This week, I have to upgrade nff-go from v0.7.0 to v0.8.1, so I changethe version first. However, I found the whole packagenff-go/low movetonff-go/internal/low, and our code directly based onlow. Aftersome research, I found all I need is call C function directly; thefunction is underlibrte_ethdev. So I add

// #include <rte_ethdev.h>import "C"

into our code. I thought since nff-go already link DPDK, I have nothingto do here, but I'm wrong. The problem is that CGO would link C objectsinto temporary objects first. So linker would complain there was noreference to the function I call. So I add another line:

// #cgo LDFLAGS: -lrte_distributor -lrte_reorder -lrte_kni -lrte_pipeline -lrte_table -lrte_port -lrte_timer -lrte_jobstats -lrte_lpm -lrte_power -lrte_acl -lrte_meter -lrte_sched -lrte_vhost -lrte_ip_frag -lrte_cfgfile -Wl,--whole-archive -Wl,--start-group -lrte_kvargs -lrte_mbuf -lrte_hash -lrte_ethdev -lrte_mempool -lrte_ring -lrte_mempool_ring -lrte_eal -lrte_cmdline -lrte_net -lrte_bus_pci -lrte_pci -lrte_bus_vdev -lrte_timer -lrte_pmd_bond -lrte_pmd_vmxnet3_uio -lrte_pmd_virtio -lrte_pmd_cxgbe -lrte_pmd_enic -lrte_pmd_i40e -lrte_pmd_fm10k -lrte_pmd_ixgbe -lrte_pmd_e1000 -lrte_pmd_ena -lrte_pmd_ring -lrte_pmd_af_packet -lrte_pmd_null -Wl,--end-group -Wl,--no-whole-archive -lrt -lm -ldl -lnuma

They are directly copied fromhttps://github.com/intel-go/nff-go/blob/v0.8.1/internal/low/low_no_mlx.go.However, linker unhappy with it, there are multiple definitions ofsymbols in the final object now, because we link two DPDK now.In pureCGO, we have no way to link only one at this situation.However, since weknow the duplicate references are the same one so whatever the linkerpicks the program would work. Once we know that, we can use#cgo LDFLAGS: -Wl,--allow-multiple-definition to force the linker toignore this duplicate. However, we won't want to have a copied fromnff-go, so I did the trick in Makefile to copied it automatically whenbuilding.