Re: [PATCH V4 net-next 5/5] icmp: add response to RFC 8335 PROBE messages

On Mon, 2021-03-15 at 04:35 +0800, kernel test robot wrote:

Hi Andreas,

[FYI, it's a private test report for your RFC patch.]
[auto build test ERROR on net-next/master]

url:    
https://github.com/0day-ci/linux/commits/Andreas-Roeseler/add-support-for-RFC-8335-PROBE/20210315-005052
base:   
https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git 6f
1629093399303bf19d6fcd5144061d1e25ec23
config: mips-allmodconfig (attached as .config)
compiler: mips-linux-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
        wget 
https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross
 -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # 
https://github.com/0day-ci/linux/commit/54d9928f1734e7b3511b945a2ce912b931a07776
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Andreas-Roeseler/add-
support-for-RFC-8335-PROBE/20210315-005052
        git checkout 54d9928f1734e7b3511b945a2ce912b931a07776
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0
make.cross ARCH=mips 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <redacted>

All errors (new ones prefixed by >>):

   mips-linux-ld: net/ipv4/icmp.o: in function `icmp_echo':

quoted

quoted

icmp.c:(.text.icmp_echo+0x658): undefined reference to
`ipv6_dev_find'

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

I'm still learning the ropes of kernel development and I was wondering
if someone could help me figure out what is causing this error.

The file compiles when compiling with allyesconfig or olddefconfig, but
it cannot find the ipv6_dev_find() function when compiling with
allmodconfig and returns the error seen above. I am including
<include/net/addrconf.h> which declares ipv6_dev_find(), and the
function is defined and exported using EXPORT_SYMBOL in
<net/ipv6/addrconf.c>. I've tried declaring the function via extern in
<include/net/icmp.h> and in <net/ipv4/icmp.c>, but neither have
resolved the error and checkpatch.pl explicitly warns against using
extern calls in .c files.

Is there something that I'm not understanding about compiling kernel
components modularly? How do I avoid this error?