Merge pull request #2561 from pacovn/Coverity_1399231_Logically_dead_code

[mirror_frr.git] / zebra / kernel_netlink.c

/* Kernel communication using netlink interface.
 * Copyright (C) 1999 Kunihiro Ishiguro
 *
 * This file is part of GNU Zebra.
 *
 * GNU Zebra is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2, or (at your option) any
 * later version.
 *
 * GNU Zebra is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; see the file COPYING; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <zebra.h>

#ifdef HAVE_NETLINK

#include "linklist.h"
#include "if.h"
#include "log.h"
#include "prefix.h"
#include "connected.h"
#include "table.h"
#include "memory.h"
#include "zebra_memory.h"
#include "rib.h"
#include "thread.h"
#include "privs.h"
#include "nexthop.h"
#include "vrf.h"
#include "mpls.h"

#include "zebra/zserv.h"
#include "zebra/zebra_ns.h"
#include "zebra/zebra_vrf.h"
#include "zebra/rt.h"
#include "zebra/debug.h"
#include "zebra/kernel_netlink.h"
#include "zebra/rt_netlink.h"
#include "zebra/if_netlink.h"
#include "zebra/rule_netlink.h"

#ifndef SO_RCVBUFFORCE
#define SO_RCVBUFFORCE  (33)
#endif

/* Hack for GNU libc version 2. */
#ifndef MSG_TRUNC
#define MSG_TRUNC      0x20
#endif /* MSG_TRUNC */

#ifndef NLMSG_TAIL
#define NLMSG_TAIL(nmsg)                                                       \
        ((struct rtattr *)(((uint8_t *)(nmsg))                                 \
                           + NLMSG_ALIGN((nmsg)->nlmsg_len)))
#endif

#ifndef RTA_TAIL
#define RTA_TAIL(rta)                                                          \
        ((struct rtattr *)(((uint8_t *)(rta)) + RTA_ALIGN((rta)->rta_len)))
#endif

#ifndef RTNL_FAMILY_IP6MR
#define RTNL_FAMILY_IP6MR 129
#endif

#ifndef RTPROT_MROUTED
#define RTPROT_MROUTED 17
#endif

static const struct message nlmsg_str[] = {{RTM_NEWROUTE, "RTM_NEWROUTE"},
                                           {RTM_DELROUTE, "RTM_DELROUTE"},
                                           {RTM_GETROUTE, "RTM_GETROUTE"},
                                           {RTM_NEWLINK, "RTM_NEWLINK"},
                                           {RTM_DELLINK, "RTM_DELLINK"},
                                           {RTM_GETLINK, "RTM_GETLINK"},
                                           {RTM_NEWADDR, "RTM_NEWADDR"},
                                           {RTM_DELADDR, "RTM_DELADDR"},
                                           {RTM_GETADDR, "RTM_GETADDR"},
                                           {RTM_NEWNEIGH, "RTM_NEWNEIGH"},
                                           {RTM_DELNEIGH, "RTM_DELNEIGH"},
                                           {RTM_GETNEIGH, "RTM_GETNEIGH"},
                                           {RTM_NEWRULE, "RTM_NEWRULE"},
                                           {RTM_DELRULE, "RTM_DELRULE"},
                                           {RTM_GETRULE, "RTM_GETRULE"},
                                           {0}};

static const struct message rtproto_str[] = {
        {RTPROT_REDIRECT, "redirect"},
        {RTPROT_KERNEL, "kernel"},
        {RTPROT_BOOT, "boot"},
        {RTPROT_STATIC, "static"},
        {RTPROT_GATED, "GateD"},
        {RTPROT_RA, "router advertisement"},
        {RTPROT_MRT, "MRT"},
        {RTPROT_ZEBRA, "Zebra"},
#ifdef RTPROT_BIRD
        {RTPROT_BIRD, "BIRD"},
#endif /* RTPROT_BIRD */
        {RTPROT_MROUTED, "mroute"},
        {RTPROT_BGP, "BGP"},
        {RTPROT_OSPF, "OSPF"},
        {RTPROT_ISIS, "IS-IS"},
        {RTPROT_RIP, "RIP"},
        {RTPROT_RIPNG, "RIPNG"},
        {RTPROT_ZSTATIC, "static"},
        {0}};

