Re: [dpdk-users] Building a shared library that uses DPDK

[Jeffrey Helt <jhelt@andrew.cmu.edu>]

> On Feb 14, 2018, at 8:08 PM, Stephen Hemminger <stephen@networkplumber.org> wrote:
> 
> On Wed, 14 Feb 2018 19:06:03 -0500
> Jeffrey Helt <jhelt@andrew.cmu.edu> wrote:
> 
>> Hi,
>> 
>> I am attempting to build a shared library that uses DPDK, specifically that wraps the Linux socket API and backs it by shared memory DPDK shared memory regions. I built DPDK 17.11 with “CONFIG_RTE_BUILD_SHARED_LIB=y”. In my shared library directory, I am using the following Makefile:
>> 
>> ifeq ($(RTE_SDK),)
>> $(error "Please define RTE_SDK environment variable")
>> endif
>> 
>> # Default target, can be overridden by command line or environment
>> RTE_TARGET ?= x86_64-native-linuxapp-gcc
>> 
>> include $(RTE_SDK)/mk/rte.vars.mk
>> 
>> # binary name
>> SHARED = libshim.so
>> 
>> # all source are stored in SRCS-y
>> SRCS-y := wrap_socket.c
>> 
>> CFLAGS += -O3
>> 
>> include $(RTE_SDK)/mk/rte.extshared.mk
>> 
>> However, whenever I try to use my library, such as with "LD_PRELOAD=./build/lib/libshim.so ./test”, I receive "symbol lookup error: ./build/lib/libshim.so: undefined symbol: rte_eal_init”. What am I missing?
>> 
>> Thank you in advance for help!
>> 
>> Jeff
> The DPDK builds lots of little shared libraries.
> You need to have all of them in your LD_LIBRARY_PATH and then add your socket wrapper.

Using `export LD_LIBRARY_PATH="/users/jhelt/dpdk/x86_64-native-linuxapp-gcc/lib/librte_eal.so”` before building and/or running doesn’t seem to change anything. Using ldd, I noticed that no dpdk shared objects are required by my library (see below), which seems like a more fundamental issue to me, although admittedly I am not that experienced in debugging linking issues.

$ ldd ./build/lib/libshim.so 
	linux-vdso.so.1 =>  (0x00007fff907e2000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fe76b06a000)
	/lib64/ld-linux-x86-64.so.2 (0x00007fe76b636000) 

Jeff