odp-util: Ignore unknown attributes in parse_key_and_mask_to_match().

When processing netlink messages, we should ignore unknown OVS_KEY_ATTR
as we can assume if newer attributes are present, they are backward
compatible.

This patch also updates the existing comments to better explain what
happens in the error cases. At this place in the code, we can not
ignore the TOO_LITTLE/MUCH errors as some instances could have
canceled processing leaving the returning match data incomplete.

Reported-at: https://bugzilla.redhat.com/show_bug.cgi?id=2089331
Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
Acked-by: Roi Dayan <roid@nvidia.com>
Reviewed-by: Michael Santana <msantana@redhat.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

1 files changed, 25 insertions, 9 deletions

diff --git a/lib/odp-util.c b/lib/odp-util.c
index fa6287f6d..7751aba14 100644
--- a/lib/odp-util.c
+++ b/lib/odp-util.c
@@ -7085,6 +7085,14 @@ parse_8021q_onward(const struct nlattr *attrs[OVS_KEY_ATTR_MAX + 1],
         }
         expected_attrs = 0;
 
+        /* For OVS to be backward compatible with newer datapath
+         * implementations, we should ignore out of range attributes. */
+        if (out_of_range_attr) {
+            VLOG_DBG("Flow key decode found unknown OVS_KEY_ATTR, %d",
+                     out_of_range_attr);
+            out_of_range_attr = 0;
+        }
+
         if (!parse_ethertype(attrs, present_attrs, &expected_attrs,
                              flow, src_flow, errorp)) {
             return ODP_FIT_ERROR;
@@ -7134,6 +7142,14 @@ odp_flow_key_to_flow__(const struct nlattr *key, size_t key_len,
     }
     expected_attrs = 0;
 
+    /* For OVS to be backward compatible with newer datapath implementations,
+     * we should ignore out of range attributes. */
+    if (out_of_range_attr) {
+        VLOG_DBG("Flow key decode found unknown OVS_KEY_ATTR, %d",
+                 out_of_range_attr);
+        out_of_range_attr = 0;
+    }
+
     /* Metadata. */
     if (present_attrs & (UINT64_C(1) << OVS_KEY_ATTR_RECIRC_ID)) {
         flow->recirc_id = nl_attr_get_u32(attrs[OVS_KEY_ATTR_RECIRC_ID]);
@@ -7368,10 +7384,12 @@ parse_key_and_mask_to_match(const struct nlattr *key, size_t key_len,
 
     fitness = odp_flow_key_to_flow(key, key_len, &match->flow, NULL);
     if (fitness) {
-        /* This should not happen: it indicates that
-         * odp_flow_key_from_flow() and odp_flow_key_to_flow() disagree on
-         * the acceptable form of a flow.  Log the problem as an error,
-         * with enough details to enable debugging. */
+        /* This will happen when the odp_flow_key_to_flow() function can't
+         * parse the netlink message to a match structure.  It will return
+         * ODP_FIT_TOO_LITTLE if there is not enough information to parse the
+         * content successfully, ODP_FIT_TOO_MUCH if there is too much netlink
+         * data and we do not know how to safely ignore it, and ODP_FIT_ERROR
+         * in any other case. */
         static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 5);
 
         if (!VLOG_DROP_ERR(&rl)) {
@@ -7379,7 +7397,8 @@ parse_key_and_mask_to_match(const struct nlattr *key, size_t key_len,
 
             ds_init(&s);
             odp_flow_format(key, key_len, NULL, 0, NULL, &s, true);
-            VLOG_ERR("internal error parsing flow key %s", ds_cstr(&s));
+            VLOG_ERR("internal error parsing flow key %s (%s)",
+                     ds_cstr(&s), odp_key_fitness_to_string(fitness));
             ds_destroy(&s);
         }
 
@@ -7389,10 +7408,7 @@ parse_key_and_mask_to_match(const struct nlattr *key, size_t key_len,
     fitness = odp_flow_key_to_mask(mask, mask_len, &match->wc, &match->flow,
                                    NULL);
     if (fitness) {
-        /* This should not happen: it indicates that
-         * odp_flow_key_from_mask() and odp_flow_key_to_mask()
-         * disagree on the acceptable form of a mask.  Log the problem
-         * as an error, with enough details to enable debugging. */
+        /* This should not happen, see comment above. */
         static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 5);
 
         if (!VLOG_DROP_ERR(&rl)) {