[Qemu-devel] [PATCH 1/4] Add 'set_link' monitor command

[Mark McLoughlin <markmc@redhat.com>]

Add a monitor command to setting a given network device's link status
to 'up' or 'down'.

Allows simulation of network cable disconnect.

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
---
 monitor.c |    1 +
 net.c     |   31 ++++++++++++++++++++++++++++++-
 net.h     |    2 ++
 3 files changed, 33 insertions(+), 1 deletions(-)

diff --git a/monitor.c b/monitor.c
index 745c335..7ff9890 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1516,6 +1516,7 @@ static const term_cmd_t term_cmds[] = {
       "value", "set maximum speed (in bytes) for migrations" },
     { "balloon", "i", do_balloon,
       "target", "request VM to change it's memory allocation (in MB)" },
+    { "set_link", "ss", do_set_link, "name [up|down]" },
     { NULL, NULL, },
 };
 
diff --git a/net.c b/net.c
index 4609be2..eef0564 100644
--- a/net.c
+++ b/net.c
@@ -386,12 +386,15 @@ void qemu_send_packet(VLANClientState *vc1, const uint8_t *buf, int size)
     VLANState *vlan = vc1->vlan;
     VLANClientState *vc;
 
+    if (vc1->link_down)
+        return;
+
 #ifdef DEBUG_NET
     printf("vlan %d send:\n", vlan->id);
     hex_dump(stdout, buf, size);
 #endif
     for(vc = vlan->first_client; vc != NULL; vc = vc->next) {
-        if (vc != vc1) {
+        if (vc != vc1 && !vc->link_down) {
             vc->fd_read(vc->opaque, buf, size);
         }
     }
@@ -1717,6 +1720,32 @@ void do_info_network(void)
     }
 }
 
+int do_set_link(const char *name, const char *up_or_down)
+{
+    VLANState *vlan;
+    VLANClientState *vc = NULL;
+
+    for (vlan = first_vlan; vlan != NULL; vlan = vlan->next)
+        for (vc = vlan->first_client; vc != NULL; vc = vc->next)
+            if (strcmp(vc->name, name) == 0)
+                break;
+
+    if (!vc) {
+        term_printf("could not find network device '%s'", name);
+        return 0;
+    }
+
+    if (strcmp(up_or_down, "up") == 0)
+        vc->link_down = 0;
+    else if (strcmp(up_or_down, "down") == 0)
+        vc->link_down = 1;
+    else
+        term_printf("invalid link status '%s'; only 'up' or 'down' valid\n",
+                    up_or_down);
+
+    return 1;
+}
+
 void net_cleanup(void)
 {
     VLANState *vlan;
diff --git a/net.h b/net.h
index 19ab649..3c0dab9 100644
--- a/net.h
+++ b/net.h
@@ -15,6 +15,7 @@ struct VLANClientState {
     /* Packets may still be sent if this returns zero.  It's used to
        rate-limit the slirp code.  */
     IOCanRWHandler *fd_can_read;
+    int link_down;
     void *opaque;
     struct VLANClientState *next;
     struct VLANState *vlan;
@@ -49,6 +50,7 @@ void qemu_check_nic_model_list(NICInfo *nd, const char * const *models,
 void qemu_handler_true(void *opaque);
 
 void do_info_network(void);
+int do_set_link(const char *name, const char *up_or_down);
 
 /* NIC info */
 
-- 
1.6.0.6