Cross compilation on macOS

[dreadl0ck]

Cross compiling from macOS to linux and windows fails for me, due to gopackets libpcap bindings.
Maybe @notti can help?

Compile for Windows:

# install compiler toolchain and libpcap headers
$ brew install mingw-w64
$ brew install libpcap

$ GOOS=windows GOARCH=amd64 CC=x86_64-w64-mingw32-gcc CGO_ENABLED=1 CGO_CFLAGS="-I/usr/local/opt/libpcap/include" go build -o netcap-windows -i github.com/dreadl0ck/netcap/cmd
# github.com/google/gopacket/pcap
/usr/local/Cellar/mingw-w64/5.0.4_1/toolchain-x86_64/bin/x86_64-w64-mingw32-ld: cannot find -lwpcap
collect2: error: ld returned 1 exit status

Compile for Linux:

$ GOOS=linux GOARCH=amd64 CGO_ENABLED=1 go build -o netcap-linux -i github.com/dreadl0ck/netcap/cmd
# github.com/dreadl0ck/netcap/cmd
/usr/local/Cellar/go/1.11.4/libexec/pkg/tool/darwin_amd64/link: running clang failed: exit status 1
ld: warning: ignoring file /var/folders/3n/1r2xxfv55d35jxh33rklbzm80000gn/T/go-link-877356077/go.o, file was built for unsupported file format ( 0x7F 0x45 0x4C 0x46 0x02 0x01 0x01 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 ) which is not the architecture being linked (x86_64): /var/folders/3n/1r2xxfv55d35jxh33rklbzm80000gn/T/go-link-877356077/go.o
Undefined symbols for architecture x86_64:
"__cgo_topofstack", referenced from:
    __cgo_f163a891a53f_Cfunc_calloc in 000001.o
    __cgo_f163a891a53f_Cfunc_pcap_activate in 000001.o
    __cgo_f163a891a53f_Cfunc_pcap_can_set_rfmon in 000001.o
    __cgo_f163a891a53f_Cfunc_pcap_compile in 000001.o
    __cgo_f163a891a53f_Cfunc_pcap_create in 000001.o
    __cgo_f163a891a53f_Cfunc_pcap_datalink in 000001.o
    __cgo_f163a891a53f_Cfunc_pcap_datalink_name_to_val in 000001.o
    ...
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

[notti]

Sorry for the late reply, but I was on winter holiday.
Hmm I don't have experience with cross-compiling cgo stuff. But I suspect one problem here will be the lines: https://github.com/google/gopacket/blob/6d81e5661bc8ae1efe3fbd78bd790daef871b489/pcap/pcap.go#L18-L20
For windows you would need the sdk for winpcap and then add the correct path to the ldflags.
With google/gopacket#568 you wouldn't need cgo for windows.
Not sure how to do the crosscompiling for linux. Maybe use travis-ci for building the linux-version?

[dreadl0ck]

Thanks for the pointers!
Will try again using your non cgo windows contribution :)

[dreadl0ck]

Thanks to google/gopacket#568 from @notti the windows cross compilation compilation works fine now :)

Linux cross compilation still gives me the same errors,
if anyone has an Idea let me know please.

Meanwhile binaries for Linux are compiled in a docker container.