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
  45 /* definitions */
  46
  47 /* static function declarations */
  48
  49 /* Private functions */
  50
  51 /* Install or uninstall specified rule for a specific interface.
  52  * Form netlink message and ship it. Currently, notify status after
  53  * waiting for netlink status.
  54  */
  55 static int netlink_rule_update(int cmd, struct zebra_pbr_rule *rule)
  56 {
  57         uint8_t protocol = RTPROT_ZEBRA;
  58         int family;
  59         int bytelen;
  60         struct {
  61                 struct nlmsghdr n;
  62                 struct fib_rule_hdr frh;
  63                 char buf[NL_PKT_BUF_SIZE];
  64         } req;
  65         struct zebra_ns *zns = zebra_ns_lookup(NS_DEFAULT);
  66         struct sockaddr_nl snl;
  67         char buf1[PREFIX_STRLEN];
  68         char buf2[PREFIX_STRLEN];
  69
  70         memset(&req, 0, sizeof(req) - NL_PKT_BUF_SIZE);
  71         family = PREFIX_FAMILY(&rule->rule.filter.src_ip);
  72         bytelen = (family == AF_INET ? 4 : 16);
  73
  74         req.n.nlmsg_type = cmd;
  75         req.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg));
  76         req.n.nlmsg_flags = NLM_F_REQUEST;
  77         req.n.nlmsg_pid = zns->netlink_cmd.snl.nl_pid;
  78
  79         req.frh.family = family;
  80         req.frh.action = FR_ACT_TO_TBL;
  81
  82         addattr_l(&req.n, sizeof(req),
  83                   FRA_PROTOCOL, &protocol, sizeof(protocol));
  84
  85         /* rule's pref # */
  86         addattr32(&req.n, sizeof(req), FRA_PRIORITY, rule->rule.priority);
  87
  88         /* interface on which applied */
  89         addattr_l(&req.n, sizeof(req), FRA_IFNAME, rule->ifname,
  90                   strlen(rule->ifname) + 1);
  91
  92         /* source IP, if specified */
  93         if (IS_RULE_FILTERING_ON_SRC_IP(rule)) {
  94                 req.frh.src_len = rule->rule.filter.src_ip.prefixlen;
  95                 addattr_l(&req.n, sizeof(req), FRA_SRC,
  96                           &rule->rule.filter.src_ip.u.prefix, bytelen);
  97         }
  98         /* destination IP, if specified */
  99         if (IS_RULE_FILTERING_ON_DST_IP(rule)) {
 100                 req.frh.dst_len = rule->rule.filter.dst_ip.prefixlen;
 101                 addattr_l(&req.n, sizeof(req), FRA_DST,
 102                           &rule->rule.filter.dst_ip.u.prefix, bytelen);
 103         }
 104
 105         /* fwmark, if specified */
 106         if (IS_RULE_FILTERING_ON_FWMARK(rule)) {
 107                 addattr32(&req.n, sizeof(req), FRA_FWMARK,
 108                           rule->rule.filter.fwmark);
 109         }
 110
 111         /* Route table to use to forward, if filter criteria matches. */
 112         if (rule->rule.action.table < 256)
 113                 req.frh.table = rule->rule.action.table;
 114         else {
 115                 req.frh.table = RT_TABLE_UNSPEC;
 116                 addattr32(&req.n, sizeof(req), FRA_TABLE,
 117                           rule->rule.action.table);
 118         }
 119
 120         if (IS_ZEBRA_DEBUG_KERNEL)
 121                 zlog_debug(
 122                         "Tx %s family %s IF %s(%u) Pref %u Fwmark %u Src %s Dst %s Table %u",
 123                         nl_msg_type_to_str(cmd), nl_family_to_str(family),
 124                         rule->ifname, rule->rule.ifindex, rule->rule.priority,
 125                         rule->rule.filter.fwmark,
 126                         prefix2str(&rule->rule.filter.src_ip, buf1,
 127                                    sizeof(buf1)),
 128                         prefix2str(&rule->rule.filter.dst_ip, buf2,
 129                                    sizeof(buf2)),
 130                         rule->rule.action.table);
 131
 132         /* Ship off the message.
 133          * Note: Currently, netlink_talk() is a blocking call which returns
 134          * back the status.
 135          */
 136         memset(&snl, 0, sizeof(snl));
 137         snl.nl_family = AF_NETLINK;
 138         return netlink_talk(netlink_talk_filter, &req.n,
 139                             &zns->netlink_cmd, zns, 0);
 140 }
 141
 142
 143 /* Public functions */
 144 /*
 145  * Install specified rule for a specific interface. The preference is what
 146  * goes in the rule to denote relative ordering; it may or may not be the
 147  * same as the rule's user-defined sequence number.
 148  */
 149 enum zebra_dplane_result kernel_add_pbr_rule(struct zebra_pbr_rule *rule)
 150 {
 151         int ret = 0;
 152
 153         ret = netlink_rule_update(RTM_NEWRULE, rule);
 154         kernel_pbr_rule_add_del_status(rule,
 155                                        (!ret) ? ZEBRA_DPLANE_INSTALL_SUCCESS
 156                                               : ZEBRA_DPLANE_INSTALL_FAILURE);
 157
 158         return ZEBRA_DPLANE_REQUEST_SUCCESS;
 159 }
 160
 161 /*
 162  * Uninstall specified rule for a specific interface.
