src/netlink.c

   1 /**
   2  * Copyright (C) 2017 Hans Dedecker <dedeckeh@gmail.com>
   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 <errno.h>
  16 #include <string.h>
  17 #include <syslog.h>
  18
  19 #include <linux/netlink.h>
  20 #include <linux/if_addr.h>
  21 #include <linux/neighbour.h>
  22 #include <linux/rtnetlink.h>
  23
  24 #include <netlink/msg.h>
  25 #include <netlink/socket.h>
  26 #include <netlink/attr.h>
  27
  28 #include "odhcpd.h"
  29
  30 static struct nl_sock *rtnl_socket = NULL;
  31
  32
  33 int netlink_init(void)
  34 {
  35         if (!(rtnl_socket = netlink_create_socket(NETLINK_ROUTE))) {
  36                 syslog(LOG_ERR, "Unable to open nl socket: %s", strerror(errno));
  37                 return -1;
  38         }
  39
  40         return 0;
  41 }
  42
  43
  44 struct nl_sock *netlink_create_socket(int protocol)
  45 {
  46         struct nl_sock *nl_sock;
  47
  48         nl_sock = nl_socket_alloc();
  49         if (!nl_sock)
  50                 goto err;
  51
  52         if (nl_connect(nl_sock, protocol) < 0)
  53                 goto err;
  54
  55         return nl_sock;
  56
  57 err:
  58         if (nl_sock)
  59                 nl_socket_free(nl_sock);
  60
  61         return NULL;
  62 }
  63
  64
  65 struct addr_info {
  66         int ifindex;
  67         int af;
  68         struct odhcpd_ipaddr **addrs;
  69         int pending;
  70         ssize_t ret;
  71 };
  72
  73
  74 static int cb_valid_handler(struct nl_msg *msg, void *arg)
  75 {
  76         struct addr_info *ctxt = (struct addr_info *)arg;
  77         struct odhcpd_ipaddr *addrs = *(ctxt->addrs);
  78         struct nlmsghdr *hdr = nlmsg_hdr(msg);
  79         struct ifaddrmsg *ifa;
  80         struct nlattr *nla[__IFA_MAX], *nla_addr = NULL;
  81
  82         if (hdr->nlmsg_type != RTM_NEWADDR)
  83                 return NL_SKIP;
  84
  85         ifa = NLMSG_DATA(hdr);
  86         if (ifa->ifa_scope != RT_SCOPE_UNIVERSE ||
  87                         (ctxt->af != ifa->ifa_family) ||
  88                         (ctxt->ifindex && ifa->ifa_index != (unsigned)ctxt->ifindex))
  89                 return NL_SKIP;
  90
  91         nlmsg_parse(hdr, sizeof(*ifa), nla, __IFA_MAX - 1, NULL);
  92
  93         switch (ifa->ifa_family) {
  94         case AF_INET6:
  95                 if (nla[IFA_ADDRESS])
  96                         nla_addr = nla[IFA_ADDRESS];
  97                 break;
  98
  99         case AF_INET:
 100                 if (nla[IFA_LOCAL])
 101                         nla_addr = nla[IFA_LOCAL];
 102                 break;
 103
 104         default:
 105                 break;
 106         }
 107         if (!nla_addr)
 108                 return NL_SKIP;
 109
 110         addrs = realloc(addrs, sizeof(*addrs)*(ctxt->ret + 1));
 111         if (!addrs)
 112                 return NL_SKIP;
 113
 114         memset(&addrs[ctxt->ret], 0, sizeof(addrs[ctxt->ret]));
 115         addrs[ctxt->ret].prefix = ifa->ifa_prefixlen;
 116
 117         nla_memcpy(&addrs[ctxt->ret].addr, nla_addr,
 118                         sizeof(addrs[ctxt->ret].addr));
 119
 120         if (nla[IFA_BROADCAST])
 121                 nla_memcpy(&addrs[ctxt->ret].broadcast, nla[IFA_BROADCAST],
 122                                 sizeof(addrs[ctxt->ret].broadcast));
 123
 124         if (nla[IFA_CACHEINFO]) {
 125                 struct ifa_cacheinfo *ifc = nla_data(nla[IFA_CACHEINFO]);
 126
 127                 addrs[ctxt->ret].preferred = ifc->ifa_prefered;
 128                 addrs[ctxt->ret].valid = ifc->ifa_valid;
 129         }
 130
 131         if (ifa->ifa_flags & IFA_F_DEPRECATED)
 132                 addrs[ctxt->ret].preferred = 0;
 133
 134         ctxt->ret++;
 135         *(ctxt->addrs) = addrs;
 136
 137         return NL_OK;
 138 }
 139
 140
 141 static int cb_finish_handler(_unused struct nl_msg *msg, void *arg)
 142 {
 143         struct addr_info *ctxt = (struct addr_info *)arg;
 144
 145         ctxt->pending = 0;
 146
 147         return NL_STOP;
 148 }
 149
 150
 151 static int cb_error_handler(_unused struct sockaddr_nl *nla, struct nlmsgerr *err,
 152                 void *arg)
 153 {
 154         struct addr_info *ctxt = (struct addr_info *)arg;
