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
  44 /* definitions */
  45
  46 /* static function declarations */
  47
  48 /* Private functions */
  49
  50 /* Install or uninstall specified rule for a specific interface.
  51  * Form netlink message and ship it. Currently, notify status after
  52  * waiting for netlink status.
  53  */
  54 static int netlink_rule_update(int cmd, struct zebra_pbr_rule *rule)
  55 {
  56         int family;
  57         int bytelen;
  58         struct {
  59                 struct nlmsghdr n;
  60                 struct fib_rule_hdr frh;
  61                 char buf[NL_PKT_BUF_SIZE];
  62         } req;
  63         struct zebra_ns *zns = zebra_ns_lookup(NS_DEFAULT);
  64         struct sockaddr_nl snl;
  65         char buf1[PREFIX_STRLEN];
  66         char buf2[PREFIX_STRLEN];
  67
  68         memset(&req, 0, sizeof(req) - NL_PKT_BUF_SIZE);
  69         family = PREFIX_FAMILY(&rule->rule.filter.src_ip);
  70         bytelen = (family == AF_INET ? 4 : 16);
  71
  72         req.n.nlmsg_type = cmd;
  73         req.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg));
  74         req.n.nlmsg_flags = NLM_F_REQUEST;
  75         req.n.nlmsg_pid = zns->netlink_cmd.snl.nl_pid;
  76
  77         req.frh.family = family;
  78         req.frh.action = FR_ACT_TO_TBL;
  79
  80         /* rule's pref # */
  81         addattr32(&req.n, sizeof(req), FRA_PRIORITY, rule->rule.priority);
  82
  83         /* interface on which applied */
  84         if (rule->ifp)
  85                 addattr_l(&req.n, sizeof(req), FRA_IFNAME, rule->ifp->name,
  86                           strlen(rule->ifp->name) + 1);
  87
  88         /* source IP, if specified */
  89         if (IS_RULE_FILTERING_ON_SRC_IP(rule)) {
  90                 req.frh.src_len = rule->rule.filter.src_ip.prefixlen;
  91                 addattr_l(&req.n, sizeof(req), FRA_SRC,
  92                           &rule->rule.filter.src_ip.u.prefix, bytelen);
  93         }
  94         /* destination IP, if specified */
  95         if (IS_RULE_FILTERING_ON_DST_IP(rule)) {
  96                 req.frh.dst_len = rule->rule.filter.dst_ip.prefixlen;
  97                 addattr_l(&req.n, sizeof(req), FRA_DST,
  98                           &rule->rule.filter.dst_ip.u.prefix, bytelen);
  99         }
 100
 101         /* fwmark, if specified */
 102         if (IS_RULE_FILTERING_ON_FWMARK(rule)) {
 103                 addattr32(&req.n, sizeof(req), FRA_FWMARK,
 104                           rule->rule.filter.fwmark);
 105         }
 106
 107         /* Route table to use to forward, if filter criteria matches. */
 108         if (rule->rule.action.table < 256)
 109                 req.frh.table = rule->rule.action.table;
 110         else {
 111                 req.frh.table = RT_TABLE_UNSPEC;
 112                 addattr32(&req.n, sizeof(req), FRA_TABLE,
 113                           rule->rule.action.table);
 114         }
 115
 116         if (IS_ZEBRA_DEBUG_KERNEL)
 117                 zlog_debug(
 118                         "Tx %s family %s IF %s(%u) Pref %u Src %s Dst %s Table %u",
 119                         nl_msg_type_to_str(cmd), nl_family_to_str(family),
 120                         rule->ifp ? rule->ifp->name : "Unknown",
 121                         rule->ifp ? rule->ifp->ifindex : 0, rule->rule.priority,
 122                         prefix2str(&rule->rule.filter.src_ip, buf1,
 123                                    sizeof(buf1)),
 124                         prefix2str(&rule->rule.filter.dst_ip, buf2,
 125                                    sizeof(buf2)),
 126                         rule->rule.action.table);
 127
 128         /* Ship off the message.
 129          * Note: Currently, netlink_talk() is a blocking call which returns
 130          * back the status.
 131          */
 132         memset(&snl, 0, sizeof(snl));
 133         snl.nl_family = AF_NETLINK;
 134         return netlink_talk(netlink_talk_filter, &req.n,
 135                             &zns->netlink_cmd, zns, 0);
 136 }
 137
 138
 139 /* Public functions */
 140 /*
 141  * Install specified rule for a specific interface. The preference is what
 142  * goes in the rule to denote relative ordering; it may or may not be the
 143  * same as the rule's user-defined sequence number.
 144  */
 145 enum dp_req_result kernel_add_pbr_rule(struct zebra_pbr_rule *rule)
 146 {
 147         int ret = 0;
 148
 149         ret = netlink_rule_update(RTM_NEWRULE, rule);
 150         kernel_pbr_rule_add_del_status(rule,
 151                                        (!ret) ? DP_INSTALL_SUCCESS
 152                                               : DP_INSTALL_FAILURE);
 153
 154         return DP_REQUEST_SUCCESS;
 155 }
 156
 157 /*
 158  * Uninstall specified rule for a specific interface.
 159  */
 160 enum dp_req_result kernel_del_pbr_rule(struct zebra_pbr_rule *rule)
 161 {
 162         int ret = 0;
 163
 164         ret = netlink_rule_update(RTM_DELRULE, rule);
 165         kernel_pbr_rule_add_del_status(rule,
 166                                        (!ret) ? DP_DELETE_SUCCESS
 167                                               : DP_DELETE_FAILURE);
 168
 169         return DP_REQUEST_SUCCESS;
 170 }
 171
 172 /*
 173  * Handle netlink notification informing a rule add or delete.
