diff --git a/src/vnet/tcp/tcp_pg.c b/src/vnet/tcp/tcp_pg.c
new file mode 100644
index 0000000..dc32404
--- /dev/null
+++ b/src/vnet/tcp/tcp_pg.c
@@ -0,0 +1,236 @@
+/*
+ * Copyright (c) 2016 Cisco and/or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+/*
+ * ip/tcp_pg: TCP packet-generator interface
+ *
+ * Copyright (c) 2008 Eliot Dresselhaus
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ *  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ *  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ *  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ *  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ *  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ *  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#include <vnet/ip/ip.h>
+#include <vnet/pg/pg.h>
+
+/* TCP flags bit 0 first. */
+#define foreach_tcp_flag			\
+  _ (FIN)					\
+  _ (SYN)					\
+  _ (RST)					\
+  _ (PSH)					\
+  _ (ACK)					\
+  _ (URG)					\
+  _ (ECE)					\
+  _ (CWR)
+
+static void
+tcp_pg_edit_function (pg_main_t * pg,
+		      pg_stream_t * s,
+		      pg_edit_group_t * g,
+		      u32 * packets,
+		      u32 n_packets)
+{
+  vlib_main_t * vm = vlib_get_main();
+  u32 ip_offset, tcp_offset;
+
+  tcp_offset = g->start_byte_offset;
+  ip_offset = (g-1)->start_byte_offset;
+
+  while (n_packets >= 1)
+    {
+      vlib_buffer_t * p0;
+      ip4_header_t * ip0;
+      tcp_header_t * tcp0;
+      ip_csum_t sum0;
+      u32 tcp_len0;
+
+      p0 = vlib_get_buffer (vm, packets[0]);
+      n_packets -= 1;
+      packets += 1;
+
+      ASSERT (p0->current_data == 0);
+      ip0 = (void *) (p0->data + ip_offset);
+      tcp0 = (void *) (p0->data + tcp_offset);
+      tcp_len0 = clib_net_to_host_u16 (ip0->length) - sizeof (ip0[0]);
+
+      /* Initialize checksum with header. */
+      if (BITS (sum0) == 32)
+	{
+	  sum0 = clib_mem_unaligned (&ip0->src_address, u32);
+	  sum0 = ip_csum_with_carry (sum0, clib_mem_unaligned (&ip0->dst_address, u32));
+	}
+      else
+	sum0 = clib_mem_unaligned (&ip0->src_address, u64);
+
+      sum0 = ip_csum_with_carry
+	(sum0, clib_host_to_net_u32 (tcp_len0 + (ip0->protocol << 16)));
+
+      /* Invalidate possibly old checksum. */
+      tcp0->checksum = 0;
+
+      sum0 = ip_incremental_checksum_buffer (vm, p0, tcp_offset, tcp_len0, sum0);
+
+      tcp0->checksum = ~ ip_csum_fold (sum0);
+    }
+}
+
+typedef struct {
+  pg_edit_t src, dst;
+  pg_edit_t seq_number, ack_number;
+  pg_edit_t data_offset_and_reserved;
+#define _(f) pg_edit_t f##_flag;
+  foreach_tcp_flag
+#undef _
+  pg_edit_t window;
+  pg_edit_t checksum;
+  pg_edit_t urgent_pointer;
+} pg_tcp_header_t;
+
+static inline void
+pg_tcp_header_init (pg_tcp_header_t * p)
+{
+  /* Initialize fields that are not bit fields in the IP header. */
+#define _(f) pg_edit_init (&p->f, tcp_header_t, f);
+  _ (src);
+  _ (dst);
+  _ (seq_number);
+  _ (ack_number);
+  _ (window);
+  _ (checksum);
+  _ (urgent_pointer);
+#undef _
+
+  /* Initialize bit fields. */
+#define _(f)						\
+  pg_edit_init_bitfield (&p->f##_flag, tcp_header_t,	\
+			 flags,				\
+			 TCP_FLAG_BIT_##f, 1);
+
+  foreach_tcp_flag
+#undef _
+
+  pg_edit_init_bitfield (&p->data_offset_and_reserved, tcp_header_t,
+			 data_offset_and_reserved,
+			 4, 4);
+}
+
+uword
+unformat_pg_tcp_header (unformat_input_t * input, va_list * args)
+{
+  pg_stream_t * s = va_arg (*args, pg_stream_t *);
+  pg_tcp_header_t * p;
+  u32 group_index;
+  
+  p = pg_create_edit_group (s, sizeof (p[0]), sizeof (tcp_header_t),
+			    &group_index);
+  pg_tcp_header_init (p);
+
+  /* Defaults. */
+  pg_edit_set_fixed (&p->seq_number, 0);
+  pg_edit_set_fixed (&p->ack_number, 0);
+
+  pg_edit_set_fixed (&p->data_offset_and_reserved, 
+                     sizeof (tcp_header_t) / sizeof (u32));
+
+  pg_edit_set_fixed (&p->window, 4096);
+  pg_edit_set_fixed (&p->urgent_pointer, 0);
+
+#define _(f) pg_edit_set_fixed (&p->f##_flag, 0);
+  foreach_tcp_flag
+#undef _
+
+  p->checksum.type = PG_EDIT_UNSPECIFIED;
+
+  if (! unformat (input, "TCP: %U -> %U",
+		  unformat_pg_edit,
+		    unformat_tcp_udp_port, &p->src,
+		  unformat_pg_edit,
+		    unformat_tcp_udp_port, &p->dst))
+    goto error;
+
+  /* Parse options. */
+  while (1)
+    {
+      if (unformat (input, "window %U",
+		    unformat_pg_edit,
+		    unformat_pg_number, &p->window))
+	;
+
+      else if (unformat (input, "checksum %U",
+			 unformat_pg_edit,
+			 unformat_pg_number, &p->checksum))
+	;
+
+      /* Flags. */
+#define _(f) else if (unformat (input, #f)) pg_edit_set_fixed (&p->f##_flag, 1);
+  foreach_tcp_flag
+#undef _
+
+      /* Can't parse input: try next protocol level. */
+      else
+	break;
+    }
+
+  {
+    ip_main_t * im = &ip_main;
+    u16 dst_port;
+    tcp_udp_port_info_t * pi;
+
+    pi = 0;
+    if (p->dst.type == PG_EDIT_FIXED)
+      {
+	dst_port = pg_edit_get_value (&p->dst, PG_EDIT_LO);
+	pi = ip_get_tcp_udp_port_info (im, dst_port);
+      }
+
+    if (pi && pi->unformat_pg_edit
+	&& unformat_user (input, pi->unformat_pg_edit, s))
+      ;
+
+    else if (! unformat_user (input, unformat_pg_payload, s))
+      goto error;
+
+    if (p->checksum.type == PG_EDIT_UNSPECIFIED)
+      {
+	pg_edit_group_t * g = pg_stream_get_group (s, group_index);
+	g->edit_function = tcp_pg_edit_function;
+	g->edit_function_opaque = 0;
+      }
+
+    return 1;
+  }
+
+ error:
+  /* Free up any edits we may have added. */
+  pg_free_edit_group (s);
+  return 0;
+}
+