diff --git a/hw/cadence_gem.c b/hw/cadence_gem.c
index b8071a4..ab86c17 100644
--- a/hw/cadence_gem.c
+++ b/hw/cadence_gem.c
@@ -409,7 +409,7 @@
 {
     GemState *s;
 
-    s = DO_UPCAST(NICState, nc, nc)->opaque;
+    s = qemu_get_nic_opaque(nc);
 
     DB_PRINT("\n");
 
@@ -612,7 +612,7 @@
     uint8_t    rxbuf[2048];
     uint8_t   *rxbuf_ptr;
 
-    s = DO_UPCAST(NICState, nc, nc)->opaque;
+    s = qemu_get_nic_opaque(nc);
 
     /* Do nothing if receive is not enabled. */
     if (!(s->regs[GEM_NWCTRL] & GEM_NWCTRL_RXENA)) {
@@ -1152,7 +1152,7 @@
 
 static void gem_cleanup(NetClientState *nc)
 {
-    GemState *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    GemState *s = qemu_get_nic_opaque(nc);
 
     DB_PRINT("\n");
     s->nic = NULL;
@@ -1161,7 +1161,7 @@
 static void gem_set_link(NetClientState *nc)
 {
     DB_PRINT("\n");
-    phy_update_link(DO_UPCAST(NICState, nc, nc)->opaque);
+    phy_update_link(qemu_get_nic_opaque(nc));
 }
 
 static NetClientInfo net_gem_info = {
diff --git a/hw/dp8393x.c b/hw/dp8393x.c
index c2d0bc8..0273fad 100644
--- a/hw/dp8393x.c
+++ b/hw/dp8393x.c
@@ -676,7 +676,7 @@
 
 static int nic_can_receive(NetClientState *nc)
 {
-    dp8393xState *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    dp8393xState *s = qemu_get_nic_opaque(nc);
 
     if (!(s->regs[SONIC_CR] & SONIC_CR_RXEN))
         return 0;
@@ -725,7 +725,7 @@
 
 static ssize_t nic_receive(NetClientState *nc, const uint8_t * buf, size_t size)
 {
-    dp8393xState *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    dp8393xState *s = qemu_get_nic_opaque(nc);
     uint16_t data[10];
     int packet_type;
     uint32_t available, address;
@@ -861,7 +861,7 @@
 
 static void nic_cleanup(NetClientState *nc)
 {
-    dp8393xState *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    dp8393xState *s = qemu_get_nic_opaque(nc);
 
     memory_region_del_subregion(s->address_space, &s->mmio);
     memory_region_destroy(&s->mmio);
diff --git a/hw/e1000.c b/hw/e1000.c
index 14b09d1..de2c700 100644
--- a/hw/e1000.c
+++ b/hw/e1000.c
@@ -748,7 +748,7 @@
 static void
 e1000_set_link_status(NetClientState *nc)
 {
-    E1000State *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    E1000State *s = qemu_get_nic_opaque(nc);
     uint32_t old_status = s->mac_reg[STATUS];
 
     if (nc->link_down) {
@@ -782,7 +782,7 @@
 static int
 e1000_can_receive(NetClientState *nc)
 {
-    E1000State *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    E1000State *s = qemu_get_nic_opaque(nc);
 
     return (s->mac_reg[RCTL] & E1000_RCTL_EN) && e1000_has_rxbufs(s, 1);
 }
@@ -798,7 +798,7 @@
 static ssize_t
 e1000_receive(NetClientState *nc, const uint8_t *buf, size_t size)
 {
-    E1000State *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    E1000State *s = qemu_get_nic_opaque(nc);
     struct e1000_rx_desc desc;
     dma_addr_t base;
     unsigned int n, rdt;
@@ -1235,7 +1235,7 @@
 static void
 e1000_cleanup(NetClientState *nc)
 {
-    E1000State *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    E1000State *s = qemu_get_nic_opaque(nc);
 
     s->nic = NULL;
 }
diff --git a/hw/eepro100.c b/hw/eepro100.c
index 5b77bdc..f9856ae 100644
--- a/hw/eepro100.c
+++ b/hw/eepro100.c
@@ -1619,7 +1619,7 @@
 
