lib/rtnetlink.c

   1 /*
   2  * Copyright (c) 2009 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
  31 #define THIS_MODULE VLM_rtnetlink
  32 #include "vlog.h"
  33
  34 /* rtnetlink socket. */
  35 static struct nl_sock *notify_sock;
  36
  37 /* All registered notifiers. */
  38 static struct list all_notifiers = LIST_INITIALIZER(&all_notifiers);
  39
  40 static void rtnetlink_report_change(const struct nlmsghdr *,
  41                                     const struct ifinfomsg *,
  42                                     struct nlattr *attrs[]);
  43 static void rtnetlink_report_notify_error(void);
  44
  45 /* Registers 'cb' to be called with auxiliary data 'aux' with network device
  46  * change notifications.  The notifier is stored in 'notifier', which the
  47  * caller must not modify or free.
  48  *
  49  * This is probably not the function that you want.  You should probably be
  50  * using dpif_port_poll() or netdev_monitor_create(), which unlike this
  51  * function are not Linux-specific.
  52  *
  53  * Returns 0 if successful, otherwise a positive errno value. */
  54 int
  55 rtnetlink_notifier_register(struct rtnetlink_notifier *notifier,
  56                             rtnetlink_notify_func *cb, void *aux)
  57 {
  58     if (!notify_sock) {
  59         int error = nl_sock_create(NETLINK_ROUTE, RTNLGRP_LINK, 0, 0,
  60                                    &notify_sock);
  61         if (error) {
  62             VLOG_WARN("could not create rtnetlink socket: %s",
  63                       strerror(error));
  64             return error;
  65         }
  66     } else {
  67         /* Catch up on notification work so that the new notifier won't
  68          * receive any stale notifications. */
  69         rtnetlink_notifier_run();
  70     }
  71
  72     list_push_back(&all_notifiers, &notifier->node);
  73     notifier->cb = cb;
  74     notifier->aux = aux;
  75     return 0;
  76 }
  77
  78 /* Cancels notification on 'notifier', which must have previously been
  79  * registered with lxnetdev_notifier_register(). */
  80 void
  81 rtnetlink_notifier_unregister(struct rtnetlink_notifier *notifier)
  82 {
  83     list_remove(&notifier->node);
  84     if (list_is_empty(&all_notifiers)) {
  85         nl_sock_destroy(notify_sock);
  86         notify_sock = NULL;
  87     }
  88 }
  89
  90 /* Calls all of the registered notifiers, passing along any as-yet-unreported
  91  * netdev change events. */
  92 void
  93 rtnetlink_notifier_run(void)
  94 {
  95     static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 5);
  96
  97     if (!notify_sock) {
  98         return;
  99     }
 100
 101     for (;;) {
 102         /* Policy for RTNLGRP_LINK messages.
 103          *
 104          * There are *many* more fields in these messages, but currently we
 105          * only care about these fields. */
 106         static const struct nl_policy rtnetlink_policy[] = {
 107             [IFLA_IFNAME] = { .type = NL_A_STRING, .optional = false },
 108             [IFLA_MASTER] = { .type = NL_A_U32, .optional = true },
 109         };
 110
 111         struct nlattr *attrs[ARRAY_SIZE(rtnetlink_policy)];
 112         struct ofpbuf *buf;
 113         int error;
 114
 115         error = nl_sock_recv(notify_sock, &buf, false);
 116         if (!error) {
 117             if (nl_policy_parse(buf, NLMSG_HDRLEN + sizeof(struct ifinfomsg),
 118                                 rtnetlink_policy,
 119                                 attrs, ARRAY_SIZE(rtnetlink_policy))) {
 120                 struct ifinfomsg *ifinfo;
 121
 122                 ifinfo = (void *) ((char *) buf->data + NLMSG_HDRLEN);
 123                 rtnetlink_report_change(buf->data, ifinfo, attrs);
 124             } else {
 125                 VLOG_WARN_RL(&rl, "received bad rtnl message");
 126                 rtnetlink_report_notify_error();
 127             }
 128             ofpbuf_delete(buf);
 129         } else if (error == EAGAIN) {
 130             return;
 131         } else {
 132             if (error == ENOBUFS) {
 133                 VLOG_WARN_RL(&rl, "rtnetlink receive buffer overflowed");
 134             } else {
 135                 VLOG_WARN_RL(&rl, "error reading rtnetlink socket: %s",
 136                              strerror(error));
 137             }
 138             rtnetlink_report_notify_error();
 139         }
 140     }
 141 }
 142
 143 /* Causes poll_block() to wake up when network device change notifications are
 144  * ready. */
 145 void
 146 rtnetlink_notifier_wait(void)
 147 {
 148     if (notify_sock) {
 149         nl_sock_wait(notify_sock, POLLIN);
 150     }
 151 }
 152
 153 static void
 154 rtnetlink_report_change(const struct nlmsghdr *nlmsg,
 155                            const struct ifinfomsg *ifinfo,
 156                            struct nlattr *attrs[])
 157 {
 158     struct rtnetlink_notifier *notifier;
 159     struct rtnetlink_change change;
 160
 161     COVERAGE_INC(rtnetlink_changed);
 162
 163     change.nlmsg_type = nlmsg->nlmsg_type;
 164     change.ifi_index = ifinfo->ifi_index;
 165     change.ifname = nl_attr_get_string(attrs[IFLA_IFNAME]);
 166     change.master_ifindex = (attrs[IFLA_MASTER]
 167                              ? nl_attr_get_u32(attrs[IFLA_MASTER]) : 0);
 168
 169     LIST_FOR_EACH (notifier, struct rtnetlink_notifier, node,
 170                    &all_notifiers) {
 171         notifier->cb(&change, notifier->aux);
 172     }
 173 }
 174
 175 static void
 176 rtnetlink_report_notify_error(void)
 177 {
 178     struct rtnetlink_notifier *notifier;
 179
 180     LIST_FOR_EACH (notifier, struct rtnetlink_notifier, node,
 181                    &all_notifiers) {
 182         notifier->cb(NULL, notifier->aux);
 183     }
 184 }