[dpdk-dev] [PATCH v3 1/2] lib/lpm:fix an issue of condition check in delete_depth_small()

[Na Na <nana.nn@alibaba-inc.com>]

Fixes an issue of check logic in delete_depth_small function.

For a tbl24 entry, the 'ext_entry' field indicates whether we need to use tbl8_gindex to read the next_hop from a tbl8 entry, or whether it can be read directly from this entry.

If a route is deleted, the prefix of previous route is used to override the deleted route.

When checking the depth of the previous route the conditional checks both the ext_entry and the depth, but the "else" leg fails to take account that the condition could fail for one of two possible reasons, leading to an incorrect flow when 'ext_entry == 0' is true , but 'lpm->tbl24[i].depth > depth' is false. The fix here is to add a condition check to the else leg so that it only executes when ext_entry is set.

Signed-off-by: Na Na <nana.nn@alibaba-inc.com>

---
 lib/librte_lpm/rte_lpm.c |    6 ++----
 1 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/lib/librte_lpm/rte_lpm.c b/lib/librte_lpm/rte_lpm.c
index 163ba3c..57ec2f0 100644
--- a/lib/librte_lpm/rte_lpm.c
+++ b/lib/librte_lpm/rte_lpm.c
@@ -734,8 +734,7 @@ delete_depth_small(struct rte_lpm *lpm, uint32_t ip_masked,
 			if (lpm->tbl24[i].ext_entry == 0 &&
 					lpm->tbl24[i].depth <= depth ) {
 				lpm->tbl24[i].valid = INVALID;
-			}
-			else {
+			} else if (lpm->tbl24[i].ext_entry == 1) {
 				/*
 				 * If TBL24 entry is extended, then there has
 				 * to be a rule with depth >= 25 in the
@@ -780,8 +779,7 @@ delete_depth_small(struct rte_lpm *lpm, uint32_t ip_masked,
 			if (lpm->tbl24[i].ext_entry == 0 &&
 					lpm->tbl24[i].depth <= depth ) {
 				lpm->tbl24[i] = new_tbl24_entry;
-			}
-			else {
+			} else  if (lpm->tbl24[i].ext_entry == 1) {
 				/*
 				 * If TBL24 entry is extended, then there has
 				 * to be a rule with depth >= 25 in the
-- 
1.7.7.6