 174  * Handling of an ADD is TBD.
 175  * DELs are notified up, if other attributes indicate it may be a
 176  * notification of interest. The expectation is that if this corresponds
 177  * to a PBR rule added by FRR, it will be readded.
 178  */
 179 int netlink_rule_change(struct nlmsghdr *h, ns_id_t ns_id, int startup)
 180 {
 181         struct zebra_ns *zns;
 182         struct fib_rule_hdr *frh;
 183         struct rtattr *tb[FRA_MAX + 1];
 184         int len;
 185         char *ifname;
 186         struct zebra_pbr_rule rule;
 187         char buf1[PREFIX_STRLEN];
 188         char buf2[PREFIX_STRLEN];
 189
 190         /* Basic validation followed by extracting attributes. */
 191         if (h->nlmsg_type != RTM_NEWRULE && h->nlmsg_type != RTM_DELRULE)
 192                 return 0;
 193
 194         /* TBD */
 195         if (h->nlmsg_type == RTM_NEWRULE)
 196                 return 0;
 197
 198         len = h->nlmsg_len - NLMSG_LENGTH(sizeof(struct fib_rule_hdr));
 199         if (len < 0) {
 200                 zlog_err("%s: Message received from netlink is of a broken size: %d %zu",
 201                          __PRETTY_FUNCTION__, h->nlmsg_len,
 202                          (size_t)NLMSG_LENGTH(sizeof(struct fib_rule_hdr)));
 203                 return -1;
 204         }
 205
 206         frh = NLMSG_DATA(h);
 207         if (frh->family != AF_INET && frh->family != AF_INET6) {
 208                 zlog_warn(
 209                         "Invalid address family: %d received from kernel rule change: %d",
 210                         frh->family, h->nlmsg_type);
 211                 return 0;
 212         }
 213         if (frh->action != FR_ACT_TO_TBL)
 214                 return 0;
 215
 216         memset(tb, 0, sizeof(tb));
 217         netlink_parse_rtattr(tb, FRA_MAX, RTM_RTA(frh), len);
 218
 219         /* TBD: We don't care about rules not specifying an IIF. */
 220         if (tb[FRA_IFNAME] == NULL)
 221                 return 0;
 222
 223         /* If we don't know the interface, we don't care. */
 224         ifname = (char *)RTA_DATA(tb[FRA_IFNAME]);
 225         zns = zebra_ns_lookup(ns_id);
 226         rule.ifp = if_lookup_by_name_per_ns(zns, ifname);
 227         if (!rule.ifp)
 228                 return 0;
 229
 230         memset(&rule, 0, sizeof(rule));
 231         if (tb[FRA_PRIORITY])
 232                 rule.rule.priority = *(uint32_t *)RTA_DATA(tb[FRA_PRIORITY]);
 233
 234         if (tb[FRA_SRC]) {
 235                 if (frh->family == AF_INET)
 236                         memcpy(&rule.rule.filter.src_ip.u.prefix4,
 237                                RTA_DATA(tb[FRA_SRC]), 4);
 238                 else
 239                         memcpy(&rule.rule.filter.src_ip.u.prefix6,
 240                                RTA_DATA(tb[FRA_SRC]), 16);
 241                 rule.rule.filter.src_ip.prefixlen = frh->src_len;
 242                 rule.rule.filter.filter_bm |= PBR_FILTER_SRC_IP;
 243         }
 244
 245         if (tb[FRA_DST]) {
 246                 if (frh->family == AF_INET)
 247                         memcpy(&rule.rule.filter.dst_ip.u.prefix4,
 248                                RTA_DATA(tb[FRA_DST]), 4);
 249                 else
 250                         memcpy(&rule.rule.filter.dst_ip.u.prefix6,
 251                                RTA_DATA(tb[FRA_DST]), 16);
 252                 rule.rule.filter.dst_ip.prefixlen = frh->dst_len;
 253                 rule.rule.filter.filter_bm |= PBR_FILTER_DST_IP;
 254         }
 255
 256         if (tb[FRA_TABLE])
 257                 rule.rule.action.table = *(uint32_t *)RTA_DATA(tb[FRA_TABLE]);
 258         else
 259                 rule.rule.action.table = frh->table;
 260
 261         if (IS_ZEBRA_DEBUG_KERNEL)
 262                 zlog_debug(
 263                         "Rx %s family %s IF %s(%u) Pref %u Src %s Dst %s Table %u",
 264                         nl_msg_type_to_str(h->nlmsg_type),
 265                         nl_family_to_str(frh->family), rule.ifp->name,
 266                         rule.ifp->ifindex, rule.rule.priority,
 267                         prefix2str(&rule.rule.filter.src_ip, buf1,
 268                                    sizeof(buf1)),
 269                         prefix2str(&rule.rule.filter.dst_ip, buf2,
 270                                    sizeof(buf2)),
 271                         rule.rule.action.table);
 272
 273         return kernel_pbr_rule_del(&rule);
 274 }
 275
 276 /*
 277  * Get to know existing PBR rules in the kernel - typically called at startup.
 278  * TBD.
 279  */
 280 int netlink_rules_read(struct zebra_ns *zns)
 281 {
 282         return 0;
 283 }
 284
 285 #endif /* HAVE_NETLINK */