[HICN-651] Offload checksum computation to VPP.

Signed-off-by: Mauro Sardara <msardara@cisco.com>
Change-Id: I42d69455542f3def0076fe58020f8f10347ef83f

4 files changed, 60 insertions, 21 deletions

diff --git a/hicn-plugin/src/faces/face_node.c b/hicn-plugin/src/faces/face_node.c
index e1fd81ca0..fd8649e6b 100644
--- a/hicn-plugin/src/faces/face_node.c
+++ b/hicn-plugin/src/faces/face_node.c
@@ -558,19 +558,34 @@ hicn_face_rewrite_interest (vlib_main_t * vm, vlib_buffer_t * b0,
   /*   return; */
 
   hicn_header_t *hicn = vlib_buffer_get_current (b0);
+  size_t l3_header_size = sizeof(ip6_header_t);
 
   //hicn_face_ip_t *ip_face = (hicn_face_ip_t *) face->data;
 
   ip46_address_t temp_addr;
   ip46_address_reset (&temp_addr);
   hicn_type_t type = hicn_get_buffer (b0)->type;
-  hicn_ops_vft[type.l1]->rewrite_interest (type, &hicn->protocol,
-                                           &face->nat_addr, &temp_addr);
+  int ret = hicn_ops_vft[type.l1]->rewrite_interest (type, &hicn->protocol,
+                                                     &face->nat_addr, &temp_addr);
 
-  if (ip46_address_is_ip4(&face->nat_addr))
+  if (ip46_address_is_ip4(&face->nat_addr)) {
     b0->flags |= VNET_BUFFER_F_OFFLOAD_IP_CKSUM;
+    l3_header_size = sizeof(ip4_header_t);
+  }
+
+  if (ret == HICN_LIB_ERROR_REWRITE_CKSUM_REQUIRED) {
+    b0->flags |= VNET_BUFFER_F_OFFLOAD_TCP_CKSUM;
 
-  b0->flags |= VNET_BUFFER_F_OFFLOAD_TCP_CKSUM;
+    /* Make sure l3_hdr_offset and l4_hdr_offset are set */
+    if (!(b0->flags & VNET_BUFFER_F_L3_HDR_OFFSET_VALID)) {
+      b0->flags |= VNET_BUFFER_F_L3_HDR_OFFSET_VALID;
+      vnet_buffer (b0)->l3_hdr_offset = b0->current_data;
+    }
+    if (!(b0->flags & VNET_BUFFER_F_L4_HDR_OFFSET_VALID)) {
+      b0->flags |= VNET_BUFFER_F_L4_HDR_OFFSET_VALID;
+      vnet_buffer (b0)->l4_hdr_offset = vnet_buffer (b0)->l3_hdr_offset + l3_header_size;
+    }
+  }
 
   ASSERT(face->flags & HICN_FACE_FLAGS_FACE);
 
diff --git a/lib/includes/hicn/error.h b/lib/includes/hicn/error.h
index 3e027c4e5..9303aeb7e 100644
--- a/lib/includes/hicn/error.h
+++ b/lib/includes/hicn/error.h
@@ -24,16 +24,17 @@
  * Error definitions
  ******************************************************************************/
 
-#define foreach_libhicn_error                                                   \
-_(NONE,                 0,      "OK")                                           \
-_(UNSPECIFIED,          128,    "Unspecified Error")                            \
-_(NOT_IMPLEMENTED,      180,    "Function not yet implemented")                 \
-_(NOT_HICN,             202,    "Non hICN packet")                              \
-_(UNKNOWN_ADDRESS,      210,    "Unknown address")                              \
-_(INVALID_PARAMETER,    220,    "Invalid parameter")                            \
-_(INVALID_IP_ADDRESS,   221,    "Invalid IP address")                           \
-_(CORRUPTED_PACKET,     222,    "Corrupted packet ")                            \
-_(UNEXPECTED,           298,    "Unexpected error")
+#define foreach_libhicn_error                                                   		\
+_(NONE,                 	0,      "OK")                                           	\
+_(UNSPECIFIED,          	128,    "Unspecified Error")                            	\
+_(NOT_IMPLEMENTED,      	180,    "Function not yet implemented")                 	\
+_(NOT_HICN,             	202,    "Non hICN packet")                              	\
+_(UNKNOWN_ADDRESS,      	210,    "Unknown address")                              	\
+_(INVALID_PARAMETER,    	220,    "Invalid parameter")                            	\
+_(INVALID_IP_ADDRESS,   	221,    "Invalid IP address")                           	\
+_(CORRUPTED_PACKET,     	222,    "Corrupted packet ")                            	\
+_(REWRITE_CKSUM_REQUIRED,	223,    "Incremental csum calculation error: cksum required.")	\
+_(UNEXPECTED,           	298,    "Unexpected error")
 
