[mirror_iproute2.git] / lib / libnetlink.c

/*
 * libnetlink.c RTnetlink service routines.
 *
 *              This program 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 of the License, or (at your option) any later version.
 *
 * Authors:     Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <unistd.h>
#include <fcntl.h>
#include <net/if_arp.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>
#include <errno.h>
#include <time.h>
#include <sys/uio.h>
#include <linux/fib_rules.h>
#include <linux/if_addrlabel.h>
#include <linux/if_bridge.h>

#include "libnetlink.h"

#ifndef SOL_NETLINK
#define SOL_NETLINK 270
#endif

#ifndef MIN
#define MIN(a, b) ((a) < (b) ? (a) : (b))
#endif

int rcvbuf = 1024 * 1024;

#ifdef HAVE_LIBMNL
#include <libmnl/libmnl.h>

static const enum mnl_attr_data_type extack_policy[NLMSGERR_ATTR_MAX + 1] = {
        [NLMSGERR_ATTR_MSG]     = MNL_TYPE_NUL_STRING,
        [NLMSGERR_ATTR_OFFS]    = MNL_TYPE_U32,
};

static int err_attr_cb(const struct nlattr *attr, void *data)
{
        const struct nlattr **tb = data;
        uint16_t type;

        if (mnl_attr_type_valid(attr, NLMSGERR_ATTR_MAX) < 0) {
                fprintf(stderr, "Invalid extack attribute\n");
                return MNL_CB_ERROR;
        }

        type = mnl_attr_get_type(attr);
        if (mnl_attr_validate(attr, extack_policy[type]) < 0) {
                fprintf(stderr, "extack attribute %d failed validation\n",
                        type);
                return MNL_CB_ERROR;
        }

        tb[type] = attr;
        return MNL_CB_OK;
}

/* dump netlink extended ack error message */
int nl_dump_ext_ack(const struct nlmsghdr *nlh, nl_ext_ack_fn_t errfn)
{
        struct nlattr *tb[NLMSGERR_ATTR_MAX + 1] = {};
        const struct nlmsgerr *err = mnl_nlmsg_get_payload(nlh);
        const struct nlmsghdr *err_nlh = NULL;
        unsigned int hlen = sizeof(*err);
        const char *msg = NULL;
        uint32_t off = 0;

        /* no TLVs, nothing to do here */
        if (!(nlh->nlmsg_flags & NLM_F_ACK_TLVS))
                return 0;

        /* if NLM_F_CAPPED is set then the inner err msg was capped */
        if (!(nlh->nlmsg_flags & NLM_F_CAPPED))
                hlen += mnl_nlmsg_get_payload_len(&err->msg);

        if (mnl_attr_parse(nlh, hlen, err_attr_cb, tb) != MNL_CB_OK)
                return 0;

        if (tb[NLMSGERR_ATTR_MSG])
                msg = mnl_attr_get_str(tb[NLMSGERR_ATTR_MSG]);

        if (tb[NLMSGERR_ATTR_OFFS]) {
                off = mnl_attr_get_u32(tb[NLMSGERR_ATTR_OFFS]);

                if (off > nlh->nlmsg_len) {
                        fprintf(stderr,
                                "Invalid offset for NLMSGERR_ATTR_OFFS\n");
                        off = 0;
                } else if (!(nlh->nlmsg_flags & NLM_F_CAPPED))
                        err_nlh = &err->msg;
        }

        if (errfn)
                return errfn(msg, off, err_nlh);

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

                fprintf(stderr, "%s: %s",
                        is_err ? "Error" : "Warning", msg);
                if (msg[strlen(msg) - 1] != '.')
                        fprintf(stderr, ".");
                fprintf(stderr, "\n");

                return is_err ? 1 : 0;
        }

        return 0;
}
#else
#warning "libmnl required for error support"

