NAT: TCP MSS clamping

NAT plugin changes the MSS value in TCP SYN packets to avoid fragmentation.
If the negotiated MSS value is greater than the configured value it is changed
to the configured value. If the negotiated MSS value is smaller than the
configured value it remains unchanged.

Change-Id: Ic3c4f94a2f1b76e2bf79f50f3ad36a4097f3f188
Signed-off-by: Matus Fabian <matfabia@cisco.com>

1 files changed, 35 insertions, 0 deletions

diff --git a/src/plugins/nat/nat.api b/src/plugins/nat/nat.api
index 1ff288dba2a..6e2d8e57853 100644
--- a/src/plugins/nat/nat.api
+++ b/src/plugins/nat/nat.api
@@ -332,6 +332,41 @@ define nat_get_addr_and_port_alloc_alg_reply {
   u16 end_port;
 };
 
+/** \brief Set TCP MSS rewriting configuration
+    @param client_index - opaque cookie to identify the sender
+    @param context - sender context, to match reply w/ request
+    @param mss_value - MSS value to be used for MSS rewriting
+    @param enable - disable(0)/enable(1) MSS rewriting feature
+*/
+autoreply define nat_set_mss_clamping {
+  u32 client_index;
+  u32 context;
+  u16 mss_value;
+  u8 enable;
+};
+
+/** \brief Get TCP MSS rewriting configuration
+    @param client_index - opaque cookie to identify the sender
+    @param context - sender context, to match reply w/ request
+*/
+define nat_get_mss_clamping {
+  u32 client_index;
+  u32 context;
+};
+
+/** \brief Get TCP MSS rewriting configuration reply
+    @param context - sender context, to match reply w/ request
+    @param retval - return code
+    @param mss_value - MSS value to be used for MSS rewriting
+    @param enable - disable(0)/enable(1) MSS rewriting feature
+*/
+define nat_get_mss_clamping_reply {
+  u32 context;
+  i32 retval;
+  u16 mss_value;
+  u8 enable;
+};
+
 /*
  * NAT44 APIs
  */