Make forcible stitching optional

`set upf proxy` force-stitching on|off controls the option.
`show upf proxy` displays "Force-stitching" status.

upf/upf_cli.c

@@ -1345,6 +1345,16 @@ upf_proxy_set_command_fn (vlib_main_t * vm, unformat_input_t * input,
       else if (unformat (input, "private-segment-size %U",
 			 unformat_memory_size, &private_segment_size))
 	;
+      else if (unformat (input, "force-stitching"))
+	{
+	  if (unformat (input, "on"))
+	    force_stitching = 1;
+	  else if (unformat (input, "off"))
+	    force_stitching = 0;
+	  else
+	    return clib_error_return (0, "unknown input `%U'",
+				      format_unformat_error, input);
+	}
       else
 	return clib_error_return (0, "unknown input `%U'",
 				  format_unformat_error, input);
@@ -1363,7 +1373,8 @@ VLIB_CLI_COMMAND (upf_proxy_set_command, static) =
   .short_help = "set upf proxy [mss <nn>] [fifo-size <nn>[k|m]]"
       "[max-fifo-size <nn>[k|m]][high-watermark <nn>]"
       "[low-watermark <nn>][prealloc-fifos <nn>]"
-      "[private-segment-size <mem>][private-segment-count <nn>]",
+      "[private-segment-size <mem>][private-segment-count <nn>]"
+      "[force-stitching <on|off>]",
   .function = upf_proxy_set_command_fn,
 };
 /* *INDENT-ON* */
@@ -1395,14 +1406,16 @@ upf_show_proxy_command_fn (vlib_main_t * vm,
 		   "Hi/Lo Watermark: %u %% / %u %%\n"
 		   "Prealloc FIFOs: %u\n"
 		   "Private Segment Count: %u\n"
-		   "Private Segment Size: %U\n",
+		   "Private Segment Size: %U\n"
+		   "Force stitching: %s\n",
 		   pm->mss,
 		   format_memory_size, pm->fifo_size,
 		   format_memory_size, pm->max_fifo_size,
 		   pm->high_watermark, pm->low_watermark,
 		   pm->prealloc_fifos,
 		   pm->private_segment_count,
-		   format_memory_size, pm->private_segment_size);
+		   format_memory_size, pm->private_segment_size,
+		   pm->force_stitching ? "on" : "off");
 
 done:
   return error;

upf/upf_proxy.c

@@ -1390,6 +1390,7 @@ upf_proxy_main_init (vlib_main_t * vm)
   pm->prealloc_fifos = 0;
   pm->private_segment_count = 0;
   pm->private_segment_size = 512 << 20;
+  pm->force_stitching = 1;
 
   pm->server_client_index = ~0;
   pm->active_open_client_index = ~0;

upf/upf_proxy.h

@@ -51,12 +51,13 @@ typedef struct
 #define foreach_upf_proxy_config_fields						\
   _(u16, mss)				/**< TCP MSS */				\
   _(uword, fifo_size)			/**< initial fifo size */		\
-  _(uword, max_fifo_size)			/**< max fifo size */			\
+  _(uword, max_fifo_size)		/**< max fifo size */			\
   _(u8, high_watermark)			/**< high watermark (%) */		\
   _(u8, low_watermark)			/**< low watermark (%) */		\
   _(u32, private_segment_count)		/**< Number of private fifo segs */	\
-  _(uword, private_segment_size)		/**< size of private fifo segs */	\
+  _(uword, private_segment_size)	/**< size of private fifo segs */	\
   _(u8, prealloc_fifos)			/**< Request fifo preallocation */	\
+  _(u8, force_stitching)		/**< Force "dirty" proxy stitching */ 	\
 
 typedef struct
 {

upf/upf_proxy_input.c

@@ -132,6 +132,7 @@ splice_tcp_connection (upf_main_t * gtm, flow_entry_t * flow,
   transport_connection_t *tc;
   tcp_connection_t *tcpRx, *tcpTx;
   session_t *s;
+  upf_proxy_main_t *pm = &upf_proxy_main;
 
   if (rev->conn_index == ~0)
     return UPF_PROXY_INPUT_NEXT_TCP_INPUT;
@@ -198,24 +199,27 @@ splice_tcp_connection (upf_main_t * gtm, flow_entry_t * flow,
       return UPF_PROXY_INPUT_NEXT_TCP_INPUT;
     }
 
-  if (flow_seq_offs (flow, origin) == 0)
-    flow_seq_offs (flow, origin) = direction == FT_ORIGIN ?
-      tcpTx->snd_nxt - tcpRx->rcv_nxt : tcpRx->rcv_nxt - tcpTx->snd_nxt;
-
-  if (flow_seq_offs (flow, reverse) == 0)
-    flow_seq_offs (flow, reverse) = direction == FT_ORIGIN ?
-      tcpTx->rcv_nxt - tcpRx->snd_nxt : tcpRx->snd_nxt - tcpTx->rcv_nxt;
-
   /* check fifo, proxy Tx/Rx are connected... */
   if (svm_fifo_max_dequeue (s->rx_fifo) != 0 ||
       svm_fifo_max_dequeue (s->tx_fifo) != 0)
     {
+      if (!pm->force_stitching)
+	return UPF_PROXY_INPUT_NEXT_TCP_INPUT;
+
       flow->spliced_dirty = 1;
       vlib_increment_simple_counter (&gtm->upf_simple_counters
 				     [UPF_FLOWS_STITCHED_DIRTY_FIFOS],
 				     vlib_get_thread_index (), 0, 1);
     }
 
+  if (flow_seq_offs (flow, origin) == 0)
+    flow_seq_offs (flow, origin) = direction == FT_ORIGIN ?
+      tcpTx->snd_nxt - tcpRx->rcv_nxt : tcpRx->rcv_nxt - tcpTx->snd_nxt;
+
+  if (flow_seq_offs (flow, reverse) == 0)
+    flow_seq_offs (flow, reverse) = direction == FT_ORIGIN ?
+      tcpTx->rcv_nxt - tcpRx->snd_nxt : tcpRx->snd_nxt - tcpTx->rcv_nxt;
+
   /* kill the TCP connections, session and proxy session */
   kill_connection_hard (tcpRx);
   kill_connection_hard (tcpTx);