[Qemu-devel] [PATCH] net: add drop_packets parameter to -net nic

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

Dropping packets is sometimes perferred behavior. Add drop_packets
parameter to NICConf struct and let nic simulation decide how to use
it.

Only e1000 supports this for now.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Documentation is missing, but I'm not even sure if there's any other
 user who finds this useful.

 hw/e1000.c |    4 +++-
 hw/qdev.c  |    1 +
 net.c      |    5 +++++
 net.h      |    9 +++++++--
 4 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/hw/e1000.c b/hw/e1000.c
index fe3e812..57ffdec 100644
--- a/hw/e1000.c
+++ b/hw/e1000.c
@@ -656,7 +656,9 @@ e1000_can_receive(VLANClientState *nc)
 {
     E1000State *s = DO_UPCAST(NICState, nc, nc)->opaque;
 
-    return (s->mac_reg[RCTL] & E1000_RCTL_EN) && e1000_has_rxbufs(s, 1);
+    return (s->conf.flags & NIC_CONF_DROP_PACKETS) ||
+           ((s->mac_reg[RCTL] & E1000_RCTL_EN) &&
+            e1000_has_rxbufs(s, 1));
 }
 
 static uint64_t rx_desc_base(E1000State *s)
diff --git a/hw/qdev.c b/hw/qdev.c
index 9519f5d..d8605d6 100644
--- a/hw/qdev.c
+++ b/hw/qdev.c
@@ -468,6 +468,7 @@ void qdev_set_nic_properties(DeviceState *dev, NICInfo *nd)
         qdev_prop_exists(dev, "vectors")) {
         qdev_prop_set_uint32(dev, "vectors", nd->nvectors);
     }
+    qdev_prop_set_bit(dev, "drop_packets", nd->drop_packets);
 }
 
 BusState *qdev_get_child_bus(DeviceState *dev, const char *name)
diff --git a/net.c b/net.c
index 6746bc7..566be48 100644
--- a/net.c
+++ b/net.c
@@ -798,6 +798,7 @@ static int net_init_nic(QemuOpts *opts,
         return -1;
     }
 
+    nd->drop_packets = qemu_opt_get_bool(opts, "drop_packets", 0);
     nd->used = 1;
     nb_nics++;
 
@@ -864,6 +865,10 @@ static const struct {
                 .name = "vectors",
                 .type = QEMU_OPT_NUMBER,
                 .help = "number of MSI-x vectors, 0 to disable MSI-X",
+            }, {
+                .name = "drop_packets",
+                .type = QEMU_OPT_BOOL,
+                .help = "drop packets if driver is not ready to receive"
             },
             { /* end of list */ }
         },
diff --git a/net.h b/net.h
index 6ceca50..a594313 100644
--- a/net.h
+++ b/net.h
@@ -12,19 +12,23 @@ struct MACAddr {
 };
 
 /* qdev nic properties */
+#define NIC_CONF_DROP_PACKETS_BIT   0
+#define NIC_CONF_DROP_PACKETS      (1 << NIC_CONF_DROP_PACKETS_BIT)
 
 typedef struct NICConf {
     MACAddr macaddr;
     VLANState *vlan;
     VLANClientState *peer;
     int32_t bootindex;
+    uint32_t flags;
 } NICConf;
 
 #define DEFINE_NIC_PROPERTIES(_state, _conf)                            \
     DEFINE_PROP_MACADDR("mac",   _state, _conf.macaddr),                \
     DEFINE_PROP_VLAN("vlan",     _state, _conf.vlan),                   \
     DEFINE_PROP_NETDEV("netdev", _state, _conf.peer),                   \
-    DEFINE_PROP_INT32("bootindex", _state, _conf.bootindex, -1)
+    DEFINE_PROP_INT32("bootindex", _state, _conf.bootindex, -1),        \
+    DEFINE_PROP_BIT("drop_packets", _state, _conf.flags, NIC_CONF_DROP_PACKETS_BIT, 0)
 
 /* VLANs support */
 
@@ -133,8 +137,9 @@ struct NICInfo {
     char *devaddr;
     VLANState *vlan;
     VLANClientState *netdev;
-    int used;
     int nvectors;
+    unsigned int used : 1;
+    unsigned int drop_packets : 1;
 };
 
 extern int nb_nics;
-- 
1.7.3.4