 static int nic_can_receive(NetClientState *nc)
 {
-    EEPRO100State *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    EEPRO100State *s = qemu_get_nic_opaque(nc);
     TRACE(RXTX, logout("%p\n", s));
     return get_ru_state(s) == ru_ready;
 #if 0
@@ -1633,7 +1633,7 @@
      * - Magic packets should set bit 30 in power management driver register.
      * - Interesting packets should set bit 29 in power management driver register.
      */
-    EEPRO100State *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    EEPRO100State *s = qemu_get_nic_opaque(nc);
     uint16_t rfd_status = 0xa000;
 #if defined(CONFIG_PAD_RECEIVED_FRAMES)
     uint8_t min_buf[60];
@@ -1835,7 +1835,7 @@
 
 static void nic_cleanup(NetClientState *nc)
 {
-    EEPRO100State *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    EEPRO100State *s = qemu_get_nic_opaque(nc);
 
     s->nic = NULL;
 }
diff --git a/hw/etraxfs_eth.c b/hw/etraxfs_eth.c
index 7c4d588..ad36411 100644
--- a/hw/etraxfs_eth.c
+++ b/hw/etraxfs_eth.c
@@ -523,7 +523,7 @@
 static ssize_t eth_receive(NetClientState *nc, const uint8_t *buf, size_t size)
 {
     unsigned char sa_bcast[6] = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
-    struct fs_eth *eth = DO_UPCAST(NICState, nc, nc)->opaque;
+    struct fs_eth *eth = qemu_get_nic_opaque(nc);
     int use_ma0 = eth->regs[RW_REC_CTRL] & 1;
     int use_ma1 = eth->regs[RW_REC_CTRL] & 2;
     int r_bcast = eth->regs[RW_REC_CTRL] & 8;
@@ -561,7 +561,7 @@
 
 static void eth_set_link(NetClientState *nc)
 {
-    struct fs_eth *eth = DO_UPCAST(NICState, nc, nc)->opaque;
+    struct fs_eth *eth = qemu_get_nic_opaque(nc);
     D(printf("%s %d\n", __func__, nc->link_down));
     eth->phy.link = !nc->link_down;
 }
@@ -578,7 +578,7 @@
 
 static void eth_cleanup(NetClientState *nc)
 {
-    struct fs_eth *eth = DO_UPCAST(NICState, nc, nc)->opaque;
+    struct fs_eth *eth = qemu_get_nic_opaque(nc);
 
     /* Disconnect the client.  */
     eth->dma_out->client.push = NULL;
diff --git a/hw/lan9118.c b/hw/lan9118.c
index 262f389..0e844e5 100644
--- a/hw/lan9118.c
+++ b/hw/lan9118.c
@@ -386,7 +386,7 @@
 
 static void lan9118_set_link(NetClientState *nc)
 {
-    phy_update_link(DO_UPCAST(NICState, nc, nc)->opaque);
+    phy_update_link(qemu_get_nic_opaque(nc));
 }
 
 static void phy_reset(lan9118_state *s)
@@ -512,7 +512,7 @@
 static ssize_t lan9118_receive(NetClientState *nc, const uint8_t *buf,
                                size_t size)
 {
-    lan9118_state *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    lan9118_state *s = qemu_get_nic_opaque(nc);
     int fifo_len;
     int offset;
     int src_pos;
@@ -1306,7 +1306,7 @@
 
 static void lan9118_cleanup(NetClientState *nc)
 {
-    lan9118_state *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    lan9118_state *s = qemu_get_nic_opaque(nc);
 
     s->nic = NULL;
 }
diff --git a/hw/lance.c b/hw/lance.c
index a5997fd..4b92425 100644
--- a/hw/lance.c
+++ b/hw/lance.c
@@ -87,7 +87,7 @@
 
 static void lance_cleanup(NetClientState *nc)
 {
-    PCNetState *d = DO_UPCAST(NICState, nc, nc)->opaque;
+    PCNetState *d = qemu_get_nic_opaque(nc);
 