static const struct message family_str[] = {{AF_INET, "ipv4"},
                                            {AF_INET6, "ipv6"},
                                            {AF_BRIDGE, "bridge"},
                                            {RTNL_FAMILY_IPMR, "ipv4MR"},
                                            {RTNL_FAMILY_IP6MR, "ipv6MR"},
                                            {0}};

static const struct message rttype_str[] = {{RTN_UNICAST, "unicast"},
                                            {RTN_MULTICAST, "multicast"},
                                            {0}};

extern struct thread_master *master;
extern uint32_t nl_rcvbufsize;

extern struct zebra_privs_t zserv_privs;

int netlink_talk_filter(struct nlmsghdr *h, ns_id_t ns_id, int startup)
{
        /*
         * This is an error condition that must be handled during
         * development.
         *
         * The netlink_talk_filter function is used for communication
         * down the netlink_cmd pipe and we are expecting
         * an ack being received.  So if we get here
         * then we did not receive the ack and instead
         * received some other message in an unexpected
         * way.
         */
        zlog_err("%s: ignoring message type 0x%04x(%s) NS %u",
                 __PRETTY_FUNCTION__, h->nlmsg_type,
                 nl_msg_type_to_str(h->nlmsg_type), ns_id);
        return 0;
}

static int netlink_recvbuf(struct nlsock *nl, uint32_t newsize)
{
        uint32_t oldsize;
        socklen_t newlen = sizeof(newsize);
        socklen_t oldlen = sizeof(oldsize);
        int ret;

        ret = getsockopt(nl->sock, SOL_SOCKET, SO_RCVBUF, &oldsize, &oldlen);
        if (ret < 0) {
                zlog_err("Can't get %s receive buffer size: %s", nl->name,
                         safe_strerror(errno));
                return -1;
        }

        /* Try force option (linux >= 2.6.14) and fall back to normal set */
        if (zserv_privs.change(ZPRIVS_RAISE))
                zlog_err("routing_socket: Can't raise privileges");
        ret = setsockopt(nl->sock, SOL_SOCKET, SO_RCVBUFFORCE, &nl_rcvbufsize,
                         sizeof(nl_rcvbufsize));
        if (zserv_privs.change(ZPRIVS_LOWER))
                zlog_err("routing_socket: Can't lower privileges");
        if (ret < 0)
                ret = setsockopt(nl->sock, SOL_SOCKET, SO_RCVBUF,
                                 &nl_rcvbufsize, sizeof(nl_rcvbufsize));
        if (ret < 0) {
                zlog_err("Can't set %s receive buffer size: %s", nl->name,
                         safe_strerror(errno));
                return -1;
        }

        ret = getsockopt(nl->sock, SOL_SOCKET, SO_RCVBUF, &newsize, &newlen);
        if (ret < 0) {
                zlog_err("Can't get %s receive buffer size: %s", nl->name,
                         safe_strerror(errno));
                return -1;
        }

        zlog_info("Setting netlink socket receive buffer size: %u -> %u",
                  oldsize, newsize);
        return 0;
}

/* Make socket for Linux netlink interface. */
static int netlink_socket(struct nlsock *nl, unsigned long groups,
                          ns_id_t ns_id)
{
        int ret;
        struct sockaddr_nl snl;
        int sock;
        int namelen;
        int save_errno;

        if (zserv_privs.change(ZPRIVS_RAISE)) {
                zlog_err("Can't raise privileges");
                return -1;
        }

        sock = ns_socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE, ns_id);
        if (sock < 0) {
                zlog_err("Can't open %s socket: %s", nl->name,
                         safe_strerror(errno));
                return -1;
        }

        memset(&snl, 0, sizeof snl);
        snl.nl_family = AF_NETLINK;
        snl.nl_groups = groups;

        /* Bind the socket to the netlink structure for anything. */
        ret = bind(sock, (struct sockaddr *)&snl, sizeof snl);
        save_errno = errno;
        if (zserv_privs.change(ZPRIVS_LOWER))
                zlog_err("Can't lower privileges");

        if (ret < 0) {
                zlog_err("Can't bind %s socket to group 0x%x: %s", nl->name,
                         snl.nl_groups, safe_strerror(save_errno));
                close(sock);
                return -1;
        }

