wimax/i2400m: support extended data RX protocol (no need to reallocate skbs)

Newer i2400m firmwares (>= v1.4) extend the data RX protocol so that
each packet has a 16 byte header. This header is mainly used to
implement host reordeing (which is addressed in later commits).

However, this header also allows us to overwrite it (once data has
been extracted) with an Ethernet header and deliver to the networking
stack without having to reallocate the skb (as it happened in fw <=
v1.3) to make room for it.

- control.c: indicate the device [dev_initialize()] that the driver
  wants to use the extended data RX protocol. Also involves adding the
  definition of the needed data types in include/linux/wimax/i2400m.h.

- rx.c: handle the new payload type for the extended RX data
  protocol. Prepares the skb for delivery to
  netdev.c:i2400m_net_erx().

- netdev.c: Introduce i2400m_net_erx() that adds the fake ethernet
  address to a prepared skb and delivers it to the networking
  stack.

- cleanup: in most instances in rx.c, the variable 'single' was
  renamed to 'single_last' for it better conveys its meaning.

Signed-off-by: Inaky Perez-Gonzalez <inaky@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 79 insertions, 25 deletions

diff --git a/drivers/net/wimax/i2400m/netdev.c b/drivers/net/wimax/i2400m/netdev.c
index be8be4d0709c..2bdd0cdbb319 100644
--- a/drivers/net/wimax/i2400m/netdev.c
+++ b/drivers/net/wimax/i2400m/netdev.c
@@ -28,13 +28,12 @@
  * space and from the other side. The world is (sadly) configured to
  * take in only Ethernet devices...
  *
- * Because of this, currently there is an copy-each-rxed-packet
- * overhead on the RX path. Each IP packet has to be reallocated to
- * add an ethernet header (as there is no space in what we get from
- * the device). This is a known drawback and coming versions of the
- * device's firmware are being changed to add header space that can be
- * used to insert the ethernet header without having to reallocate and
- * copy.
+ * Because of this, when using firmwares <= v1.3, there is an
+ * copy-each-rxed-packet overhead on the RX path. Each IP packet has
+ * to be reallocated to add an ethernet header (as there is no space
+ * in what we get from the device). This is a known drawback and
+ * firmwares >= 1.4 add header space that can be used to insert the
+ * ethernet header without having to reallocate and copy.
  *
  * TX error handling is tricky; because we have to FIFO/queue the
  * buffers for transmission (as the hardware likes it aggregated), we
@@ -67,7 +66,9 @@
  * i2400m_tx_timeout      Called when the device times out
  *
  * i2400m_net_rx          Called by the RX code when a data frame is
- *                        available.
+ *                        available (firmware <= 1.3)
+ * i2400m_net_erx         Called by the RX code when a data frame is
+ *                        available (firmware >= 1.4).
  * i2400m_netdev_setup    Called to setup all the netdev stuff from
  *                        alloc_netdev.
  */
@@ -396,30 +397,18 @@ void i2400m_tx_timeout(struct net_device *net_dev)
  * Create a fake ethernet header
  *
  * For emulating an ethernet device, every received IP header has to
- * be prefixed with an ethernet header.
- *
- * What we receive has (potentially) many IP packets concatenated with
- * no ETH_HLEN bytes prefixed. Thus there is no space for an eth
- * header.
- *
- * We would have to reallocate or do ugly fragment tricks in order to
- * add it.
- *
- * But what we do is use the header space of the RX transaction
- * (*msg_hdr) as we don't need it anymore; then we'll point all the
- * data skbs there, as they share the same backing store.
- *
- * We only support IPv4 for v3 firmware.
+ * be prefixed with an ethernet header. Fake it with the given
+ * protocol.
  */
 static
 void i2400m_rx_fake_eth_header(struct net_device *net_dev,
-			       void *_eth_hdr)
+			       void *_eth_hdr, int protocol)
 {
 	struct ethhdr *eth_hdr = _eth_hdr;
 
 	memcpy(eth_hdr->h_dest, net_dev->dev_addr, sizeof(eth_hdr->h_dest));
 	memset(eth_hdr->h_source, 0, sizeof(eth_hdr->h_dest));
-	eth_hdr->h_proto = cpu_to_be16(ETH_P_IP);
+	eth_hdr->h_proto = cpu_to_be16(protocol);
 }
 