     pcnet_common_cleanup(d);
 }
diff --git a/hw/mcf_fec.c b/hw/mcf_fec.c
index 8a90bf8..909e32b 100644
--- a/hw/mcf_fec.c
+++ b/hw/mcf_fec.c
@@ -353,13 +353,13 @@
 
 static int mcf_fec_can_receive(NetClientState *nc)
 {
-    mcf_fec_state *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    mcf_fec_state *s = qemu_get_nic_opaque(nc);
     return s->rx_enabled;
 }
 
 static ssize_t mcf_fec_receive(NetClientState *nc, const uint8_t *buf, size_t size)
 {
-    mcf_fec_state *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    mcf_fec_state *s = qemu_get_nic_opaque(nc);
     mcf_fec_bd bd;
     uint32_t flags = 0;
     uint32_t addr;
@@ -441,7 +441,7 @@
 
 static void mcf_fec_cleanup(NetClientState *nc)
 {
-    mcf_fec_state *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    mcf_fec_state *s = qemu_get_nic_opaque(nc);
 
     memory_region_del_subregion(s->sysmem, &s->iomem);
     memory_region_destroy(&s->iomem);
diff --git a/hw/milkymist-minimac2.c b/hw/milkymist-minimac2.c
index 2a8a4ef..9992dcc 100644
--- a/hw/milkymist-minimac2.c
+++ b/hw/milkymist-minimac2.c
@@ -280,7 +280,7 @@
 
 static ssize_t minimac2_rx(NetClientState *nc, const uint8_t *buf, size_t size)
 {
-    MilkymistMinimac2State *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    MilkymistMinimac2State *s = qemu_get_nic_opaque(nc);
 
     uint32_t r_count;
     uint32_t r_state;
@@ -410,7 +410,7 @@
 
 static int minimac2_can_rx(NetClientState *nc)
 {
-    MilkymistMinimac2State *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    MilkymistMinimac2State *s = qemu_get_nic_opaque(nc);
 
     if (s->regs[R_STATE0] == STATE_LOADED) {
         return 1;
@@ -424,7 +424,7 @@
 
 static void minimac2_cleanup(NetClientState *nc)
 {
-    MilkymistMinimac2State *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    MilkymistMinimac2State *s = qemu_get_nic_opaque(nc);
 
     s->nic = NULL;
 }
diff --git a/hw/mipsnet.c b/hw/mipsnet.c
index 15761b1..ff6bf7f 100644
--- a/hw/mipsnet.c
+++ b/hw/mipsnet.c
@@ -64,7 +64,7 @@
 
 static int mipsnet_can_receive(NetClientState *nc)
 {
-    MIPSnetState *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    MIPSnetState *s = qemu_get_nic_opaque(nc);
 
     if (s->busy)
         return 0;
@@ -73,7 +73,7 @@
 
 static ssize_t mipsnet_receive(NetClientState *nc, const uint8_t *buf, size_t size)
 {
-    MIPSnetState *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    MIPSnetState *s = qemu_get_nic_opaque(nc);
 
     trace_mipsnet_receive(size);
     if (!mipsnet_can_receive(nc))
@@ -211,7 +211,7 @@
 
 static void mipsnet_cleanup(NetClientState *nc)
 {
-    MIPSnetState *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    MIPSnetState *s = qemu_get_nic_opaque(nc);
 
     s->nic = NULL;
 }
diff --git a/hw/musicpal.c b/hw/musicpal.c
index 9e22f69..272cb80 100644
--- a/hw/musicpal.c
+++ b/hw/musicpal.c
@@ -190,7 +190,7 @@
 
 static ssize_t eth_receive(NetClientState *nc, const uint8_t *buf, size_t size)
 {
-    mv88w8618_eth_state *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    mv88w8618_eth_state *s = qemu_get_nic_opaque(nc);
     uint32_t desc_addr;
     mv88w8618_rx_desc desc;
     int i;
@@ -369,7 +369,7 @@
 
 static void eth_cleanup(NetClientState *nc)
 {
-    mv88w8618_eth_state *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    mv88w8618_eth_state *s = qemu_get_nic_opaque(nc);
 
