Subject: Re: [PATCH net-next v3 2/3] bonding: modify the old and add new xmit hash policies

From: Veaceslav Falico <[email-masked]>
Date: Thu, 26 Sep 2013 16:34:23 +0200

On Thu, Sep 26, 2013 at 04:09:41PM +0200, Nikolay Aleksandrov wrote:
>This patch adds two new hash policy modes which use skb_flow_dissect:
>3 - Encapsulated layer 2+3
>4 - Encapsulated layer 3+4
>There should be a good improvement for tunnel users in those modes.
>It also changes the old hash functions to:
>hash ^= (__force u32)flow.dst ^ (__force u32)flow.src;
>hash ^= (hash >> 16);
>hash ^= (hash >> 8);
>
>Where hash will be initialized either to L2 hash, that is
>SRCMAC[5] XOR DSTMAC[5], or to flow->ports which should be extracted
>from the upper layer. Flow's dst and src are also extracted based on the
>xmit policy either directly from the buffer or by using skb_flow_dissect,
>but in both cases if the protocol is IPv6 then dst and src are obtained by
>ipv6_addr_hash() on the real addresses. In case of a non-dissectable
>packet, the algorithms fall back to L2 hashing.
>The bond_set_mode_ops() function is now obsolete and thus deleted
>because it was used only to set the proper hash policy. Also we trim a
>pointer from struct bonding because we no longer need to keep the hash
>function, now there's only a single hash function - bond_xmit_hash that
>works based on bond->params.xmit_policy.
>
>The hash function and skb_flow_dissect were suggested by Eric Dumazet.
>The layer names were suggested by Andy Gospodarek, because I suck at
>semantics.
>
>Signed-off-by: Nikolay Aleksandrov <[email-masked]>
>---
>v2: fix a bug in bond_flow_dissect which might've caused the use of
>    uninitalized flow_keys and make use of skb_flow_get_ports
>v3: no change
>One line is intentionally left at 82 chars since it's the whole function
>and IMO looks better that way.
>
> drivers/net/bonding/bond_3ad.c   |   2 +-
> drivers/net/bonding/bond_main.c  | 197 ++++++++++++++-------------------------
> drivers/net/bonding/bond_sysfs.c |   2 -
> drivers/net/bonding/bonding.h    |   3 +-
> include/uapi/linux/if_bonding.h  |   2 +
> 5 files changed, 72 insertions(+), 134 deletions(-)

-62 lines, even better :).

Acked-by: Veaceslav Falico <[email-masked]>

>
>diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
>index 0d8f427..b3ab703 100644
>--- a/drivers/net/bonding/bond_3ad.c
>+++ b/drivers/net/bonding/bond_3ad.c
>@@ -2442,7 +2442,7 @@ int bond_3ad_xmit_xor(struct sk_buff *skb, struct net_device *dev)
> 		goto out;
> 	}
>
>-	slave_agg_no = bond->xmit_hash_policy(skb, slaves_in_agg);
>+	slave_agg_no = bond_xmit_hash(bond, skb, slaves_in_agg);
>
> 	bond_for_each_slave(bond, slave) {
> 		struct aggregator *agg = SLAVE_AD_INFO(slave).port.aggregator;
>diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>index 55bbb8b..498e9e1 100644
>--- a/drivers/net/bonding/bond_main.c
>+++ b/drivers/net/bonding/bond_main.c
>@@ -78,6 +78,7 @@
> #include <net/netns/generic.h>
