[Qemu-devel] [Bug 1469946] Re: guest can't get IP when create guest with bridge.

[chao zhou]

Since commit 6e99c63 "net/socket: Drop net_socket_can_send" and friends,
net queues need to be explicitly flushed after qemu_can_send_packet()
returns false, because the netdev side will disable the polling of fd.

This fixes the case of "cont" after "stop" (or migration), i.e.
vm_running changes to true, by listening to vm state changes.

Signed-off-by: Fam Zheng <address@hidden>
---
 include/net/net.h |  2 ++
 net/net.c         | 14 +++++++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/include/net/net.h b/include/net/net.h index 6a6cbef..619a6e1 100644
--- a/include/net/net.h
+++ b/include/net/net.h
@@ -8,6 +8,7 @@
 #include "net/queue.h"
 #include "migration/vmstate.h"
 #include "qapi-types.h"
+#include "sysemu/sysemu.h"
 
 #define MAX_QUEUE_NUM 1024
 
@@ -92,6 +93,7 @@ struct NetClientState {
     NetClientDestructor *destructor;
     unsigned int queue_index;
     unsigned rxfilter_notify_enabled:1;
+    VMChangeStateEntry *vmcse;
 };
 
 typedef struct NICState {
diff --git a/net/net.c b/net/net.c
index 6ff7fec..edfa6a0 100644
--- a/net/net.c
+++ b/net/net.c
@@ -43,7 +43,6 @@
 #include "qapi-visit.h"
 #include "qapi/opts-visitor.h"
 #include "qapi/dealloc-visitor.h"
-#include "sysemu/sysemu.h"
 
 /* Net bridge is currently not supported for W32. */  #if !defined(_WIN32) @@ 
-263,6 +262,16 @@ static void qemu_net_client_destructor(NetClientState *nc)
     g_free(nc);
 }
 
+static void qemu_net_client_handle_vmstate(void *opaque,
+                                           int running,
+                                           RunState state) {
+    NetClientState *nc = opaque;
+    if (running && qemu_can_send_packet(nc) && nc->peer) {
+        qemu_flush_queued_packets(nc->peer);
+    }
+}
+
 static void qemu_net_client_setup(NetClientState *nc,
                                   NetClientInfo *info,
                                   NetClientState *peer, @@ -287,6 +296,8 @@ 
static void qemu_net_client_setup(NetClientState *nc,
 
     nc->incoming_queue = qemu_new_net_queue(nc);
     nc->destructor = destructor;
+    nc->vmcse = 
qemu_add_vm_change_state_handler(qemu_net_client_handle_vmstate,
+                                                 nc);
 }
 
 NetClientState *qemu_new_net_client(NetClientInfo *info, @@ -395,6 +406,7 @@ 
void qemu_del_net_client(NetClientState *nc)
                                           MAX_QUEUE_NUM);
     assert(queues != 0);
 
+    qemu_del_vm_change_state_handler(nc->vmcse);
     /* 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 = qemu_get_nic(nc->peer);
--
2.4.3


after try this patch and 
http://lists.nongnu.org/archive/html/qemu-devel/2015-06/msg07377.html  with 
qemu.git d2966f804d70a244f5dde395fc5d22a50ed3e74e
 after save/retore or live migration, the guest is alive,  ping or ssh guest's 
IP , it is fine

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https://bugs.launchpad.net/bugs/1469946

Title:
  guest can't get IP when create guest with bridge.

Status in QEMU:
  New

Bug description:
  Environment:
  ------------
  Host OS (ia32/ia32e/IA64):ia32e
  Guest OS (ia32/ia32e/IA64):ia32e
  Guest OS Type (Linux/Windows):linux
  kvm.git Commit:aefbef10e3ae6e2c6e3c54f906f10b34c73a2c66
  qemu.git Commit:dc1e1350f8061021df765b396295329797d66933
  Host Kernel Version:4.1.0
  Hardware:Ivytown_EP, Haswell_EP

  
  Bug detailed description:
  --------------------------
  when create guest with bridge, the guest can not get ip.

  note:
  1. fail rate: 3/5
  2. this is a qemu bug:
  kvm      + qemu   =  result
  aefbef10 + dc1e1350    =  bad 
  aefbef10 + a4ef02fd   =  good

  Reproduce steps:
  ----------------
  1. create guest:
  qemu-system-x86_64 -enable-kvm -m 2G -smp 4 -device 
virtio-net-pci,netdev=net0,mac=$random_mac -netdev 
tap,id=net0,script=/etc/kvm/qemu-ifup rhel6u5.qcow

  Current result:
  ----------------
  guest can't get IP

  Expected result:
  ----------------
  guest can get ip

  Basic root-causing log:
  ----------------------

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