     s->nic = NULL;
 }
diff --git a/hw/ne2000-isa.c b/hw/ne2000-isa.c
index fa47e12..342c6bd 100644
--- a/hw/ne2000-isa.c
+++ b/hw/ne2000-isa.c
@@ -38,7 +38,7 @@
 
 static void isa_ne2000_cleanup(NetClientState *nc)
 {
-    NE2000State *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    NE2000State *s = qemu_get_nic_opaque(nc);
 
     s->nic = NULL;
 }
diff --git a/hw/ne2000.c b/hw/ne2000.c
index 03c4209..c989190 100644
--- a/hw/ne2000.c
+++ b/hw/ne2000.c
@@ -167,7 +167,7 @@
 
 int ne2000_can_receive(NetClientState *nc)
 {
-    NE2000State *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    NE2000State *s = qemu_get_nic_opaque(nc);
 
     if (s->cmd & E8390_STOP)
         return 1;
@@ -178,7 +178,7 @@
 
 ssize_t ne2000_receive(NetClientState *nc, const uint8_t *buf, size_t size_)
 {
-    NE2000State *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    NE2000State *s = qemu_get_nic_opaque(nc);
     int size = size_;
     uint8_t *p;
     unsigned int total_len, next, avail, len, index, mcast_idx;
@@ -706,7 +706,7 @@
 
 static void ne2000_cleanup(NetClientState *nc)
 {
-    NE2000State *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    NE2000State *s = qemu_get_nic_opaque(nc);
 
     s->nic = NULL;
 }
diff --git a/hw/opencores_eth.c b/hw/opencores_eth.c
index 2496d4e..f9ba5ee 100644
--- a/hw/opencores_eth.c
+++ b/hw/opencores_eth.c
@@ -313,7 +313,7 @@
 
 static void open_eth_set_link_status(NetClientState *nc)
 {
-    OpenEthState *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    OpenEthState *s = qemu_get_nic_opaque(nc);
 
     if (GET_REGBIT(s, MIICOMMAND, SCANSTAT)) {
         SET_REGFIELD(s, MIISTATUS, LINKFAIL, nc->link_down);
@@ -344,7 +344,7 @@
 
 static int open_eth_can_receive(NetClientState *nc)
 {
-    OpenEthState *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    OpenEthState *s = qemu_get_nic_opaque(nc);
 
     return GET_REGBIT(s, MODER, RXEN) &&
         (s->regs[TX_BD_NUM] < 0x80) &&
@@ -354,7 +354,7 @@
 static ssize_t open_eth_receive(NetClientState *nc,
         const uint8_t *buf, size_t size)
 {
-    OpenEthState *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    OpenEthState *s = qemu_get_nic_opaque(nc);
     size_t maxfl = GET_REGFIELD(s, PACKETLEN, MAXFL);
     size_t minfl = GET_REGFIELD(s, PACKETLEN, MINFL);
     size_t fcsl = 4;
diff --git a/hw/pcnet-pci.c b/hw/pcnet-pci.c
index 54a849d..26c90bf 100644
--- a/hw/pcnet-pci.c
+++ b/hw/pcnet-pci.c
@@ -266,7 +266,7 @@
 
 static void pci_pcnet_cleanup(NetClientState *nc)
 {
-    PCNetState *d = DO_UPCAST(NICState, nc, nc)->opaque;
+    PCNetState *d = qemu_get_nic_opaque(nc);
 
     pcnet_common_cleanup(d);
 }
diff --git a/hw/pcnet.c b/hw/pcnet.c
index 2126e22..e0de1e3 100644
--- a/hw/pcnet.c
+++ b/hw/pcnet.c
@@ -1006,7 +1006,7 @@
 
 int pcnet_can_receive(NetClientState *nc)
 {
-    PCNetState *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    PCNetState *s = qemu_get_nic_opaque(nc);
     if (CSR_STOP(s) || CSR_SPND(s))
         return 0;
 
