zebra/rule_netlink.c

   1 /*
   2  * Zebra Policy Based Routing (PBR) interaction with the kernel using
   3  * netlink.
   4  * Copyright (C) 2018  Cumulus Networks, Inc.
   5  *
   6  * This file is part of FRR.
   7  *
   8  * FRR is free software; you can redistribute it and/or modify it
   9  * under the terms of the GNU General Public License as published by the
  10  * Free Software Foundation; either version 2, or (at your option) any
  11  * later version.
  12  *
  13  * FRR is distributed in the hope that it will be useful, but
  14  * WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with FRR; see the file COPYING.  If not, write to the Free
  20  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  21  * 02111-1307, USA.
  22  */
  23
  24 #include <zebra.h>
  25
  26 #ifdef HAVE_NETLINK
  27
  28 #include "if.h"
  29 #include "prefix.h"
  30 #include "vrf.h"
  31
  32 #include <linux/fib_rules.h>
  33 #include "zebra/zserv.h"
  34 #include "zebra/zebra_ns.h"
  35 #include "zebra/zebra_vrf.h"
  36 #include "zebra/rt.h"
  37 #include "zebra/interface.h"
  38 #include "zebra/debug.h"
  39 #include "zebra/rtadv.h"
  40 #include "zebra/kernel_netlink.h"
  41 #include "zebra/rule_netlink.h"
  42 #include "zebra/zebra_pbr.h"
  43 #include "zebra/zebra_errors.h"
  44 #include "zebra/zebra_dplane.h"
  45
  46 /* definitions */
  47
  48 /* static function declarations */
  49
  50 /* Private functions */
  51
  52
  53 /*
  54  * netlink_rule_msg_encode
  55  *
  56  * Encodes netlink RTM_ADDRULE/RTM_DELRULE message to buffer buf of size buflen.
  57  *
  58  * Returns -1 on failure, 0 when the msg doesn't fit entirely in the buffer
  59  * or the number of bytes written to buf.
  60  */
  61 static ssize_t netlink_rule_msg_encode(
  62         int cmd, const struct zebra_dplane_ctx *ctx, uint32_t filter_bm,
  63         uint32_t priority, uint32_t table, const struct prefix *src_ip,
  64         const struct prefix *dst_ip, uint32_t fwmark, uint8_t dsfield,
  65         uint8_t ip_protocol, void *buf, size_t buflen)
  66 {
  67         uint8_t protocol = RTPROT_ZEBRA;
  68         int family;
  69         int bytelen;
  70         struct {
  71                 struct nlmsghdr n;
  72                 struct fib_rule_hdr frh;
  73                 char buf[];
  74         } *req = buf;
  75
  76         const char *ifname = dplane_ctx_rule_get_ifname(ctx);
  77
  78         if (buflen < sizeof(*req))
  79                 return 0;
  80         memset(req, 0, sizeof(*req));
  81
  82         /* Assume ipv4 if no src/dst set, we only support ipv4/ipv6 */
  83         if (PREFIX_FAMILY(src_ip))
  84                 family = PREFIX_FAMILY(src_ip);
  85         else if (PREFIX_FAMILY(dst_ip))
  86                 family = PREFIX_FAMILY(dst_ip);
  87         else
  88                 family = AF_INET;
  89
  90         bytelen = (family == AF_INET ? 4 : 16);
  91
  92         req->n.nlmsg_type = cmd;
  93         req->n.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg));
  94         req->n.nlmsg_flags = NLM_F_REQUEST;
  95
  96         req->frh.family = family;
  97         req->frh.action = FR_ACT_TO_TBL;
  98
  99         if (!nl_attr_put(&req->n, buflen, FRA_PROTOCOL, &protocol,
 100                          sizeof(protocol)))
 101                 return 0;
 102
 103         /* rule's pref # */
 104         if (!nl_attr_put32(&req->n, buflen, FRA_PRIORITY, priority))
 105                 return 0;
 106
 107         /* interface on which applied */
 108         if (!nl_attr_put(&req->n, buflen, FRA_IFNAME, ifname,
 109                          strlen(ifname) + 1))
 110                 return 0;
 111
 112         /* source IP, if specified */
 113         if (filter_bm & PBR_FILTER_SRC_IP) {
 114                 req->frh.src_len = src_ip->prefixlen;
 115                 if (!nl_attr_put(&req->n, buflen, FRA_SRC, &src_ip->u.prefix,
 116                                  bytelen))
 117                         return 0;
 118         }
