will be different from the real timestamp of
the server. In order to now break PAWS, the timestamps are translated in
the direction server->client.
Signed-off-by: Patrick McHardy <kaber@trash.net>
Tested-by: Martin Topholm <mph@one.com>
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/include/net/netfilter/nf_conntrack_extend.h b/include/net/netfilter/nf_conntrack_extend.h
index 2a22bcb..ff95434 100644
--- a/include/net/netfilter/nf_conntrack_extend.h
+++ b/include/net/netfilter/nf_conntrack_extend.h
@@ -9,8 +9,8 @@
NF_CT_EXT_HELPER,
#if defined(CONFIG_NF_NAT) || defined(CONFIG_NF_NAT_MODULE)
NF_CT_EXT_NAT,
- NF_CT_EXT_SEQADJ,
#endif
+ NF_CT_EXT_SEQADJ,
NF_CT_EXT_ACCT,
#ifdef CONFIG_NF_CONNTRACK_EVENTS
NF_CT_EXT_ECACHE,
@@ -27,6 +27,9 @@
#ifdef CONFIG_NF_CONNTRACK_LABELS
NF_CT_EXT_LABELS,
#endif
+#if IS_ENABLED(CONFIG_NETFILTER_SYNPROXY)
+ NF_CT_EXT_SYNPROXY,
+#endif
NF_CT_EXT_NUM,
};
@@ -39,6 +42,7 @@
#define NF_CT_EXT_TSTAMP_TYPE struct nf_conn_tstamp
#define NF_CT_EXT_TIMEOUT_TYPE struct nf_conn_timeout
#define NF_CT_EXT_LABELS_TYPE struct nf_conn_labels
+#define NF_CT_EXT_SYNPROXY_TYPE struct nf_conn_synproxy
/* Extensions: optional stuff which isn't permanently in struct. */
struct nf_ct_ext {