@@ -1017,7 +1017,7 @@
 
 ssize_t pcnet_receive(NetClientState *nc, const uint8_t *buf, size_t size_)
 {
-    PCNetState *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    PCNetState *s = qemu_get_nic_opaque(nc);
     int is_padr = 0, is_bcast = 0, is_ladr = 0;
     uint8_t buf1[60];
     int remaining;
@@ -1199,7 +1199,7 @@
 
 void pcnet_set_link_status(NetClientState *nc)
 {
-    PCNetState *d = DO_UPCAST(NICState, nc, nc)->opaque;
+    PCNetState *d = qemu_get_nic_opaque(nc);
 
     d->lnkst = nc->link_down ? 0 : 0x40;
 }
diff --git a/hw/rtl8139.c b/hw/rtl8139.c
index 22d24ae..b825e83 100644
--- a/hw/rtl8139.c
+++ b/hw/rtl8139.c
@@ -786,7 +786,7 @@
 
 static int rtl8139_can_receive(NetClientState *nc)
 {
-    RTL8139State *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    RTL8139State *s = qemu_get_nic_opaque(nc);
     int avail;
 
     /* Receive (drop) packets if card is disabled.  */
@@ -808,7 +808,7 @@
 
 static ssize_t rtl8139_do_receive(NetClientState *nc, const uint8_t *buf, size_t size_, int do_interrupt)
 {
-    RTL8139State *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    RTL8139State *s = qemu_get_nic_opaque(nc);
     /* size is the length of the buffer passed to the driver */
     int size = size_;
     const uint8_t *dot1q_buf = NULL;
@@ -3429,7 +3429,7 @@
 
 static void rtl8139_cleanup(NetClientState *nc)
 {
-    RTL8139State *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    RTL8139State *s = qemu_get_nic_opaque(nc);
 
     s->nic = NULL;
 }
@@ -3451,7 +3451,7 @@
 
 static void rtl8139_set_link_status(NetClientState *nc)
 {
-    RTL8139State *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    RTL8139State *s = qemu_get_nic_opaque(nc);
 
     if (nc->link_down) {
         s->BasicModeStatus &= ~0x04;
diff --git a/hw/smc91c111.c b/hw/smc91c111.c
index cf79c69..67fd074 100644
--- a/hw/smc91c111.c
+++ b/hw/smc91c111.c
@@ -631,7 +631,7 @@
 
 static int smc91c111_can_receive(NetClientState *nc)
 {
-    smc91c111_state *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    smc91c111_state *s = qemu_get_nic_opaque(nc);
 
     if ((s->rcr & RCR_RXEN) == 0 || (s->rcr & RCR_SOFT_RST))
         return 1;
@@ -642,7 +642,7 @@
 
 static ssize_t smc91c111_receive(NetClientState *nc, const uint8_t *buf, size_t size)
 {
-    smc91c111_state *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    smc91c111_state *s = qemu_get_nic_opaque(nc);
     int status;
     int packetsize;
     uint32_t crc;
@@ -731,7 +731,7 @@
 
 static void smc91c111_cleanup(NetClientState *nc)
 {
-    smc91c111_state *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    smc91c111_state *s = qemu_get_nic_opaque(nc);
 
     s->nic = NULL;
 }
diff --git a/hw/spapr_llan.c b/hw/spapr_llan.c
index d53d4ae..6ef2936 100644
--- a/hw/spapr_llan.c
+++ b/hw/spapr_llan.c
@@ -85,7 +85,7 @@
 
 static int spapr_vlan_can_receive(NetClientState *nc)
 {
-    VIOsPAPRVLANDevice *dev = DO_UPCAST(NICState, nc, nc)->opaque;
+    VIOsPAPRVLANDevice *dev = qemu_get_nic_opaque(nc);
 
