lib/rtnetlink.c

   1 /*
   2  * Copyright (c) 2009, 2010 Nicira Networks.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at:
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #include <config.h>
  18
  19 #include "rtnetlink.h"
  20
  21 #include <errno.h>
  22 #include <sys/socket.h>
  23 #include <linux/rtnetlink.h>
  24 #include <net/if.h>
  25 #include <poll.h>
  26
  27 #include "coverage.h"
  28 #include "netlink.h"
  29 #include "ofpbuf.h"
  30 #include "vlog.h"
  31
  32 VLOG_DEFINE_THIS_MODULE(rtnetlink);
  33
  34 COVERAGE_DEFINE(rtnetlink_changed);
  35
  36 /* rtnetlink socket. */
  37 static struct nl_sock *notify_sock;
  38
  39 /* All registered notifiers. */
  40 static struct list all_notifiers = LIST_INITIALIZER(&all_notifiers);
  41
  42 static void rtnetlink_report_change(const struct nlmsghdr *,
  43                                     const struct ifinfomsg *,
  44                                     struct nlattr *attrs[]);
  45 static void rtnetlink_report_notify_error(void);
  46
  47 /* Registers 'cb' to be called with auxiliary data 'aux' with network device
  48  * change notifications.  The notifier is stored in 'notifier', which the
  49  * caller must not modify or free.
  50  *
  51  * This is probably not the function that you want.  You should probably be
  52  * using dpif_port_poll() or netdev_monitor_create(), which unlike this
  53  * function are not Linux-specific.
  54  *
  55  * Returns 0 if successful, otherwise a positive errno value. */
  56 int
  57 rtnetlink_notifier_register(struct rtnetlink_notifier *notifier,
  58                             rtnetlink_notify_func *cb, void *aux)
  59 {
  60     if (!notify_sock) {
  61         int error = nl_sock_create(NETLINK_ROUTE, RTNLGRP_LINK, 0, 0,
  62                                    &notify_sock);
  63         if (error) {
  64             VLOG_WARN("could not create rtnetlink socket: %s",
  65                       strerror(error));
  66             return error;
  67         }
  68     } else {
  69         /* Catch up on notification work so that the new notifier won't
  70          * receive any stale notifications. */
  71         rtnetlink_notifier_run();
  72     }
  73
  74     list_push_back(&all_notifiers, &notifier->node);
  75     notifier->cb = cb;
  76     notifier->aux = aux;
  77     return 0;
  78 }
  79
  80 /* Cancels notification on 'notifier', which must have previously been
  81  * registered with rtnetlink_notifier_register(). */
  82 void
  83 rtnetlink_notifier_unregister(struct rtnetlink_notifier *notifier)
  84 {
  85     list_remove(&notifier->node);
  86     if (list_is_empty(&all_notifiers)) {
  87         nl_sock_destroy(notify_sock);
  88         notify_sock = NULL;
  89     }
  90 }
  91
  92 /* Calls all of the registered notifiers, passing along any as-yet-unreported
  93  * netdev change events. */
  94 void
  95 rtnetlink_notifier_run(void)
  96 {
  97     static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 5);
  98
  99     if (!notify_sock) {
 100         return;
 101     }
 102
 103     for (;;) {
 104         /* Policy for RTNLGRP_LINK messages.
 105          *
 106          * There are *many* more fields in these messages, but currently we
 107          * only care about these fields. */
 108         static const struct nl_policy rtnetlink_policy[] = {
 109             [IFLA_IFNAME] = { .type = NL_A_STRING, .optional = false },
 110             [IFLA_MASTER] = { .type = NL_A_U32, .optional = true },
 111         };
 112
 113         struct nlattr *attrs[ARRAY_SIZE(rtnetlink_policy)];
 114         struct ofpbuf *buf;
 115         int error;
 116
 117         error = nl_sock_recv(notify_sock, &buf, false);
 118         if (!error) {
 119             if (nl_policy_parse(buf, NLMSG_HDRLEN + sizeof(struct ifinfomsg),
 120                                 rtnetlink_policy,
 121                                 attrs, ARRAY_SIZE(rtnetlink_policy))) {
 122                 struct ifinfomsg *ifinfo;
 123
 124                 ifinfo = (void *) ((char *) buf->data + NLMSG_HDRLEN);
 125                 rtnetlink_report_change(buf->data, ifinfo, attrs);
 126             } else {
 127                 VLOG_WARN_RL(&rl, "received bad rtnl message");
 128                 rtnetlink_report_notify_error();
 129             }
 130             ofpbuf_delete(buf);
 131         } else if (error == EAGAIN) {
 132             return;
 133         } else {
 134             if (error == ENOBUFS) {
 135                 VLOG_WARN_RL(&rl, "rtnetlink receive buffer overflowed");
 136             } else {
 137                 VLOG_WARN_RL(&rl, "error reading rtnetlink socket: %s",
 138                              strerror(error));
 139             }
 140             rtnetlink_report_notify_error();
 141         }
 142     }
 143 }
 144
 145 /* Causes poll_block() to wake up when network device change notifications are
 146  * ready. */
 147 void
 148 rtnetlink_notifier_wait(void)
 149 {
 150     if (notify_sock) {
 151         nl_sock_wait(notify_sock, POLLIN);
 152     }
 153 }
 154
 155 static void
 156 rtnetlink_report_change(const struct nlmsghdr *nlmsg,
 157                            const struct ifinfomsg *ifinfo,
 158                            struct nlattr *attrs[])
 159 {
 160     struct rtnetlink_notifier *notifier;
 161     struct rtnetlink_change change;
 162
 163     COVERAGE_INC(rtnetlink_changed);
 164
 165     change.nlmsg_type = nlmsg->nlmsg_type;
 166     change.ifi_index = ifinfo->ifi_index;
 167     change.ifname = nl_attr_get_string(attrs[IFLA_IFNAME]);
 168     change.master_ifindex = (attrs[IFLA_MASTER]
 169                              ? nl_attr_get_u32(attrs[IFLA_MASTER]) : 0);
 170
 171     LIST_FOR_EACH (notifier, node, &all_notifiers) {
 172         notifier->cb(&change, notifier->aux);
 173     }
 174 }
 175
 176 static void
 177 rtnetlink_report_notify_error(void)
 178 {
 179     struct rtnetlink_notifier *notifier;
 180
 181     LIST_FOR_EACH (notifier, node, &all_notifiers) {
 182         notifier->cb(NULL, notifier->aux);
 183     }
 184 }