Subject: Re: [RFC PATCH net-next] bonding: add a vlan+srcmac tx hashing option

From: Jay Vosburgh <[email-masked]>
Date: Fri, 18 Dec 2020 16:18:59 -0800

Jarod Wilson <[email-masked]> wrote:

>This comes from an end-user request, where they're running multiple VMs on
>hosts with bonded interfaces connected to some interest switch topologies,
>where 802.3ad isn't an option. They're currently running a proprietary
>solution that effectively achieves load-balancing of VMs and bandwidth
>utilization improvements with a similar form of transmission algorithm.
>
>Basically, each VM has it's own vlan, so it always sends its traffic out
>the same interface, unless that interface fails. Traffic gets split
>between the interfaces, maintaining a consistent path, with failover still
>available if an interface goes down.
>
>This has been rudimetarily tested to provide similar results, suitable for
>them to use to move off their current proprietary solution.
>
>Still on the TODO list, if these even looks sane to begin with, is
>fleshing out Documentation/networking/bonding.rst.

	I'm sure you're aware, but any final submission will also need
to include netlink and iproute2 support.

>Cc: Jay Vosburgh <[email-masked]>
>Cc: Veaceslav Falico <[email-masked]>
>Cc: Andy Gospodarek <[email-masked]>
>Cc: "David S. Miller" <[email-masked]>
>Cc: Jakub Kicinski <[email-masked]>
>Cc: Thomas Davis <[email-masked]>
>Cc: [email-masked]
>Signed-off-by: Jarod Wilson <[email-masked]>
>---
> drivers/net/bonding/bond_main.c    | 27 +++++++++++++++++++++++++--
> drivers/net/bonding/bond_options.c |  1 +
> include/linux/netdevice.h          |  1 +
> include/uapi/linux/if_bonding.h    |  1 +
> 4 files changed, 28 insertions(+), 2 deletions(-)
>
>diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>index 5fe5232cc3f3..151ce8c7a56f 100644
>--- a/drivers/net/bonding/bond_main.c
>+++ b/drivers/net/bonding/bond_main.c
>@@ -164,7 +164,7 @@ module_param(xmit_hash_policy, charp, 0);
> MODULE_PARM_DESC(xmit_hash_policy, "balance-alb, balance-tlb, balance-xor, 802.3ad hashing method; "
> 				   "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");
>+				   "4 for encap layer 3+4, 5 for vlan+srcmac");
> module_param(arp_interval, int, 0);
> MODULE_PARM_DESC(arp_interval, "arp interval in milliseconds");
> module_param_array(arp_ip_target, charp, NULL, 0);
>@@ -1434,6 +1434,8 @@ static enum netdev_lag_hash bond_lag_hash_type(struct bonding *bond,
> 		return NETDEV_LAG_HASH_E23;
> 	case BOND_XMIT_POLICY_ENCAP34:
> 		return NETDEV_LAG_HASH_E34;
>+	case BOND_XMIT_POLICY_VLAN_SRCMAC:
>+		return NETDEV_LAG_HASH_VLAN_SRCMAC;
> 	default:
> 		return NETDEV_LAG_HASH_UNKNOWN;
> 	}
>@@ -3494,6 +3496,20 @@ static bool bond_flow_ip(struct sk_buff *skb, struct flow_keys *fk,
> 	return true;
> }
> 
>+static inline u32 bond_vlan_srcmac_hash(struct sk_buff *skb)
>+{
>+	struct ethhdr *mac_hdr = (struct ethhdr *)skb_mac_header(skb);
>+	u32 srcmac = mac_hdr->h_source[5];
>+	u16 vlan;
>+
>+	if (!skb_vlan_tag_present(skb))
>+		return srcmac;
>+
>+	vlan = skb_vlan_tag_get(skb);
>+
>+	return srcmac ^ vlan;

	For the common configuration wherein multiple VLANs are
configured atop a single interface (and thus by default end up with the
same MAC address), this seems like a fairly weak hash.  The TCI is 16
bits (12 of which are the VID), but only 8 are used from the MAC, which
will be a constant.

	Is this algorithm copying the proprietary solution you mention?

	-J

>+}
>+
> /* 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)
>@@ -3501,10 +3517,14 @@ static bool bond_flow_dissect(struct bonding *bond, struct sk_buff *skb,
> 	bool l34 = bond->params.xmit_policy == BOND_XMIT_POLICY_LAYER34;
> 	int noff, proto = -1;
> 
>-	if (bond->params.xmit_policy > BOND_XMIT_POLICY_LAYER23) {
>+	switch (bond->params.xmit_policy) {
>+	case BOND_XMIT_POLICY_ENCAP23:
>+	case BOND_XMIT_POLICY_ENCAP34:
> 		memset(fk, 0, sizeof(*fk));
> 		return __skb_flow_dissect(NULL, skb, &flow_keys_bonding,
> 					  fk, NULL, 0, 0, 0, 0);
>+	default:
>+		break;
> 	}
> 
> 	fk->ports.ports = 0;
>@@ -3556,6 +3576,9 @@ u32 bond_xmit_hash(struct bonding *bond, struct sk_buff *skb)
> 	    skb->l4_hash)
> 		return skb->hash;
> 
>+	if (bond->params.xmit_policy == BOND_XMIT_POLICY_VLAN_SRCMAC)
>+		return bond_vlan_srcmac_hash(skb);
>+
> 	if (bond->params.xmit_policy == BOND_XMIT_POLICY_LAYER2 ||
> 	    !bond_flow_dissect(bond, skb, &flow))
> 		return bond_eth_hash(skb);
>diff --git a/drivers/net/bonding/bond_options.c b/drivers/net/bonding/bond_options.c
>index a4e4e15f574d..9826fe46fca1 100644
>--- a/drivers/net/bonding/bond_options.c
>+++ b/drivers/net/bonding/bond_options.c
>@@ -101,6 +101,7 @@ static const struct bond_opt_value bond_xmit_hashtype_tbl[] = {
> 	{ "layer2+3", BOND_XMIT_POLICY_LAYER23, 0},
> 	{ "encap2+3", BOND_XMIT_POLICY_ENCAP23, 0},
> 	{ "encap3+4", BOND_XMIT_POLICY_ENCAP34, 0},
>+	{ "vlansrc",  BOND_XMIT_POLICY_VLAN_SRCMAC,  0},
> 	{ NULL,       -1,                       0},
> };
> 
>diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
>index 7bf167993c05..551eac4ab747 100644
>--- a/include/linux/netdevice.h
>+++ b/include/linux/netdevice.h
>@@ -2633,6 +2633,7 @@ enum netdev_lag_hash {
> 	NETDEV_LAG_HASH_L23,
> 	NETDEV_LAG_HASH_E23,
> 	NETDEV_LAG_HASH_E34,
>+	NETDEV_LAG_HASH_VLAN_SRCMAC,
> 	NETDEV_LAG_HASH_UNKNOWN,
> };
> 
>diff --git a/include/uapi/linux/if_bonding.h b/include/uapi/linux/if_bonding.h
>index 45f3750aa861..e8eb4ad03cf1 100644
>--- a/include/uapi/linux/if_bonding.h
>+++ b/include/uapi/linux/if_bonding.h
>@@ -94,6 +94,7 @@
> #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 */
>+#define BOND_XMIT_POLICY_VLAN_SRCMAC	5 /* vlan + source MAC */
> 
> /* 802.3ad port state definitions (43.4.2.2 in the 802.3ad standard) */
> #define LACP_STATE_LACP_ACTIVITY   0x1
>-- 
>2.29.2
>

---
	-Jay Vosburgh, [email-masked]