     return (dev->isopen && dev->rx_bufs > 0);
 }
@@ -93,7 +93,7 @@
 static ssize_t spapr_vlan_receive(NetClientState *nc, const uint8_t *buf,
                                   size_t size)
 {
-    VIOsPAPRDevice *sdev = DO_UPCAST(NICState, nc, nc)->opaque;
+    VIOsPAPRDevice *sdev = qemu_get_nic_opaque(nc);
     VIOsPAPRVLANDevice *dev = (VIOsPAPRVLANDevice *)sdev;
     vlan_bd_t rxq_bd = vio_ldq(sdev, dev->buf_list + VLAN_RXQ_BD_OFF);
     vlan_bd_t bd;
diff --git a/hw/stellaris_enet.c b/hw/stellaris_enet.c
index 99d4730..6c701fb 100644
--- a/hw/stellaris_enet.c
+++ b/hw/stellaris_enet.c
@@ -80,7 +80,7 @@
 /* TODO: Implement MAC address filtering.  */
 static ssize_t stellaris_enet_receive(NetClientState *nc, const uint8_t *buf, size_t size)
 {
-    stellaris_enet_state *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    stellaris_enet_state *s = qemu_get_nic_opaque(nc);
     int n;
     uint8_t *p;
     uint32_t crc;
@@ -122,7 +122,7 @@
 
 static int stellaris_enet_can_receive(NetClientState *nc)
 {
-    stellaris_enet_state *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    stellaris_enet_state *s = qemu_get_nic_opaque(nc);
 
     if ((s->rctl & SE_RCTL_RXEN) == 0)
         return 1;
@@ -384,7 +384,7 @@
 
 static void stellaris_enet_cleanup(NetClientState *nc)
 {
-    stellaris_enet_state *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    stellaris_enet_state *s = qemu_get_nic_opaque(nc);
 
     unregister_savevm(&s->busdev.qdev, "stellaris_enet", s);
 
diff --git a/hw/usb/dev-network.c b/hw/usb/dev-network.c
index a131f9c..abc6eac 100644
--- a/hw/usb/dev-network.c
+++ b/hw/usb/dev-network.c
@@ -1261,7 +1261,7 @@
 
 static ssize_t usbnet_receive(NetClientState *nc, const uint8_t *buf, size_t size)
 {
-    USBNetState *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    USBNetState *s = qemu_get_nic_opaque(nc);
     uint8_t *in_buf = s->in_buf;
     size_t total_size = size;
 
@@ -1308,7 +1308,7 @@
 
 static int usbnet_can_receive(NetClientState *nc)
 {
-    USBNetState *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    USBNetState *s = qemu_get_nic_opaque(nc);
 
     if (is_rndis(s) && s->rndis_state != RNDIS_DATA_INITIALIZED) {
         return 1;
@@ -1319,7 +1319,7 @@
 
 static void usbnet_cleanup(NetClientState *nc)
 {
-    USBNetState *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    USBNetState *s = qemu_get_nic_opaque(nc);
 
     s->nic = NULL;
 }
diff --git a/hw/virtio-net.c b/hw/virtio-net.c
index 7ad65a2..e69313b 100644
--- a/hw/virtio-net.c
+++ b/hw/virtio-net.c
@@ -170,7 +170,7 @@
 
 static void virtio_net_set_link_status(NetClientState *nc)
 {
-    VirtIONet *n = DO_UPCAST(NICState, nc, nc)->opaque;
+    VirtIONet *n = qemu_get_nic_opaque(nc);
     uint16_t old_status = n->status;
 
     if (nc->link_down)
@@ -506,7 +506,7 @@
 
 static int virtio_net_can_receive(NetClientState *nc)
 {
-    VirtIONet *n = DO_UPCAST(NICState, nc, nc)->opaque;
+    VirtIONet *n = qemu_get_nic_opaque(nc);
     if (!n->vdev.vm_running) {
         return 0;
     }
@@ -637,7 +637,7 @@
 
 static ssize_t virtio_net_receive(NetClientState *nc, const uint8_t *buf, size_t size)
 {
-    VirtIONet *n = DO_UPCAST(NICState, nc, nc)->opaque;
+    VirtIONet *n = qemu_get_nic_opaque(nc);
     struct iovec mhdr_sg[VIRTQUEUE_MAX_SIZE];
     struct virtio_net_hdr_mrg_rxbuf mhdr;
     unsigned mhdr_cnt = 0;
@@ -736,7 +736,7 @@
 
 static void virtio_net_tx_complete(NetClientState *nc, ssize_t len)
 {
-    VirtIONet *n = DO_UPCAST(NICState, nc, nc)->opaque;
+    VirtIONet *n = qemu_get_nic_opaque(nc);
 
