[PATCH net-next v3 1/2] bonding: add pure source-mac-based tx hashing option

[Jarod Wilson <jarod@redhat.com>]

As it turns out, a pure source-mac only tx hash has a place for some VM
setups. The previously added vlan+srcmac hash doesn't work as well for a
VM with a single MAC and multiple vlans -- these types of setups path
traffic more efficiently if the load is split by source mac alone. Enable
this by way of an extra module parameter, rather than adding yet another
hashing method in the tx fast path.

Cc: Jay Vosburgh <j.vosburgh@gmail.com>
Cc: Veaceslav Falico <vfalico@gmail.com>
Cc: Andy Gospodarek <andy@greyhouse.net>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Thomas Davis <tadavis@lbl.gov>
Cc: Nikolay Aleksandrov <nikolay@nvidia.com>
Cc: netdev@vger.kernel.org
Signed-off-by: Jarod Wilson <jarod@redhat.com>
---
 Documentation/networking/bonding.rst | 13 +++++++++++++
 drivers/net/bonding/bond_main.c      | 18 ++++++++++++------
 2 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/Documentation/networking/bonding.rst b/Documentation/networking/bonding.rst
index 62f2aab8eaec..767dbb49018b 100644
--- a/Documentation/networking/bonding.rst
+++ b/Documentation/networking/bonding.rst
@@ -707,6 +707,13 @@ mode
 		swapped with the new curr_active_slave that was
 		chosen.
 
+novlan_srcmac
+
+	When using the vlan+srcmac xmit_hash_policy, there may be cases where
+	omitting the vlan from the hash is beneficial. This can be done with
+	an extra module parameter here. The default value is 0 to include
+	vlan ID in the transmit hash.
+
 num_grat_arp,
 num_unsol_na
 
@@ -964,6 +971,12 @@ xmit_hash_policy
 
 		hash = (vlan ID) XOR (source MAC vendor) XOR (source MAC dev)
 
+		Optionally, if the module parameter novlan_srcmac=1 is set,
+		the vlan ID is omitted from the hash and only the source MAC
+		address is used, reducing the hash to
+
+		hash = (source MAC vendor) XOR (source MAC dev)
+
 	The default value is layer2.  This option was added in bonding
 	version 2.6.3.  In earlier versions of bonding, this parameter
 	does not exist, and the layer2 policy is the only policy.  The
diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 7e469c203ca5..666051f91d70 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -107,6 +107,7 @@ static char *lacp_rate;
 static int min_links;
 static char *ad_select;
 static char *xmit_hash_policy;
+static int novlan_srcmac;
 static int arp_interval;
 static char *arp_ip_target[BOND_MAX_ARP_TARGETS];
 static char *arp_validate;
@@ -168,6 +169,9 @@ MODULE_PARM_DESC(xmit_hash_policy, "balance-alb, balance-tlb, balance-xor, 802.3
 				   "0 for layer 2 (default), 1 for layer 3+4, "
 				   "2 for layer 2+3, 3 for encap layer 2+3, "
 				   "4 for encap layer 3+4, 5 for vlan+srcmac");
+module_param(novlan_srcmac, int, 0);
+MODULE_PARM_DESC(novlan_srcmac, "include vlan ID in vlan+srcmac xmit_hash_policy or not; "
+			      "0 to include it (default), 1 to exclude it");
 module_param(arp_interval, int, 0);
 MODULE_PARM_DESC(arp_interval, "arp interval in milliseconds");
 module_param_array(arp_ip_target, charp, NULL, 0);
@@ -3523,9 +3527,9 @@ static bool bond_flow_ip(struct sk_buff *skb, struct flow_keys *fk,
 
 static u32 bond_vlan_srcmac_hash(struct sk_buff *skb)
 {
-	struct ethhdr *mac_hdr = (struct ethhdr *)skb_mac_header(skb);
+	struct ethhdr *mac_hdr = eth_hdr(skb);
 	u32 srcmac_vendor = 0, srcmac_dev = 0;
-	u16 vlan;
+	u32 hash;
 	int i;
 
 	for (i = 0; i < 3; i++)
@@ -3534,12 +3538,14 @@ static u32 bond_vlan_srcmac_hash(struct sk_buff *skb)
 	for (i = 3; i < ETH_ALEN; i++)
 		srcmac_dev = (srcmac_dev << 8) | mac_hdr->h_source[i];
 
-	if (!skb_vlan_tag_present(skb))
-		return srcmac_vendor ^ srcmac_dev;
+	hash = srcmac_vendor ^ srcmac_dev;
+
+	if (novlan_srcmac || !skb_vlan_tag_present(skb))
+		return hash;
 
-	vlan = skb_vlan_tag_get(skb);
+	hash ^= skb_vlan_tag_get(skb);
 
-	return vlan ^ srcmac_vendor ^ srcmac_dev;
+	return hash;
 }
 
 /* Extract the appropriate headers based on bond's xmit policy */
-- 
2.30.2