[dpdk-dev] [PATCH 2/2] ip_frag: use key length for key comparision

[Konstantin Ananyev <konstantin.ananyev@intel.com>]

Right now reassembly code relies on src_dst[] being all zeroes to
determine is it  free/occupied entry in the fragments table.
This is suboptimal and error prone - user can crash DPDK ip_reassembly
app by something like the following scapy script:
x=Ether(src=...,dst=...)/IP(dst='0.0.0.0',src='0.0.0.0',id=0)/('X'*1000)
frags=fragment(x, fragsize=500)
sendp(frags, iface=...)
To overcome that issue and reduce overhead of
'key invalidate'  and 'key is empty' operations -
add key_len into keys comparision procedure.

Reported-by: <ryan.e.hall@intel.com>
Reported-by: <alexander.v.gutkin@intel.com>

Fixes: 4f1a8f633862 ("ip_frag: add IPv6 reassembly")
Cc: stable@dpdk.org

Signed-off-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
---
 lib/librte_ip_frag/ip_frag_common.h | 14 ++++----------
 lib/librte_ip_frag/rte_ip_frag.h    | 14 +++++++++++---
 2 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/lib/librte_ip_frag/ip_frag_common.h b/lib/librte_ip_frag/ip_frag_common.h
index 0f62e2e16..a17a74076 100644
--- a/lib/librte_ip_frag/ip_frag_common.h
+++ b/lib/librte_ip_frag/ip_frag_common.h
@@ -58,20 +58,14 @@ struct rte_mbuf *ipv6_frag_reassemble(struct ip_frag_pkt *fp);
 static inline int
 ip_frag_key_is_empty(const struct ip_frag_key * key)
 {
-	uint32_t i;
-	for (i = 0; i < RTE_MIN(key->key_len, RTE_DIM(key->src_dst)); i++)
-		if (key->src_dst[i] != 0)
-			return 0;
-	return 1;
+	return (key->key_len == 0);
 }
 
-/* empty the key */
+/* invalidate the key */
 static inline void
 ip_frag_key_invalidate(struct ip_frag_key * key)
 {
-	uint32_t i;
-	for (i = 0; i < key->key_len; i++)
-		key->src_dst[i] = 0;
+	key->key_len = 0;
 }
 
 /* compare two keys */
@@ -80,7 +74,7 @@ ip_frag_key_cmp(const struct ip_frag_key * k1, const struct ip_frag_key * k2)
 {
 	uint32_t i;
 	uint64_t val;
-	val = k1->id ^ k2->id;
+	val = k1->id_key_len ^ k2->id_key_len;
 	for (i = 0; i < k1->key_len; i++)
 		val |= k1->src_dst[i] ^ k2->src_dst[i];
 	return val;
diff --git a/lib/librte_ip_frag/rte_ip_frag.h b/lib/librte_ip_frag/rte_ip_frag.h
index 7f425f610..a4ccaf9d1 100644
--- a/lib/librte_ip_frag/rte_ip_frag.h
+++ b/lib/librte_ip_frag/rte_ip_frag.h
@@ -44,9 +44,17 @@ struct ip_frag {
 
 /** @internal <src addr, dst_addr, id> to uniquely identify fragmented datagram. */
 struct ip_frag_key {
-	uint64_t src_dst[4];      /**< src address, first 8 bytes used for IPv4 */
-	uint32_t id;           /**< dst address */
-	uint32_t key_len;      /**< src/dst key length */
+	uint64_t src_dst[4];
+	/**< src and dst address, only first 8 bytes used for IPv4 */
+	RTE_STD_C11
+	union {
+		uint64_t id_key_len; /**< combined for easy fetch */
+		__extension__
+		struct {
+			uint32_t id;       /**< packet id */
+			uint32_t key_len;  /**< src/dst key length */
+		};
+	};
 };
 
 /**
-- 
2.17.1