defrag: fix check for complete packet

The list of fragments may still contain overlaps, so adding up the
fragment lengths is flawed. Instead track the largest size of
contiguous data that can be re-assembled.

Bug: #6675
(cherry picked from commit d226d0a3fc)

src/defrag.c

@@ -247,7 +247,8 @@ static Packet *Defrag4Reassemble(ThreadVars *tv, DefragTracker *tracker, Packet
              * fragment.  We have a hole. */
             goto done;
         } else {
-            len += frag->data_len;
+            /* Update the packet length to the largest known data offset. */
+            len = MAX(len, frag->offset + frag->data_len);
         }
     }
 
@@ -397,7 +398,7 @@ static Packet *Defrag6Reassemble(ThreadVars *tv, DefragTracker *tracker, Packet
                  * fragment.  We have a hole. */
                 goto done;
             } else {
-                len += frag->data_len;
+                len = MAX(len, frag->offset + frag->data_len);
             }
         }
     }
@@ -2922,6 +2923,115 @@ static int DefragBsdSubsequentOverlapsStartOfOriginalIpv6Test(void)
     PASS;
 }
 
+/**
+ * Reassembly should fail.
+ *
+ * |0       |8       |16      |24      |32      |40      |48      |
+ * |========|========|========|========|========|========|========|
+ * |        |        |AABBCCDD|AABBDDCC|        |        |        |
+ * |        |        |        |        |        |AACCBBDD|        |
+ * |        |AACCDDBB|AADDBBCC|        |        |        |        |
+ * |ZZZZZZZZ|        |        |        |        |        |        |
+ * |        |        |        |        |        |        |DDCCBBAA|
+ */
+static int DefragBsdPeose173Ipv4Test(void)
+{
+    DefragInit();
+    default_policy = DEFRAG_POLICY_BSD;
+    Packet *packets[5];
+
+    packets[0] = BuildIpv4TestPacketWithContent(
+            IPPROTO_ICMP, 189, 16 >> 3, 1, (uint8_t *)"AABBCCDDAABBDDCC", 16);
+
+    packets[1] =
+            BuildIpv4TestPacketWithContent(IPPROTO_ICMP, 189, 40 >> 3, 1, (uint8_t *)"AACCBBDD", 8);
+
+    packets[2] = BuildIpv4TestPacketWithContent(
+            IPPROTO_ICMP, 189, 8 >> 3, 1, (uint8_t *)"AACCDDBBAADDBBCC", 16);
+
+    /* ICMP header. */
+    packets[3] = BuildIpv4TestPacketWithContent(IPPROTO_ICMP, 189, 0, 1, (uint8_t *)"ZZZZZZZZ", 8);
+
+    packets[4] =
+            BuildIpv4TestPacketWithContent(IPPROTO_ICMP, 189, 48 >> 3, 0, (uint8_t *)"DDCCBBAA", 8);
+
+    Packet *r = Defrag(NULL, NULL, packets[0]);
+    FAIL_IF_NOT_NULL(r);
+
+    r = Defrag(NULL, NULL, packets[1]);
+    FAIL_IF_NOT_NULL(r);
+
+    r = Defrag(NULL, NULL, packets[2]);
+    FAIL_IF_NOT_NULL(r);
+
+    r = Defrag(NULL, NULL, packets[3]);
+    FAIL_IF_NOT_NULL(r);
+
+    r = Defrag(NULL, NULL, packets[4]);
+    FAIL_IF_NOT_NULL(r);
+
+#if 0
+    PrintRawDataFp(stdout, GET_PKT_DATA(r) + 20, GET_PKT_LEN(r) - 20);
+#endif
+
+    for (int i = 0; i < 5; i++) {
+        SCFree(packets[i]);
+    }
+
+    DefragDestroy();
+
+    PASS;
+}
+
+static int DefragBsdPeose173Ipv6Test(void)
+{
+    DefragInit();
+    default_policy = DEFRAG_POLICY_BSD;
+    Packet *packets[5];
+
+    packets[0] = BuildIpv6TestPacketWithContent(
+            IPPROTO_ICMP, 189, 16 >> 3, 1, (uint8_t *)"AABBCCDDAABBDDCC", 16);
+
+    packets[1] =
+            BuildIpv6TestPacketWithContent(IPPROTO_ICMP, 189, 40 >> 3, 1, (uint8_t *)"AACCBBDD", 8);
+
+    packets[2] = BuildIpv6TestPacketWithContent(
+            IPPROTO_ICMP, 189, 8 >> 3, 1, (uint8_t *)"AACCDDBBAADDBBCC", 16);
+
+    /* ICMP header. */
+    packets[3] = BuildIpv6TestPacketWithContent(IPPROTO_ICMP, 189, 0, 1, (uint8_t *)"ZZZZZZZZ", 8);
+
+    packets[4] =
+            BuildIpv6TestPacketWithContent(IPPROTO_ICMP, 189, 48 >> 3, 0, (uint8_t *)"DDCCBBAA", 8);
+
+    Packet *r = Defrag(NULL, NULL, packets[0]);
+    FAIL_IF_NOT_NULL(r);
+
+    r = Defrag(NULL, NULL, packets[1]);
+    FAIL_IF_NOT_NULL(r);
+
+    r = Defrag(NULL, NULL, packets[2]);
+    FAIL_IF_NOT_NULL(r);
+
+    r = Defrag(NULL, NULL, packets[3]);
+    FAIL_IF_NOT_NULL(r);
+
+    r = Defrag(NULL, NULL, packets[4]);
+    FAIL_IF_NOT_NULL(r);
+
+#if 0
+    PrintRawDataFp(stdout, GET_PKT_DATA(r) + 40, GET_PKT_LEN(r) - 40);
+#endif
+
+    for (int i = 0; i < 5; i++) {
+        SCFree(packets[i]);
+    }
+
+    DefragDestroy();
+
+    PASS;
+}
+
 #endif /* UNITTESTS */
 
 void DefragRegisterTests(void)
@@ -2968,5 +3078,7 @@ void DefragRegisterTests(void)
             DefragBsdSubsequentOverlapsStartOfOriginalIpv4Test_2);
     UtRegisterTest("DefragBsdSubsequentOverlapsStartOfOriginalIpv6Test_2",
             DefragBsdSubsequentOverlapsStartOfOriginalIpv6Test_2);
+    UtRegisterTest("DefragBsdPeose173Ipv4Test", DefragBsdPeose173Ipv4Test);
+    UtRegisterTest("DefragBsdPeose173Ipv6Test", DefragBsdPeose173Ipv6Test);
 #endif /* UNITTESTS */
 }