[libvirt] [PATCH] qemu: get VM's ip address from the output of arp command

[Chen Hanxiao]

From: Chen Hanxiao <chenhanxiao at gmail.com>

Introduce VIR_DOMAIN_INTERFACE_ADDRESSES_SRC_ARP to get ip address
of VM from the output of `arp -an` command.

We can use:
  domifaddr f26-cloud --source arp
to get the address.

Signed-off-by: Chen Hanxiao <chenhanxiao at gmail.com>
---
 include/libvirt/libvirt-domain.h |   1 +
 src/qemu/qemu_driver.c           | 102 +++++++++++++++++++++++++++++++++++++++
 tools/virsh-domain-monitor.c     |   2 +
 3 files changed, 105 insertions(+)

diff --git a/include/libvirt/libvirt-domain.h b/include/libvirt/libvirt-domain.h
index 4048acf38..38e2d9a3e 100644
--- a/include/libvirt/libvirt-domain.h
+++ b/include/libvirt/libvirt-domain.h
@@ -4665,6 +4665,7 @@ typedef virMemoryParameter *virMemoryParameterPtr;
 typedef enum {
     VIR_DOMAIN_INTERFACE_ADDRESSES_SRC_LEASE = 0, /* Parse DHCP lease file */
     VIR_DOMAIN_INTERFACE_ADDRESSES_SRC_AGENT = 1, /* Query qemu guest agent */
+    VIR_DOMAIN_INTERFACE_ADDRESSES_SRC_ARP = 2, /* Query ARP tables */
 
 # ifdef VIR_ENUM_SENTINELS
     VIR_DOMAIN_INTERFACE_ADDRESSES_SRC_LAST
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index a203c9297..5aaf69442 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -160,6 +160,9 @@ static int qemuGetDHCPInterfaces(virDomainPtr dom,
                                  virDomainObjPtr vm,
                                  virDomainInterfacePtr **ifaces);
 
+static int qemuARPGetInterfaces(virDomainObjPtr vm,
+                                virDomainInterfacePtr **ifaces);
+
 static virQEMUDriverPtr qemu_driver;
 
 
@@ -20384,6 +20387,10 @@ qemuDomainInterfaceAddresses(virDomainPtr dom,
 
         break;
 
+    case VIR_DOMAIN_INTERFACE_ADDRESSES_SRC_ARP:
+        ret = qemuARPGetInterfaces(vm, ifaces);
+        break;
+
     default:
         virReportError(VIR_ERR_ARGUMENT_UNSUPPORTED,
                        _("Unknown IP address data source %d"),
@@ -20494,6 +20501,101 @@ qemuGetDHCPInterfaces(virDomainPtr dom,
 }
 
 
+static int
+qemuARPGetInterfaces(virDomainObjPtr vm,
+                     virDomainInterfacePtr **ifaces)
+{
+    size_t i, j;
+    size_t ifaces_count = 0;
+    int ret = -1;
+    char macaddr[VIR_MAC_STRING_BUFLEN];
+    virDomainInterfacePtr *ifaces_ret = NULL;
+    virDomainInterfacePtr iface = NULL;
+    virCommandPtr cmd = NULL;
+    char *outbuf;
+    char **lines = NULL;
+    char **matches = NULL;
+#define ARP_CMD "/usr/sbin/arp"
+
+    if (!(cmd = virCommandNewArgList(ARP_CMD,
+                                     "-an",
+                                     NULL)))
+        goto cleanup;
+
+    virCommandSetOutputBuffer(cmd, &outbuf);
+
+    if (virCommandRun(cmd, NULL) < 0)
+        goto cleanup;
+
+    lines = virStringSplit(outbuf, "\n", 0);
+    if (lines == NULL)
+        goto cleanup;
+
+    for (i = 0; i < vm->def->nnets; i++) {
+        if (vm->def->nets[i]->type != VIR_DOMAIN_NET_TYPE_NETWORK)
+            continue;
+
+        virMacAddrFormat(&(vm->def->nets[i]->mac), macaddr);
+
+        if (strstr(outbuf, macaddr)) {
+            for (j = 0; lines[j]; j++) {
+                const char *line = lines[j];
+                if (line == NULL)
+                    break;
+                if (strstr(line, macaddr) &&
+                    virStringSearch(line, "\\b([0-9]{1,3}\\.){3}[0-9]{1,3}\\b",
+                                    1, &matches) == 1) {
+
+                    if (VIR_EXPAND_N(ifaces_ret, ifaces_count, 1) < 0)
+                        goto error;
+
+                    if (VIR_ALLOC(ifaces_ret[ifaces_count - 1]) < 0)
+                        goto error;
+
+                    iface = ifaces_ret[ifaces_count - 1];
+                    iface->naddrs = 1;
+                    if (VIR_ALLOC_N(iface->addrs, iface->naddrs) < 0)
+                        goto error;
+
+                    if (VIR_STRDUP(iface->name, vm->def->nets[i]->ifname) < 0)
+                        goto cleanup;
+
+                    if (VIR_STRDUP(iface->hwaddr, macaddr) < 0)
+                        goto cleanup;
+
+                    if (VIR_STRDUP(iface->addrs->addr, matches[0]) < 0)
+                        goto cleanup;
+                }
+            }
+        } else {
+            VIR_DEBUG("Got nothing");
+            continue;
+        }
+    }
+
+    *ifaces = ifaces_ret;
+    ifaces_ret = NULL;
+    ret = ifaces_count;
+
+ cleanup:
+    virCommandFree(cmd);
+    VIR_FREE(outbuf);
+    virStringListFree(lines);
+    virStringListFree(matches);
+    cmd = NULL;
+    return ret;
+
+ error:
+    if (ifaces_ret) {
+        for (i = 0; i < ifaces_count; i++)
+            virDomainInterfaceFree(ifaces_ret[i]);
+    }
+    VIR_FREE(ifaces_ret);
+
+    goto cleanup;
+}
+
+
 static int
 qemuDomainSetUserPassword(virDomainPtr dom,
                           const char *user,
diff --git a/tools/virsh-domain-monitor.c b/tools/virsh-domain-monitor.c
index 32a42707e..68da11ed5 100644
--- a/tools/virsh-domain-monitor.c
+++ b/tools/virsh-domain-monitor.c
@@ -2190,6 +2190,8 @@ cmdDomIfAddr(vshControl *ctl, const vshCmd *cmd)
             source = VIR_DOMAIN_INTERFACE_ADDRESSES_SRC_LEASE;
         } else if (STREQ(sourcestr, "agent")) {
             source = VIR_DOMAIN_INTERFACE_ADDRESSES_SRC_AGENT;
+        } else if (STREQ(sourcestr, "arp")) {
+            source = VIR_DOMAIN_INTERFACE_ADDRESSES_SRC_ARP;
         } else {
             vshError(ctl, _("Unknown data source '%s'"), sourcestr);
             goto cleanup;
-- 
2.14.3