misc: classifier-based packet trace filter

See .../src/vnet/classify/trace_classify.h for the business end
of the scheme.

It would be best to hash pkts, prefetch buckets, and do the primary
table lookups two at a time. The inline as given works, but perf
tuning will be required. "At least it works..."

Add "classify filter" debug cli, for example:
classify filter mask l3 ip4 src dst \
  match l3 ip4 dst 192.168.2.10 src 192.168.1.10

Add "pcap rx | tx trace ... filter" to use the current classify filter chain

Patch includes sphinx documentation and doxygen tags.

Next step: device-driver integration

Type: feature

Signed-off-by: Dave Barach <dave@barachs.net>
Change-Id: I05b1358a769f61e6d32470e0c87058f640486b26
(cherry picked from commit 9137e5400699bed9f7c0095187839a8b38273100)

1 files changed, 100 insertions, 0 deletions

diff --git a/src/vnet/classify/trace_classify.h b/src/vnet/classify/trace_classify.h
new file mode 100644
index 00000000000..bc25ecd0ff7
--- /dev/null
+++ b/src/vnet/classify/trace_classify.h
@@ -0,0 +1,100 @@
+/*
+ * trace_classify.h - Use the classifier to decide if a packet is traced
+ *
+ * Copyright (c) 2019 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.
+ */
+#include <vlib/vlib.h>
+#include <vnet/vnet.h>
+#include <vppinfra/error.h>
+#include <vnet/classify/vnet_classify.h>
+
+/** @file trace_classify.h
+ * Use the vpp classifier to decide whether to trace packets
+ */
+
+/** @brief vnet_is_packet_traced
+ * @param vlib_buffer_t *b - packet to classify
+ * @param int func - 0 => use classifier w/ supplied table index
+ * @param u32 classify_table_index - classifier table index
+ * @return 0 => no trace, 1 => trace, -1 => error
+ */
+
+static inline int
+vnet_is_packet_traced_inline (vlib_buffer_t * b,
+			      u32 classify_table_index, int func)
+{
+  vnet_classify_main_t *vcm = &vnet_classify_main;
+  vnet_classify_table_t *t;
+  vnet_classify_entry_t *e;
+  u64 hash;
+
+  /*$$$ add custom classifiers here, if any */
+  if (func != 0)
+    return -1;
+
+  /* This will happen... */
+  if (pool_is_free_index (vcm->tables, classify_table_index))
+    return -1;
+
+  /* Get the table */
+  t = pool_elt_at_index (vcm->tables, classify_table_index);
+
+  /* Hash the packet */
+  hash = vnet_classify_hash_packet (t, vlib_buffer_get_current (b));
+
+  /* See if there's a matching entry */
+  e = vnet_classify_find_entry (t, vlib_buffer_get_current (b), hash,
+				0 /* time = 0, disables hit-counter */ );
+  /* Hit means trace the packet... */
+  if (e)
+    {
+      /* Manual hit accounting */
+      e->hits++;
+      return 1;
+    }
+
+  /*
+   * Look for a hit in a less-specific table.
+   * Performance hint: for this use-case, don't go there.
+   */
+  while (1)
+    {
+      /* Most likely, we're done right now */
+      if (PREDICT_TRUE (t->next_table_index == ~0))
+	return 0;
+      t = pool_elt_at_index (vcm->tables, t->next_table_index);
+
+      /* Compute hash for this table */
+      hash = vnet_classify_hash_packet (t, vlib_buffer_get_current (b));
+
+      /* See if there's a matching entry */
+      e = vnet_classify_find_entry (t, vlib_buffer_get_current (b), hash,
+				    0 /* time = 0, disables hit-counter */ );
+      if (e)
+	{
+	  /* Manual hit accounting */
+	  e->hits++;
+	  return 1;
+	}
+    }
+  /* NOTREACHED */
+}
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */