Re: [Xen-devel] [PATCH net-next 8/8] xen-netback: add support for toeplitz hashing

[Wei Liu]

On Wed, Oct 21, 2015 at 11:36:25AM +0100, Paul Durrant wrote:
> This patch adds all the necessary infrastructure to allow a frontend to
> specify toeplitz hashing of network packets on its receive side. (See
> netif.h for details of the xenbus protocol).
> 
> The toeplitz hash algorithm itself was based on pseudo-code provided by
> Microsoft at:
> 
> https://msdn.microsoft.com/en-us/library/windows/hardware/ff570725.aspx
> 
> Signed-off-by: Paul Durrant 
> Cc: Ian Campbell 
> Cc: Wei Liu 
[...]
>  
> diff --git a/drivers/net/xen-netback/interface.c 
> b/drivers/net/xen-netback/interface.c
> index 0c7da7b..38eee4f 100644
> --- a/drivers/net/xen-netback/interface.c
> +++ b/drivers/net/xen-netback/interface.c
> @@ -142,17 +142,122 @@ void xenvif_wake_queue(struct xenvif_queue *queue)
>   netif_tx_wake_queue(netdev_get_tx_queue(dev, id));
>  }
>  

I skipped the hash implementation because I don't think I know enough to
tell if it is correct or not, and protocol negotiation because I think
that's going to change in next version.

> +
> +
> +static void xen_net_read_toeplitz_key(struct xenvif *vif,
> +   const char *node)
> +{
> + struct xenbus_device *dev = xenvif_to_xenbus_device(vif);
> + char *str, *token;
> + u8 key[40];

This should use the macro.

> + unsigned int n, i;
> +
> + str = xenbus_read(XBT_NIL, node, "key", NULL);
> + if (IS_ERR(str))
> + goto fail1;
> +
> + memset(key, 0, sizeof(key));
> +
> + n = 0;
> + while ((token = strsep(, ",")) != NULL) {
> + int rc;
> +
> + if (n >= ARRAY_SIZE(vif->hash_params.toeplitz.key)) {
> + pr_err("%s: key too big\n",
> +dev->nodename);
> + goto fail2;
> + }
> +
> + rc = kstrtou8(token, 0, [n]);
> + if (rc < 0) {
> + pr_err("%s: invalid key value (%s at index %u)\n",
> +dev->nodename, token, n);
> + goto fail2;
> + }
> +
> + n++;
> + }
> +
> + for (i = 0; i < ARRAY_SIZE(vif->hash_params.toeplitz.key); i++)
> + vif->hash_params.toeplitz.key[i] = key[i];
> +
> + kfree(str);
> + return;
> +
> +fail2:
> + kfree(str);
> +fail1:
> + vif->hash_params.toeplitz.types = 0;
> +}
> +
[...]
> +
> +static void xen_hash_changed(struct xenbus_watch *watch,
> +  const char **vec, unsigned int len)
> +{
> + struct xenvif *vif = container_of(watch, struct xenvif, hash_watch);
> +
> + xen_net_read_hash(vif);

I think the same question for previous patch applies here, too.

Is there any concern of correctness and security implication that you
just change the hash without stopping the vif?

Wei.

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[Xen-devel] [PATCH net-next 8/8] xen-netback: add support for toeplitz hashing

[Paul Durrant]

This patch adds all the necessary infrastructure to allow a frontend to
specify toeplitz hashing of network packets on its receive side. (See
netif.h for details of the xenbus protocol).

The toeplitz hash algorithm itself was based on pseudo-code provided by
Microsoft at:

https://msdn.microsoft.com/en-us/library/windows/hardware/ff570725.aspx

Signed-off-by: Paul Durrant 
Cc: Ian Campbell 
Cc: Wei Liu 
---
 drivers/net/xen-netback/common.h|  32 ++
 drivers/net/xen-netback/interface.c | 111 +++-
 drivers/net/xen-netback/xenbus.c| 195 
 3 files changed, 335 insertions(+), 3 deletions(-)

diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index 23f2275..4ebfad9 100644
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -214,6 +214,31 @@ struct xenvif_mcast_addr {
 