> #include <net/pkt_sched.h>
> #include <linux/rculist.h>
>+#include <net/flow_keys.h>
> #include "bonding.h"
> #include "bond_3ad.h"
> #include "bond_alb.h"
>@@ -159,7 +160,8 @@ MODULE_PARM_DESC(min_links, "Minimum number of available links before turning on
> module_param(xmit_hash_policy, charp, 0);
> MODULE_PARM_DESC(xmit_hash_policy, "balance-xor and 802.3ad hashing method; "
> 				   "0 for layer 2 (default), 1 for layer 3+4, "
>-				   "2 for layer 2+3");
>+				   "2 for layer 2+3, 3 for encap layer 2+3, "
>+				   "4 for encap layer 3+4");
> module_param(arp_interval, int, 0);
> MODULE_PARM_DESC(arp_interval, "arp interval in milliseconds");
> module_param_array(arp_ip_target, charp, NULL, 0);
>@@ -217,6 +219,8 @@ const struct bond_parm_tbl xmit_hashtype_tbl[] = {
> {	"layer2",		BOND_XMIT_POLICY_LAYER2},
> {	"layer3+4",		BOND_XMIT_POLICY_LAYER34},
> {	"layer2+3",		BOND_XMIT_POLICY_LAYER23},
>+{	"encap2+3",		BOND_XMIT_POLICY_ENCAP23},
>+{	"encap3+4",		BOND_XMIT_POLICY_ENCAP34},
> {	NULL,			-1},
> };
>
>@@ -3026,99 +3030,85 @@ static struct notifier_block bond_netdev_notifier = {
>
> /*---------------------------- Hashing Policies -----------------------------*/
>
>-/*
>- * Hash for the output device based upon layer 2 data
>- */
>-static int bond_xmit_hash_policy_l2(struct sk_buff *skb, int count)
>+/* L2 hash helper */
>+static inline u32 bond_eth_hash(struct sk_buff *skb)
> {
> 	struct ethhdr *data = (struct ethhdr *)skb->data;
>
> 	if (skb_headlen(skb) >= offsetof(struct ethhdr, h_proto))
>-		return (data->h_dest[5] ^ data->h_source[5]) % count;
>+		return data->h_dest[5] ^ data->h_source[5];
>
> 	return 0;
> }
>
>-/*
>- * Hash for the output device based upon layer 2 and layer 3 data. If
>- * the packet is not IP, fall back on bond_xmit_hash_policy_l2()
>- */
>-static int bond_xmit_hash_policy_l23(struct sk_buff *skb, int count)
>+/* Extract the appropriate headers based on bond's xmit policy */
>+static bool bond_flow_dissect(struct bonding *bond, struct sk_buff *skb,
>+			      struct flow_keys *fk)
> {
>-	const struct ethhdr *data;
>+	const struct ipv6hdr *iph6;
> 	const struct iphdr *iph;
>-	const struct ipv6hdr *ipv6h;
>-	u32 v6hash;
>-	const __be32 *s, *d;
>+	int noff, proto = -1;
>
>-	if (skb->protocol == htons(ETH_P_IP) &&
>-	    pskb_network_may_pull(skb, sizeof(*iph))) {
>+	if (bond->params.xmit_policy > BOND_XMIT_POLICY_LAYER23)
>+		return skb_flow_dissect(skb, fk);
>+
>+	fk->ports = 0;
>+	noff = skb_network_offset(skb);
>+	if (skb->protocol == htons(ETH_P_IP)) {
>+		if (!pskb_may_pull(skb, noff + sizeof(*iph)))
>+			return false;
> 		iph = ip_hdr(skb);
>-		data = (struct ethhdr *)skb->data;
>-		return ((ntohl(iph->saddr ^ iph->daddr) & 0xffff) ^
>-			(data->h_dest[5] ^ data->h_source[5])) % count;
>-	} else if (skb->protocol == htons(ETH_P_IPV6) &&
>-		   pskb_network_may_pull(skb, sizeof(*ipv6h))) {
>-		ipv6h = ipv6_hdr(skb);
>-		data = (struct ethhdr *)skb->data;
>-		s = &ipv6h->saddr.s6_addr32[0];