 155
 156         ctxt->pending = 0;
 157         ctxt->ret = err->error;
 158
 159         return NL_STOP;
 160 }
 161
 162
 163 static int prefix_cmp(const void *va, const void *vb)
 164 {
 165         const struct odhcpd_ipaddr *a = va, *b = vb;
 166         int ret = 0;
 167
 168         if (a->prefix == b->prefix) {
 169                 ret = (ntohl(a->addr.in.s_addr) < ntohl(b->addr.in.s_addr)) ? 1 :
 170                         (ntohl(a->addr.in.s_addr) > ntohl(b->addr.in.s_addr)) ? -1 : 0;
 171         } else
 172                 ret = a->prefix < b->prefix ? 1 : -1;
 173
 174         return ret;
 175 }
 176
 177
 178 // compare IPv6 prefixes
 179 static int prefix6_cmp(const void *va, const void *vb)
 180 {
 181         const struct odhcpd_ipaddr *a = va, *b = vb;
 182         uint32_t a_pref = IN6_IS_ADDR_ULA(&a->addr.in6) ? 1 : a->preferred;
 183         uint32_t b_pref = IN6_IS_ADDR_ULA(&b->addr.in6) ? 1 : b->preferred;
 184         return (a_pref < b_pref) ? 1 : (a_pref > b_pref) ? -1 : 0;
 185 }
 186
 187
 188 // Detect an IPV6-address currently assigned to the given interface
 189 ssize_t netlink_get_interface_addrs(int ifindex, bool v6, struct odhcpd_ipaddr **addrs)
 190 {
 191         struct nl_msg *msg;
 192         struct ifaddrmsg ifa = {
 193                 .ifa_family = v6? AF_INET6: AF_INET,
 194                 .ifa_prefixlen = 0,
 195                 .ifa_flags = 0,
 196                 .ifa_scope = 0,
 197                 .ifa_index = ifindex, };
 198         struct nl_cb *cb = nl_cb_alloc(NL_CB_DEFAULT);
 199         struct addr_info ctxt = {
 200                 .ifindex = ifindex,
 201                 .af = v6? AF_INET6: AF_INET,
 202                 .addrs = addrs,
 203                 .ret = 0,
 204                 .pending = 1,
 205         };
 206
 207         if (!cb) {
 208                 ctxt.ret = -1;
 209                 goto out;
 210         }
 211
 212         msg = nlmsg_alloc_simple(RTM_GETADDR, NLM_F_REQUEST | NLM_F_DUMP);
 213
 214         if (!msg) {
 215                 ctxt.ret = - 1;
 216                 goto out;
 217         }
 218
 219         nlmsg_append(msg, &ifa, sizeof(ifa), 0);
 220
 221         nl_cb_set(cb, NL_CB_VALID, NL_CB_CUSTOM, cb_valid_handler, &ctxt);
 222         nl_cb_set(cb, NL_CB_FINISH, NL_CB_CUSTOM, cb_finish_handler, &ctxt);
 223         nl_cb_err(cb, NL_CB_CUSTOM, cb_error_handler, &ctxt);
 224
 225         nl_send_auto_complete(rtnl_socket, msg);
 226         while (ctxt.pending > 0)
 227                 nl_recvmsgs(rtnl_socket, cb);
 228
 229         nlmsg_free(msg);
 230
 231         if (ctxt.ret <= 0)
 232                 goto out;
 233
 234         time_t now = odhcpd_time();
 235         struct odhcpd_ipaddr *addr = *addrs;
 236
 237         qsort(addr, ctxt.ret, sizeof(*addr), v6 ? prefix6_cmp : prefix_cmp);
 238
 239         for (ssize_t i = 0; i < ctxt.ret; ++i) {
 240                 if (addr[i].preferred < UINT32_MAX - now)
 241                         addr[i].preferred += now;
 242
 243                 if (addr[i].valid < UINT32_MAX - now)
 244                         addr[i].valid += now;
 245         }
 246
 247 out:
 248         nl_cb_put(cb);
 249
 250         return ctxt.ret;
 251 }
 252
 253
 254 int netlink_setup_route(const struct in6_addr *addr, const int prefixlen,
 255                 const struct interface *iface, const struct in6_addr *gw,
 256                 const uint32_t metric, const bool add)
 257 {
 258         struct nl_msg *msg;
 259         struct rtmsg rtm = {
 260                 .rtm_family = AF_INET6,
 261                 .rtm_dst_len = prefixlen,
 262                 .rtm_src_len = 0,
 263                 .rtm_table = RT_TABLE_MAIN,
 264                 .rtm_protocol = (add ? RTPROT_STATIC : RTPROT_UNSPEC),
 265                 .rtm_scope = (add ? (gw ? RT_SCOPE_UNIVERSE : RT_SCOPE_LINK) : RT_SCOPE_NOWHERE),
 266                 .rtm_type = (add ? RTN_UNICAST : RTN_UNSPEC),
 267         };
 268         int ret = 0;
 269
 270         msg = nlmsg_alloc_simple(add ? RTM_NEWROUTE : RTM_DELROUTE,
 271                                         add ? NLM_F_CREATE | NLM_F_REPLACE : 0);
 272         if (!msg)
 273                 return -1;
 274
