Re: [PATCH] netfilter: xt_HL: add pr_fmt, default case and NULL checks

[kernel test robot]

Hi Marino,

kernel test robot noticed the following build errors:

[auto build test ERROR on netfilter-nf/main]
[also build test ERROR on linus/master v7.0 next-20260420]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Marino-Dzalto/netfilter-xt_HL-add-pr_fmt-default-case-and-NULL-checks/20260420-185652
base:   https://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf.git main
patch link:    https://lore.kernel.org/r/20260403193929.89449-1-marino.dzalto%40gmail.com
patch subject: [PATCH] netfilter: xt_HL: add pr_fmt, default case and NULL checks
config: s390-allmodconfig (https://download.01.org/0day-ci/archive/20260422/202604220024.iITt6Hv8-lkp@xxxxxxxxx/config)
compiler: clang version 18.1.8 (https://github.com/llvm/llvm-project 3b5b5c1ec4a3095ab096dd780e84d7ab81f3d7ff)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260422/202604220024.iITt6Hv8-lkp@xxxxxxxxx/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-kbuild-all/202604220024.iITt6Hv8-lkp@xxxxxxxxx/

All errors (new ones prefixed by >>):

>> net/netfilter/xt_hl.c:34:6: error: cannot assign to variable 'ttl' with const-qualified type 'const u8' (aka 'const unsigned char')
      34 |         ttl = ip_hdr(skb)->ttl;
         |         ~~~ ^
   net/netfilter/xt_hl.c:29:11: note: variable 'ttl' declared const here
      29 |         const u8 ttl;
         |         ~~~~~~~~~^~~
   1 error generated.


vim +34 net/netfilter/xt_hl.c

    25	
    26	static bool ttl_mt(const struct sk_buff *skb, struct xt_action_param *par)
    27	{
    28		const struct ipt_ttl_info *info = par->matchinfo;
    29		const u8 ttl;
    30	
    31		if (!skb)
    32			return false;
    33	
  > 34		ttl = ip_hdr(skb)->ttl;
    35	
    36		switch (info->mode) {
    37		case IPT_TTL_EQ:
    38			return ttl == info->ttl;
    39		case IPT_TTL_NE:
    40			return ttl != info->ttl;
    41		case IPT_TTL_LT:
    42			return ttl < info->ttl;
    43		case IPT_TTL_GT:
    44			return ttl > info->ttl;
    45		default:
    46			pr_warn("Unknown TTL match mode: %d\n", info->mode);
    47			return false;
    48		}
    49	}
    50	

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