>-		d = &ipv6h->daddr.s6_addr32[0];
>-		v6hash = (s[1] ^ d[1]) ^ (s[2] ^ d[2]) ^ (s[3] ^ d[3]);
>-		v6hash ^= (v6hash >> 24) ^ (v6hash >> 16) ^ (v6hash >> 8);
>-		return (v6hash ^ data->h_dest[5] ^ data->h_source[5]) % count;
>-	}
>-
>-	return bond_xmit_hash_policy_l2(skb, count);
>+		fk->src = iph->saddr;
>+		fk->dst = iph->daddr;
>+		noff += iph->ihl << 2;
>+		if (!ip_is_fragment(iph))
>+			proto = iph->protocol;
>+	} else if (skb->protocol == htons(ETH_P_IPV6)) {
>+		if (!pskb_may_pull(skb, noff + sizeof(*iph6)))
>+			return false;
>+		iph6 = ipv6_hdr(skb);
>+		fk->src = (__force __be32)ipv6_addr_hash(&iph6->saddr);
>+		fk->dst = (__force __be32)ipv6_addr_hash(&iph6->daddr);
>+		noff += sizeof(*iph6);
>+		proto = iph6->nexthdr;
>+	} else {
>+		return false;
>+	}
>+	if (bond->params.xmit_policy == BOND_XMIT_POLICY_LAYER34 && proto >= 0)
>+		fk->ports = skb_flow_get_ports(skb, &noff, proto);
>+
>+	return true;
> }
>
>-/*
>- * Hash for the output device based upon layer 3 and layer 4 data. If
>- * the packet is a frag or not TCP or UDP, just use layer 3 data.  If it is
>- * altogether not IP, fall back on bond_xmit_hash_policy_l2()
>+/**
>+ * bond_xmit_hash - generate a hash value based on the xmit policy
>+ * @bond: bonding device
>+ * @skb: buffer to use for headers
>+ * @count: modulo value
>+ *
>+ * This function will extract the necessary headers from the skb buffer and use
>+ * them to generate a hash based on the xmit_policy set in the bonding device
>+ * which will be reduced modulo count before returning.
>  */
>-static int bond_xmit_hash_policy_l34(struct sk_buff *skb, int count)
>+int bond_xmit_hash(struct bonding *bond, struct sk_buff *skb, int count)
> {
>-	u32 layer4_xor = 0;
>-	const struct iphdr *iph;
>-	const struct ipv6hdr *ipv6h;
>-	const __be32 *s, *d;
>-	const __be16 *l4 = NULL;
>-	__be16 _l4[2];
>-	int noff = skb_network_offset(skb);
>-	int poff;
>-
>-	if (skb->protocol == htons(ETH_P_IP) &&
>-	    pskb_may_pull(skb, noff + sizeof(*iph))) {
>-		iph = ip_hdr(skb);
>-		poff = proto_ports_offset(iph->protocol);
>+	struct flow_keys flow;
>+	u32 hash;
>
>-		if (!ip_is_fragment(iph) && poff >= 0) {
>-			l4 = skb_header_pointer(skb, noff + (iph->ihl << 2) + poff,
>-						sizeof(_l4), &_l4);
>-			if (l4)
>-				layer4_xor = ntohs(l4[0] ^ l4[1]);
>-		}
>-		return (layer4_xor ^
>-			((ntohl(iph->saddr ^ iph->daddr)) & 0xffff)) % count;
>-	} else if (skb->protocol == htons(ETH_P_IPV6) &&
>-		   pskb_may_pull(skb, noff + sizeof(*ipv6h))) {
>-		ipv6h = ipv6_hdr(skb);
>-		poff = proto_ports_offset(ipv6h->nexthdr);
>-		if (poff >= 0) {
>-			l4 = skb_header_pointer(skb, noff + sizeof(*ipv6h) + poff,
>-						sizeof(_l4), &_l4);
>-			if (l4)
>-				layer4_xor = ntohs(l4[0] ^ l4[1]);
>-		}
>-		s = &ipv6h->saddr.s6_addr32[0];
>-		d = &ipv6h->daddr.s6_addr32[0];
>-		layer4_xor ^= (s[1] ^ d[1]) ^ (s[2] ^ d[2]) ^ (s[3] ^ d[3]);
>-		layer4_xor ^= (layer4_xor >> 24) ^ (layer4_xor >> 16) ^
