ION-DTN是DTN协议栈的具体实现，广泛应用在深空通信等恶劣环境下，RTEMS作为星载操作系统之一，若能在RTEMS上实现DTN协议栈，能够为RTEMS的提供更为广泛的应用。

接下来详细描述如何将ION-DTN移植到RTEMS上。

ION-DTN的3.5.0版本中有关于RTEMS移植的一个模板，而不知为何，在最新的3.6.0中却删除了该模板。因此选用3.5.0进行移植。

ION源码中RTEMS的模板文件夹为arch-rtems，其中内容如下：

一、最为重要的是Makefile文件，接下来对Makefile进行分析：

IONFLAGS_T = -DRTEMS -DBP_EXTENDED -DGDSSYMTAB -DGDSLOGGER \
-DUSING_SDR_POINTERS -DNO_SDR_TRACE -DNO_PSM_TRACE \
-DNO_PROXY -DNO_DIRLIST
# Add -DBPSEC if building with bpsec.
# -DBPSEC
# Add -DAGENT_ROLE if building with nm.
# -DAGENT_ROLE
# -DENABLE_IMC
# -DENABLE_BPACSPGM=${ARCH}/ion.exeION_OPEN_SOURCE = 1

IONFLAGS_T表示一些开关的使能，比如-DRTEMS表示使能RTEMS接口。

PGM=${ARCH}/ion.exe

表示最后make生成的目标为ion.exe

ICISOURCES =     \platform.c    \platform_sm.c \memmgr.c      \llcv.c        \lyst.c        \psm.c         \smlist.c      \smrbt.c       \ion.c         \rfx.c         \zco.c         \sdrtable.c    \sdrhash.c     \sdrxn.c       \sdrmgt.c      \sdrstring.c   \sdrlist.c     \sdrcatlg.c    \rfxclock.c    \ionadmin.c    \sdrmend.c     \ionsec.c      \ionsecadmin.c \crypto.c      \csi.c         \bulk.c        \ionwarn.c     \ionrestart.c  \ionexit.c#  bloom.c       \
#  MurmurHash2.c \LTPSOURCES =     \libltp.c     \libltpP.c    \libltpnm.c   \ltpei.c      \ltpclock.c   \ltpmeter.c   \pmqlsi.c     \pmqlso.c     \ltpadmin.c   \udplsi.c     \udplso.c BPSOURCES =      \

这些就是make需要编译的源文件，如果要使能某个功能，就要在makefile中加上对应的函数进行编译。

include $(RTEMS_MAKEFILE_PATH)/Makefile.inc
include $(RTEMS_CUSTOM)
LD_LIBS += $(RTEMS_MAKEFILE_PATH)/../lib/libm.a
include $(PROJECT_ROOT)/make/leaf.cfg

上面的是移植过程中最为重要的步骤，为ION的makefile提供RTEMS的一些API接口以及一些库和工具。

首先Makefile.inc是提供特定BSP的一些API接口，用于include进应用程序的makefile中。

而libm.a是RTEMS的二进制函数库。

leaf.cfg非常重要，定义了叶子节点，也就是RTEMS其他模块，比如应用程序模块中makefile的一些命令的具体实现。

# make/leaf.cfg
#
#   Make(1) configuration file include'd by all leaf-node Makefiles
##
# LIBSUFFIX_VA, will "index" into LIBSUFF-*-v macros and
#   convert our ${ARCH} back into .a or _g.a or _p.a based on debug.
#   Useful for installing libraries.
#LIBSUFFIX_OPTIMIZE_V=
LIBSUFFIX_DEBUG_V=_gLIB_VARIANT=$(LIBSUFFIX_$(VARIANT_V)_V)
LIBSUFFIX_VA = $(LIB_VARIANT).a# Pull in the desired "target" compiler
# Programs built on the host use automake generated rules.
# This will not change $(ARCH) -- binaries will still be place as per target
include ${CONFIG.CC}
ifeq (${DEPEND},$(wildcard ${DEPEND}))
include ${DEPEND}            # pull in dependencies if they exist
endififndef AUTOMAKE
#
# Builtin targets for compilation variants
#
debug:$(MAKE) -f $(MAKEFILE) MAKEFILE=$(MAKEFILE) VARIANT=DEBUG
endif#
# VARIANT_VA will convert our ${ARCH} back into "" or "debug".
#   Handy when one makefile wants to hop over into a peer's tree and
#   build something "the same" way.
#VARIANT-OPTIMIZE-v =
VARIANT-DEBUG-v = debugVARIANT_VA = $(VARIANT-$(VARIANT_V)-v)#
# TARGET_VA will convert $@ (expected to be 'debug' etc.)
#   into "" or "install" as appropriate.
#   Used for variant recursion.
#TARGET_debug_V = allTARGET_VA = $(TARGET_$@_V)#
# Builtin clean and distclean rules
# Individual makefiles can add stuff via CLEAN_ADDITIONS and CLOBBER_ADDITIONS
# If desperate to save something, they can override CLEAN_OS, CLEAN_CC, etc.
#clean-am: clean-generic-$(RM) -r $(CLEAN_OS) $(CLEAN_CC) $(CLEAN_DEPEND)-$(RM) -r $(VARIANTS)distclean-am: distclean-generic clean-am-$(RM) -r $(CLOBBER_OS) $(CLOBBER_CC) $(CLOBBER_DEPEND)ifndef AUTOMAKE
preinstall-am:
preinstall: preinstall-amdistclean: distclean-am-$(RM) ./config.statusclean: clean-am.PHONY: distclean distclean-am
.PHONY: clean clean-am
endifEXEEXT?=.exe
DOWNEXT?=.ralfdefine bsp-link-c$(LINK.c) $(CPU_CFLAGS) $(AM_CFLAGS) $(AM_LDFLAGS) \-o $(basename $@)$(EXEEXT) $(LINK_OBJS) $(LINK_LIBS)
endefdefine bsp-link-cxx$(LINK.cc) $(CPU_CFLAGS) $(AM_CFLAGS) $(AM_LDFLAGS) \-o $(basename $@)$(EXEEXT) $(LINK_OBJS) $(LINK_LIBS)
endefdefine default-bsp-post-link$(NM) -g -n $@ > $(basename $@).num$(SIZE) $@
endefifndef bsp-post-link
define bsp-post-link$(default-bsp-post-link)cp $(basename $@)$(EXEEXT) $(basename $@)$(DOWNEXT)
endef
endifdefine make-exe$(bsp-link-c)$(bsp-post-link)
endefdefine make-cxx-exe$(bsp-link-cxx)$(bsp-post-link)
endef