 163  */
 164 enum zebra_dplane_result kernel_del_pbr_rule(struct zebra_pbr_rule *rule)
 165 {
 166         int ret = 0;
 167
 168         ret = netlink_rule_update(RTM_DELRULE, rule);
 169         kernel_pbr_rule_add_del_status(rule,
 170                                        (!ret) ? ZEBRA_DPLANE_DELETE_SUCCESS
 171                                               : ZEBRA_DPLANE_DELETE_FAILURE);
 172
 173         return ZEBRA_DPLANE_REQUEST_SUCCESS;
 174 }
 175
 176 /*
 177  * Handle netlink notification informing a rule add or delete.
 178  * Handling of an ADD is TBD.
 179  * DELs are notified up, if other attributes indicate it may be a
 180  * notification of interest. The expectation is that if this corresponds
 181  * to a PBR rule added by FRR, it will be readded.
 182  */
 183 int netlink_rule_change(struct nlmsghdr *h, ns_id_t ns_id, int startup)
 184 {
 185         struct zebra_ns *zns;
 186         struct fib_rule_hdr *frh;
 187         struct rtattr *tb[FRA_MAX + 1];
 188         int len;
 189         char *ifname;
 190         struct zebra_pbr_rule rule = {};
 191         char buf1[PREFIX_STRLEN];
 192         char buf2[PREFIX_STRLEN];
 193
 194         /* Basic validation followed by extracting attributes. */
 195         if (h->nlmsg_type != RTM_NEWRULE && h->nlmsg_type != RTM_DELRULE)
 196                 return 0;
 197
 198         /* TBD */
 199         if (h->nlmsg_type == RTM_NEWRULE)
 200                 return 0;
 201
 202         len = h->nlmsg_len - NLMSG_LENGTH(sizeof(struct fib_rule_hdr));
 203         if (len < 0) {
 204                 zlog_err("%s: Message received from netlink is of a broken size: %d %zu",
 205                          __PRETTY_FUNCTION__, h->nlmsg_len,
 206                          (size_t)NLMSG_LENGTH(sizeof(struct fib_rule_hdr)));
 207                 return -1;
 208         }
 209
 210         frh = NLMSG_DATA(h);
 211         if (frh->family != AF_INET && frh->family != AF_INET6) {
 212                 flog_warn(
 213                         EC_ZEBRA_NETLINK_INVALID_AF,
 214                         "Invalid address family: %u received from kernel rule change: %u",
 215                         frh->family, h->nlmsg_type);
 216                 return 0;
 217         }
 218         if (frh->action != FR_ACT_TO_TBL)
 219                 return 0;
 220
 221         memset(tb, 0, sizeof(tb));
 222         netlink_parse_rtattr(tb, FRA_MAX, RTM_RTA(frh), len);
 223
 224         /* TBD: We don't care about rules not specifying an IIF. */
 225         if (tb[FRA_IFNAME] == NULL)
 226                 return 0;
 227
 228         ifname = (char *)RTA_DATA(tb[FRA_IFNAME]);
 229         zns = zebra_ns_lookup(ns_id);
 230
 231         /* If we don't know the interface, we don't care. */
 232         if (!if_lookup_by_name_per_ns(zns, ifname))
 233                 return 0;
 234
 235         strlcpy(rule.ifname, ifname, sizeof(rule.ifname));
 236
 237         if (tb[FRA_PRIORITY])
 238                 rule.rule.priority = *(uint32_t *)RTA_DATA(tb[FRA_PRIORITY]);
 239
 240         if (tb[FRA_SRC]) {
 241                 if (frh->family == AF_INET)
 242                         memcpy(&rule.rule.filter.src_ip.u.prefix4,
 243                                RTA_DATA(tb[FRA_SRC]), 4);
 244                 else
 245                         memcpy(&rule.rule.filter.src_ip.u.prefix6,
 246                                RTA_DATA(tb[FRA_SRC]), 16);
 247                 rule.rule.filter.src_ip.prefixlen = frh->src_len;
 248                 rule.rule.filter.filter_bm |= PBR_FILTER_SRC_IP;
 249         }
 250
 251         if (tb[FRA_DST]) {
 252                 if (frh->family == AF_INET)
 253                         memcpy(&rule.rule.filter.dst_ip.u.prefix4,
 254                                RTA_DATA(tb[FRA_DST]), 4);
 255                 else
 256                         memcpy(&rule.rule.filter.dst_ip.u.prefix6,
 257                                RTA_DATA(tb[FRA_DST]), 16);
 258                 rule.rule.filter.dst_ip.prefixlen = frh->dst_len;
 259                 rule.rule.filter.filter_bm |= PBR_FILTER_DST_IP;
 260         }
 261
 262         if (tb[FRA_TABLE])
 263                 rule.rule.action.table = *(uint32_t *)RTA_DATA(tb[FRA_TABLE]);
 264         else
 265                 rule.rule.action.table = frh->table;
 266
 267         if (IS_ZEBRA_DEBUG_KERNEL)
 268                 zlog_debug(
 269                         "Rx %s family %s IF %s(%u) Pref %u Src %s Dst %s Table %u",
 270                         nl_msg_type_to_str(h->nlmsg_type),
 271                         nl_family_to_str(frh->family), rule.ifname,
 272                         rule.rule.ifindex, rule.rule.priority,
 273                         prefix2str(&rule.rule.filter.src_ip, buf1,
 274                                    sizeof(buf1)),
 275                         prefix2str(&rule.rule.filter.dst_ip, buf2,
 276                                    sizeof(buf2)),
 277                         rule.rule.action.table);
 278
 279         return kernel_pbr_rule_del(&rule);
 280 }
 281
 282 /*
 283  * Get to know existing PBR rules in the kernel - typically called at startup.
 284  * TBD.
 285  */
 286 int netlink_rules_read(struct zebra_ns *zns)
 287 {
 288         return 0;
 289 }
 290
 291 #endif /* HAVE_NETLINK */