NSH: Minor bugfixes

- Fix 2 incorrect length checks
- Remove unnecessary limit of MD length to 16 bytes
- Remove incorrect comments stating MD2 was not supported
- Pad metadata in encap_nsh with zeroes if not multiple of 4 bytes

Signed-off-by: Jan Scheurich <jan.scheurich@ericsson.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>

datapath/linux/compat/include/linux/openvswitch.h

@@ -793,15 +793,15 @@ struct ovs_action_push_eth {
 	struct ovs_key_ethernet addresses;
 };
 
-#define OVS_ENCAP_NSH_MAX_MD_LEN 16
+#define OVS_ENCAP_NSH_MAX_MD_LEN 248
 /*
  * struct ovs_action_encap_nsh - %OVS_ACTION_ATTR_ENCAP_NSH
  * @flags: NSH header flags.
  * @mdtype: NSH metadata type.
- * @mdlen: Length of NSH metadata in bytes.
+ * @mdlen: Length of NSH metadata in bytes, including padding.
  * @np: NSH next_protocol: Inner packet type.
  * @path_hdr: NSH service path id and service index.
- * @metadata: NSH metadata for MD type 1 or 2
+ * @metadata: NSH context metadata, padded to 4-bytes
  */
 struct ovs_action_encap_nsh {
     uint8_t flags;

lib/flow.c

@@ -540,7 +540,7 @@ parse_nsh(const void **datap, size_t *sizep, struct flow_nsh *key)
     /* Check if it is long enough for NSH header, doesn't support
      * MD type 2 yet
      */
-    if (OVS_UNLIKELY(*sizep < NSH_M_TYPE1_LEN)) {
+    if (OVS_UNLIKELY(*sizep < NSH_BASE_HDR_LEN)) {
         return false;
     }
 
@@ -557,10 +557,6 @@ parse_nsh(const void **datap, size_t *sizep, struct flow_nsh *key)
         return false;
     }
 
-    if (length != NSH_M_TYPE1_LEN) {
-        return false;
-    }
-
     key->flags = flags;
     key->mdtype = nsh->md_type;
     key->np = nsh->next_proto;
@@ -571,14 +567,17 @@ parse_nsh(const void **datap, size_t *sizep, struct flow_nsh *key)
 
     switch (key->mdtype) {
         case NSH_M_TYPE1:
+            if (length != NSH_M_TYPE1_LEN) {
+                return false;
+            }
             for (size_t i = 0; i < 4; i++) {
                 key->c[i] = get_16aligned_be32(&nsh->md1.c[i]);
             }
             break;
         case NSH_M_TYPE2:
-            /* Don't support MD type 2 yet, so return false */
         default:
-            return false;
+            /* We don't parse other context headers yet. */
+            break;
     }
 
     data_pull(datap, sizep, length);

lib/odp-util.c

@@ -1864,12 +1864,17 @@ parse_odp_encap_nsh_action(const char *s, struct ofpbuf *actions)
         else if (encap_nsh.mdtype == NSH_M_TYPE2) {
             struct ofpbuf b;
             char buf[512];
-            size_t mdlen;
+            size_t mdlen, padding;
             if (ovs_scan_len(s, &n, "md2=0x%511[0-9a-fA-F]", buf)) {
                 ofpbuf_use_stub(&b, encap_nsh.metadata,
                                 OVS_ENCAP_NSH_MAX_MD_LEN);
                 ofpbuf_put_hex(&b, buf, &mdlen);
-                encap_nsh.mdlen = mdlen;
+                /* Pad metadata to 4 bytes. */
+                padding = PAD_SIZE(mdlen, 4);
+                if (padding > 0) {
+                    ofpbuf_push_zeros(&b, padding);
+                }
+                encap_nsh.mdlen = mdlen + padding;
                 ofpbuf_uninit(&b);
             }
             continue;

lib/packets.c

@@ -439,8 +439,7 @@ encap_nsh(struct dp_packet *packet, const struct ovs_action_encap_nsh *encap)
             break;
         case NSH_M_TYPE2: {
             /* The MD2 metadata in encap is already padded to 4 bytes. */
-            size_t len = ROUND_UP(encap->mdlen, 4);
-            memcpy(&nsh->md2, encap->metadata, len);
+            memcpy(&nsh->md2, encap->metadata, encap->mdlen);
             break;
         }
         default: