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      1 /*
      2  * Copyright 2012 Daniel Drown
      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  * netlink_msg.c - send an ifaddrmsg/ifinfomsg/rtmsg via netlink
     17  */
     18 
     19 #include <netinet/in.h>
     20 #include <linux/netlink.h>
     21 #include <linux/rtnetlink.h>
     22 #include <string.h>
     23 #include <errno.h>
     24 
     25 #include <netlink-local.h>
     26 #include <netlink-types.h>
     27 #include <netlink/socket.h>
     28 #include <netlink/netlink.h>
     29 #include <netlink/msg.h>
     30 
     31 #include "netlink_msg.h"
     32 #include "netlink_callbacks.h"
     33 
     34 /* function: family_size
     35  * returns the size of the address structure for the given family, or 0 on error
     36  * family - AF_INET or AF_INET6
     37  */
     38 size_t inet_family_size(int family) {
     39   if(family == AF_INET) {
     40     return sizeof(struct in_addr);
     41   } else if(family == AF_INET6) {
     42     return sizeof(struct in6_addr);
     43   } else {
     44     return 0;
     45   }
     46 }
     47 
     48 /* function: nlmsg_alloc_generic
     49  * allocates a netlink message with the given struct inside of it. returns NULL on failure
     50  * type           - netlink message type
     51  * flags          - netlink message flags
     52  * payload_struct - pointer to a struct to add to netlink message
     53  * payload_len    - bytelength of structure
     54  */
     55 struct nl_msg *nlmsg_alloc_generic(uint16_t type, uint16_t flags, void *payload_struct, size_t payload_len) {
     56   struct nl_msg *msg;
     57 
     58   msg = nlmsg_alloc();
     59   if(!msg) {
     60     return NULL;
     61   }
     62 
     63   if ((sizeof(struct nl_msg) + payload_len) > msg->nm_size) {
     64     nlmsg_free(msg);
     65     return NULL;
     66   }
     67 
     68   msg->nm_nlh->nlmsg_len = NLMSG_LENGTH(payload_len);
     69   msg->nm_nlh->nlmsg_flags = flags;
     70   msg->nm_nlh->nlmsg_type = type;
     71 
     72   memcpy(nlmsg_data(msg->nm_nlh), payload_struct, payload_len);
     73 
     74   return msg;
     75 }
     76 
     77 /* function: nlmsg_alloc_ifaddr
     78  * allocates a netlink message with a struct ifaddrmsg inside of it. returns NULL on failure
     79  * type  - netlink message type
     80  * flags - netlink message flags
     81  * ifa   - ifaddrmsg to copy into the new netlink message
     82  */
     83 struct nl_msg *nlmsg_alloc_ifaddr(uint16_t type, uint16_t flags, struct ifaddrmsg *ifa) {
     84   return nlmsg_alloc_generic(type, flags, ifa, sizeof(*ifa));
     85 }
     86 
     87 /* function: nlmsg_alloc_ifinfo
     88  * allocates a netlink message with a struct ifinfomsg inside of it. returns NULL on failure
     89  * type  - netlink message type
     90  * flags - netlink message flags
     91  * ifi   - ifinfomsg to copy into the new netlink message
     92  */
     93 struct nl_msg *nlmsg_alloc_ifinfo(uint16_t type, uint16_t flags, struct ifinfomsg *ifi) {
     94   return nlmsg_alloc_generic(type, flags, ifi, sizeof(*ifi));
     95 }
     96 
     97 /* function: nlmsg_alloc_rtmsg
     98  * allocates a netlink message with a struct rtmsg inside of it. returns NULL on failure
     99  * type  - netlink message type
    100  * flags - netlink message flags
    101  * rt    - rtmsg to copy into the new netlink message
    102  */
    103 struct nl_msg *nlmsg_alloc_rtmsg(uint16_t type, uint16_t flags, struct rtmsg *rt) {
    104   return nlmsg_alloc_generic(type, flags, rt, sizeof(*rt));
    105 }
    106 
    107 /* function: netlink_set_kernel_only
    108  * sets a socket to receive messages only from the kernel
    109  * sock - socket to connect
    110  */
    111 int netlink_set_kernel_only(struct nl_sock *nl_sk) {
    112   struct sockaddr_nl addr = { AF_NETLINK, 0, 0, 0 };
    113 
    114   if (!nl_sk) {
    115     return -EFAULT;
    116   }
    117 
    118   int sockfd = nl_socket_get_fd(nl_sk);
    119   return connect(sockfd, (struct sockaddr *) &addr, sizeof(addr));
    120 }
    121 
    122 /* function: send_netlink_msg
    123  * sends a netlink message, reads a response, and hands the response(s) to the callbacks
    124  * msg       - netlink message to send
    125  * callbacks - callbacks to use on responses
    126  */
    127 void send_netlink_msg(struct nl_msg *msg, struct nl_cb *callbacks) {
    128   struct nl_sock *nl_sk;
    129 
    130   nl_sk = nl_socket_alloc();
    131   if(!nl_sk)
    132     goto cleanup;
    133 
    134   if(nl_connect(nl_sk, NETLINK_ROUTE) != 0)
    135     goto cleanup;
    136 
    137   if(nl_send_auto_complete(nl_sk, msg) < 0)
    138     goto cleanup;
    139 
    140   if(netlink_set_kernel_only(nl_sk) < 0)
    141     goto cleanup;
    142 
    143   nl_recvmsgs(nl_sk, callbacks);
    144 
    145 cleanup:
    146   if(nl_sk)
    147     nl_socket_free(nl_sk);
    148 }
    149 
    150 /* function: send_ifaddrmsg
    151  * sends a netlink/ifaddrmsg message and hands the responses to the callbacks
    152  * type      - netlink message type
    153  * flags     - netlink message flags
    154  * ifa       - ifaddrmsg to send
    155  * callbacks - callbacks to use with the responses
    156  */
    157 void send_ifaddrmsg(uint16_t type, uint16_t flags, struct ifaddrmsg *ifa, struct nl_cb *callbacks) {
    158   struct nl_msg *msg = NULL;
    159 
    160   msg = nlmsg_alloc_ifaddr(type, flags, ifa);
    161   if(!msg)
    162     return;
    163 
    164   send_netlink_msg(msg, callbacks);
    165 
    166   nlmsg_free(msg);
    167 }
    168 
    169 /* function: netlink_sendrecv
    170  * send a nl_msg and return an int status - only supports OK/ERROR responses
    171  * msg - msg to send
    172  */
    173 int netlink_sendrecv(struct nl_msg *msg) {
    174   struct nl_cb *callbacks = NULL;
    175   int retval = -EIO;
    176 
    177   callbacks = alloc_ack_callbacks(&retval);
    178   if(!callbacks) {
    179     return -ENOMEM;
    180   }
    181 
    182   send_netlink_msg(msg, callbacks);
    183 
    184   nl_cb_put(callbacks);
    185 
    186   return retval;
    187 }
    188