netdev - Re: Multicast routing stops functioning after 4G multicast packets recived.

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Date:	Tue, 07 Jan 2014 12:26:53 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:	Bob Falken <NetFestivalHaveFun@....com>,
	Julian Anastasov <ja@....bg>, netdev@...r.kernel.org
Subject: Re: Multicast routing stops functioning after 4G multicast packets
 recived.

On Tue, 2014-01-07 at 21:11 +0100, Hannes Frederic Sowa wrote:

> It seems ip(6)mr_fib_lookup is not always called  from rcu section
> (ndo_start_xmit), so I had to restructure a bit. Could you retest this
> patch as preparation for a submission to stable? Thanks!
> 
> RCU conversion can be done later then.
> 
> diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
> index 421a249..9ae4ae7 100644
> --- a/net/ipv4/ipmr.c
> +++ b/net/ipv4/ipmr.c

>  
>  static netdev_tx_t reg_vif_xmit(struct sk_buff *skb, struct net_device *dev)
>  {
> +	int err;
> +	struct ipmr_result res;
>  	struct net *net = dev_net(dev);
> -	struct mr_table *mrt;
> +
> +	struct fib_lookup_arg arg = {
> +		.result = &res,
> +		.flags = FIB_LOOKUP_NOREF,
> +	};
> +
>  	struct flowi4 fl4 = {
>  		.flowi4_oif	= dev->ifindex,
>  		.flowi4_iif	= skb->skb_iif,
>  		.flowi4_mark	= skb->mark,
>  	};
> -	int err;

Technically speaking, I don't think reg_vif_xmit() is enclosed
in rcu_read_lock() section.

>  
> -	err = ipmr_fib_lookup(net, &fl4, &mrt);
> +	err = fib_rules_lookup(net->ipv4.mr_rules_ops,
> +			       flowi4_to_flowi(&fl4), 0, &arg);
>  	if (err < 0) {
>  		kfree_skb(skb);
>  		return err;
> @@ -466,9 +476,12 @@ static netdev_tx_t reg_vif_xmit(struct sk_buff *skb, struct net_device *dev)
>  	read_lock(&mrt_lock);
>  	dev->stats.tx_bytes += skb->len;
>  	dev->stats.tx_packets++;
> -	ipmr_cache_report(mrt, skb, mrt->mroute_reg_vif_num, IGMPMSG_WHOLEPKT);
> +	ipmr_cache_report(res.mrt, skb, res.mrt->mroute_reg_vif_num,
> +			  IGMPMSG_WHOLEPKT);
>  	read_unlock(&mrt_lock);
>  	kfree_skb(skb);
> +	if (arg.rule)
> +		fib_rule_put(arg.rule);
>  	return NETDEV_TX_OK;
>  }
>  

Hmm... Are you sure you meant to use FIB_LOOKUP_NOREF in
reg_vif_xmit() ?




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