caif: Use link layer MTU instead of fixed MTU

Previously CAIF supported maximum transfer size of ~4050.
The transfer size is now calculated dynamically based on the
link layers mtu size.

Signed-off-by: Sjur Braendeland@stericsson.com
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 57 insertions, 10 deletions

diff --git a/net/caif/chnl_net.c b/net/caif/chnl_net.c
index 610966abe2dc..4293e190ec53 100644
--- a/net/caif/chnl_net.c
+++ b/net/caif/chnl_net.c
@@ -23,7 +23,7 @@
 #include <net/caif/caif_dev.h>
 
 /* GPRS PDP connection has MTU to 1500 */
-#define SIZE_MTU 1500
+#define GPRS_PDP_MTU 1500
 /* 5 sec. connect timeout */
 #define CONNECT_TIMEOUT (5 * HZ)
 #define CAIF_NET_DEFAULT_QUEUE_LEN 500
@@ -232,6 +232,8 @@ static int chnl_net_open(struct net_device *dev)
 {
         struct chnl_net *priv = NULL;
         int result = -1;
+        int llifindex, headroom, tailroom, mtu;
+        struct net_device *lldev;
         ASSERT_RTNL();
         priv = netdev_priv(dev);
         if (!priv) {
@@ -241,41 +243,88 @@ static int chnl_net_open(struct net_device *dev)
 
         if (priv->state != CAIF_CONNECTING) {
                 priv->state = CAIF_CONNECTING;
-                result = caif_connect_client(&priv->conn_req, &priv->chnl);
+                result = caif_connect_client(&priv->conn_req, &priv->chnl,
+                                        &llifindex, &headroom, &tailroom);
                 if (result != 0) {
-                                priv->state = CAIF_DISCONNECTED;
                                 pr_debug("CAIF: %s(): err: "
                                         "Unable to register and open device,"
                                         " Err:%d\n",
                                         __func__,
                                         result);
-                                return result;
+                                goto error;
+                }
+
+                lldev = dev_get_by_index(dev_net(dev), llifindex);
+
+                if (lldev == NULL) {
+                        pr_debug("CAIF: %s(): no interface?\n", __func__);
+                        result = -ENODEV;
+                        goto error;
+                }
+
+                dev->needed_tailroom = tailroom + lldev->needed_tailroom;
+                dev->hard_header_len = headroom + lldev->hard_header_len +
+                        lldev->needed_tailroom;
+
+                /*
+                 * MTU, head-room etc is not know before we have a
+                 * CAIF link layer device available. MTU calculation may
+                 * override initial RTNL configuration.
+                 * MTU is minimum of current mtu, link layer mtu pluss
+                 * CAIF head and tail, and PDP GPRS contexts max MTU.
+                 */
+                mtu = min_t(int, dev->mtu, lldev->mtu - (headroom + tailroom));
+                mtu = min_t(int, GPRS_PDP_MTU, mtu);
+                dev_set_mtu(dev, mtu);
+                dev_put(lldev);
+
+                if (mtu < 100) {
+                        pr_warning("CAIF: %s(): "
+                                "CAIF Interface MTU too small (%d)\n",
+                                __func__, mtu);
+                        result = -ENODEV;
+                        goto error;
                 }
         }
 
+        rtnl_unlock();  /* Release RTNL lock during connect wait */
+
         result = wait_event_interruptible_timeout(priv->netmgmt_wq,
                                                 priv->state != CAIF_CONNECTING,
                                                 CONNECT_TIMEOUT);
 
+        rtnl_lock();
+
         if (result == -ERESTARTSYS) {
                 pr_debug("CAIF: %s(): wait_event_interruptible"
                          " woken by a signal\n", __func__);
-                return -ERESTARTSYS;
+                result = -ERESTARTSYS;
+                goto error;
         }
+
         if (result == 0) {
                 pr_debug("CAIF: %s(): connect timeout\n", __func__);
                 caif_disconnect_client(&priv->chnl);
                 priv->state = CAIF_DISCONNECTED;
                 pr_debug("CAIF: %s(): state disconnected\n", __func__);
-                return -ETIMEDOUT;
+                result = -ETIMEDOUT;
+                goto error;
         }
 
         if (priv->state != CAIF_CONNECTED) {
                 pr_debug("CAIF: %s(): connect failed\n", __func__);
-                return -ECONNREFUSED;
+                result = -ECONNREFUSED;
+                goto error;
         }
         pr_debug("CAIF: %s(): CAIF Netdevice connected\n", __func__);
         return 0;
+
+error:
+        caif_disconnect_client(&priv->chnl);
+        priv->state = CAIF_DISCONNECTED;
+        pr_debug("CAIF: %s(): state disconnected\n", __func__);
+        return result;
+
 }
 
 static int chnl_net_stop(struct net_device *dev)
@@ -321,9 +370,7 @@ static void ipcaif_net_setup(struct net_device *dev)
         dev->destructor = free_netdev;
         dev->flags |= IFF_NOARP;
         dev->flags |= IFF_POINTOPOINT;
-        dev->needed_headroom = CAIF_NEEDED_HEADROOM;
-        dev->needed_tailroom = CAIF_NEEDED_TAILROOM;
-        dev->mtu = SIZE_MTU;
+        dev->mtu = GPRS_PDP_MTU;
         dev->tx_queue_len = CAIF_NET_DEFAULT_QUEUE_LEN;
 
         priv = netdev_priv(dev);