util: netlink: Introduce virNetlinkNewLink helper

This patch introduces virNetlinkNewLink helper which wraps the common
libnl/netlink code to create a new link.

Signed-off-by: Shi Lei <shi_lei@massclouds.com>
Signed-off-by: Erik Skultety <eskultet@redhat.com>

src/libvirt_private.syms

@@ -2446,6 +2446,7 @@ virNetlinkEventServiceStop;
 virNetlinkEventServiceStopAll;
 virNetlinkGetErrorCode;
 virNetlinkGetNeighbor;
+virNetlinkNewLink;
 virNetlinkShutdown;
 virNetlinkStartup;
 

src/util/virnetlink.c

@@ -488,6 +488,131 @@ virNetlinkDumpLink(const char *ifname, int ifindex,
 }
 
 
+/**
+ * virNetlinkNewLink:
+ *
+ * @ifname: name of the link
+ * @type: the type of the device, i.e. "bridge", "macvtap", "macvlan"
+ * @extra_args: the extra args for creating the netlink interface
+ * @error: netlink error code
+ *
+ * A generic wrapper to create a network link.
+ *
+ * Returns 0 on success, -1 on error. Additionally, if the @error is
+ * non-zero, then a failure occurred during virNetlinkCommand, but
+ * no error message is generated leaving it up to the caller to handle
+ * the condition.
+ */
+int
+virNetlinkNewLink(const char *ifname,
+                  const char *type,
+                  virNetlinkNewLinkDataPtr extra_args,
+                  int *error)
+{
+    struct nlmsgerr *err;
+    struct nlattr *linkinfo = NULL;
+    struct nlattr *infodata = NULL;
+    unsigned int buflen;
+    struct ifinfomsg ifinfo = { .ifi_family = AF_UNSPEC };
+    VIR_AUTOPTR(virNetlinkMsg) nl_msg = NULL;
+    VIR_AUTOFREE(struct nlmsghdr *) resp = NULL;
+
+    *error = 0;
+
+    VIR_DEBUG("Creating %s interface '%s'", type, ifname);
+
+    if (!ifname || !type) {
+        virReportError(VIR_ERR_INVALID_ARG, "%s",
+                       _("both interface name and type must not be NULL"));
+        return -1;
+    }
+
+    nl_msg = nlmsg_alloc_simple(RTM_NEWLINK,
+                                NLM_F_REQUEST | NLM_F_CREATE | NLM_F_EXCL);
+    if (!nl_msg) {
+        virReportOOMError();
+        return -1;
+    }
+
+    if (nlmsg_append(nl_msg,  &ifinfo, sizeof(ifinfo), NLMSG_ALIGNTO) < 0)
+        goto buffer_too_small;
+
+    if (ifname && nla_put(nl_msg, IFLA_IFNAME,
+                          (strlen(ifname) + 1), ifname) < 0)
+        goto buffer_too_small;
+
+    if (!(linkinfo = nla_nest_start(nl_msg, IFLA_LINKINFO)))
+        goto buffer_too_small;
+
+    if (type && nla_put(nl_msg, IFLA_INFO_KIND, (strlen(type) + 1), type) < 0)
+        goto buffer_too_small;
+
+    if ((STREQ(type, "macvtap") || STREQ(type, "macvlan")) &&
+         extra_args &&
+         extra_args->macvlan_mode &&
+         *extra_args->macvlan_mode > 0) {
+        if (!(infodata = nla_nest_start(nl_msg, IFLA_INFO_DATA)))
+            goto buffer_too_small;
+
+        if (nla_put(nl_msg, IFLA_MACVLAN_MODE,
+                    sizeof(uint32_t), extra_args->macvlan_mode) < 0)
+            goto buffer_too_small;
+
+        nla_nest_end(nl_msg, infodata);
+    }
+
+    nla_nest_end(nl_msg, linkinfo);
+
+    if (extra_args) {
+        if (extra_args->ifindex &&
+            nla_put(nl_msg, IFLA_LINK,
+                    sizeof(uint32_t), extra_args->ifindex) < 0)
+            goto buffer_too_small;
+
+        if (extra_args->mac &&
+            nla_put(nl_msg, IFLA_ADDRESS, VIR_MAC_BUFLEN, extra_args->mac) < 0)
+            goto buffer_too_small;
+    }
+
+    if (virNetlinkCommand(nl_msg, &resp, &buflen, 0, 0, NETLINK_ROUTE, 0) < 0)
+        return -1;
+
+    if (buflen < NLMSG_LENGTH(0) || resp == NULL)
+        goto malformed_resp;
+
+    switch (resp->nlmsg_type) {
+    case NLMSG_ERROR:
+        err = (struct nlmsgerr *)NLMSG_DATA(resp);
+        if (resp->nlmsg_len < NLMSG_LENGTH(sizeof(*err)))
+            goto malformed_resp;
+
+        if (err->error < 0) {
+            *error = err->error;
+            return -1;
+        }
+        break;
+
+    case NLMSG_DONE:
+        break;
+
+    default:
+        goto malformed_resp;
+    }
+
+    return 0;
+
+ malformed_resp:
+    virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                   _("malformed netlink response message"));
+    return -1;
+
+ buffer_too_small:
+    virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                   _("allocated netlink buffer is too small"));
+    return -1;
+}
+
+
 /**
  * virNetlinkDelLink:
  *
@@ -1182,6 +1307,17 @@ virNetlinkDelLink(const char *ifname ATTRIBUTE_UNUSED,
 }
 
 
+int
+virNetlinkNewLink(const char *ifname ATTRIBUTE_UNUSED,
+                  const char *type ATTRIBUTE_UNUSED,
+                  virNetlinkNewLinkDataPtr extra_args ATTRIBUTE_UNUSED,
+                  int *error ATTRIBUTE_UNUSED)
+{
+    virReportError(VIR_ERR_INTERNAL_ERROR, "%s", _(unsupported));
+    return -1;
+}
+
+
 int
 virNetlinkGetNeighbor(void **nlData ATTRIBUTE_UNUSED,
                       uint32_t src_pid ATTRIBUTE_UNUSED,

src/util/virnetlink.h

@@ -65,6 +65,19 @@ int virNetlinkDumpCommand(struct nl_msg *nl_msg,
                           unsigned int protocol, unsigned int groups,
                           void *opaque);
 
+typedef struct _virNetlinkNewLinkData virNetlinkNewLinkData;
+typedef virNetlinkNewLinkData *virNetlinkNewLinkDataPtr;
+struct _virNetlinkNewLinkData {
+    const int *ifindex;             /* The index for the 'link' device */
+    const virMacAddr *mac;          /* The MAC address of the device */
+    const uint32_t *macvlan_mode;   /* The mode of macvlan */
+};
+
+int virNetlinkNewLink(const char *ifname,
+                      const char *type,
+                      virNetlinkNewLinkDataPtr data,
+                      int *error);
+
 typedef int (*virNetlinkDelLinkFallback)(const char *ifname);
 
 int virNetlinkDelLink(const char *ifname, virNetlinkDelLinkFallback fallback);