 #define XEN_NETBK_MAX_HASH_MAPPING_SIZE 128
 
+enum xenvif_hash_alg {
+   XEN_NETBK_HASH_UNSPECIFIED,
+   XEN_NETBK_HASH_TOEPLITZ,
+};
+
+#define XEN_NETBK_MAX_TOEPLITZ_KEY_LENGTH 40
+
+struct xenvif_toeplitz_params {
+   union {
+   struct {
+   u8 ipv4_enabled:1;
+   u8 ipv4_tcp_enabled:1;
+   u8 ipv6_enabled:1;
+   u8 ipv6_tcp_enabled:1;
+   };
+   u8 types;
+   };
+
+   u8 key[XEN_NETBK_MAX_TOEPLITZ_KEY_LENGTH];
+};
+
+union xenvif_hash_params {
+   struct xenvif_toeplitz_params toeplitz;
+};
+
 struct xenvif {
/* Unique identifier for this interface. */
domid_t  domid;
@@ -250,8 +275,15 @@ struct xenvif {
unsigned int table[XEN_NETBK_MAX_HASH_MAPPING_SIZE];
unsigned int length;
} hash_mapping;
+
+   /* Hash */
+   enum xenvif_hash_alg hash_alg;
+   union xenvif_hash_params hash_params;
+
struct xenbus_watch credit_watch;
struct xenbus_watch hash_mapping_watch;
+   struct xenbus_watch hash_watch;
+   struct xenbus_watch hash_params_watch;
 
spinlock_t lock;
 
diff --git a/drivers/net/xen-netback/interface.c 
b/drivers/net/xen-netback/interface.c
index 0c7da7b..38eee4f 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -142,17 +142,122 @@ void xenvif_wake_queue(struct xenvif_queue *queue)
netif_tx_wake_queue(netdev_get_tx_queue(dev, id));
 }
 
+static u32 toeplitz_hash(const u8 *k, unsigned int klen,
+const u8 *d, unsigned int dlen)
+{
+   unsigned int di, ki;
+   u64 prefix = 0;
+   u64 hash = 0;
+
+   for (ki = 0; ki < 8; ki++) {
+   prefix |= ki < klen ? k[ki] : 0;
+   prefix <<= 8;
+   }
+
+   for (di = 0; di < dlen; di++) {
+   u8 byte = d[di];
+   unsigned int bit;
+
+   prefix |= ki < klen ? k[ki] : 0;
+   ki++;
+
+   for (bit = 0; bit < 8; bit++) {
+   if (byte & 0x80)
+   hash ^= prefix;
+   byte <<= 1;
+   prefix <<= 1;
+   }
+   }
+
+   return hash >> 32;
+}
+
+static void xenvif_set_toeplitz_hash(struct xenvif *vif, struct sk_buff *skb)
+{
+   struct flow_keys flow;
+   u32 hash = 0;
+   enum pkt_hash_types type = PKT_HASH_TYPE_NONE;
+   const u8 *key = vif->hash_params.toeplitz.key;
+   const unsigned int len = ARRAY_SIZE(vif->hash_params.toeplitz.key);
+
+   memset(, 0, sizeof(flow));
+   if (!skb_flow_dissect_flow_keys(skb, , 0))
+   goto done;
+
+   if (flow.basic.n_proto == htons(ETH_P_IP)) {
+   if (vif->hash_params.toeplitz.ipv4_tcp_enabled &&
+   flow.basic.ip_proto == IPPROTO_TCP) {
+   u8 data[12];
+
+   memcpy([0], , 4);
+   memcpy([4], , 4);
+   memcpy([8], , 2);
+   memcpy([10], , 2);
+
+   hash = toeplitz_hash(key, len,
+data, sizeof(data));
+   type = PKT_HASH_TYPE_L4;
+   } else if (vif->hash_params.toeplitz.ipv4_enabled) {
+   u8 data[8];
+
+   memcpy([0], , 4);
+   memcpy([4], , 4);
+
+   hash = toeplitz_hash(key, len,
+data, sizeof(data));
+   type = PKT_HASH_TYPE_L3;
+   }
+   } else if (flow.basic.n_proto == htons(ETH_P_IPV6)) {
+   if (vif->hash_params.toeplitz.ipv6_tcp_enabled &&
+   flow.basic.ip_proto == IPPROTO_TCP) {
+   u8 data[36];
+
+   memcpy([0], , 16);
+   memcpy([16], ,