        /* multiple netlink sockets will have different nl_pid */
        namelen = sizeof snl;
        ret = getsockname(sock, (struct sockaddr *)&snl, (socklen_t *)&namelen);
        if (ret < 0 || namelen != sizeof snl) {
                zlog_err("Can't get %s socket name: %s", nl->name,
                         safe_strerror(errno));
                close(sock);
                return -1;
        }

        nl->snl = snl;
        nl->sock = sock;
        return ret;
}

static int netlink_information_fetch(struct nlmsghdr *h, ns_id_t ns_id,
                                     int startup)
{
        /*
         * When we handle new message types here
         * because we are starting to install them
         * then lets check the netlink_install_filter
         * and see if we should add the corresponding
         * allow through entry there.
         * Probably not needed to do but please
         * think about it.
         */
        switch (h->nlmsg_type) {
        case RTM_NEWROUTE:
                return netlink_route_change(h, ns_id, startup);
        case RTM_DELROUTE:
                return netlink_route_change(h, ns_id, startup);
        case RTM_NEWLINK:
                return netlink_link_change(h, ns_id, startup);
        case RTM_DELLINK:
                return netlink_link_change(h, ns_id, startup);
        case RTM_NEWADDR:
                return netlink_interface_addr(h, ns_id, startup);
        case RTM_DELADDR:
                return netlink_interface_addr(h, ns_id, startup);
        case RTM_NEWNEIGH:
                return netlink_neigh_change(h, ns_id);
        case RTM_DELNEIGH:
                return netlink_neigh_change(h, ns_id);
        case RTM_NEWRULE:
                return netlink_rule_change(h, ns_id, startup);
        case RTM_DELRULE:
                return netlink_rule_change(h, ns_id, startup);
        default:
                /*
                 * If we have received this message then
                 * we have made a mistake during development
                 * and we need to write some code to handle
                 * this message type or not ask for
                 * it to be sent up to us
                 */
                zlog_err("Unknown netlink nlmsg_type %s(%d) vrf %u\n",
                         nl_msg_type_to_str(h->nlmsg_type), h->nlmsg_type,
                         ns_id);
                break;
        }
        return 0;
}

static int kernel_read(struct thread *thread)
{
        struct zebra_ns *zns = (struct zebra_ns *)THREAD_ARG(thread);
        netlink_parse_info(netlink_information_fetch, &zns->netlink, zns, 5, 0);
        zns->t_netlink = NULL;
        thread_add_read(zebrad.master, kernel_read, zns, zns->netlink.sock,
                        &zns->t_netlink);

        return 0;
}

/*
 * Filter out messages from self that occur on listener socket,
 * caused by our actions on the command socket
 *
 * When we add new Netlink message types we probably
 * do not need to add them here as that we are filtering
 * on the routes we actually care to receive( which is rarer
 * then the normal course of operations).  We are intentionally
 * allowing some messages from ourselves through
 * ( I'm looking at you Interface based netlink messages )
 * so that we only had to write one way to handle incoming
 * address add/delete changes.
 */
static void netlink_install_filter(int sock, __u32 pid)
{
        /*
         * BPF_JUMP instructions and where you jump to are based upon
         * 0 as being the next statement.  So count from 0.  Writing
         * this down because every time I look at this I have to
         * re-remember it.
         */
        struct sock_filter filter[] = {
                /*
                 * Logic:
                 *   if (nlmsg_pid == pid) {
                 *       if (the incoming nlmsg_type ==
                 *           RTM_NEWADDR | RTM_DELADDR)
                 *           keep this message
                 *       else
                 *           skip this message
                 *   } else
                 *       keep this netlink message
                 */
                /*
                 * 0: Load the nlmsg_pid into the BPF register
                 */
                BPF_STMT(BPF_LD | BPF_ABS | BPF_W,
                         offsetof(struct nlmsghdr, nlmsg_pid)),
                /*
                 * 1: Compare to pid
                 */
                BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, htonl(pid), 0, 4),
                /*
                 * 2: Load the nlmsg_type into BPF register
                 */
                BPF_STMT(BPF_LD | BPF_ABS | BPF_H,
                         offsetof(struct nlmsghdr, nlmsg_type)),
                /*
                 * 3: Compare to RTM_NEWADDR
                 */
                BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, htons(RTM_NEWADDR), 2, 0),
                /*
                 * 4: Compare to RTM_DELADDR
                 */
                BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, htons(RTM_DELADDR), 1, 0),
                /*
                 * 5: This is the end state of we want to skip the
                 *    message
                 */
                BPF_STMT(BPF_RET | BPF_K, 0),
                /* 6: This is the end state of we want to keep
                 *     the message
                 */
                BPF_STMT(BPF_RET | BPF_K, 0xffff),
        };

