src/rtnetlink.c

   1 /**
   2  * Copyright (C) 2012 Steven Barth <steven@midlink.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License v2 as published by
   6  * the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  */
  14
  15 #include <time.h>
  16 #include <errno.h>
  17 #include <stdlib.h>
  18 #include <string.h>
  19 #include <syslog.h>
  20 #include <stdbool.h>
  21 #include <arpa/inet.h>
  22 #include <sys/socket.h>
  23 #include <linux/rtnetlink.h>
  24
  25 #include "odhcp6c.h"
  26
  27
  28 static int sock = -1;
  29 static unsigned seq = 0;
  30
  31
  32 // Init rtnetlink socket
  33 int init_rtnetlink(void)
  34 {
  35         sock = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE);
  36         struct sockaddr_nl rtnl_kernel = { .nl_family = AF_NETLINK };
  37         if (connect(sock, (struct sockaddr*)&rtnl_kernel, sizeof(rtnl_kernel)))
  38                 return -1;
  39
  40         return 0;
  41 }
  42
  43
  44 // CRUD addresses to interface
  45 int set_rtnetlink_addr(int ifindex, const struct in6_addr *addr,
  46                 time_t pref, time_t valid)
  47 {
  48         int flags = NLM_F_REQUEST | NLM_F_ACK;
  49         int cmd = RTM_DELADDR;
  50
  51         if (valid > 0) {
  52                 flags |= NLM_F_CREATE | NLM_F_REPLACE;
  53                 cmd = RTM_NEWADDR;
  54         }
  55
  56         struct {
  57                 struct nlmsghdr nhm;
  58                 struct ifaddrmsg ifa;
  59                 struct rtattr rta_addr;
  60                 struct in6_addr addr;
  61                 struct rtattr rta_local;
  62                 struct in6_addr local;
  63                 struct rtattr rta_info;
  64                 struct ifa_cacheinfo info;
  65         } req = {
  66                 {sizeof(req), cmd, flags, ++seq, 0},
  67                 {AF_INET6, 128, 0, RT_SCOPE_UNIVERSE, ifindex},
  68                 {sizeof(req.rta_addr) + sizeof(req.addr), IFA_ADDRESS},
  69                 *addr,
  70                 {sizeof(req.rta_local) + sizeof(req.local), IFA_LOCAL},
  71                 *addr,
  72                 {sizeof(req.rta_info) + sizeof(req.info), IFA_CACHEINFO},
  73                 {pref, valid, 0, 0}
  74         };
  75         send(sock, &req, sizeof(req), 0);
  76
  77         struct {
  78                 struct nlmsghdr nhm;
  79                 struct nlmsgerr err;
  80         } reply;
  81         recv(sock, &reply, sizeof(reply), 0);
  82
  83         char buf[INET6_ADDRSTRLEN];
  84         inet_ntop(AF_INET6, addr, buf, sizeof(buf));
  85         syslog(LOG_WARNING, "%s address %s/128 for iface %i: %s",
  86                         (valid) ? "assigning" : "removing", buf,
  87                         ifindex, strerror(-reply.err.error));
  88
  89         if (reply.err.error < 0 || valid == 0)
  90                 return reply.err.error;
  91
  92         // Check for duplicate addresses
  93         struct timespec ts = {1, 0};
  94         nanosleep(&ts, NULL);
  95
  96         req.nhm.nlmsg_type = RTM_GETADDR;
  97         req.nhm.nlmsg_seq = ++seq;
  98         req.nhm.nlmsg_flags = NLM_F_REQUEST;
  99         send(sock, &req, sizeof(req), 0);
 100
 101         struct {
 102                 struct nlmsghdr nhm;
 103                 struct ifaddrmsg ifa;
 104                 uint8_t buf[1024];
 105         } dad_reply;
 106         recv(sock, &dad_reply, sizeof(dad_reply), 0);
 107
 108         if (dad_reply.nhm.nlmsg_type != RTM_NEWADDR ||
 109                         (dad_reply.ifa.ifa_flags & IFA_F_DADFAILED)) {
 110                 syslog(LOG_WARNING, "Removing duplicate address %s", buf);
 111                 set_rtnetlink_addr(ifindex, addr, 0, 0);
 112                 return -EADDRNOTAVAIL;
 113         }
 114         return 0;
 115 }