 
@@ -432,6 +421,13 @@ void i2400m_rx_fake_eth_header(struct net_device *net_dev,
  * @buf: pointer to the buffer containing the data
  * @len: buffer's length
  *
+ * This is only used now for the v1.3 firmware. It will be deprecated
+ * in >= 2.6.31.
+ *
+ * Note that due to firmware limitations, we don't have space to add
+ * an ethernet header, so we need to copy each packet. Firmware
+ * versions >= v1.4 fix this [see i2400m_net_erx()].
+ *
  * We just clone the skb and set it up so that it's skb->data pointer
  * points to "buf" and it's length.
  *
@@ -478,7 +474,7 @@ void i2400m_net_rx(struct i2400m *i2400m, struct sk_buff *skb_rx,
 		memcpy(skb_put(skb, buf_len), buf, buf_len);
 	}
 	i2400m_rx_fake_eth_header(i2400m->wimax_dev.net_dev,
-				  skb->data - ETH_HLEN);
+				  skb->data - ETH_HLEN, ETH_P_IP);
 	skb_set_mac_header(skb, -ETH_HLEN);
 	skb->dev = i2400m->wimax_dev.net_dev;
 	skb->protocol = htons(ETH_P_IP);
@@ -493,6 +489,64 @@ error_skb_realloc:
 		i2400m, buf, buf_len);
 }
 
+
+/*
+ * i2400m_net_erx - pass a network packet to the stack (extended version)
+ *
+ * @i2400m: device descriptor
+ * @skb: the skb where the packet is - the skb should be set to point
+ *     at the IP packet; this function will add ethernet headers if
+ *     needed.
+ * @cs: packet type
+ *
+ * This is only used now for firmware >= v1.4. Note it is quite
+ * similar to i2400m_net_rx() (used only for v1.3 firmware).
+ *
+ * This function is normally run from a thread context. However, we
+ * still use netif_rx() instead of netif_receive_skb() as was
+ * recommended in the mailing list. Reason is in some stress tests
+ * when sending/receiving a lot of data we seem to hit a softlock in
+ * the kernel's TCP implementation [aroudn tcp_delay_timer()]. Using
+ * netif_rx() took care of the issue.
+ *
+ * This is, of course, still open to do more research on why running
+ * with netif_receive_skb() hits this softlock. FIXME.
+ */
+void i2400m_net_erx(struct i2400m *i2400m, struct sk_buff *skb,
+		    enum i2400m_cs cs)
+{
+	struct net_device *net_dev = i2400m->wimax_dev.net_dev;
+	struct device *dev = i2400m_dev(i2400m);
+	int protocol;
+
+	d_fnstart(2, dev, "(i2400m %p skb %p [%zu] cs %d)\n",
+		  i2400m, skb, skb->len, cs);
+	switch(cs) {
+	case I2400M_CS_IPV4_0:
+	case I2400M_CS_IPV4:
+		protocol = ETH_P_IP;
+		i2400m_rx_fake_eth_header(i2400m->wimax_dev.net_dev,
+					  skb->data - ETH_HLEN, ETH_P_IP);
+		skb_set_mac_header(skb, -ETH_HLEN);
+		skb->dev = i2400m->wimax_dev.net_dev;
+		skb->protocol = htons(ETH_P_IP);
+		net_dev->stats.rx_packets++;
+		net_dev->stats.rx_bytes += skb->len;
+		break;
+	default:
+		dev_err(dev, "ERX: BUG? CS type %u unsupported\n", cs);
+		goto error;
+
+	}
+	d_printf(3, dev, "ERX: receiving %d bytes to the network stack\n",
+		 skb->len);
+	d_dump(4, dev, skb->data, skb->len);
+	netif_rx_ni(skb);	/* see notes in function header */
+error:
+	d_fnend(2, dev, "(i2400m %p skb %p [%zu] cs %d) = void\n",
+		i2400m, skb, skb->len, cs);
+}
+
 static const struct net_device_ops i2400m_netdev_ops = {
 	.ndo_open = i2400m_open,
 	.ndo_stop = i2400m_stop,