        struct sock_fprog prog = {
                .len = array_size(filter), .filter = filter,
        };

        if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER, &prog, sizeof(prog))
            < 0)
                zlog_warn("Can't install socket filter: %s\n",
                          safe_strerror(errno));
}

void netlink_parse_rtattr(struct rtattr **tb, int max, struct rtattr *rta,
                          int len)
{
        while (RTA_OK(rta, len)) {
                if (rta->rta_type <= max)
                        tb[rta->rta_type] = rta;
                rta = RTA_NEXT(rta, len);
        }
}

int addattr_l(struct nlmsghdr *n, unsigned int maxlen, int type, void *data,
              unsigned int alen)
{
        int len;
        struct rtattr *rta;

        len = RTA_LENGTH(alen);

        if (NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len) > maxlen)
                return -1;

        rta = (struct rtattr *)(((char *)n) + NLMSG_ALIGN(n->nlmsg_len));
        rta->rta_type = type;
        rta->rta_len = len;

        if (data)
                memcpy(RTA_DATA(rta), data, alen);
        else
                assert(alen == 0);

        n->nlmsg_len = NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len);

        return 0;
}

int rta_addattr_l(struct rtattr *rta, unsigned int maxlen, int type, void *data,
                  unsigned int alen)
{
        unsigned int len;
        struct rtattr *subrta;

        len = RTA_LENGTH(alen);

        if (RTA_ALIGN(rta->rta_len) + RTA_ALIGN(len) > maxlen)
                return -1;

        subrta = (struct rtattr *)(((char *)rta) + RTA_ALIGN(rta->rta_len));
        subrta->rta_type = type;
        subrta->rta_len = len;

        if (data)
                memcpy(RTA_DATA(subrta), data, alen);
        else
                assert(alen == 0);

        rta->rta_len = NLMSG_ALIGN(rta->rta_len) + RTA_ALIGN(len);

        return 0;
}

int addattr16(struct nlmsghdr *n, unsigned int maxlen, int type, uint16_t data)
{
        return addattr_l(n, maxlen, type, &data, sizeof(uint16_t));
}

int addattr32(struct nlmsghdr *n, unsigned int maxlen, int type, int data)
{
        return addattr_l(n, maxlen, type, &data, sizeof(uint32_t));
}

struct rtattr *addattr_nest(struct nlmsghdr *n, int maxlen, int type)
{
        struct rtattr *nest = NLMSG_TAIL(n);

        addattr_l(n, maxlen, type, NULL, 0);
        return nest;
}

int addattr_nest_end(struct nlmsghdr *n, struct rtattr *nest)
{
        nest->rta_len = (uint8_t *)NLMSG_TAIL(n) - (uint8_t *)nest;
        return n->nlmsg_len;
}

struct rtattr *rta_nest(struct rtattr *rta, int maxlen, int type)
{
        struct rtattr *nest = RTA_TAIL(rta);

        rta_addattr_l(rta, maxlen, type, NULL, 0);
        return nest;
}

int rta_nest_end(struct rtattr *rta, struct rtattr *nest)
{
        nest->rta_len = (uint8_t *)RTA_TAIL(rta) - (uint8_t *)nest;
        return rta->rta_len;
}

const char *nl_msg_type_to_str(uint16_t msg_type)
{
        return lookup_msg(nlmsg_str, msg_type, "");
}

const char *nl_rtproto_to_str(uint8_t rtproto)
{
        return lookup_msg(rtproto_str, rtproto, "");
}

const char *nl_family_to_str(uint8_t family)
{
        return lookup_msg(family_str, family, "");
}

const char *nl_rttype_to_str(uint8_t rttype)
{
        return lookup_msg(rttype_str, rttype, "");
}

