netdev - Re: [PATCH net] vrf: Increment Icmp6InMsgs on the original netdev

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Date:   Sat, 1 Jun 2019 14:14:29 -0400
From:   Stephen Suryaputra <ssuryaextr@...il.com>
To:     David Ahern <dsahern@...il.com>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net] vrf: Increment Icmp6InMsgs on the original netdev

On Fri, May 31, 2019 at 05:06:16PM -0600, David Ahern wrote:
> On 5/29/19 11:08 PM, Stephen Suryaputra wrote:
> > diff --git a/net/ipv6/reassembly.c b/net/ipv6/reassembly.c
> > index 1a832f5e190b..9b365c345c34 100644
> > --- a/net/ipv6/reassembly.c
> > +++ b/net/ipv6/reassembly.c
> > @@ -260,6 +260,9 @@ static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *skb,
> >  	int payload_len;
> >  	u8 ecn;
> >  
> > +	if (netif_is_l3_master(dev))
> > +		dev = dev_get_by_index_rcu(net, inet6_iif(skb));
> > +
> >  	inet_frag_kill(&fq->q);
> >  
> >  	ecn = ip_frag_ecn_table[fq->ecn];
> > 
> 
> this part changes skb->dev. Seems like it has an unintended effect if
> the packet is delivered locally.

Ah, right. How about this then?

+/**
+ * __in6_dev_stats_get - get inet6_dev pointer for stats
+ * @dev: network device
+ * @skb: skb for original incoming interface if neeeded
+ *
+ * Caller must hold rcu_read_lock or RTNL, because this function
+ * does not take a reference on the inet6_dev.
+ */
+static inline struct inet6_dev *__in6_dev_stats_get(const struct net_device *dev,
+						    const struct sk_buff *skb)
+{
+	if (netif_is_l3_master(dev))
+		dev = dev_get_by_index_rcu(dev_net(dev), inet6_iif(skb));
+	return __in6_dev_get(dev);
+}

@@ -260,9 +260,6 @@ static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *skb,
 	int payload_len;
 	u8 ecn;
 
-	if (netif_is_l3_master(dev))
-		dev = dev_get_by_index_rcu(net, inet6_iif(skb));
-
 	inet_frag_kill(&fq->q);
 
 	ecn = ip_frag_ecn_table[fq->ecn];
@@ -305,7 +302,7 @@ static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *skb,
 			   skb_network_header_len(skb));
 
 	rcu_read_lock();
-	__IP6_INC_STATS(net, __in6_dev_get(dev), IPSTATS_MIB_REASMOKS);
+	__IP6_INC_STATS(net, __in6_dev_stats_get(dev, skb), IPSTATS_MIB_REASMOKS);
 	rcu_read_unlock();
 	fq->q.rb_fragments = RB_ROOT;
 	fq->q.fragments_tail = NULL;
@@ -319,7 +316,7 @@ static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *skb,
 	net_dbg_ratelimited("ip6_frag_reasm: no memory for reassembly\n");
 out_fail:
 	rcu_read_lock();
-	__IP6_INC_STATS(net, __in6_dev_get(dev), IPSTATS_MIB_REASMFAILS);
+	__IP6_INC_STATS(net, __in6_dev_stats_get(dev, skb), IPSTATS_MIB_REASMFAILS);
 	rcu_read_unlock();
 	inet_frag_kill(&fq->q);
 	return -1;

Thanks.