     virtqueue_push(n->tx_vq, &n->async_tx.elem, 0);
     virtio_notify(&n->vdev, n->tx_vq);
@@ -1035,7 +1035,7 @@
 
 static void virtio_net_cleanup(NetClientState *nc)
 {
-    VirtIONet *n = DO_UPCAST(NICState, nc, nc)->opaque;
+    VirtIONet *n = qemu_get_nic_opaque(nc);
 
     n->nic = NULL;
 }
diff --git a/hw/xen_nic.c b/hw/xen_nic.c
index d5b39ea..55b7960 100644
--- a/hw/xen_nic.c
+++ b/hw/xen_nic.c
@@ -236,7 +236,7 @@
 
 static int net_rx_ok(NetClientState *nc)
 {
-    struct XenNetDev *netdev = DO_UPCAST(NICState, nc, nc)->opaque;
+    struct XenNetDev *netdev = qemu_get_nic_opaque(nc);
     RING_IDX rc, rp;
 
     if (netdev->xendev.be_state != XenbusStateConnected) {
@@ -257,7 +257,7 @@
 
 static ssize_t net_rx_packet(NetClientState *nc, const uint8_t *buf, size_t size)
 {
-    struct XenNetDev *netdev = DO_UPCAST(NICState, nc, nc)->opaque;
+    struct XenNetDev *netdev = qemu_get_nic_opaque(nc);
     netif_rx_request_t rxreq;
     RING_IDX rc, rp;
     void *page;
diff --git a/hw/xgmac.c b/hw/xgmac.c
index 4d7bb13..5072298 100644
--- a/hw/xgmac.c
+++ b/hw/xgmac.c
@@ -310,7 +310,7 @@
 
 static int eth_can_rx(NetClientState *nc)
 {
-    struct XgmacState *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    struct XgmacState *s = qemu_get_nic_opaque(nc);
 
     /* RX enabled?  */
     return s->regs[DMA_CONTROL] & DMA_CONTROL_SR;
@@ -318,7 +318,7 @@
 
 static ssize_t eth_rx(NetClientState *nc, const uint8_t *buf, size_t size)
 {
-    struct XgmacState *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    struct XgmacState *s = qemu_get_nic_opaque(nc);
     static const unsigned char sa_bcast[6] = {0xff, 0xff, 0xff,
                                               0xff, 0xff, 0xff};
     int unicast, broadcast, multicast;
@@ -366,7 +366,7 @@
 
 static void eth_cleanup(NetClientState *nc)
 {
-    struct XgmacState *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    struct XgmacState *s = qemu_get_nic_opaque(nc);
     s->nic = NULL;
 }
 
diff --git a/hw/xilinx_axienet.c b/hw/xilinx_axienet.c
index a7e8e2c..34e344c 100644
--- a/hw/xilinx_axienet.c
+++ b/hw/xilinx_axienet.c
@@ -617,7 +617,7 @@
 
 static int eth_can_rx(NetClientState *nc)
 {
-    struct XilinxAXIEnet *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    struct XilinxAXIEnet *s = qemu_get_nic_opaque(nc);
 
     /* RX enabled?  */
     return !axienet_rx_resetting(s) && axienet_rx_enabled(s);
@@ -640,7 +640,7 @@
 
 static ssize_t eth_rx(NetClientState *nc, const uint8_t *buf, size_t size)
 {
-    struct XilinxAXIEnet *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    struct XilinxAXIEnet *s = qemu_get_nic_opaque(nc);
     static const unsigned char sa_bcast[6] = {0xff, 0xff, 0xff,
                                               0xff, 0xff, 0xff};
     static const unsigned char sa_ipmcast[3] = {0x01, 0x00, 0x52};
@@ -785,7 +785,7 @@
 static void eth_cleanup(NetClientState *nc)
 {
     /* FIXME.  */
-    struct XilinxAXIEnet *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    struct XilinxAXIEnet *s = qemu_get_nic_opaque(nc);
     g_free(s->rxmem);
     g_free(s);
 }
diff --git a/hw/xilinx_ethlite.c b/hw/xilinx_ethlite.c
index bdd6ab2..21c6f8c 100644
--- a/hw/xilinx_ethlite.c
+++ b/hw/xilinx_ethlite.c
@@ -167,7 +167,7 @@
 