 typedef enum
 {
diff --git a/lib/src/protocol/tcp.c b/lib/src/protocol/tcp.c
index 31c495ff4..7b7c44ef7 100644
--- a/lib/src/protocol/tcp.c
+++ b/lib/src/protocol/tcp.c
@@ -48,15 +48,20 @@ DECLARE_set_payload_length (tcp, UNEXPECTED);
 int
 tcp_init_packet_header (hicn_type_t type, hicn_protocol_t * h)
 {
-  h->tcp = (_tcp_header_t)
-  {
-  .sport = htons (TCP_DEFAULT_SRC_PORT),.dport =
-      htons (TCP_DEFAULT_DST_PORT),.seq = 0,.seq_ack =
-      0,.data_offset_and_reserved = TCP_DEFAULT_DATA_OFFSET_RES,.flags =
+  h->tcp = (_tcp_header_t) {
+    .sport = htons (TCP_DEFAULT_SRC_PORT),
+    .dport = htons (TCP_DEFAULT_DST_PORT),
+    .seq = 0,
+    .seq_ack = 0,
+    .data_offset_and_reserved = TCP_DEFAULT_DATA_OFFSET_RES,
+    .flags =
       TCP_DEFAULT_CWR << 7 | TCP_DEFAULT_ECE << 6 | TCP_DEFAULT_URG << 5 |
       TCP_DEFAULT_ACK << 4 | TCP_DEFAULT_PSH << 3 | TCP_DEFAULT_RST << 2 |
-      TCP_DEFAULT_SYN << 1 | TCP_DEFAULT_FIN << 0,.window =
-      htons (TCP_DEFAULT_WINDOW_SIZE),.csum = 0,.urg_ptr = 65000,};
+      TCP_DEFAULT_SYN << 1 | TCP_DEFAULT_FIN << 0,
+    .window = htons (TCP_DEFAULT_WINDOW_SIZE),
+    .csum = 0xffff,
+    .urg_ptr = 65000,
+  };
 
   uint8_t ah_flag = type.l2 == IPPROTO_AH ? AH_FLAG : 0;
 
@@ -253,6 +258,21 @@ tcp_rewrite_interest (hicn_type_t type, hicn_protocol_t * h,
 {
   u16 *tcp_checksum = &(h->tcp.csum);
 
+  /* As per RFC1624
+   * In one's complement, there are two representations of zero: the all
+   * zero and the all one bit values, often referred to as +0 and -0.
+   * One's complement addition of non-zero inputs can produce -0 as a
+   * result, but never +0.  Since there is guaranteed to be at least one
+   * non-zero field in the IP header, and the checksum field in the
+   * protocol header is the complement of the sum, the checksum field can
+   * never contain ~(+0), which is -0 (0xFFFF).  It can, however, contain
+   * ~(-0), which is +0 (0x0000).
+   */
+  if (*tcp_checksum == 0xffff) {
+    /* Invalid checksum, no need to compute incremental update */
+    return HICN_LIB_ERROR_REWRITE_CKSUM_REQUIRED;
+  }
+
   /*
    * Padding fields are set to zero so we can apply checksum on the
    * whole struct by interpreting it as IPv6 in all cases
diff --git a/libtransport/src/core/forwarder_interface.h b/libtransport/src/core/forwarder_interface.h
index 3b016c4bb..772cfbb52 100644
--- a/libtransport/src/core/forwarder_interface.h
+++ b/libtransport/src/core/forwarder_interface.h
@@ -95,7 +95,10 @@ class ForwarderInterface {
       packet.setLocator(inet6_address_);
     }
 
+#ifndef __vpp__
+    /* In the case of VPP we try to offload checksum computation to hardware  */
     packet.setChecksum();
+#endif
     connector_.send(packet.acquireMemBufReference());
   }