Add ION-DTN host integration: memory allocators, BIB source fix, and WriteBTSD realloc

[iondev33]

This PR enables BSL to be built and linked as part of the ION-DTN bundle protocol stack. It
adds an ION_INTEGRATION build option that redirects BSL's memory allocators
(BSL_MALLOC/BSL_CALLOC/BSL_REALLOC/BSL_FREE) to ION's shared working memory system, and
fixes two bugs discovered during end-to-end multinode testing with ION.

This is based on the work done initially by Scott Burleigh as identified in issue: #135 and expanded through debugging and testing process.

The changes in this PR will be required for ION 4.2.0-a.1 release which is integrated with BSL. Current a BSL fork with this branch is part of ION's submodule. ION automake system is updated to automatically build BSL with ION together. The ION 4.2.0-a.1 release is planned for mid-March release.

Changes

1. ION memory allocator integration (ionpatch.c, ionpatch.h, CMake changes)

When built with -DION_INTEGRATION=ON, BSL uses ION's allocFromIonMemory() /
releaseToIonMemory() instead of the standard C allocator. This is required because ION
manages its own shared memory partition; mixing malloc/free with ION-allocated memory
causes munmap_chunk() crashes.

Files:

• src/ION_integration/ionpatch.h — Redefines BSL_MALLOC/BSL_CALLOC/BSL_REALLOC/BSL_FREE
  macros to ION wrappers
• src/ION_integration/ionpatch.c — Implements ion_malloc, ion_calloc, ion_realloc, ion_free
  using ION's memory API. Note: ion_realloc copies to a new block because ION's memory
  layout does not support in-place expansion
• src/BSLConfig.h.in — Includes ionpatch.h before default allocator definitions when
  ION_INTEGRATION is defined
• CMakeLists.txt — Adds ION_INTEGRATION option, finds ION headers/library, builds
  bsl_ionpatch static library, adds platform defines required by ION's platform.h
• src/CMakeLists.txt — Links all BSL component libraries against bsl_ionpatch and libici
  when ION_INTEGRATION is enabled
• build-for-ion.sh — Convenience script for building BSL with ION integration
• src/BPSecLib_Private.h — Adds #ifndef guards around CHKVOID/CHKNULL macros to avoid
  redefinition conflicts with ION's platform.h

With this change, all BSL heap allocations go through ION's memory manager, eliminating the
cross-allocator corruption that occurred when ION passed its own memory to BSL and BSL
later called free() on it.

2. Fix BSL_ExecBIBSource missing block number assignment (SecurityContext.c)

BSL_ExecBIBSource was not storing the newly created BIB block number in
sec_oper->sec_block_num after calling BSL_BundleCtx_CreateBlock. The security context
execution function needs this value to retrieve the block's metadata (BTSD buffer).
BSL_ExecBCBSource already had this assignment; this fix brings BIB in line.

Without this fix, BIB source operations fail because the security context cannot locate the
block it needs to write the integrity signature into.

3. Fix BSL_BundleCtx_WriteBTSD to realloc before write (HostInterface.c)

BSL_BundleCtx_WriteBTSD was calling the host's write callback without first ensuring the
BTSD buffer was large enough. When ION creates extension blocks, they start with a 1-byte
placeholder. BSL would then attempt to write the full security result (e.g., 82 bytes for a
BIB HMAC signature) into that 1-byte buffer.

The fix calls block_realloc_btsd_fn before block_write_btsd_fn to expand the buffer to the
needed size. If realloc fails, the function returns NULL with an error log.

4. Simplify BSL_PrimaryBlock_deinit (PublicInterfaceImpl.c)

Adds a NULL check before calling BSL_FREE(obj->block_numbers). With the ION memory
allocator integration, BSL_FREE routes to the correct allocator regardless of who allocated
the memory, so the previously added ownership-tracking field (block_numbers_owned) was
removed in favor of this simpler approach.

5. Fix mock BPA test policy (policy_provider_test.json)

• Change "loc" from "clin" to "appin" for source-role policy rules (source rules apply at
  application ingress, not convergence layer ingress)
• Add "src": "ipn:2." and "dest": "ipn:3." EID filter patterns (previously missing,
  causing rules to not match any bundles)

Build & Test

Standard BSL build (no ION, unchanged behavior)

./build.sh

BSL build with ION integration

ION_ROOT=/path/to/ion ./build-for-ion.sh

Or manually:

./build.sh prep -DION_INTEGRATION=ON -DION_ROOT=/path/to/ion
./build.sh

Tested with ION's tests/bpsec/bpsec-all-multinode-test.bsl — 3-node topology (nodes 2, 3,
4) over LTP, 6 bundles with BIB+BCB, all tests passing.

Notes for reviewers

• The 4 commits on this branch reflect the debugging sequence. Commit 1
  (block_numbers_owned) was a temporary fix that commit 3 (ION_INTEGRATION) superseded — the
  net diff to BPSecLib_Public.h and mock_bpa/agent.c is zero. Consider squash-merging if a
  cleaner history is preferred.
• ion_realloc includes a detailed comment explaining why it copies to a new block rather
  than attempting in-place expansion — ION's memory partition does not support that.
• The #ifndef CHKVOID/#ifndef CHKNULL guards are needed because ION's platform.h defines
  the same macro names.