#define NL_OK(nla, len)                                                        \
        ((len) >= (int)sizeof(struct nlattr)                                   \
         && (nla)->nla_len >= sizeof(struct nlattr)                            \
         && (nla)->nla_len <= (len))
#define NL_NEXT(nla, attrlen)                                                  \
        ((attrlen) -= RTA_ALIGN((nla)->nla_len),                               \
         (struct nlattr *)(((char *)(nla)) + RTA_ALIGN((nla)->nla_len)))
#define NL_RTA(r)                                                              \
        ((struct nlattr *)(((char *)(r))                                       \
                           + NLMSG_ALIGN(sizeof(struct nlmsgerr))))

static void netlink_parse_nlattr(struct nlattr **tb, int max,
                                 struct nlattr *nla, int len)
{
        while (NL_OK(nla, len)) {
                if (nla->nla_type <= max)
                        tb[nla->nla_type] = nla;
                nla = NL_NEXT(nla, len);
        }
}

static void netlink_parse_extended_ack(struct nlmsghdr *h)
{
        struct nlattr *tb[NLMSGERR_ATTR_MAX + 1];
        const struct nlmsgerr *err =
                (const struct nlmsgerr *)((uint8_t *)h
                                          + NLMSG_ALIGN(
                                                    sizeof(struct nlmsghdr)));
        const struct nlmsghdr *err_nlh = NULL;
        uint32_t hlen = sizeof(*err);
        const char *msg = NULL;
        uint32_t off = 0;

        if (!(h->nlmsg_flags & NLM_F_CAPPED))
                hlen += h->nlmsg_len - NLMSG_ALIGN(sizeof(struct nlmsghdr));

        memset(tb, 0, sizeof(tb));
        netlink_parse_nlattr(tb, NLMSGERR_ATTR_MAX, NL_RTA(h), hlen);

        if (tb[NLMSGERR_ATTR_MSG])
                msg = (const char *)RTA_DATA(tb[NLMSGERR_ATTR_MSG]);

        if (tb[NLMSGERR_ATTR_OFFS]) {
                off = *(uint32_t *)RTA_DATA(tb[NLMSGERR_ATTR_OFFS]);

                if (off > h->nlmsg_len) {
                        zlog_err("Invalid offset for NLMSGERR_ATTR_OFFS\n");
                        off = 0;
                } else if (!(h->nlmsg_flags & NLM_F_CAPPED)) {
                        /*
                         * Header of failed message
                         * we are not doing anything currently with it
                         * but noticing it for later.
                         */
                        err_nlh = &err->msg;
                        zlog_warn("%s: Received %d extended Ack",
                                  __PRETTY_FUNCTION__, err_nlh->nlmsg_type);
                }
        }

        if (msg && *msg != '\0') {
                bool is_err = !!err->error;

                if (is_err)
                        zlog_err("Extended Error: %s", msg);
                else
                        zlog_warn("Extended Warning: %s", msg);
        }
}

/*
 * netlink_parse_info
 *
 * Receive message from netlink interface and pass those information
 *  to the given function.
 *
 * filter  -> Function to call to read the results
 * nl      -> netlink socket information
 * zns     -> The zebra namespace data
 * count   -> How many we should read in, 0 means as much as possible
 * startup -> Are we reading in under startup conditions? passed to
 *            the filter.
 */
int netlink_parse_info(int (*filter)(struct nlmsghdr *, ns_id_t, int),
                       struct nlsock *nl, struct zebra_ns *zns, int count,
                       int startup)
{
        int status;
        int ret = 0;
        int error;
        int read_in = 0;

        while (1) {
                char buf[NL_RCV_PKT_BUF_SIZE];
                struct iovec iov = {.iov_base = buf, .iov_len = sizeof buf};
                struct sockaddr_nl snl;
                struct msghdr msg = {.msg_name = (void *)&snl,
                                     .msg_namelen = sizeof snl,
                                     .msg_iov = &iov,
                                     .msg_iovlen = 1};
                struct nlmsghdr *h;

                if (count && read_in >= count)
                        return 0;

                status = recvmsg(nl->sock, &msg, 0);
                if (status < 0) {
                        if (errno == EINTR)
                                continue;
                        if (errno == EWOULDBLOCK || errno == EAGAIN)
                                break;
                        zlog_err("%s recvmsg overrun: %s", nl->name,
                                 safe_strerror(errno));
                        /*
                         *  In this case we are screwed.
                         *  There is no good way to
                         *  recover zebra at this point.
                         */
                        exit(-1);
                        continue;
                }

                if (status == 0) {
                        zlog_err("%s EOF", nl->name);
                        return -1;
                }

                if (msg.msg_namelen != sizeof snl) {
                        zlog_err("%s sender address length error: length %d",
                                 nl->name, msg.msg_namelen);
                        return -1;
                }

                if (IS_ZEBRA_DEBUG_KERNEL_MSGDUMP_RECV) {
                        zlog_debug("%s: << netlink message dump [recv]",
                                   __func__);
                        zlog_hexdump(buf, status);
                }

                read_in++;
                for (h = (struct nlmsghdr *)buf;
                     NLMSG_OK(h, (unsigned int)status);
                     h = NLMSG_NEXT(h, status)) {
                        /* Finish of reading. */
                        if (h->nlmsg_type == NLMSG_DONE)
                                return ret;