>-			       (layer4_xor >> 8);
>-		return layer4_xor % count;
>-	}
>+	if (bond->params.xmit_policy == BOND_XMIT_POLICY_LAYER2 ||
>+	    !bond_flow_dissect(bond, skb, &flow))
>+		return bond_eth_hash(skb) % count;
>+
>+	if (bond->params.xmit_policy == BOND_XMIT_POLICY_LAYER23 ||
>+	    bond->params.xmit_policy == BOND_XMIT_POLICY_ENCAP23)
>+		hash = bond_eth_hash(skb);
>+	else
>+		hash = (__force u32)flow.ports;
>+	hash ^= (__force u32)flow.dst ^ (__force u32)flow.src;
>+	hash ^= (hash >> 16);
>+	hash ^= (hash >> 8);
>
>-	return bond_xmit_hash_policy_l2(skb, count);
>+	return hash % count;
> }
>
> /*-------------------------- Device entry points ----------------------------*/
>@@ -3700,8 +3690,7 @@ static int bond_xmit_activebackup(struct sk_buff *skb, struct net_device *bond_d
> 	return NETDEV_TX_OK;
> }
>
>-/*
>- * In bond_xmit_xor() , we determine the output device by using a pre-
>+/* In bond_xmit_xor() , we determine the output device by using a pre-
>  * determined xmit_hash_policy(), If the selected device is not enabled,
>  * find the next active slave.
>  */
>@@ -3709,8 +3698,7 @@ static int bond_xmit_xor(struct sk_buff *skb, struct net_device *bond_dev)
> {
> 	struct bonding *bond = netdev_priv(bond_dev);
>
>-	bond_xmit_slave_id(bond, skb,
>-			   bond->xmit_hash_policy(skb, bond->slave_cnt));
>+	bond_xmit_slave_id(bond, skb, bond_xmit_hash(bond, skb, bond->slave_cnt));
>
> 	return NETDEV_TX_OK;
> }
>@@ -3746,22 +3734,6 @@ static int bond_xmit_broadcast(struct sk_buff *skb, struct net_device *bond_dev)
>
> /*------------------------- Device initialization ---------------------------*/
>
>-static void bond_set_xmit_hash_policy(struct bonding *bond)
>-{
>-	switch (bond->params.xmit_policy) {
>-	case BOND_XMIT_POLICY_LAYER23:
>-		bond->xmit_hash_policy = bond_xmit_hash_policy_l23;
>-		break;
>-	case BOND_XMIT_POLICY_LAYER34:
>-		bond->xmit_hash_policy = bond_xmit_hash_policy_l34;
>-		break;
>-	case BOND_XMIT_POLICY_LAYER2:
>-	default:
>-		bond->xmit_hash_policy = bond_xmit_hash_policy_l2;
>-		break;
>-	}
>-}
>-
> /*
>  * Lookup the slave that corresponds to a qid
>  */
>@@ -3871,38 +3843,6 @@ static netdev_tx_t bond_start_xmit(struct sk_buff *skb, struct net_device *dev)
> 	return ret;
> }
>
>-/*
>- * set bond mode specific net device operations
>- */
>-void bond_set_mode_ops(struct bonding *bond, int mode)
>-{
>-	struct net_device *bond_dev = bond->dev;
>-
>-	switch (mode) {
>-	case BOND_MODE_ROUNDROBIN:
>-		break;
>-	case BOND_MODE_ACTIVEBACKUP:
>-		break;
>-	case BOND_MODE_XOR:
>-		bond_set_xmit_hash_policy(bond);
>-		break;
>-	case BOND_MODE_BROADCAST:
>-		break;
>-	case BOND_MODE_8023AD:
>-		bond_set_xmit_hash_policy(bond);
>-		break;
>-	case BOND_MODE_ALB:
>-		/* FALLTHRU */
>-	case BOND_MODE_TLB:
>-		break;
>-	default:
>-		/* Should never happen, mode already checked */
>-		pr_err("%s: Error: Unknown bonding mode %d\n",
>-		       bond_dev->name, mode);
>-		break;
>-	}
>-}
>-
