netdev - Re: [patch net-next-2.6 V3] net: convert bonding to use rx

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Message-ID: <20110227200628.GA2984@psychotron.redhat.com>
Date:	Sun, 27 Feb 2011 21:06:30 +0100
From:	Jiri Pirko <jpirko@...hat.com>
To:	Nicolas de Pesloüan 
	<nicolas.2p.debian@...il.com>
Cc:	David Miller <davem@...emloft.net>, kaber@...sh.net,
	eric.dumazet@...il.com, netdev@...r.kernel.org,
	shemminger@...ux-foundation.org, fubar@...ibm.com,
	andy@...yhouse.net
Subject: Re: [patch net-next-2.6 V3] net: convert bonding to use rx_handler

Sun, Feb 27, 2011 at 03:17:01PM CET, nicolas.2p.debian@...il.com wrote:
>Le 23/02/2011 20:05, Jiri Pirko a écrit :
>>This patch converts bonding to use rx_handler. Results in cleaner
>>__netif_receive_skb() with much less exceptions needed. Also
>>bond-specific work is moved into bond code.
>>
>>Did performance test using pktgen and counting incoming packets by
>>iptables. No regression noted.
>>
>>Signed-off-by: Jiri Pirko<jpirko@...hat.com>
>>
>>v1->v2:
>>         using skb_iif instead of new input_dev to remember original
>>	device
>>
>>v2->v3:
>>	do another loop in case skb->dev is changed. That way orig_dev
>>	core can be left untouched.
>>
>>Signed-off-by: Jiri Pirko<jpirko@...hat.com>
>>---
>
>[snip]
>
>>+static struct sk_buff *bond_handle_frame(struct sk_buff *skb)
>>+{
>>+	struct net_device *slave_dev;
>>+	struct net_device *bond_dev;
>>+
>>+	skb = skb_share_check(skb, GFP_ATOMIC);
>>+	if (unlikely(!skb))
>>+		return NULL;
>>+	slave_dev = skb->dev;
>>+	bond_dev = ACCESS_ONCE(slave_dev->master);
>>+	if (unlikely(!bond_dev))
>>+		return skb;
>>+
>>+	if (bond_dev->priv_flags&  IFF_MASTER_ARPMON)
>>+		slave_dev->last_rx = jiffies;
>>+
>>+	if (bond_should_deliver_exact_match(skb, slave_dev, bond_dev)) {
>>+		skb->deliver_no_wcard = 1;
>>+		return skb;
>
>Shouldn't we return NULL here ?

No we shouldn't. We need sbk to be delivered to exact match.

>
>>+	}
>>+
>>+	skb->dev = bond_dev;
>>+
>>+	if (bond_dev->priv_flags&  IFF_MASTER_ALB&&
>>+	    bond_dev->priv_flags&  IFF_BRIDGE_PORT&&
>>+	    skb->pkt_type == PACKET_HOST) {
>>+		u16 *dest = (u16 *) eth_hdr(skb)->h_dest;
>>+
>>+		memcpy(dest, bond_dev->dev_addr, ETH_ALEN);
>>+	}
>>+
>>+	return skb;
>>+}
>>+
>
>[snip]
>
>>+static void vlan_on_bond_hook(struct sk_buff *skb)
>>  {
>>-	if (skb->pkt_type == PACKET_HOST) {
>>-		u16 *dest = (u16 *) eth_hdr(skb)->h_dest;
>>+	/*
>>+	 * Make sure ARP frames received on VLAN interfaces stacked on
>>+	 * bonding interfaces still make their way to any base bonding
>>+	 * device that may have registered for a specific ptype.
>>+	 */
>>+	if (skb->dev->priv_flags&  IFF_802_1Q_VLAN&&
>>+	    vlan_dev_real_dev(skb->dev)->priv_flags&  IFF_BONDING&&
>>+	    skb->protocol == htons(ETH_P_ARP)) {
>
>The vlan_on_bond case used to be cost effective. Now, we clone the skb and call netif_rx...

This should not cost too much overhead considering only few packets are
going thru this. This hook shouldn't have exited in the fisrt place. I
think introducing this functionality was a big mistake.
>
>>+		struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);
>>
>>-		memcpy(dest, master->dev_addr, ETH_ALEN);
>>+		if (!skb2)
>>+			return;
>>+		skb2->dev = vlan_dev_real_dev(skb->dev);
>>+		netif_rx(skb2);
>>  	}
>>  }
>
>[snip]
>
>>  	if (rx_handler) {
>>+		struct net_device *prev_dev;
>>+
>>  		if (pt_prev) {
>>  			ret = deliver_skb(skb, pt_prev, orig_dev);
>>  			pt_prev = NULL;
>>  		}
>>+		prev_dev = skb->dev;
>>  		skb = rx_handler(skb);
>>  		if (!skb)
>>  			goto out;
>
>I would instead consider NULL as meaning exact-match-delivery-only.
>(The same effect as dev_bond_should_drop() returning true).

we can change the behaviour later on.

>
>>+		if (skb->dev != prev_dev)
>>+			goto another_round;
>>  	}
>
>Anyway, all my comments can't be postponed to follow-up patchs. Thanks Jiri.
>
>Reviewed-by: Nicolas de Pesloüan <nicolas.2p.debian@...e.fr>
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