 119
 120         /* destination IP, if specified */
 121         if (filter_bm & PBR_FILTER_DST_IP) {
 122                 req->frh.dst_len = dst_ip->prefixlen;
 123                 if (!nl_attr_put(&req->n, buflen, FRA_DST, &dst_ip->u.prefix,
 124                                  bytelen))
 125                         return 0;
 126         }
 127
 128         /* fwmark, if specified */
 129         if (filter_bm & PBR_FILTER_FWMARK) {
 130                 if (!nl_attr_put32(&req->n, buflen, FRA_FWMARK, fwmark))
 131                         return 0;
 132         }
 133
 134         /* dsfield, if specified */
 135         if (filter_bm & PBR_FILTER_DSFIELD)
 136                 req->frh.tos = dsfield;
 137
 138         /* protocol to match on */
 139         if (filter_bm & PBR_FILTER_IP_PROTOCOL)
 140                 nl_attr_put8(&req->n, buflen, FRA_IP_PROTO, ip_protocol);
 141
 142         /* Route table to use to forward, if filter criteria matches. */
 143         if (table < 256)
 144                 req->frh.table = table;
 145         else {
 146                 req->frh.table = RT_TABLE_UNSPEC;
 147                 if (!nl_attr_put32(&req->n, buflen, FRA_TABLE, table))
 148                         return 0;
 149         }
 150
 151         if (IS_ZEBRA_DEBUG_KERNEL)
 152                 zlog_debug(
 153                         "Tx %s family %s IF %s Pref %u Fwmark %u Src %pFX Dst %pFX Table %u",
 154                         nl_msg_type_to_str(cmd), nl_family_to_str(family),
 155                         ifname, priority, fwmark, src_ip, dst_ip, table);
 156
 157         return NLMSG_ALIGN(req->n.nlmsg_len);
 158 }
 159
 160 static ssize_t netlink_rule_msg_encoder(struct zebra_dplane_ctx *ctx, void *buf,
 161                                         size_t buflen)
 162 {
 163         int cmd = RTM_NEWRULE;
 164
 165         if (dplane_ctx_get_op(ctx) == DPLANE_OP_RULE_DELETE)
 166                 cmd = RTM_DELRULE;
 167
 168         return netlink_rule_msg_encode(
 169                 cmd, ctx, dplane_ctx_rule_get_filter_bm(ctx),
 170                 dplane_ctx_rule_get_priority(ctx),
 171                 dplane_ctx_rule_get_table(ctx), dplane_ctx_rule_get_src_ip(ctx),
 172                 dplane_ctx_rule_get_dst_ip(ctx),
 173                 dplane_ctx_rule_get_fwmark(ctx),
 174                 dplane_ctx_rule_get_dsfield(ctx),
 175                 dplane_ctx_rule_get_ipproto(ctx), buf, buflen);
 176 }
 177
 178 static ssize_t netlink_oldrule_msg_encoder(struct zebra_dplane_ctx *ctx,
 179                                            void *buf, size_t buflen)
 180 {
 181         return netlink_rule_msg_encode(
 182                 RTM_DELRULE, ctx, dplane_ctx_rule_get_old_filter_bm(ctx),
 183                 dplane_ctx_rule_get_old_priority(ctx),
 184                 dplane_ctx_rule_get_old_table(ctx),
 185                 dplane_ctx_rule_get_old_src_ip(ctx),
 186                 dplane_ctx_rule_get_old_dst_ip(ctx),
 187                 dplane_ctx_rule_get_old_fwmark(ctx),
 188                 dplane_ctx_rule_get_old_dsfield(ctx),
 189                 dplane_ctx_rule_get_old_ipproto(ctx), buf, buflen);
 190 }
 191
 192 /* Public functions */
 193
 194 enum netlink_msg_status
 195 netlink_put_rule_update_msg(struct nl_batch *bth, struct zebra_dplane_ctx *ctx)
 196 {
 197         enum dplane_op_e op;
 198         enum netlink_msg_status ret;
 199
 200         op = dplane_ctx_get_op(ctx);
 201         if (!(op == DPLANE_OP_RULE_ADD || op == DPLANE_OP_RULE_UPDATE
 202               || op == DPLANE_OP_RULE_DELETE)) {
 203                 flog_err(
 204                         EC_ZEBRA_PBR_RULE_UPDATE,
 205                         "Context received for kernel rule update with incorrect OP code (%u)",
 206                         op);
 207                 return FRR_NETLINK_ERROR;
 208         }
 209
 210         ret = netlink_batch_add_msg(bth, ctx, netlink_rule_msg_encoder, false);
 211
 212         /**
 213          * Delete the old one.
