learn: Allow read-only fields to be matched.

nxm_dst_check() requires a writable field.  Since NX_LEARN_DST_MATCH only
matches on a field and doesn't write to a field, use nxm_src_check() for
that case instead.

Bug #7507.
Reported-by: Michael Mao <mmao@nicira.com>

diff --git a/lib/learn.c b/lib/learn.c
index 8927ff8..8d7e0b0 100644 (file)
--- a/lib/learn.c
+++ b/lib/learn.c
@@ -160,7 +160,9 @@ learn_check(const struct nx_action_learn *learn, const struct flow *flow)
             int dst_ofs = ntohs(get_be16(&p));
             int error;
 
-            error = nxm_dst_check(dst_field, dst_ofs, n_bits, &rule.flow);
+            error = (dst_type == NX_LEARN_DST_LOAD
+                     ? nxm_dst_check(dst_field, dst_ofs, n_bits, &rule.flow)
+                     : nxm_src_check(dst_field, dst_ofs, n_bits, &rule.flow));
             if (error) {
                 return error;
             }