Date:	Sat, 19 Feb 2011 08:44:03 +0100
From:	Jiri Pirko <jpirko@...hat.com>
To:	Jay Vosburgh <fubar@...ibm.com>
Cc:	David Miller <davem@...emloft.net>, kaber@...sh.net,
	eric.dumazet@...il.com, netdev@...r.kernel.org,
	shemminger@...ux-foundation.org, nicolas.2p.debian@...il.com,
	andy@...yhouse.net
Subject: Re: [patch net-next-2.6 V2] net: convert bonding to use rx_handler

Sat, Feb 19, 2011 at 12:06:11AM CET, fubar@...ibm.com wrote:
>Jiri Pirko <jpirko@...hat.com> wrote:
>
>>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.
>>
>>Signed-off-by: Jiri Pirko <jpirko@...hat.com>
>>
>>v1->v2:
>>	using skb_iif instead of new input_dev to remember original device
>>
>>---
>> drivers/net/bonding/bond_main.c |   75 ++++++++++++++++++++++++++-
>> net/core/dev.c                  |  111 ++++++++-------------------------------
>> 2 files changed, 97 insertions(+), 89 deletions(-)
>>
>>diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>>index 77e3c6a..a856a11 100644
>>--- a/drivers/net/bonding/bond_main.c
>>+++ b/drivers/net/bonding/bond_main.c
>>@@ -1423,6 +1423,68 @@ static void bond_setup_by_slave(struct net_device *bond_dev,
>> 	bond->setup_by_slave = 1;
>> }
>>
>>+/* On bonding slaves other than the currently active slave, suppress
>>+ * duplicates except for 802.3ad ETH_P_SLOW, alb non-mcast/bcast, and
>>+ * ARP on active-backup slaves with arp_validate enabled.
>>+ */
>>+static bool bond_should_deliver_exact_match(struct sk_buff *skb,
>>+					    struct net_device *slave_dev,
>>+					    struct net_device *bond_dev)
>>+{
>>+	if (slave_dev->priv_flags & IFF_SLAVE_INACTIVE) {
>>+		if (slave_dev->priv_flags & IFF_SLAVE_NEEDARP &&
>>+		    skb->protocol == __cpu_to_be16(ETH_P_ARP))
>>+			return false;
>>+
>>+		if (bond_dev->priv_flags & IFF_MASTER_ALB &&
>>+		    skb->pkt_type != PACKET_BROADCAST &&
>>+		    skb->pkt_type != PACKET_MULTICAST)
>>+				return false;
>>+
>>+		if (bond_dev->priv_flags & IFF_MASTER_8023AD &&
>>+		    skb->protocol == __cpu_to_be16(ETH_P_SLOW))
>>+			return false;
>
>	Since this is all in the bonding code now, it should be possible
>to do away with using priv_flags for all (or at least most) of this.
>Perhaps in a follow-on patch.

follow-on patch was exatly my intension to do this in.

>
>>+
>>+		return true;
>>+	}
>>+	return false;
>>+}
>>+
>>+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;
>
>	The last_rx field could probably move into bonding as well,
>although it looks like there are a couple of drivers using last_rx for
>something (more than just setting it).

I'll leave this to follow-on patch also.