 214          *
 215          * Don't care about this result right?
 216          */
 217         if (op == DPLANE_OP_RULE_UPDATE)
 218                 netlink_batch_add_msg(bth, ctx, netlink_oldrule_msg_encoder,
 219                                       true);
 220
 221         return ret;
 222 }
 223
 224 /*
 225  * Handle netlink notification informing a rule add or delete.
 226  * Handling of an ADD is TBD.
 227  * DELs are notified up, if other attributes indicate it may be a
 228  * notification of interest. The expectation is that if this corresponds
 229  * to a PBR rule added by FRR, it will be readded.
 230  *
 231  * If startup and we see a rule we created, delete it as its leftover
 232  * from a previous instance and should have been removed on shutdown.
 233  *
 234  */
 235 int netlink_rule_change(struct nlmsghdr *h, ns_id_t ns_id, int startup)
 236 {
 237         struct zebra_ns *zns;
 238         struct fib_rule_hdr *frh;
 239         struct rtattr *tb[FRA_MAX + 1];
 240         int len;
 241         char *ifname;
 242         struct zebra_pbr_rule rule = {};
 243         uint8_t proto = 0;
 244         uint8_t ip_proto = 0;
 245
 246         /* Basic validation followed by extracting attributes. */
 247         if (h->nlmsg_type != RTM_NEWRULE && h->nlmsg_type != RTM_DELRULE)
 248                 return 0;
 249
 250         len = h->nlmsg_len - NLMSG_LENGTH(sizeof(struct fib_rule_hdr));
 251         if (len < 0) {
 252                 zlog_err(
 253                         "%s: Message received from netlink is of a broken size: %d %zu",
 254                         __func__, h->nlmsg_len,
 255                         (size_t)NLMSG_LENGTH(sizeof(struct fib_rule_hdr)));
 256                 return -1;
 257         }
 258
 259         frh = NLMSG_DATA(h);
 260
 261         if (frh->family != AF_INET && frh->family != AF_INET6) {
 262                 if (frh->family == RTNL_FAMILY_IPMR
 263                     || frh->family == RTNL_FAMILY_IP6MR) {
 264                         if (IS_ZEBRA_DEBUG_KERNEL)
 265                                 zlog_debug(
 266                                         "Received rule netlink that we are ignoring for family %u, rule change: %u",
 267                                         frh->family, h->nlmsg_type);
 268                         return 0;
 269                 }
 270                 flog_warn(
 271                         EC_ZEBRA_NETLINK_INVALID_AF,
 272                         "Invalid address family: %u received from kernel rule change: %u",
 273                         frh->family, h->nlmsg_type);
 274                 return 0;
 275         }
 276         if (frh->action != FR_ACT_TO_TBL)
 277                 return 0;
 278
 279         memset(tb, 0, sizeof(tb));
 280         netlink_parse_rtattr(tb, FRA_MAX, RTM_RTA(frh), len);
 281
 282         if (tb[FRA_PRIORITY])
 283                 rule.rule.priority = *(uint32_t *)RTA_DATA(tb[FRA_PRIORITY]);
 284
 285         if (tb[FRA_SRC]) {
 286                 if (frh->family == AF_INET)
 287                         memcpy(&rule.rule.filter.src_ip.u.prefix4,
 288                                RTA_DATA(tb[FRA_SRC]), 4);
 289                 else
 290                         memcpy(&rule.rule.filter.src_ip.u.prefix6,
 291                                RTA_DATA(tb[FRA_SRC]), 16);
 292                 rule.rule.filter.src_ip.prefixlen = frh->src_len;
 293                 rule.rule.filter.src_ip.family = frh->family;
 294                 rule.rule.filter.filter_bm |= PBR_FILTER_SRC_IP;
 295         }
 296
 297         if (tb[FRA_DST]) {
 298                 if (frh->family == AF_INET)
 299                         memcpy(&rule.rule.filter.dst_ip.u.prefix4,
 300                                RTA_DATA(tb[FRA_DST]), 4);
 301                 else
 302                         memcpy(&rule.rule.filter.dst_ip.u.prefix6,
 303                                RTA_DATA(tb[FRA_DST]), 16);
 304                 rule.rule.filter.dst_ip.prefixlen = frh->dst_len;
 305                 rule.rule.filter.dst_ip.family = frh->family;
 306                 rule.rule.filter.filter_bm |= PBR_FILTER_DST_IP;
 307         }
 308
 309         if (tb[FRA_TABLE])
 310                 rule.rule.action.table = *(uint32_t *)RTA_DATA(tb[FRA_TABLE]);
 311         else
 312                 rule.rule.action.table = frh->table;
 313
 314         /* TBD: We don't care about rules not specifying an IIF. */
 315         if (tb[FRA_IFNAME] == NULL)
 316                 return 0;
 317
 318         if (tb[FRA_PROTOCOL])
 319                 proto = *(uint8_t *)RTA_DATA(tb[FRA_PROTOCOL]);
 320
 321         if (tb[FRA_IP_PROTO])
 322                 ip_proto = *(uint8_t *)RTA_DATA(tb[FRA_IP_PROTO]);
 323
 324         ifname = (char *)RTA_DATA(tb[FRA_IFNAME]);
 325         strlcpy(rule.ifname, ifname, sizeof(rule.ifname));
 326
 327         if (h->nlmsg_type == RTM_NEWRULE) {
 328                 /*
 329                  * If we see a rule at startup we created, delete it now.