 275         nlmsg_append(msg, &rtm, sizeof(rtm), 0);
 276
 277         nla_put(msg, RTA_DST, sizeof(*addr), addr);
 278         nla_put_u32(msg, RTA_OIF, iface->ifindex);
 279         nla_put_u32(msg, RTA_PRIORITY, metric);
 280
 281         if (gw)
 282                 nla_put(msg, RTA_GATEWAY, sizeof(*gw), gw);
 283
 284         ret = nl_send_auto_complete(rtnl_socket, msg);
 285         nlmsg_free(msg);
 286
 287         if (ret < 0)
 288                 return ret;
 289
 290         return nl_wait_for_ack(rtnl_socket);
 291 }
 292
 293
 294 int netlink_setup_proxy_neigh(const struct in6_addr *addr,
 295                 const struct interface *iface, const bool add)
 296 {
 297         struct nl_msg *msg;
 298         struct ndmsg ndm = {
 299                 .ndm_family = AF_INET6,
 300                 .ndm_flags = NTF_PROXY,
 301                 .ndm_ifindex = iface->ifindex,
 302         };
 303         int ret = 0, flags = NLM_F_REQUEST;
 304
 305         if (add)
 306                 flags |= NLM_F_REPLACE | NLM_F_CREATE;
 307
 308         msg = nlmsg_alloc_simple(add ? RTM_NEWNEIGH : RTM_DELNEIGH, flags);
 309         if (!msg)
 310                 return -1;
 311
 312         nlmsg_append(msg, &ndm, sizeof(ndm), 0);
 313
 314         nla_put(msg, NDA_DST, sizeof(*addr), addr);
 315
 316         ret = nl_send_auto_complete(rtnl_socket, msg);
 317         nlmsg_free(msg);
 318
 319         if (ret < 0)
 320                 return ret;
 321
 322         return nl_wait_for_ack(rtnl_socket);
 323 }
 324
 325
 326 int netlink_setup_addr(struct odhcpd_ipaddr *addr,
 327                 const struct interface *iface, const bool v6,
 328                 const bool add)
 329 {
 330         struct nl_msg *msg;
 331         struct ifaddrmsg ifa = {
 332                 .ifa_family = v6 ? AF_INET6 : AF_INET,
 333                 .ifa_prefixlen = addr->prefix,
 334                 .ifa_flags = 0,
 335                 .ifa_scope = 0,
 336                 .ifa_index = iface->ifindex, };
 337         int ret = 0, flags = NLM_F_REQUEST;
 338
 339         if (add)
 340                 flags |= NLM_F_REPLACE | NLM_F_CREATE;
 341
 342         msg = nlmsg_alloc_simple(add ? RTM_NEWADDR : RTM_DELADDR, 0);
 343         if (!msg)
 344                 return -1;
 345
 346         nlmsg_append(msg, &ifa, sizeof(ifa), flags);
 347         nla_put(msg, IFA_LOCAL, v6 ? 16 : 4, &addr->addr);
 348         if (v6) {
 349                 struct ifa_cacheinfo cinfo = {  .ifa_prefered = 0xffffffffU,
 350                                                 .ifa_valid = 0xffffffffU,
 351                                                 .cstamp = 0,
 352                                                 .tstamp = 0 };
 353                 time_t now = odhcpd_time();
 354
 355                 if (addr->preferred) {
 356                         int64_t preferred = addr->preferred - now;
 357                         if (preferred < 0)
 358                                 preferred = 0;
 359                         else if (preferred > UINT32_MAX)
 360                                 preferred = UINT32_MAX;
 361
 362                         cinfo.ifa_prefered = preferred;
 363                 }
 364
 365                 if (addr->valid) {
 366                         int64_t valid = addr->valid - now;
 367                         if (valid <= 0) {
 368                                 nlmsg_free(msg);
 369                                 return -1;
 370                         }
 371                         else if (valid > UINT32_MAX)
 372                                 valid = UINT32_MAX;
 373
 374                         cinfo.ifa_valid = valid;
 375                 }
 376
 377                 nla_put(msg, IFA_CACHEINFO, sizeof(cinfo), &cinfo);
 378
 379                 nla_put_u32(msg, IFA_FLAGS, IFA_F_NOPREFIXROUTE);
 380         } else {
 381                 if (addr->broadcast.s_addr)
 382                         nla_put_u32(msg, IFA_BROADCAST, addr->broadcast.s_addr);
 383         }
 384
 385         ret = nl_send_auto_complete(rtnl_socket, msg);
 386         nlmsg_free(msg);
 387
 388         if (ret < 0)
 389                 return ret;
 390
 391         return nl_wait_for_ack(rtnl_socket);
 392 }