                        /* Error handling. */
                        if (h->nlmsg_type == NLMSG_ERROR) {
                                struct nlmsgerr *err =
                                        (struct nlmsgerr *)NLMSG_DATA(h);
                                int errnum = err->error;
                                int msg_type = err->msg.nlmsg_type;

                                if (h->nlmsg_len
                                    < NLMSG_LENGTH(sizeof(struct nlmsgerr))) {
                                        zlog_err("%s error: message truncated",
                                                 nl->name);
                                        return -1;
                                }

                                /*
                                 * Parse the extended information before
                                 * we actually handle it.
                                 * At this point in time we do not
                                 * do anything other than report the
                                 * issue.
                                 */
                                if (h->nlmsg_flags & NLM_F_ACK_TLVS)
                                        netlink_parse_extended_ack(h);

                                /* If the error field is zero, then this is an
                                 * ACK */
                                if (err->error == 0) {
                                        if (IS_ZEBRA_DEBUG_KERNEL) {
                                                zlog_debug(
                                                        "%s: %s ACK: type=%s(%u), seq=%u, pid=%u",
                                                        __FUNCTION__, nl->name,
                                                        nl_msg_type_to_str(
                                                                err->msg.nlmsg_type),
                                                        err->msg.nlmsg_type,
                                                        err->msg.nlmsg_seq,
                                                        err->msg.nlmsg_pid);
                                        }

                                        /* return if not a multipart message,
                                         * otherwise continue */
                                        if (!(h->nlmsg_flags & NLM_F_MULTI))
                                                return 0;
                                        continue;
                                }

                                /* Deal with errors that occur because of races
                                 * in link handling */
                                if (nl == &zns->netlink_cmd
                                    && ((msg_type == RTM_DELROUTE
                                         && (-errnum == ENODEV
                                             || -errnum == ESRCH))
                                        || (msg_type == RTM_NEWROUTE
                                            && (-errnum == ENETDOWN
                                                || -errnum == EEXIST)))) {
                                        if (IS_ZEBRA_DEBUG_KERNEL)
                                                zlog_debug(
                                                        "%s: error: %s type=%s(%u), seq=%u, pid=%u",
                                                        nl->name,
                                                        safe_strerror(-errnum),
                                                        nl_msg_type_to_str(
                                                                msg_type),
                                                        msg_type,
                                                        err->msg.nlmsg_seq,
                                                        err->msg.nlmsg_pid);
                                        return 0;
                                }

                                /* We see RTM_DELNEIGH when shutting down an
                                 * interface with an IPv4
                                 * link-local.  The kernel should have already
                                 * deleted the neighbor
                                 * so do not log these as an error.
                                 */
                                if (msg_type == RTM_DELNEIGH
                                    || (nl == &zns->netlink_cmd
                                        && msg_type == RTM_NEWROUTE
                                        && (-errnum == ESRCH
                                            || -errnum == ENETUNREACH))) {
                                        /* This is known to happen in some
                                         * situations, don't log
                                         * as error.
                                         */
                                        if (IS_ZEBRA_DEBUG_KERNEL)
                                                zlog_debug(
                                                        "%s error: %s, type=%s(%u), seq=%u, pid=%u",
                                                        nl->name,
                                                        safe_strerror(-errnum),
                                                        nl_msg_type_to_str(
                                                                msg_type),
                                                        msg_type,
                                                        err->msg.nlmsg_seq,
                                                        err->msg.nlmsg_pid);
                                } else
                                        zlog_err(
                                                "%s error: %s, type=%s(%u), seq=%u, pid=%u",
                                                nl->name,
                                                safe_strerror(-errnum),
                                                nl_msg_type_to_str(msg_type),
                                                msg_type, err->msg.nlmsg_seq,
                                                err->msg.nlmsg_pid);

