On Thu, Nov 21, 2013 at 08:45:22PM -0800, Andy Zhou wrote:
> Noting updating slow path subfacet's time stamp can cause their datapath
> flows deleted periodically. For example, CFM datapath flow have usespace
> actions that are handled in dpif slow path. They are deleted and
> recreated periodically without the fix.
>
> This bug are not obvious during normal operation. Deleted CFM flow
> would cause CFM packets to be handled by flow miss handler which will
> reinstall the flow in the datapath. The only potentially observable
> behavior is that when the user space is overwhelmed with flow miss packets,
> the periodic CFM miss packets may get stuck behind other miss packets,
> cause tunnel flapping.
>
> Reported-by: Guolin Yang <gy...@nicira.com>
> Signed-off-by: Andy Zhou <az...@nicira.com>
I agree that this fixes the problem. However, it seems to duplicate
some logic. What do you think about this alternative patch, which
instead refactors slightly to avoid code duplication?
diff --git a/ofproto/ofproto-dpif.c b/ofproto/ofproto-dpif.c
index c1c206b..b56202c 100644
--- a/ofproto/ofproto-dpif.c
+++ b/ofproto/ofproto-dpif.c
@@ -213,7 +213,8 @@ struct subfacet {
#define SUBFACET_DESTROY_MAX_BATCH 50
-static struct subfacet *subfacet_create(struct facet *, struct flow_miss *);
+static struct subfacet *subfacet_create(struct facet *, struct flow_miss *,
+ uint32_t key_hash);
static struct subfacet *subfacet_find(struct dpif_backer *,
const struct nlattr *key, size_t key_len,
uint32_t key_hash);
@@ -3222,13 +3223,32 @@ handle_flow_miss_with_facet(struct flow_miss *miss,
struct facet *facet,
{
enum subfacet_path want_path;
struct subfacet *subfacet;
+ uint32_t key_hash;
+ /* Update facet stats. */
facet->packet_count += miss->stats.n_packets;
facet->prev_packet_count += miss->stats.n_packets;
facet->byte_count += miss->stats.n_bytes;
facet->prev_byte_count += miss->stats.n_bytes;
- want_path = facet->xout.slow ? SF_SLOW_PATH : SF_FAST_PATH;
+ /* Look for an existing subfacet. If we find one, update its used time. */
+ key_hash = odp_flow_key_hash(miss->key, miss->key_len);
+ if (!list_is_empty(&facet->subfacets)) {
+ subfacet = subfacet_find(miss->ofproto->backer,
+ miss->key, miss->key_len, key_hash);
+ if (subfacet) {
+ if (subfacet->facet == facet) {
+ subfacet->used = MAX(subfacet->used, miss->stats.used);
+ } else {
+ /* This shouldn't happen. */
+ VLOG_ERR_RL(&rl, "subfacet with wrong facet");
+ subfacet_destroy(subfacet);
+ subfacet = NULL;
+ }
+ }
+ } else {
+ subfacet = NULL;
+ }
/* Don't install the flow if it's the result of the "userspace"
* action for an already installed facet. This can occur when a
@@ -3240,7 +3260,13 @@ handle_flow_miss_with_facet(struct flow_miss *miss,
struct facet *facet,
return;
}
- subfacet = subfacet_create(facet, miss);
+ /* Create a subfacet, if we don't already have one. */
+ if (!subfacet) {
+ subfacet = subfacet_create(facet, miss, key_hash);
+ }
+
+ /* Install the subfacet, if it's not already installed. */
+ want_path = facet->xout.slow ? SF_SLOW_PATH : SF_FAST_PATH;
if (subfacet->path != want_path) {
struct flow_miss_op *op = &ops[(*n_ops)++];
struct dpif_flow_put *put = &op->dpif_op.u.flow_put;
@@ -4382,37 +4408,20 @@ subfacet_find(struct dpif_backer *backer, const struct
nlattr *key,
return NULL;
}
-/* Searches 'facet' (within 'ofproto') for a subfacet with the specified
- * 'key_fitness', 'key', and 'key_len' members in 'miss'. Returns the
- * existing subfacet if there is one, otherwise creates and returns a
- * new subfacet. */
+/* Creates and returns a new subfacet within 'facet' for the flow in 'miss'.
+ * 'key_hash' must be a hash over miss->key. The caller must have already
+ * ensured that no subfacet subfacet already exists. */
static struct subfacet *
-subfacet_create(struct facet *facet, struct flow_miss *miss)
+subfacet_create(struct facet *facet, struct flow_miss *miss, uint32_t key_hash)
{
struct dpif_backer *backer = miss->ofproto->backer;
const struct nlattr *key = miss->key;
size_t key_len = miss->key_len;
- uint32_t key_hash;
struct subfacet *subfacet;
- key_hash = odp_flow_key_hash(key, key_len);
-
- if (list_is_empty(&facet->subfacets)) {
- subfacet = &facet->one_subfacet;
- } else {
- subfacet = subfacet_find(backer, key, key_len, key_hash);
- if (subfacet) {
- if (subfacet->facet == facet) {
- return subfacet;
- }
-
- /* This shouldn't happen. */
- VLOG_ERR_RL(&rl, "subfacet with wrong facet");
- subfacet_destroy(subfacet);
- }
-
- subfacet = xmalloc(sizeof *subfacet);
- }
+ subfacet = (list_is_empty(&facet->subfacets)
+ ? &facet->one_subfacet
+ : xmalloc(sizeof *subfacet));
COVERAGE_INC(subfacet_create);
hmap_insert(&backer->subfacets, &subfacet->hmap_node, key_hash);
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