Wrong munmap() used instead of shmdt() with System V shared memory

[jaasco]

Problem:
The current code always calls munmap() when freeing shared memory in DataPlaneInSharedMemory::UnmapBuffers, regardless of the actual shared memory backend. However, munmap() is only correct for POSIX shared memory (mmap()), not for System V (shmat()).

When compiled without YANET_USE_POSIX_SHARED_MEMORY, shmget()/shmat() is used, so shmdt() must be called to detach the segment. Otherwise, munmap() fails with EINVAL (22) and memory cleanup is broken.

Example Log Output:
[ERROR] Error munmap 22: Invalid argument

Impact

• noisy error messages on every restart/shutdown
• shared-memory segment is not detached → kernel IPC table slowly fills
• potential memory-leak symptoms in long-running environments

Possible fix

(common/sdpcommon.h)

void UnmapBuffers(uint64_t size) {
    if (!dataplane_data) return;

#ifdef YANET_USE_POSIX_SHARED_MEMORY
    if (munmap(dataplane_data, size) < 0) {
        YANET_LOG_ERROR("Error munmap %d: %s", errno, strerror(errno));
    }
#else
    if (shmdt(dataplane_data) < 0) {
        YANET_LOG_ERROR("Error shmdt %d: %s", errno, strerror(errno));
    }
#endif
    dataplane_data = nullptr;
}