1 /* dnsmasq is Copyright (c) 2000-2009 Simon Kelley 2 3 This program is free software; you can redistribute it and/or modify 4 it under the terms of the GNU General Public License as published by 5 the Free Software Foundation; version 2 dated June, 1991, or 6 (at your option) version 3 dated 29 June, 2007. 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 You should have received a copy of the GNU General Public License 14 along with this program. If not, see <http://www.gnu.org/licenses/>. 15 */ 16 17 #include "dnsmasq.h" 18 19 #ifdef HAVE_LINUX_NETWORK 20 21 #include <linux/types.h> 22 #include <linux/netlink.h> 23 #include <linux/rtnetlink.h> 24 25 /* linux 2.6.19 buggers up the headers, patch it up here. */ 26 #ifndef IFA_RTA 27 # define IFA_RTA(r) \ 28 ((struct rtattr*)(((char*)(r)) + NLMSG_ALIGN(sizeof(struct ifaddrmsg)))) 29 30 # include <linux/if_addr.h> 31 #endif 32 33 static struct iovec iov; 34 static u32 netlink_pid; 35 36 static void nl_err(struct nlmsghdr *h); 37 static void nl_routechange(struct nlmsghdr *h); 38 39 void netlink_init(void) 40 { 41 struct sockaddr_nl addr; 42 socklen_t slen = sizeof(addr); 43 44 addr.nl_family = AF_NETLINK; 45 addr.nl_pad = 0; 46 addr.nl_pid = 0; /* autobind */ 47 #ifdef HAVE_IPV6 48 addr.nl_groups = RTMGRP_IPV4_ROUTE | RTMGRP_IPV6_ROUTE; 49 #else 50 addr.nl_groups = RTMGRP_IPV4_ROUTE; 51 #endif 52 53 /* May not be able to have permission to set multicast groups don't die in that case */ 54 if ((daemon->netlinkfd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE)) != -1) 55 { 56 if (bind(daemon->netlinkfd, (struct sockaddr *)&addr, sizeof(addr)) == -1) 57 { 58 addr.nl_groups = 0; 59 if (errno != EPERM || bind(daemon->netlinkfd, (struct sockaddr *)&addr, sizeof(addr)) == -1) 60 daemon->netlinkfd = -1; 61 } 62 } 63 64 if (daemon->netlinkfd == -1 || 65 getsockname(daemon->netlinkfd, (struct sockaddr *)&addr, &slen) == 1) 66 die(_("cannot create netlink socket: %s"), NULL, EC_MISC); 67 68 /* save pid assigned by bind() and retrieved by getsockname() */ 69 netlink_pid = addr.nl_pid; 70 71 iov.iov_len = 100; 72 iov.iov_base = safe_malloc(iov.iov_len); 73 } 74 75 static ssize_t netlink_recv(void) 76 { 77 struct msghdr msg; 78 struct sockaddr_nl nladdr; 79 ssize_t rc; 80 81 while (1) 82 { 83 msg.msg_control = NULL; 84 msg.msg_controllen = 0; 85 msg.msg_name = &nladdr; 86 msg.msg_namelen = sizeof(nladdr); 87 msg.msg_iov = &iov; 88 msg.msg_iovlen = 1; 89 msg.msg_flags = 0; 90 91 while ((rc = recvmsg(daemon->netlinkfd, &msg, MSG_PEEK | MSG_TRUNC)) == -1 && errno == EINTR); 92 93 /* make buffer big enough */ 94 if (rc != -1 && (msg.msg_flags & MSG_TRUNC)) 95 { 96 /* Very new Linux kernels return the actual size needed, older ones always return truncated size */ 97 if ((size_t)rc == iov.iov_len) 98 { 99 if (expand_buf(&iov, rc + 100)) 100 continue; 101 } 102 else 103 expand_buf(&iov, rc); 104 } 105 106 /* read it for real */ 107 msg.msg_flags = 0; 108 while ((rc = recvmsg(daemon->netlinkfd, &msg, 0)) == -1 && errno == EINTR); 109 110 /* Make sure this is from the kernel */ 111 if (rc == -1 || nladdr.nl_pid == 0) 112 break; 113 } 114 115 /* discard stuff which is truncated at this point (expand_buf() may fail) */ 116 if (msg.msg_flags & MSG_TRUNC) 117 { 118 rc = -1; 119 errno = ENOMEM; 120 } 121 122 return rc; 123 } 124 125 int iface_enumerate(void *parm, int (*ipv4_callback)(), int (*ipv6_callback)()) 126 { 127 struct sockaddr_nl addr; 128 struct nlmsghdr *h; 129 ssize_t len; 130 static unsigned int seq = 0; 131 int family = AF_INET; 132 133 struct { 134 struct nlmsghdr nlh; 135 struct rtgenmsg g; 136 } req; 137 138 addr.nl_family = AF_NETLINK; 139 addr.nl_pad = 0; 140 addr.nl_groups = 0; 141 addr.nl_pid = 0; /* address to kernel */ 142 143 again: 144 req.nlh.nlmsg_len = sizeof(req); 145 req.nlh.nlmsg_type = RTM_GETADDR; 146 req.nlh.nlmsg_flags = NLM_F_ROOT | NLM_F_MATCH | NLM_F_REQUEST | NLM_F_ACK; 147 req.nlh.nlmsg_pid = 0; 148 req.nlh.nlmsg_seq = ++seq; 149 req.g.rtgen_family = family; 150 151 /* Don't block in recvfrom if send fails */ 152 