/usr/include/sipxtapi/os/linux/ is in libsipxtapi-dev 3.3.0~test17-1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/sipxtapi/os/linux/AdapterInfo.h
/usr/include/sipxtapi/os/linux/OsBSemLinux.h
/usr/include/sipxtapi/os/linux/OsCSemLinux.h
/usr/include/sipxtapi/os/linux/OsDateTimeLinux.h
/usr/include/sipxtapi/os/linux/OsDirLinux.h
/usr/include/sipxtapi/os/linux/OsFileInfoLinux.h
/usr/include/sipxtapi/os/linux/OsFileIteratorLinux.h
/usr/include/sipxtapi/os/linux/OsFileLinux.h
/usr/include/sipxtapi/os/linux/OsLinuxDefs.h
/usr/include/sipxtapi/os/linux/OsMutexLinux.h
/usr/include/sipxtapi/os/linux/OsPathLinux.h
/usr/include/sipxtapi/os/linux/OsProcessIteratorLinux.h
/usr/include/sipxtapi/os/linux/OsProcessLinux.h
/usr/include/sipxtapi/os/linux/OsRWMutexLinux.h
/usr/include/sipxtapi/os/linux/OsSharedLibMgrLinux.h
/usr/include/sipxtapi/os/linux/OsTaskLinux.h
/usr/include/sipxtapi/os/linux/OsUtilLinux.h
/usr/include/sipxtapi/os/linux/host_address.h
/usr/include/sipxtapi/os/linux/pt_csem.h
/usr/include/sipxtapi/os/linux/pt_mutex.h