> static int bond_ethtool_get_settings(struct net_device *bond_dev,
> 				     struct ethtool_cmd *ecmd)
> {
>@@ -4004,7 +3944,6 @@ static void bond_setup(struct net_device *bond_dev)
> 	ether_setup(bond_dev);
> 	bond_dev->netdev_ops = &bond_netdev_ops;
> 	bond_dev->ethtool_ops = &bond_ethtool_ops;
>-	bond_set_mode_ops(bond, bond->params.mode);
>
> 	bond_dev->destructor = bond_destructor;
>
>diff --git a/drivers/net/bonding/bond_sysfs.c b/drivers/net/bonding/bond_sysfs.c
>index c29b836..dba3b9b 100644
>--- a/drivers/net/bonding/bond_sysfs.c
>+++ b/drivers/net/bonding/bond_sysfs.c
>@@ -352,7 +352,6 @@ static ssize_t bonding_store_mode(struct device *d,
> 	/* don't cache arp_validate between modes */
> 	bond->params.arp_validate = BOND_ARP_VALIDATE_NONE;
> 	bond->params.mode = new_value;
>-	bond_set_mode_ops(bond, bond->params.mode);
> 	pr_info("%s: setting mode to %s (%d).\n",
> 		bond->dev->name, bond_mode_tbl[new_value].modename,
> 		new_value);
>@@ -392,7 +391,6 @@ static ssize_t bonding_store_xmit_hash(struct device *d,
> 		ret = -EINVAL;
> 	} else {
> 		bond->params.xmit_policy = new_value;
>-		bond_set_mode_ops(bond, bond->params.mode);
> 		pr_info("%s: setting xmit hash policy to %s (%d).\n",
> 			bond->dev->name,
> 			xmit_hashtype_tbl[new_value].modename, new_value);
>diff --git a/drivers/net/bonding/bonding.h b/drivers/net/bonding/bonding.h
>index 03cf3fd..4db9ec4 100644
>--- a/drivers/net/bonding/bonding.h
>+++ b/drivers/net/bonding/bonding.h
>@@ -245,7 +245,6 @@ struct bonding {
> 	char     proc_file_name[IFNAMSIZ];
> #endif /* CONFIG_PROC_FS */
> 	struct   list_head bond_list;
>-	int      (*xmit_hash_policy)(struct sk_buff *, int);
> 	u16      rr_tx_counter;
> 	struct   ad_bond_info ad_info;
> 	struct   alb_bond_info alb_info;
>@@ -446,7 +445,7 @@ int bond_release(struct net_device *bond_dev, struct net_device *slave_dev);
> void bond_mii_monitor(struct work_struct *);
> void bond_loadbalance_arp_mon(struct work_struct *);
> void bond_activebackup_arp_mon(struct work_struct *);
>-void bond_set_mode_ops(struct bonding *bond, int mode);
>+int bond_xmit_hash(struct bonding *bond, struct sk_buff *skb, int count);
> int bond_parse_parm(const char *mode_arg, const struct bond_parm_tbl *tbl);
> void bond_select_active_slave(struct bonding *bond);
> void bond_change_active_slave(struct bonding *bond, struct slave *new_active);
>diff --git a/include/uapi/linux/if_bonding.h b/include/uapi/linux/if_bonding.h
>index a17edda..9635a62 100644
>--- a/include/uapi/linux/if_bonding.h
>+++ b/include/uapi/linux/if_bonding.h
>@@ -91,6 +91,8 @@
> #define BOND_XMIT_POLICY_LAYER2		0 /* layer 2 (MAC only), default */
> #define BOND_XMIT_POLICY_LAYER34	1 /* layer 3+4 (IP ^ (TCP || UDP)) */
> #define BOND_XMIT_POLICY_LAYER23	2 /* layer 2+3 (IP ^ MAC) */
>+#define BOND_XMIT_POLICY_ENCAP23	3 /* encapsulated layer 2+3 */
>+#define BOND_XMIT_POLICY_ENCAP34	4 /* encapsulated layer 3+4 */
>
> typedef struct ifbond {
> 	__s32 bond_mode;
>-- 
>1.8.1.4
>