netdev - Re: [PATCH net-next 4/4] act_mirred: use ACT

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Message-ID: <201807200115.LRLDfYYV%fengguang.wu@intel.com>
Date:   Fri, 20 Jul 2018 01:16:00 +0800
From:   kbuild test robot <lkp@...el.com>
To:     Paolo Abeni <pabeni@...hat.com>
Cc:     kbuild-all@...org, netdev@...r.kernel.org,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Subject: Re: [PATCH net-next 4/4] act_mirred: use ACT_REDIRECT when possible

Hi Paolo,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on net-next/master]

url:    https://github.com/0day-ci/linux/commits/Paolo-Abeni/TC-refactor-TC_ACT_REDIRECT-action/20180716-011055
reproduce:
        # apt-get install sparse
        make ARCH=x86_64 allmodconfig
        make C=1 CF=-D__CHECK_ENDIAN__


sparse warnings: (new ones prefixed by >>)

>> net/sched/act_mirred.c:195:17: sparse: dubious: x | !y
   net/sched/act_mirred.c:260:23: sparse: expression using sizeof(void)
   net/sched/act_mirred.c:260:23: sparse: expression using sizeof(void)

vim +195 net/sched/act_mirred.c

   169	
   170	static int tcf_mirred(struct sk_buff *skb, const struct tc_action *a,
   171			      struct tcf_result *res)
   172	{
   173		struct tcf_mirred *m = to_mirred(a);
   174		bool m_mac_header_xmit;
   175		struct net_device *dev;
   176		struct sk_buff *skb2;
   177		int retval, err = 0;
   178		bool want_ingress;
   179		int m_eaction;
   180		int mac_len;
   181	
   182		tcf_lastuse_update(&m->tcf_tm);
   183		bstats_cpu_update(this_cpu_ptr(m->common.cpu_bstats), skb);
   184	
   185		m_mac_header_xmit = READ_ONCE(m->tcfm_mac_header_xmit);
   186		m_eaction = READ_ONCE(m->tcfm_eaction);
   187		retval = READ_ONCE(m->tcf_action);
   188		dev = rcu_dereference_bh(m->tcfm_dev);
   189		want_ingress = tcf_mirred_act_wants_ingress(m_eaction);
   190		if (skb_at_tc_ingress(skb) && tcf_mirred_is_act_redirect(m_eaction)) {
   191			skb->tc_redirected = 1;
   192			skb->tc_from_ingress = 1;
   193	
   194			/* the core redirect code will check dev and its status */
 > 195			TCF_RESULT_SET_REDIRECT(res, dev, want_ingress);
   196			res->qstats = this_cpu_ptr(m->common.cpu_qstats);
   197			return TC_ACT_REDIRECT;
   198		}
   199	
   200		if (unlikely(!dev)) {
   201			pr_notice_once("tc mirred: target device is gone\n");
   202			goto out;
   203		}
   204	
   205		if (unlikely(!(dev->flags & IFF_UP))) {
   206			net_notice_ratelimited("tc mirred to Houston: device %s is down\n",
   207					       dev->name);
   208			goto out;
   209		}
   210	
   211		skb2 = skb_clone(skb, GFP_ATOMIC);
   212		if (!skb2)
   213			goto out;
   214	
   215		/* If action's target direction differs than filter's direction,
   216		 * and devices expect a mac header on xmit, then mac push/pull is
   217		 * needed.
   218		 */
   219		if (skb_at_tc_ingress(skb) != want_ingress && m_mac_header_xmit) {
   220			if (!skb_at_tc_ingress(skb)) {
   221				/* caught at egress, act ingress: pull mac */
   222				mac_len = skb_network_header(skb) - skb_mac_header(skb);
   223				skb_pull_rcsum(skb2, mac_len);
   224			} else {
   225				/* caught at ingress, act egress: push mac */
   226				skb_push_rcsum(skb2, skb->mac_len);
   227			}
   228		}
   229	
   230		/* mirror is always swallowed */
   231		if (tcf_mirred_is_act_redirect(m_eaction)) {
   232			skb2->tc_redirected = 1;
   233			skb2->tc_from_ingress = skb2->tc_at_ingress;
   234		}
   235	
   236		skb2->skb_iif = skb->dev->ifindex;
   237		skb2->dev = dev;
   238		if (!tcf_mirred_act_wants_ingress(m_eaction))
   239			err = dev_queue_xmit(skb2);
   240		else
   241			err = netif_receive_skb(skb2);
   242	
   243		if (err) {
   244	out:
   245			qstats_overlimit_inc(this_cpu_ptr(m->common.cpu_qstats));
   246			if (tcf_mirred_is_act_redirect(m_eaction))
   247				retval = TC_ACT_SHOT;
   248		}
   249	
   250		return retval;
   251	}
   252	

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