加上这些库后，还要加上rtems-libbsd编译后生成的libbsd二进制库，里面包含了libbsd的一些库函数，比如socket等网络协议栈标准接口函数等。非常非常重要。

LINK_LIBS += /home/c/development/rtems/rtems-4.12/arm-rtems4.12/beagleboneblack/lib/libbsd.a

以上对makefile的修改使得ION-DTN可以RTEMS为目标进行编译。

二、srclinks文件

在Makefile中添加的source文件，都要在srclinks文件中添加，保证source文件能够以链接的形式复制到arch-rtems文件夹下。

三、mysymtab.c文件

该文件是为RTEMS移植过程中，函数的模板的私有符号表，也就是如果要在应用程序中调用ION的功能函数的话，需要在此文件中声明。

/*mysymtab.c:    template private symbol table for RTEMS portof the ION stack, with definition ofsm_FindFunction(), which accesses this table.Author: Scott Burleigh, JPLCopyright (c) 2010, California Institute of Technology.ALL RIGHTS RESERVED.  U.S. Government Sponsorshipacknowledged.*/extern int   ionadmin(int, int, int, int, int, int, int, int, int, int);
extern int  ionexit(int, int, int, int, int, int, int, int, int, int);
extern int  rfxclock(int, int, int, int, int, int, int, int, int, int);
extern int  ionsecadmin(int, int, int, int, int, int, int, int, int, int);
extern int  ionwarn(int, int, int, int, int, int, int, int, int, int);
extern int  ionrestart(int, int, int, int, int, int, int, int, int, int);
extern int  ltpadmin(int, int, int, int, int, int, int, int, int, int);
extern int  ltpclock(int, int, int, int, int, int, int, int, int, int);
extern int  ltpmeter(int, int, int, int, int, int, int, int, int, int);
extern int  pmqlsi(int, int, int, int, int, int, int, int, int, int);
extern int  pmqlso(int, int, int, int, int, int, int, int, int, int);
extern int  bpadmin(int, int, int, int, int, int, int, int, int, int);
extern int  bpclock(int, int, int, int, int, int, int, int, int, int);
extern int  bptransit(int, int, int, int, int, int, int, int, int, int);
extern int  ltpcli(int, int, int, int, int, int, int, int, int, int);
extern int  ltpclo(int, int, int, int, int, int, int, int, int, int);
extern int  bibeclo(int, int, int, int, int, int, int, int, int, int);
extern int  ipnadmin(int, int, int, int, int, int, int, int, int, int);
extern int  ipnfw(int, int, int, int, int, int, int, int, int, int);
extern int  ipnadminep(int, int, int, int, int, int, int, int, int, int);
extern int  lgagent(int, int, int, int, int, int, int, int, int, int);
extern int  bpsource(int, int, int, int, int, int, int, int, int, int);
extern int  bpsink(int, int, int, int, int, int, int, int, int, int);
extern int  bpdriver(int, int, int, int, int, int, int, int, int, int);
extern int  bpcounter(int, int, int, int, int, int, int, int, int, int);
extern int  ltpcounter(int, int, int, int, int, int, int, int, int, int);
extern int  ltpdriver(int, int, int, int, int, int, int, int, int, int);
extern int  udplsi(int, int, int, int, int, int, int, int, int, int);
extern int  udplso(int, int, int, int, int, int, int, int, int, int);
#ifndef NASA_PROTECTED_FLIGHT_CODE
extern int  cfdpadmin(int, int, int, int, int, int, int, int, int, int);
extern int  cfdpclock(int, int, int, int, int, int, int, int, int, int);
extern int  bputa(int, int, int, int, int, int, int, int, int, int);
#endif
#if 0

四、修改ionrtems.c文件

该文件是ion.exe应用程序功能实现的具体源文件，里面包含main函数以及其他功能函数。是ion.exe执行的文件。根据需要的功能要求修改即可。