Because enumerate() for value based arrays returns a pointer directly to
the internal array elements and because array_remove_at() or rather the
called array_remove() may move elements over the element at the currently
enumerated position, the pointer passed to enumerate() will point to a
different array element after the array_remove_at() call. The caller
will thus operate on the wrong element if that pointer is accessed again
before calling enumerate().
For performance reasons we currently don't change the implementation to copy
each array element during enumeration to a private member of the enumerator and
return a pointer to that. Similarly, due to the danger of subtle bugs we don't
remember the pointer passed to enumerate() to later redirect it to a copy
created during the array_remove_at() call.
Currently we use the very versatile linked-list collection to store elements
with variable count. This is fine, but very inefficient: Due to the many
methods in the linked list, on 64-bit platforms an empty list alone is more
than 200 bytes. As we currently have about 50 lists per IKE_SA/CHILD_SA pair,
this takes up to 10KB just for managing the empty lists. This is about the
half of memory used by an IKE_SA/CHILD_SA pair, and obviously way too much.
The new array type is not an object, but a collection of functions on an
abstract type.
The following lists are per IKE_SA and should be considered for a replacement
with more efficient arrays (this uses load-testers on-demand created dynamic
configurations, other scenarios have different lists):
14 -> ike_sa_create() @ src/libcharon/sa/ike_sa.c:2198
10 -> auth_cfg_create() @ src/libstrongswan/credentials/auth_cfg.c:1088
6 -> task_manager_v2_create() @ src/libcharon/sa/ikev2/task_manager_v2.c:1505
6 -> proposal_create() @ src/libcharon/config/proposal.c:592
5 -> peer_cfg_create() @ src/libcharon/config/peer_cfg.c:657
4 -> child_sa_create() @ src/libcharon/sa/child_sa.c:1090
2 -> child_cfg_create() @ src/libcharon/config/child_cfg.c:536
1 -> ike_cfg_create() @ src/libcharon/config/ike_cfg.c:330
1 -> put_connected_peers() @ src/libcharon/sa/ike_sa_manager.c:854
Andreas Steffen