netdev - Re: [PATCH] net/ipv4: always honour route mtu during forwarding

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Date:   Thu, 24 Sep 2020 12:21:24 +0800
From:   kernel test robot <lkp@...el.com>
To:     Maciej Żenczykowski <zenczykowski@...il.com>,
        Maciej Żenczykowski <maze@...gle.com>,
        "David S . Miller" <davem@...emloft.net>
Cc:     kbuild-all@...ts.01.org,
        Linux Network Development Mailing List 
        <netdev@...r.kernel.org>, Willem de Bruijn <willemb@...gle.com>,
        Lorenzo Colitti <lorenzo@...gle.com>,
        Sunmeet Gill <sgill@...cinc.com>,
        Vinay Paradkar <vparadka@....qualcomm.com>,
        Tyler Wear <twear@...cinc.com>,
        David Ahern <dsahern@...nel.org>
Subject: Re: [PATCH] net/ipv4: always honour route mtu during forwarding

Hi "Maciej,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on net-next/master]
[also build test WARNING on net/master linus/master sparc-next/master next-20200923]
[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]

url:    https://github.com/0day-ci/linux/commits/Maciej-enczykowski/net-ipv4-always-honour-route-mtu-during-forwarding/20200923-124249
base:   https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git 748d1c8a425ec529d541f082ee7a81f6a51fa120
config: parisc-randconfig-c003-20200923 (attached as .config)
compiler: hppa64-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
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=parisc 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@...el.com>

All warnings (new ones prefixed by >>):

   In file included from include/net/busy_poll.h:18,
                    from fs/select.c:32:
   include/net/ip.h: In function 'ip_dst_mtu_maybe_forward':
>> include/net/ip.h:446:2: warning: ISO C90 forbids mixed declarations and code [-Wdeclaration-after-statement]
     446 |  unsigned int mtu = dst_metric_raw(dst, RTAX_MTU);
         |  ^~~~~~~~

# https://github.com/0day-ci/linux/commit/d9552d77468fe90224e07225cfc8c3f838b28b1b
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Maciej-enczykowski/net-ipv4-always-honour-route-mtu-during-forwarding/20200923-124249
git checkout d9552d77468fe90224e07225cfc8c3f838b28b1b
vim +446 include/net/ip.h

   434	
   435	static inline unsigned int ip_dst_mtu_maybe_forward(const struct dst_entry *dst,
   436							    bool forwarding)
   437	{
   438		struct net *net = dev_net(dst->dev);
   439	
   440		if (net->ipv4.sysctl_ip_fwd_use_pmtu ||
   441		    ip_mtu_locked(dst) ||
   442		    !forwarding)
   443			return dst_mtu(dst);
   444	
   445		/* 'forwarding = true' case should always honour route mtu */
 > 446		unsigned int mtu = dst_metric_raw(dst, RTAX_MTU);
   447		if (mtu) return mtu;
   448	
   449		return min(READ_ONCE(dst->dev->mtu), IP_MAX_MTU);
   450	}
   451	

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

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