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 void 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) ? SOUTHBOUND_INSTALL_SUCCESS
 152                                               : SOUTHBOUND_INSTALL_FAILURE);
 153 }
 154
 155 /*
 156  * Uninstall specified rule for a specific interface.
 157  */
 158 void kernel_del_pbr_rule(struct zebra_pbr_rule *rule)
 159 {
 160         int ret = 0;
 161
 162         ret = netlink_rule_update(RTM_DELRULE, rule);
 163         kernel_pbr_rule_add_del_status(rule,
 164                                        (!ret) ? SOUTHBOUND_DELETE_SUCCESS
 165                                               : SOUTHBOUND_DELETE_FAILURE);
 166 }
 167
 168 /*
 169  * Handle netlink notification informing a rule add or delete.
 170  * Handling of an ADD is TBD.
 171  * DELs are notified up, if other attributes indicate it may be a
 172  * notification of interest. The expectation is that if this corresponds
 173  * to a PBR rule added by FRR, it will be readded.
 174  */
 175 int netlink_rule_change(struct nlmsghdr *h, ns_id_t ns_id, int startup)
 176 {
 177         struct zebra_ns *zns;
 178         struct fib_rule_hdr *frh;
 179         struct rtattr *tb[FRA_MAX + 1];
 180         int len;
 181         char *ifname;
 182         struct zebra_pbr_rule rule;
 183         char buf1[PREFIX_STRLEN];
 184         char buf2[PREFIX_STRLEN];
 185
 186         /* Basic validation followed by extracting attributes. */
 187         if (h->nlmsg_type != RTM_NEWRULE && h->nlmsg_type != RTM_DELRULE)
 188                 return 0;
 189
 190         /* TBD */
 191         if (h->nlmsg_type == RTM_NEWRULE)
 192                 return 0;
 193
 194         len = h->nlmsg_len - NLMSG_LENGTH(sizeof(struct fib_rule_hdr));
 195         if (len < 0)
 196                 return -1;
 197
 198         frh = NLMSG_DATA(h);
 199         if (frh->family != AF_INET && frh->family != AF_INET6)
 200                 return 0;
 201         if (frh->action != FR_ACT_TO_TBL)
 202                 return 0;
 203
 204         memset(tb, 0, sizeof(tb));
 205         netlink_parse_rtattr(tb, FRA_MAX, RTM_RTA(frh), len);
 206
 207         /* TBD: We don't care about rules not specifying an IIF. */
 208         if (tb[FRA_IFNAME] == NULL)
 209                 return 0;
 210
 211         /* If we don't know the interface, we don't care. */
 212         ifname = (char *)RTA_DATA(tb[FRA_IFNAME]);
 213         zns = zebra_ns_lookup(ns_id);
 214         rule.ifp = if_lookup_by_name_per_ns(zns, ifname);
 215         if (!rule.ifp)
 216                 return 0;
 217
 218         memset(&rule, 0, sizeof(rule));
 219         if (tb[FRA_PRIORITY])
 220                 rule.rule.priority = *(uint32_t *)RTA_DATA(tb[FRA_PRIORITY]);
 221
 222         if (tb[FRA_SRC]) {
 223                 if (frh->family == AF_INET)
 224                         memcpy(&rule.rule.filter.src_ip.u.prefix4,
 225                                RTA_DATA(tb[FRA_SRC]), 4);
 226                 else
 227                         memcpy(&rule.rule.filter.src_ip.u.prefix6,
 228                                RTA_DATA(tb[FRA_SRC]), 16);
 229                 rule.rule.filter.src_ip.prefixlen = frh->src_len;
 230                 rule.rule.filter.filter_bm |= PBR_FILTER_SRC_IP;
 231         }
 232
 233         if (tb[FRA_DST]) {
 234                 if (frh->family == AF_INET)
 235                         memcpy(&rule.rule.filter.dst_ip.u.prefix4,
 236                                RTA_DATA(tb[FRA_DST]), 4);
 237                 else
 238                         memcpy(&rule.rule.filter.dst_ip.u.prefix6,
 239                                RTA_DATA(tb[FRA_DST]), 16);
 240                 rule.rule.filter.dst_ip.prefixlen = frh->dst_len;
 241                 rule.rule.filter.filter_bm |= PBR_FILTER_DST_IP;
 242         }
 243
 244         if (tb[FRA_TABLE])
 245                 rule.rule.action.table = *(uint32_t *)RTA_DATA(tb[FRA_TABLE]);
 246         else
 247                 rule.rule.action.table = frh->table;
 248
 249         if (IS_ZEBRA_DEBUG_KERNEL)
 250                 zlog_debug(
 251                         "Rx %s family %s IF %s(%u) Pref %u Src %s Dst %s Table %u",
 252                         nl_msg_type_to_str(h->nlmsg_type),
 253                         nl_family_to_str(frh->family), rule.ifp->name,
 254                         rule.ifp->ifindex, rule.rule.priority,
 255                         prefix2str(&rule.rule.filter.src_ip, buf1,
 256                                    sizeof(buf1)),
 257                         prefix2str(&rule.rule.filter.dst_ip, buf2,
 258                                    sizeof(buf2)),
 259                         rule.rule.action.table);
 260
 261         return kernel_pbr_rule_del(&rule);
 262 }
 263
 264 /*
 265  * Get to know existing PBR rules in the kernel - typically called at startup.
 266  * TBD.
 267  */
 268 int netlink_rules_read(struct zebra_ns *zns)
 269 {
 270         return 0;
 271 }
 272
 273 #endif /* HAVE_NETLINK */