 330                  * It should have been flushed on a previous shutdown.
 331                  */
 332                 if (startup && proto == RTPROT_ZEBRA) {
 333                         enum zebra_dplane_result ret;
 334
 335                         ret = dplane_pbr_rule_delete(&rule);
 336
 337                         zlog_debug(
 338                                 "%s: %s leftover rule: family %s IF %s Pref %u Src %pFX Dst %pFX Table %u ip-proto: %u",
 339                                 __func__,
 340                                 ((ret == ZEBRA_DPLANE_REQUEST_FAILURE)
 341                                          ? "Failed to remove"
 342                                          : "Removed"),
 343                                 nl_family_to_str(frh->family), rule.ifname,
 344                                 rule.rule.priority, &rule.rule.filter.src_ip,
 345                                 &rule.rule.filter.dst_ip,
 346                                 rule.rule.action.table, ip_proto);
 347                 }
 348
 349                 /* TBD */
 350                 return 0;
 351         }
 352
 353         zns = zebra_ns_lookup(ns_id);
 354
 355         /* If we don't know the interface, we don't care. */
 356         if (!if_lookup_by_name_per_ns(zns, ifname))
 357                 return 0;
 358
 359         if (IS_ZEBRA_DEBUG_KERNEL)
 360                 zlog_debug(
 361                         "Rx %s family %s IF %s Pref %u Src %pFX Dst %pFX Table %u ip-proto: %u",
 362                         nl_msg_type_to_str(h->nlmsg_type),
 363                         nl_family_to_str(frh->family), rule.ifname,
 364                         rule.rule.priority, &rule.rule.filter.src_ip,
 365                         &rule.rule.filter.dst_ip, rule.rule.action.table,
 366                         ip_proto);
 367
 368         return kernel_pbr_rule_del(&rule);
 369 }
 370
 371 /*
 372  * Request rules from the kernel
 373  */
 374 static int netlink_request_rules(struct zebra_ns *zns, int family, int type)
 375 {
 376         struct {
 377                 struct nlmsghdr n;
 378                 struct fib_rule_hdr frh;
 379                 char buf[NL_PKT_BUF_SIZE];
 380         } req;
 381
 382         memset(&req, 0, sizeof(req));
 383         req.n.nlmsg_type = type;
 384         req.n.nlmsg_flags = NLM_F_ROOT | NLM_F_MATCH | NLM_F_REQUEST;
 385         req.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct fib_rule_hdr));
 386         req.frh.family = family;
 387
 388         return netlink_request(&zns->netlink_cmd, &req);
 389 }
 390
 391 /*
 392  * Get to know existing PBR rules in the kernel - typically called at startup.
 393  */
 394 int netlink_rules_read(struct zebra_ns *zns)
 395 {
 396         int ret;
 397         struct zebra_dplane_info dp_info;
 398
 399         zebra_dplane_info_from_zns(&dp_info, zns, true);
 400
 401         ret = netlink_request_rules(zns, AF_INET, RTM_GETRULE);
 402         if (ret < 0)
 403                 return ret;
 404
 405         ret = netlink_parse_info(netlink_rule_change, &zns->netlink_cmd,
 406                                  &dp_info, 0, 1);
 407         if (ret < 0)
 408                 return ret;
 409
 410         ret = netlink_request_rules(zns, AF_INET6, RTM_GETRULE);
 411         if (ret < 0)
 412                 return ret;
 413
 414         ret = netlink_parse_info(netlink_rule_change, &zns->netlink_cmd,
 415                                  &dp_info, 0, 1);
 416         return ret;
 417 }
 418
 419 #endif /* HAVE_NETLINK */