while((len = sendto(daemon->netlinkfd, (void *)&req, sizeof(req), 0, 153 (struct sockaddr *)&addr, sizeof(addr))) == -1 && retry_send()); 154 155 if (len == -1) 156 return 0; 157 158 while (1) 159 { 160 if ((len = netlink_recv()) == -1) 161 { 162 if (errno == ENOBUFS) 163 { 164 sleep(1); 165 goto again; 166 } 167 return 0; 168 } 169 170 for (h = (struct nlmsghdr *)iov.iov_base; NLMSG_OK(h, (size_t)len); h = NLMSG_NEXT(h, len)) 171 if (h->nlmsg_seq != seq || h->nlmsg_pid != netlink_pid) 172 nl_routechange(h); /* May be multicast arriving async */ 173 else if (h->nlmsg_type == NLMSG_ERROR) 174 nl_err(h); 175 else if (h->nlmsg_type == NLMSG_DONE) 176 { 177 #ifdef HAVE_IPV6 178 if (family == AF_INET && ipv6_callback) 179 { 180 family = AF_INET6; 181 goto again; 182 } 183 #endif 184 return 1; 185 } 186 else if (h->nlmsg_type == RTM_NEWADDR) 187 { 188 struct ifaddrmsg *ifa = NLMSG_DATA(h); 189 struct rtattr *rta = IFA_RTA(ifa); 190 unsigned int len1 = h->nlmsg_len - NLMSG_LENGTH(sizeof(*ifa)); 191 192 if (ifa->ifa_family == AF_INET) 193 { 194 struct in_addr netmask, addr, broadcast; 195 196 netmask.s_addr = htonl(0xffffffff << (32 - ifa->ifa_prefixlen)); 197 addr.s_addr = 0; 198 broadcast.s_addr = 0; 199 200 while (RTA_OK(rta, len1)) 201 { 202 if (rta->rta_type == IFA_LOCAL) 203 addr = *((struct in_addr *)(rta+1)); 204 else if (rta->rta_type == IFA_BROADCAST) 205 broadcast = *((struct in_addr *)(rta+1)); 206 207 rta = RTA_NEXT(rta, len1); 208 } 209 210 if (addr.s_addr && ipv4_callback) 211 if (!((*ipv4_callback)(addr, ifa->ifa_index, netmask, broadcast, parm))) 212 return 0; 213 } 214 #ifdef HAVE_IPV6 215 else if (ifa->ifa_family == AF_INET6) 216 { 217 struct in6_addr *addrp = NULL; 218 while (RTA_OK(rta, len1)) 219 { 220 if (rta->rta_type == IFA_ADDRESS) 221 addrp = ((struct in6_addr *)(rta+1)); 222 223 rta = RTA_NEXT(rta, len1); 224 } 225 226 if (addrp && ipv6_callback) 227 if (!((*ipv6_callback)(addrp, ifa->ifa_index, ifa->ifa_index, parm))) 228 return 0; 229 } 230 #endif 231 } 232 } 233 } 234 235 236 void netlink_multicast(void) 237 { 238 ssize_t len; 239 struct nlmsghdr *h; 240 int flags; 241 242 /* don't risk blocking reading netlink messages here. */ 243 if ((flags = fcntl(daemon->netlinkfd, F_GETFL)) == -1 || 244 fcntl(daemon->netlinkfd, F_SETFL, flags | O_NONBLOCK) == -1) 245 return; 246 247 if ((len = netlink_recv()) != -1) 248 { 249 for (h = (struct nlmsghdr *)iov.iov_base; NLMSG_OK(h, (size_t)len); h = NLMSG_NEXT(h, len)) 250 if (h->nlmsg_type == NLMSG_ERROR) 251 nl_err(h); 252 else 253 nl_routechange(h); 254 } 255 256 /* restore non-blocking status */ 257 fcntl(daemon->netlinkfd, F_SETFL, flags); 258 } 259 260 static void nl_err(struct nlmsghdr *h) 261 { 262 struct nlmsgerr *err = NLMSG_DATA(h); 263 264 if (err->error != 0) 265 my_syslog(LOG_ERR, _("netlink returns error: %s"), strerror(-(err->error))); 266 } 267 268 /* We arrange to receive netlink multicast messages whenever the network route is added. 269 If this happens and we still have a DNS packet in the buffer, we re-send it. 270 This helps on DoD links, where frequently the packet which triggers dialling is 271 a DNS query, which then gets lost. By re-sending, we can avoid the lookup 272 failing. Note that we only accept these messages from the kernel (pid == 0) */ 273 static void nl_routechange(struct nlmsghdr *h) 274 { 275 if (h->nlmsg_pid == 0 && h->nlmsg_type == RTM_NEWROUTE) 276 { 277 struct rtmsg *rtm = NLMSG_DATA(h); 278 int fd; 279 280 if (rtm->rtm_type != RTN_UNICAST || rtm->rtm_scope != RT_SCOPE_LINK) 281 return; 282 283 /* Force re-reading resolv file right now, for luck. */ 284 daemon->last_resolv = 0; 285 286 if (daemon->srv_save) 287 { 288 if (daemon->srv_save->sfd) 289 fd = daemon->srv_save->sfd->fd; 290 else if (daemon->rfd_save && daemon->rfd_save->refcount != 0) 291 fd = daemon->rfd_save->fd; 292 else 293 return; 294 295 while(sendto(fd, daemon->packet, daemon->packet_len, 0, 296 &daemon->srv_save->addr.sa, sa_len(&daemon->srv_save->addr)) == -1 && retry_send()); 297 } 298 } 299 } 300 301 #endif 302 303 304
