[PATCH v2] mini-os: netfront: Handle init failure when no vifs are provided

[Costin Lupu <costin.lupu@xxxxxxxxx>]

These changes deal with the case when no vifs are created. This can happen when
no vif is provided in the config file for mini-os images with netfront support.

Signed-off-by: Costin Lupu <costin.lupu@xxxxxxxxx>
---
 lwip-net.c | 4 ++++
 netfront.c | 9 +++++++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/lwip-net.c b/lwip-net.c
index 7e0d871..16950d3 100644
--- a/lwip-net.c
+++ b/lwip-net.c
@@ -348,6 +348,10 @@ void start_networking(void)
   tprintk("Waiting for network.\n");
 
   dev = init_netfront(NULL, NULL, rawmac, &ip);
+  if (!dev) {
+      tprintk("Error initializing netfront.\n");
+      return;
+  }
   netmask_str = netfront_get_netmask(dev);
   gw_str = netfront_get_gateway(dev);
   
diff --git a/netfront.c b/netfront.c
index 2075410..f927e99 100644
--- a/netfront.c
+++ b/netfront.c
@@ -383,6 +383,7 @@ char *netfront_get_gateway(struct netfront_dev *dev)
 
 static struct netfront_dev *_init_netfront(struct netfront_dev *dev)
 {
+    int domid;
     xenbus_transaction_t xbt;
     char* err = NULL;
     char* message=NULL;
@@ -393,6 +394,12 @@ static struct netfront_dev *_init_netfront(struct 
netfront_dev *dev)
     int i;
     char path[256];
 
+    snprintf(path, sizeof(path), "%s/backend-id", dev->nodename);
+    domid = xenbus_read_integer(path);
+    if (domid < 0)
+        return NULL;
+    dev->dom = domid;
+
     printk("net TX ring size %lu\n", (unsigned long) NET_TX_RING_SIZE);
     printk("net RX ring size %lu\n", (unsigned long) NET_RX_RING_SIZE);
     init_SEMAPHORE(&dev->tx_sem, NET_TX_RING_SIZE);
@@ -407,8 +414,6 @@ static struct netfront_dev *_init_netfront(struct 
netfront_dev *dev)
         BUG_ON(dev->rx_buffers[i].page == NULL);
     }
 
-    snprintf(path, sizeof(path), "%s/backend-id", dev->nodename);
-    dev->dom = xenbus_read_integer(path);
 #ifdef HAVE_LIBC
     if (dev->netif_rx == NETIF_SELECT_RX)
         evtchn_alloc_unbound(dev->dom, netfront_select_handler, dev, 
&dev->evtchn);
-- 
2.20.1