src: introduce SYNPROXY matching

Add support for "synproxy" statement. For example (for TCP port 8888):

table ip x {
	chain y {
		type filter hook prerouting priority raw; policy accept;
		tcp dport 8888 tcp flags syn notrack
	}

	chain z {
		type filter hook input priority filter; policy accept;
		tcp dport 8888 ct state invalid,untracked synproxy mss 1460 wscale 7 timestamp sack-perm
		ct state invalid drop
	}
}

Signed-off-by: Fernando Fernandez Mancera <ffmancera@riseup.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

3 files changed, 156 insertions, 0 deletions

diff --git a/tests/py/inet/synproxy.t b/tests/py/inet/synproxy.t
new file mode 100644
index 00000000..55a05e1e
--- /dev/null
+++ b/tests/py/inet/synproxy.t
@@ -0,0 +1,13 @@
+:synproxychain;type filter hook input priority 0
+
+*ip;synproxyip;synproxychain
+*ip6;synproxyip6;synproxychain
+*inet;synproxyinet;synproxychain
+
+synproxy;ok
+synproxy mss 1460 wscale 7;ok
+synproxy mss 1460 wscale 5 timestamp sack-perm;ok
+synproxy timestamp sack-perm;ok
+synproxy timestamp;ok
+synproxy sack-perm;ok
+
diff --git a/tests/py/inet/synproxy.t.json b/tests/py/inet/synproxy.t.json
new file mode 100644
index 00000000..313fa9fe
--- /dev/null
+++ b/tests/py/inet/synproxy.t.json
@@ -0,0 +1,71 @@
+# synproxy
+[
+    {
+        "synproxy":null
+    }
+]
+
+# synproxy mss 1460
+[
+    {
+        "synproxy": {
+            "mss": 1460
+        }
+    }
+]
+
+# synproxy wscale 7
+[
+    {
+        "synproxy": {
+            "wscale": 7
+        }
+    }
+]
+
+# synproxy mss 1460 wscale 7
+[
+    {
+        "synproxy": {
+            "mss": 1460,
+            "wscale": 7
+        }
+    }
+]
+
+# synproxy timestamp
+[
+    {
+        "synproxy": {
+            "flags": [
+                "timestamp"
+            ]
+        }
+    }
+]
+
+# synproxy timestamp sack-perm
+[
+    {
+        "synproxy": {
+            "flags": [
+                "timestamp",
+                "sack-perm"
+            ]
+        }
+    }
+]
+
+# synproxy mss 1460 wscale 7 timestamp sack-perm
+[
+    {
+        "synproxy": {
+            "mss": 1460,
+            "wscale": 7,
+            "flags": [
+                "timestamp",
+                "sack-perm"
+            ]
+        }
+    }
+]
diff --git a/tests/py/inet/synproxy.t.payload b/tests/py/inet/synproxy.t.payload
new file mode 100644
index 00000000..2e6feaaf
--- /dev/null
+++ b/tests/py/inet/synproxy.t.payload
@@ -0,0 +1,72 @@
+# synproxy
+ip synproxyip synproxychain
+  [ synproxy mss 0 wscale 0 ]
+
+# synproxy
+ip6 synproxyip6 synproxychain
+  [ synproxy mss 0 wscale 0 ]
+
+# synproxy
+inet synproxyinet synproxychain
+  [ synproxy mss 0 wscale 0 ]
+
+# synproxy mss 1460 wscale 7
+ip synproxyip synproxychain
+  [ synproxy mss 1460 wscale 7 ]
+
+# synproxy mss 1460 wscale 7
+ip6 synproxyip6 synproxychain
+  [ synproxy mss 1460 wscale 7 ]
+
+# synproxy mss 1460 wscale 7
+inet synproxyinet synproxychain
+  [ synproxy mss 1460 wscale 7 ]
+
+# synproxy mss 1460 wscale 5 timestamp sack-perm
+ip synproxyip synproxychain
+  [ synproxy mss 1460 wscale 5 ]
+
+# synproxy mss 1460 wscale 5 timestamp sack-perm
+ip6 synproxyip6 synproxychain
+  [ synproxy mss 1460 wscale 5 ]
+
+# synproxy mss 1460 wscale 5 timestamp sack-perm
+inet synproxyinet synproxychain
+  [ synproxy mss 1460 wscale 5 ]
+
+# synproxy timestamp sack-perm
+ip synproxyip synproxychain
+  [ synproxy mss 0 wscale 0 ]
+
+# synproxy timestamp sack-perm
+ip6 synproxyip6 synproxychain
+  [ synproxy mss 0 wscale 0 ]
+
+# synproxy timestamp sack-perm
+inet synproxyinet synproxychain
+  [ synproxy mss 0 wscale 0 ]
+
+# synproxy timestamp
+ip synproxyip synproxychain
+  [ synproxy mss 0 wscale 0 ]
+
+# synproxy timestamp
+ip6 synproxyip6 synproxychain
+  [ synproxy mss 0 wscale 0 ]
+
+# synproxy timestamp
+inet synproxyinet synproxychain
+  [ synproxy mss 0 wscale 0 ]
+
+# synproxy sack-perm
+ip synproxyip synproxychain
+  [ synproxy mss 0 wscale 0 ]
+
+# synproxy sack-perm
+ip6 synproxyip6 synproxychain
+  [ synproxy mss 0 wscale 0 ]
+
+# synproxy sack-perm
+inet synproxyinet synproxychain
+  [ synproxy mss 0 wscale 0 ]
+