 static int eth_can_rx(NetClientState *nc)
 {
-    struct xlx_ethlite *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    struct xlx_ethlite *s = qemu_get_nic_opaque(nc);
     unsigned int rxbase = s->rxbuf * (0x800 / 4);
 
     return !(s->regs[rxbase + R_RX_CTRL0] & CTRL_S);
@@ -175,7 +175,7 @@
 
 static ssize_t eth_rx(NetClientState *nc, const uint8_t *buf, size_t size)
 {
-    struct xlx_ethlite *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    struct xlx_ethlite *s = qemu_get_nic_opaque(nc);
     unsigned int rxbase = s->rxbuf * (0x800 / 4);
 
     /* DA filter.  */
@@ -201,7 +201,7 @@
 
 static void eth_cleanup(NetClientState *nc)
 {
-    struct xlx_ethlite *s = DO_UPCAST(NICState, nc, nc)->opaque;
+    struct xlx_ethlite *s = qemu_get_nic_opaque(nc);
 
     s->nic = NULL;
 }
diff --git a/include/net/net.h b/include/net/net.h
index 5d8aecf..96e05c4 100644
--- a/include/net/net.h
+++ b/include/net/net.h
@@ -78,6 +78,8 @@
                        const char *name,
                        void *opaque);
 NetClientState *qemu_get_queue(NICState *nic);
+NICState *qemu_get_nic(NetClientState *nc);
+void *qemu_get_nic_opaque(NetClientState *nc);
 void qemu_del_net_client(NetClientState *nc);
 NetClientState *qemu_find_vlan_client_by_name(Monitor *mon, int vlan_id,
                                               const char *client_str);
diff --git a/net/net.c b/net/net.c
index b986161..606e860 100644
--- a/net/net.c
+++ b/net/net.c
@@ -227,7 +227,7 @@
 
     nc = qemu_new_net_client(info, conf->peer, model, name);
 
-    nic = DO_UPCAST(NICState, nc, nc);
+    nic = qemu_get_nic(nc);
     nic->conf = conf;
     nic->opaque = opaque;
 
@@ -239,6 +239,18 @@
     return &nic->nc;
 }
 
+NICState *qemu_get_nic(NetClientState *nc)
+{
+    return DO_UPCAST(NICState, nc, nc);
+}
+
+void *qemu_get_nic_opaque(NetClientState *nc)
+{
+    NICState *nic = qemu_get_nic(nc);
+
+    return nic->opaque;
+}
+
 static void qemu_cleanup_net_client(NetClientState *nc)
 {
     QTAILQ_REMOVE(&net_clients, nc, next);
@@ -265,7 +277,7 @@
 {
     /* If there is a peer NIC, delete and cleanup client, but do not free. */
     if (nc->peer && nc->peer->info->type == NET_CLIENT_OPTIONS_KIND_NIC) {
-        NICState *nic = DO_UPCAST(NICState, nc, nc->peer);
+        NICState *nic = qemu_get_nic(nc->peer);
         if (nic->peer_deleted) {
             return;
         }
@@ -281,7 +293,7 @@
 
     /* If this is a peer NIC and peer has already been deleted, free it now. */
     if (nc->peer && nc->info->type == NET_CLIENT_OPTIONS_KIND_NIC) {
-        NICState *nic = DO_UPCAST(NICState, nc, nc);
+        NICState *nic = qemu_get_nic(nc);
         if (nic->peer_deleted) {
             qemu_free_net_client(nc->peer);
         }
@@ -297,7 +309,7 @@
 
     QTAILQ_FOREACH(nc, &net_clients, next) {
         if (nc->info->type == NET_CLIENT_OPTIONS_KIND_NIC) {
-            func(DO_UPCAST(NICState, nc, nc), opaque);
+            func(qemu_get_nic(nc), opaque);
         }
     }
 }