>
>>+	if (bond_should_deliver_exact_match(skb, slave_dev, bond_dev)) {
>>+		skb->deliver_no_wcard = 1;
>>+		return skb;
>>+	}
>>+
>>+	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);
>>+	}
>>+
>>+	netif_rx(skb);
>>+	return NULL;
>>+}
>>+
>> /* enslave device <slave> to bond device <master> */
>> int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
>> {
>>@@ -1599,11 +1661,17 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
>> 		pr_debug("Error %d calling netdev_set_bond_master\n", res);
>> 		goto err_restore_mac;
>> 	}
>>+	res = netdev_rx_handler_register(slave_dev, bond_handle_frame, NULL);
>>+	if (res) {
>>+		pr_debug("Error %d calling netdev_rx_handler_register\n", res);
>>+		goto err_unset_master;
>>+	}
>>+
>> 	/* open the slave since the application closed it */
>> 	res = dev_open(slave_dev);
>> 	if (res) {
>> 		pr_debug("Opening slave %s failed\n", slave_dev->name);
>>-		goto err_unset_master;
>>+		goto err_unreg_rxhandler;
>> 	}
>>
>> 	new_slave->dev = slave_dev;
>>@@ -1811,6 +1879,9 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
>> err_close:
>> 	dev_close(slave_dev);
>>
>>+err_unreg_rxhandler:
>>+	netdev_rx_handler_unregister(slave_dev);
>>+
>> err_unset_master:
>> 	netdev_set_bond_master(slave_dev, NULL);
>>
>>@@ -1992,6 +2063,7 @@ int bond_release(struct net_device *bond_dev, struct net_device *slave_dev)
>> 		netif_addr_unlock_bh(bond_dev);
>> 	}
>>
>>+	netdev_rx_handler_unregister(slave_dev);
>> 	netdev_set_bond_master(slave_dev, NULL);
>>
>> #ifdef CONFIG_NET_POLL_CONTROLLER
>>@@ -2114,6 +2186,7 @@ static int bond_release_all(struct net_device *bond_dev)
>> 			netif_addr_unlock_bh(bond_dev);
>> 		}
>>
>>+		netdev_rx_handler_unregister(slave_dev);
>> 		netdev_set_bond_master(slave_dev, NULL);
>>
>> 		/* close slave before restoring its mac address */
>>diff --git a/net/core/dev.c b/net/core/dev.c
>>index 4f69439..580cff1 100644
>>--- a/net/core/dev.c
>>+++ b/net/core/dev.c
>>@@ -3092,63 +3092,31 @@ void netdev_rx_handler_unregister(struct net_device *dev)
>> }
>> EXPORT_SYMBOL_GPL(netdev_rx_handler_unregister);
>>
>>-static inline void skb_bond_set_mac_by_master(struct sk_buff *skb,
>>-					      struct net_device *master)
>>+static void vlan_on_bond_hook(struct sk_buff *skb)
>> {
>>-	if (skb->pkt_type == PACKET_HOST) {
>>-		u16 *dest = (u16 *) eth_hdr(skb)->h_dest;
>>-
>>-		memcpy(dest, master->dev_addr, ETH_ALEN);
>>-	}
>>-}
>>-
>>-/* On bonding slaves other than the currently active slave, suppress
>>- * duplicates except for 802.3ad ETH_P_SLOW, alb non-mcast/bcast, and
>>- * ARP on active-backup slaves with arp_validate enabled.
>>- */
>>-static int __skb_bond_should_drop(struct sk_buff *skb,
>>-				  struct net_device *master)
>>-{
>>-	struct net_device *dev = skb->dev;
>>-
>>-	if (master->priv_flags & IFF_MASTER_ARPMON)
>>-		dev->last_rx = jiffies;
>>-
>>-	if ((master->priv_flags & IFF_MASTER_ALB) &&
>>-	    (master->priv_flags & IFF_BRIDGE_PORT)) {
>>-		/* Do address unmangle. The local destination address
>>-		 * will be always the one master has. Provides the right
>>-		 * functionality in a bridge.
>>-		 */
>>-		skb_bond_set_mac_by_master(skb, master);
>>-	}
>>-
>>-	if (dev->priv_flags & IFF_SLAVE_INACTIVE) {
>>-		if ((dev->priv_flags & IFF_SLAVE_NEEDARP) &&
>>-		    skb->protocol == __cpu_to_be16(ETH_P_ARP))
>>-			return 0;
>>-
>>-		if (master->priv_flags & IFF_MASTER_ALB) {
>>-			if (skb->pkt_type != PACKET_BROADCAST &&
>>-			    skb->pkt_type != PACKET_MULTICAST)
>>-				return 0;
>>-		}
>>-		if (master->priv_flags & IFF_MASTER_8023AD &&
>>-		    skb->protocol == __cpu_to_be16(ETH_P_SLOW))
>>-			return 0;
>>+	/*
>>+	 * 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)) {
>>+		struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);
>>
>>-		return 1;
>>+		if (!skb2)
>>+			return;
>>+		skb2->dev = vlan_dev_real_dev(skb->dev);
>>+		netif_rx(skb2);
>> 	}
>>-	return 0;
>> }
>>
>> static int __netif_receive_skb(struct sk_buff *skb)
>> {
>> 	struct packet_type *ptype, *pt_prev;
>> 	rx_handler_func_t *rx_handler;
>>+	struct net_device *null_or_dev;
>> 	struct net_device *orig_dev;
>>-	struct net_device *null_or_orig;
>>-	struct net_device *orig_or_bond;
>> 	int ret = NET_RX_DROP;
>> 	__be16 type;
>>
>>@@ -3164,30 +3132,6 @@ static int __netif_receive_skb(struct sk_buff *skb)
>> 	if (!skb->skb_iif)
>> 		skb->skb_iif = skb->dev->ifindex;
>>
>>-	/*
>>-	 * bonding note: skbs received on inactive slaves should only
>>-	 * be delivered to pkt handlers that are exact matches.  Also
>>-	 * the deliver_no_wcard flag will be set.  If packet handlers
>>-	 * are sensitive to duplicate packets these skbs will need to
>>-	 * be dropped at the handler.
>>-	 */
>>-	null_or_orig = NULL;
>>-	orig_dev = skb->dev;
>>-	if (skb->deliver_no_wcard)
>>-		null_or_orig = orig_dev;
>>-	else if (netif_is_bond_slave(orig_dev)) {
>>-		struct net_device *bond_master = ACCESS_ONCE(orig_dev->master);
>>-
>>-		if (likely(bond_master)) {
>>-			if (__skb_bond_should_drop(skb, bond_master)) {
>>-				skb->deliver_no_wcard = 1;
>>-				/* deliver only exact match */
>>-				null_or_orig = orig_dev;
>>-			} else
>>-				skb->dev = bond_master;
>>-		}
>>-	}
>>-
>> 	__this_cpu_inc(softnet_data.processed);
>> 	skb_reset_network_header(skb);
>> 	skb_reset_transport_header(skb);
>>@@ -3196,6 +3140,7 @@ static int __netif_receive_skb(struct sk_buff *skb)
>> 	pt_prev = NULL;
>>
>> 	rcu_read_lock();
>>+	orig_dev = dev_get_by_index_rcu(dev_net(skb->dev), skb->skb_iif);
>
>	Aren't most packets going to have orig_dev == skb->dev at this
>point?  Can this be combined with the skb_iif test a few lines above
>this in __netif_receive_skb, looking something like:
>
>	if (!skb->skb_iif) {
>		skb->skb_iif = skb->dev->ifindex;
>		orig_dev = skb->dev;
>	else {
>		orig_dev = dev_get_by_index_rcu(...);
>	}
>
>	Presumably moving the whole thing down inside the rcu_read_lock.

