1 | /* $Id: rtmon_bsd.c 106061 2024-09-16 14:03:52Z vboxsync $ */
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2 | /** @file
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3 | * NAT Network - IPv6 default route monitor for BSD routing sockets.
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4 | */
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5 |
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6 | /*
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7 | * Copyright (C) 2013-2024 Oracle and/or its affiliates.
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8 | *
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9 | * This file is part of VirtualBox base platform packages, as
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10 | * available from https://www.virtualbox.org.
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11 | *
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12 | * This program is free software; you can redistribute it and/or
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13 | * modify it under the terms of the GNU General Public License
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14 | * as published by the Free Software Foundation, in version 3 of the
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15 | * License.
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16 | *
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17 | * This program is distributed in the hope that it will be useful, but
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18 | * WITHOUT ANY WARRANTY; without even the implied warranty of
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19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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20 | * General Public License for more details.
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21 | *
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22 | * You should have received a copy of the GNU General Public License
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23 | * along with this program; if not, see <https://www.gnu.org/licenses>.
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24 | *
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25 | * SPDX-License-Identifier: GPL-3.0-only
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26 | */
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27 |
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28 |
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29 | #define LOG_GROUP LOG_GROUP_NAT_SERVICE
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30 |
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31 | #include "proxy.h"
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32 |
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33 | #include <sys/types.h>
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34 | #include <sys/socket.h>
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35 |
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36 | #include <net/if_dl.h>
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37 | #include <net/route.h>
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38 |
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39 | #include <netinet/in.h>
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40 | #include <netinet/ip6.h>
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41 |
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42 | #include <errno.h>
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43 | #include <string.h>
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44 | #include <unistd.h>
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45 |
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46 |
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47 | /**
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48 | * Query IPv6 routing table - BSD routing sockets version.
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49 | *
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50 | * We don't actually monitor the routing socket for updates, and
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51 | * instead query the kernel each time.
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52 | *
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53 | * We take a shortcut and don't read the reply to our RTM_GET - if
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54 | * there's no default IPv6 route, write(2) will fail with ESRCH
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55 | * synchronously. In theory it may fail asynchronously and we should
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56 | * wait for the RTM_GET reply and check rt_msghdr::rtm_errno.
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57 | *
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58 | * KAME code in *BSD maintains internally a list of default routers
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59 | * that it learned from RAs, and installs only one of them into the
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60 | * routing table (actually, I'm not sure if BSD routing table can
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61 | * handle multiple routes to the same destination). One side-effect
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62 | * of this is that when manually configured route (e.g. teredo) is
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63 | * deleted, the system will lose its default route even when KAME IPv6
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64 | * has default router(s) in its internal list. Next RA will force the
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65 | * update, though.
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66 | *
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67 | * Solaris does expose multiple routes in the routing table and
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68 | * replies to RTM_GET with "default default".
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69 | */
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70 | int
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71 | rtmon_get_defaults(void)
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72 | {
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73 | int rtsock;
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74 | struct req {
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75 | struct rt_msghdr rtm;
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76 | struct sockaddr_in6 dst;
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77 | struct sockaddr_in6 mask;
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78 | struct sockaddr_dl ifp;
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79 | } req;
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80 | ssize_t nsent;
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81 |
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82 | rtsock = socket(PF_ROUTE, SOCK_RAW, AF_INET6);
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83 | if (rtsock < 0) {
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84 | DPRINTF0(("rtmon: failed to create routing socket\n"));
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85 | return -1;
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86 | }
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87 |
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88 | memset(&req, 0, sizeof(req));
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89 |
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90 | req.rtm.rtm_type = RTM_GET;
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91 | req.rtm.rtm_version = RTM_VERSION;
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92 | req.rtm.rtm_msglen = sizeof(req);
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93 | req.rtm.rtm_seq = 0x12345;
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94 |
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95 | req.rtm.rtm_flags = RTF_UP;
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96 | req.rtm.rtm_addrs = RTA_DST | RTA_NETMASK | RTA_IFP;
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97 |
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98 | req.dst.sin6_family = AF_INET6;
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99 | #if HAVE_SA_LEN
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100 | req.dst.sin6_len = sizeof(req.dst);
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101 | #endif
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102 |
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103 | req.mask.sin6_family = AF_INET6;
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104 | #if HAVE_SA_LEN
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105 | req.mask.sin6_len = sizeof(req.mask);
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106 | #endif
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107 |
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108 | req.ifp.sdl_family = AF_LINK;
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109 | #if HAVE_SA_LEN
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110 | req.ifp.sdl_len = sizeof(req.ifp);
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111 | #endif
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112 |
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113 | int rc = 1;
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114 | nsent = write(rtsock, &req, req.rtm.rtm_msglen);
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115 | if (nsent < 0) {
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116 | if (errno == ESRCH) {
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117 | /* there's no default route */
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118 | rc = 0;
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119 | }
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120 | else {
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121 | DPRINTF0(("rtmon: failed to send RTM_GET\n"));
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122 | rc = -1;
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123 | }
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124 | }
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125 |
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126 | close(rtsock);
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127 | return rc;
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128 | }
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