                                return -1;
                        }

                        /* OK we got netlink message. */
                        if (IS_ZEBRA_DEBUG_KERNEL)
                                zlog_debug(
                                        "netlink_parse_info: %s type %s(%u), len=%d, seq=%u, pid=%u",
                                        nl->name,
                                        nl_msg_type_to_str(h->nlmsg_type),
                                        h->nlmsg_type, h->nlmsg_len,
                                        h->nlmsg_seq, h->nlmsg_pid);


                        /*
                         * Ignore messages that maybe sent from
                         * other actors besides the kernel
                         */
                        if (snl.nl_pid != 0) {
                                zlog_err("Ignoring message from pid %u",
                                         snl.nl_pid);
                                continue;
                        }

                        error = (*filter)(h, zns->ns_id, startup);
                        if (error < 0) {
                                zlog_err("%s filter function error", nl->name);
                                zlog_backtrace(LOG_ERR);
                                ret = error;
                        }
                }

                /* After error care. */
                if (msg.msg_flags & MSG_TRUNC) {
                        zlog_err("%s error: message truncated", nl->name);
                        continue;
                }
                if (status) {
                        zlog_err("%s error: data remnant size %d", nl->name,
                                 status);
                        return -1;
                }
        }
        return ret;
}

/*
 * netlink_talk
 *
 * sendmsg() to netlink socket then recvmsg().
 * Calls netlink_parse_info to parse returned data
 *
 * filter   -> The filter to read final results from kernel
 * nlmsghdr -> The data to send to the kernel
 * nl       -> The netlink socket information
 * zns      -> The zebra namespace information
 * startup  -> Are we reading in under startup conditions
 *             This is passed through eventually to filter.
 */
int netlink_talk(int (*filter)(struct nlmsghdr *, ns_id_t, int startup),
                 struct nlmsghdr *n, struct nlsock *nl, struct zebra_ns *zns,
                 int startup)
{
        int status;
        struct sockaddr_nl snl;
        struct iovec iov;
        struct msghdr msg;
        int save_errno;

        memset(&snl, 0, sizeof snl);
        memset(&iov, 0, sizeof iov);
        memset(&msg, 0, sizeof msg);

        iov.iov_base = n;
        iov.iov_len = n->nlmsg_len;
        msg.msg_name = (void *)&snl;
        msg.msg_namelen = sizeof snl;
        msg.msg_iov = &iov;
        msg.msg_iovlen = 1;

        snl.nl_family = AF_NETLINK;

        n->nlmsg_seq = ++nl->seq;
        n->nlmsg_pid = nl->snl.nl_pid;

        /* Request an acknowledgement by setting NLM_F_ACK */
        n->nlmsg_flags |= NLM_F_ACK;

        if (IS_ZEBRA_DEBUG_KERNEL)
                zlog_debug(
                        "netlink_talk: %s type %s(%u), len=%d seq=%u flags 0x%x",
                        nl->name, nl_msg_type_to_str(n->nlmsg_type),
                        n->nlmsg_type, n->nlmsg_len, n->nlmsg_seq,
                        n->nlmsg_flags);

        /* Send message to netlink interface. */
        if (zserv_privs.change(ZPRIVS_RAISE))
                zlog_err("Can't raise privileges");
        status = sendmsg(nl->sock, &msg, 0);
        save_errno = errno;
        if (zserv_privs.change(ZPRIVS_LOWER))
                zlog_err("Can't lower privileges");

        if (IS_ZEBRA_DEBUG_KERNEL_MSGDUMP_SEND) {
                zlog_debug("%s: >> netlink message dump [sent]", __func__);
                zlog_hexdump(n, n->nlmsg_len);
        }

        if (status < 0) {
                zlog_err("netlink_talk sendmsg() error: %s",
                         safe_strerror(save_errno));
                return -1;
        }


        /*
         * Get reply from netlink socket.
         * The reply should either be an acknowlegement or an error.
         */
        return netlink_parse_info(filter, nl, zns, 0, startup);
}

/* Issue request message to kernel via netlink socket. GET messages
 * are issued through this interface.
 */
int netlink_request(struct nlsock *nl, struct nlmsghdr *n)
{
        int ret;
        struct sockaddr_nl snl;
        int save_errno;

        /* Check netlink socket. */
        if (nl->sock < 0) {
                zlog_err("%s socket isn't active.", nl->name);
                return -1;
        }