Yep, that's reasonable. Thanks.

>
>	VLAN packets should come through here twice, but the first time
>through is before the call to vlan_hwaccel_do_receive, so skb->dev
>hasn't been set to the VLAN's dev yet.
>
>	Unless, of course, you find a place to store the orig_dev.
>
>	-J
>
>> #ifdef CONFIG_NET_CLS_ACT
>> 	if (skb->tc_verd & TC_NCLS) {
>>@@ -3205,8 +3150,7 @@ static int __netif_receive_skb(struct sk_buff *skb)
>> #endif
>>
>> 	list_for_each_entry_rcu(ptype, &ptype_all, list) {
>>-		if (ptype->dev == null_or_orig || ptype->dev == skb->dev ||
>>-		    ptype->dev == orig_dev) {
>>+		if (!ptype->dev || ptype->dev == skb->dev) {
>> 			if (pt_prev)
>> 				ret = deliver_skb(skb, pt_prev, orig_dev);
>> 			pt_prev = ptype;
>>@@ -3220,7 +3164,6 @@ static int __netif_receive_skb(struct sk_buff *skb)
>> ncls:
>> #endif
>>
>>-	/* Handle special case of bridge or macvlan */
>> 	rx_handler = rcu_dereference(skb->dev->rx_handler);
>> 	if (rx_handler) {
>> 		if (pt_prev) {
>>@@ -3244,24 +3187,16 @@ ncls:
>> 			goto out;
>> 	}
>>
>>-	/*
>>-	 * Make sure 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.  The
>>-	 * handler may have to adjust skb->dev and orig_dev.
>>-	 */
>>-	orig_or_bond = orig_dev;
>>-	if ((skb->dev->priv_flags & IFF_802_1Q_VLAN) &&
>>-	    (vlan_dev_real_dev(skb->dev)->priv_flags & IFF_BONDING)) {
>>-		orig_or_bond = vlan_dev_real_dev(skb->dev);
>>-	}
>>+	vlan_on_bond_hook(skb);
>>+
>>+	/* deliver only exact match when indicated */
>>+	null_or_dev = skb->deliver_no_wcard ? skb->dev : NULL;
>>
>> 	type = skb->protocol;
>> 	list_for_each_entry_rcu(ptype,
>> 			&ptype_base[ntohs(type) & PTYPE_HASH_MASK], list) {
>>-		if (ptype->type == type && (ptype->dev == null_or_orig ||
>>-		     ptype->dev == skb->dev || ptype->dev == orig_dev ||
>>-		     ptype->dev == orig_or_bond)) {
>>+		if (ptype->type == type &&
>>+		    (ptype->dev == null_or_dev || ptype->dev == skb->dev)) {
>> 			if (pt_prev)
>> 				ret = deliver_skb(skb, pt_prev, orig_dev);
>> 			pt_prev = ptype;
>>-- 
>>1.7.3.4
>>
>
>---
>	-Jay Vosburgh, IBM Linux Technology Center, fubar@...ibm.com
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