Add RX quotas to the net device poll() method. This avoids the problem

of alloc_pkb() exhaustion when e.g. an iSCSI-booted DOS session is left
idle for a long time at the C:\ prompt and builds up a huge packet
backlog.

3 files changed, 10 insertions, 5 deletions

diff --git a/src/drivers/net/legacy.c b/src/drivers/net/legacy.c
index 2d952aac0..091cdcc20 100644
--- a/src/drivers/net/legacy.c
+++ b/src/drivers/net/legacy.c
@@ -38,10 +38,13 @@ static int legacy_transmit ( struct net_device *netdev, struct pk_buff *pkb ) {
 	return 0;
 }
 
-static void legacy_poll ( struct net_device *netdev ) {
+static void legacy_poll ( struct net_device *netdev, unsigned int rx_quota ) {
 	struct nic *nic = netdev->priv;
 	struct pk_buff *pkb;
 
+	if ( ! rx_quota )
+		return;
+
 	pkb = alloc_pkb ( ETH_FRAME_LEN );
 	if ( ! pkb )
 		return;
diff --git a/src/drivers/net/pnic.c b/src/drivers/net/pnic.c
index 09ac92a47..c74e7b508 100644
--- a/src/drivers/net/pnic.c
+++ b/src/drivers/net/pnic.c
@@ -112,14 +112,14 @@ static int pnic_api_check ( uint16_t api_version ) {
 /**************************************************************************
 POLL - Wait for a frame
 ***************************************************************************/
-static void pnic_poll ( struct net_device *netdev ) {
+static void pnic_poll ( struct net_device *netdev, unsigned int rx_quota ) {
 	struct pnic *pnic = netdev->priv;
 	struct pk_buff *pkb;
 	uint16_t length;
 	uint16_t qlen;
 
 	/* Fetch all available packets */
-	while ( 1 ) {
+	while ( rx_quota ) {
 		if ( pnic_command ( pnic, PNIC_CMD_RECV_QLEN, NULL, 0,
 				    &qlen, sizeof ( qlen ), NULL )
 		     != PNIC_STATUS_OK )
@@ -139,6 +139,7 @@ static void pnic_poll ( struct net_device *netdev ) {
 		}
 		pkb_put ( pkb, length );
 		netdev_rx ( netdev, pkb );
+		--rx_quota;
 	}
 }
 
diff --git a/src/drivers/net/rtl8139.c b/src/drivers/net/rtl8139.c
index 4981329c3..a25755c2d 100644
--- a/src/drivers/net/rtl8139.c
+++ b/src/drivers/net/rtl8139.c
@@ -413,8 +413,9 @@ static int rtl_transmit ( struct net_device *netdev, struct pk_buff *pkb ) {
  * Poll for received packets
  *
  * @v netdev	Network device
+ * @v rx_quota	Maximum number of packets to receive
  */
-static void rtl_poll ( struct net_device *netdev ) {
+static void rtl_poll ( struct net_device *netdev, unsigned int rx_quota ) {
 	struct rtl8139_nic *rtl = netdev->priv;
 	unsigned int status;
 	unsigned int tsad;
@@ -441,7 +442,7 @@ static void rtl_poll ( struct net_device *netdev ) {
 	}
 
 	/* Handle received packets */
-	while ( ! ( inw ( rtl->ioaddr + ChipCmd ) & RxBufEmpty ) ) {
+	while ( rx_quota && ! ( inw ( rtl->ioaddr + ChipCmd ) & RxBufEmpty ) ){
 		rx_status = * ( ( uint16_t * )
 				( rtl->rx.ring + rtl->rx.offset ) );
 		rx_len = * ( ( uint16_t * )