        /* Fill common fields for all requests. */
        n->nlmsg_flags = NLM_F_ROOT | NLM_F_MATCH | NLM_F_REQUEST;
        n->nlmsg_pid = nl->snl.nl_pid;
        n->nlmsg_seq = ++nl->seq;

        memset(&snl, 0, sizeof snl);
        snl.nl_family = AF_NETLINK;

        /* Raise capabilities and send message, then lower capabilities. */
        if (zserv_privs.change(ZPRIVS_RAISE)) {
                zlog_err("Can't raise privileges");
                return -1;
        }

        ret = sendto(nl->sock, (void *)n, n->nlmsg_len, 0,
                     (struct sockaddr *)&snl, sizeof snl);
        save_errno = errno;

        if (zserv_privs.change(ZPRIVS_LOWER))
                zlog_err("Can't lower privileges");

        if (ret < 0) {
                zlog_err("%s sendto failed: %s", nl->name,
                         safe_strerror(save_errno));
                return -1;
        }

        return 0;
}

/* Exported interface function.  This function simply calls
   netlink_socket (). */
void kernel_init(struct zebra_ns *zns)
{
        unsigned long groups;
#if defined SOL_NETLINK
        int one, ret;
#endif

        /*
         * Initialize netlink sockets
         *
         * If RTMGRP_XXX exists use that, but at some point
         * I think the kernel developers realized that
         * keeping track of all the different values would
         * lead to confusion, so we need to convert the
         * RTNLGRP_XXX to a bit position for ourself
         */
        groups = RTMGRP_LINK                   |
                RTMGRP_IPV4_ROUTE              |
                RTMGRP_IPV4_IFADDR             |
                RTMGRP_IPV6_ROUTE              |
                RTMGRP_IPV6_IFADDR             |
                RTMGRP_IPV4_MROUTE             |
                RTMGRP_NEIGH                   |
                (1 << (RTNLGRP_IPV4_RULE - 1)) |
                (1 << (RTNLGRP_IPV6_RULE - 1));

        snprintf(zns->netlink.name, sizeof(zns->netlink.name),
                 "netlink-listen (NS %u)", zns->ns_id);
        zns->netlink.sock = -1;
        netlink_socket(&zns->netlink, groups, zns->ns_id);

        snprintf(zns->netlink_cmd.name, sizeof(zns->netlink_cmd.name),
                 "netlink-cmd (NS %u)", zns->ns_id);
        zns->netlink_cmd.sock = -1;
        netlink_socket(&zns->netlink_cmd, 0, zns->ns_id);

        /*
         * SOL_NETLINK is not available on all platforms yet
         * apparently.  It's in bits/socket.h which I am not
         * sure that we want to pull into our build system.
         */
#if defined SOL_NETLINK
        /*
         * Let's tell the kernel that we want to receive extended
         * ACKS over our command socket
         */
        one = 1;
        ret = setsockopt(zns->netlink_cmd.sock, SOL_NETLINK, NETLINK_EXT_ACK,
                         &one, sizeof(one));

        if (ret < 0)
                zlog_notice("Registration for extended ACK failed : %d %s",
                            errno, safe_strerror(errno));
#endif

        /* Register kernel socket. */
        if (zns->netlink.sock > 0) {
                /* Only want non-blocking on the netlink event socket */
                if (fcntl(zns->netlink.sock, F_SETFL, O_NONBLOCK) < 0)
                        zlog_err("Can't set %s socket flags: %s",
                                 zns->netlink.name, safe_strerror(errno));

                /* Set receive buffer size if it's set from command line */
                if (nl_rcvbufsize)
                        netlink_recvbuf(&zns->netlink, nl_rcvbufsize);

                netlink_install_filter(zns->netlink.sock,
                                       zns->netlink_cmd.snl.nl_pid);
                zns->t_netlink = NULL;

                thread_add_read(zebrad.master, kernel_read, zns,
                                zns->netlink.sock, &zns->t_netlink);
        }

        rt_netlink_init();
}

void kernel_terminate(struct zebra_ns *zns)
{
        THREAD_READ_OFF(zns->t_netlink);

        if (zns->netlink.sock >= 0) {
                close(zns->netlink.sock);
                zns->netlink.sock = -1;
        }

        if (zns->netlink_cmd.sock >= 0) {
                close(zns->netlink_cmd.sock);
                zns->netlink_cmd.sock = -1;
        }
}

#endif /* HAVE_NETLINK */