sitnl: implement net_iface_new and net_iface_del

These two new methods can be used to create and delete a tun or an
ovpn-dco interface via RTNL API.

Signed-off-by: Antonio Quartulli <antonio@openvpn.net>
Signed-off-by: Lev Stipakov <lev@openvpn.net>

openvpn/tun/linux/client/sitnl.hpp

@@ -831,6 +831,80 @@ err:
 	return ret;
       }
 
+      /**
+       * @brief Add new interface (similar to ip link add)
+       *
+       * @param iface interface name
+       * @param type interface link type (for example "ovpn-dco")
+       * @return int 0 on success, negative error code on error
+       */
+      static int
+      net_iface_new(const std::string& iface, const std::string& type)
+      {
+	struct sitnl_link_req req = { };
+	struct rtattr *tail = NULL;
+	int ret = -1;
+
+	if (iface.empty())
+	{
+	  OPENVPN_LOG(__func__ << ": passed empty interface");
+	  return -EINVAL;
+	}
+
+	req.n.nlmsg_len = NLMSG_LENGTH(sizeof(req.i));
+	req.n.nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE | NLM_F_EXCL;
+	req.n.nlmsg_type = RTM_NEWLINK;
+
+	SITNL_ADDATTR(&req.n, sizeof(req), IFLA_IFNAME, iface.c_str(),
+		      iface.length() + 1);
+	tail = NLMSG_TAIL(&req.n);
+	SITNL_ADDATTR(&req.n, sizeof(req), IFLA_LINKINFO, NULL, 0);
+	SITNL_ADDATTR(&req.n, sizeof(req), IFLA_INFO_KIND, type.c_str(),
+		      type.length() + 1);
+	tail->rta_len = (uint8_t *)NLMSG_TAIL(&req.n) - (uint8_t *)tail;
+
+	req.i.ifi_family = AF_PACKET;
+	req.i.ifi_index = 0;
+
+	OPENVPN_LOG(__func__ << ": add " << iface << " type " << type);
+
+	ret = sitnl_send(&req.n, 0, 0, NULL, NULL);
+err:
+	return ret;
+      }
+
+      static int
+      net_iface_del(const std::string& iface)
+      {
+	struct sitnl_link_req req = { };
+	int ifindex;
+
+	if (iface.empty())
+	{
+	  OPENVPN_LOG(__func__ << ": passed empty interface");
+	  return -EINVAL;
+	}
+
+	ifindex = if_nametoindex(iface.c_str());
+	if (ifindex == 0)
+	{
+	  OPENVPN_LOG(__func__ << ": rtnl: cannot get ifindex for " << iface
+		      << ": " << strerror(errno));
+	  return -ENOENT;
+	}
+
+	req.n.nlmsg_len = NLMSG_LENGTH(sizeof(req.i));
+	req.n.nlmsg_flags = NLM_F_REQUEST;
+	req.n.nlmsg_type = RTM_DELLINK;
+
+	req.i.ifi_family = AF_PACKET;
+	req.i.ifi_index = ifindex;
+
+	OPENVPN_LOG(__func__ << ": idel " << iface);
+
+	return sitnl_send(&req.n, 0, 0, NULL, NULL);
+      }
+
       static int
       net_iface_up(std::string& iface, bool up)
       {

openvpn/tun/linux/client/tunnetlink.hpp

@@ -431,6 +431,58 @@ namespace openvpn {
       R_ADD_ALL=R_ADD_SYS|R_ADD_DCO,
     };
 
+    /**
+     * @brief Add new interface
+     *
+     * @param os output stream to where error message is written
+     * @param dev interface name
+     * @param type interface link type (such as "ovpn-dco")
+     * @return int 0 on success, negative error code on error
+     */
+    inline int iface_new(std::ostringstream& os, const std::string& dev, const std::string& type)
+    {
+      int ret = -1;
+
+      if (dev.empty())
+      {
+	os << "Error: can't call NetlinkLinkNew with no interface" << std::endl;
+	return ret;
+      }
+
+      if (type.empty())
+      {
+	os << "Error: can't call NetlinkLinkNew with no interfacei type" << std::endl;
+	return ret;
+      }
+
+      ret = SITNL::net_iface_new(dev, type);
+      if (ret)
+      {
+	os << "Error while executing NetlinkLinkNew " << dev << ": " << ret << std::endl;
+      }
+
+      return ret;
+    }
+
+    inline int iface_del(std::ostringstream& os, const std::string& dev)
+    {
+      int ret = -1;
+
+      if (dev.empty())
+      {
+	os << "Error: can't call NetlinkLinkDel with no interface" << std::endl;
+	return ret;
+      }
+
+      ret = SITNL::net_iface_del(dev);
+      if (ret)
+      {
+	os << "Error while executing NetlinkLinkDel " << dev << ": " << ret << std::endl;
+      }
+
+      return ret;
+    }
+
     /*inline IPv4::Addr cvt_pnr_ip_v4(const std::string& hexaddr)
     {
       BufferAllocated v(4, BufferAllocated::CONSTRUCT_ZERO);