/* No extended error ack without libmnl */
int nl_dump_ext_ack(const struct nlmsghdr *nlh, nl_ext_ack_fn_t errfn)
{
        return 0;
}
#endif

void rtnl_close(struct rtnl_handle *rth)
{
        if (rth->fd >= 0) {
                close(rth->fd);
                rth->fd = -1;
        }
}

int rtnl_open_byproto(struct rtnl_handle *rth, unsigned int subscriptions,
                      int protocol)
{
        socklen_t addr_len;
        int sndbuf = 32768;
        int one = 1;

        memset(rth, 0, sizeof(*rth));

        rth->proto = protocol;
        rth->fd = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, protocol);
        if (rth->fd < 0) {
                perror("Cannot open netlink socket");
                return -1;
        }

        if (setsockopt(rth->fd, SOL_SOCKET, SO_SNDBUF,
                       &sndbuf, sizeof(sndbuf)) < 0) {
                perror("SO_SNDBUF");
                return -1;
        }

        if (setsockopt(rth->fd, SOL_SOCKET, SO_RCVBUF,
                       &rcvbuf, sizeof(rcvbuf)) < 0) {
                perror("SO_RCVBUF");
                return -1;
        }

        /* Older kernels may no support extended ACK reporting */
        setsockopt(rth->fd, SOL_NETLINK, NETLINK_EXT_ACK,
                   &one, sizeof(one));

        memset(&rth->local, 0, sizeof(rth->local));
        rth->local.nl_family = AF_NETLINK;
        rth->local.nl_groups = subscriptions;

        if (bind(rth->fd, (struct sockaddr *)&rth->local,
                 sizeof(rth->local)) < 0) {
                perror("Cannot bind netlink socket");
                return -1;
        }
        addr_len = sizeof(rth->local);
        if (getsockname(rth->fd, (struct sockaddr *)&rth->local,
                        &addr_len) < 0) {
                perror("Cannot getsockname");
                return -1;
        }
        if (addr_len != sizeof(rth->local)) {
                fprintf(stderr, "Wrong address length %d\n", addr_len);
                return -1;
        }
        if (rth->local.nl_family != AF_NETLINK) {
                fprintf(stderr, "Wrong address family %d\n",
                        rth->local.nl_family);
                return -1;
        }
        rth->seq = time(NULL);
        return 0;
}

int rtnl_open(struct rtnl_handle *rth, unsigned int subscriptions)
{
        return rtnl_open_byproto(rth, subscriptions, NETLINK_ROUTE);
}

int rtnl_addrdump_req(struct rtnl_handle *rth, int family)
{
        struct {
                struct nlmsghdr nlh;
                struct ifaddrmsg ifm;
        } req = {
                .nlh.nlmsg_len = sizeof(req),
                .nlh.nlmsg_type = RTM_GETADDR,
                .nlh.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST,
                .nlh.nlmsg_seq = rth->dump = ++rth->seq,
                .ifm.ifa_family = family,
        };

        return send(rth->fd, &req, sizeof(req), 0);
}

int rtnl_addrlbldump_req(struct rtnl_handle *rth, int family)
{
        struct {
                struct nlmsghdr nlh;
                struct ifaddrlblmsg ifal;
        } req = {
                .nlh.nlmsg_len = sizeof(req),
                .nlh.nlmsg_type = RTM_GETADDRLABEL,
                .nlh.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST,
                .nlh.nlmsg_seq = rth->dump = ++rth->seq,
                .ifal.ifal_family = family,
        };

        return send(rth->fd, &req, sizeof(req), 0);
}

int rtnl_routedump_req(struct rtnl_handle *rth, int family)
{
        struct {
                struct nlmsghdr nlh;
                struct rtmsg rtm;
        } req = {
                .nlh.nlmsg_len = sizeof(req),
                .nlh.nlmsg_type = RTM_GETROUTE,
                .nlh.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST,
                .nlh.nlmsg_seq = rth->dump = ++rth->seq,
                .rtm.rtm_family = family,
        };

        return send(rth->fd, &req, sizeof(req), 0);
}

int rtnl_ruledump_req(struct rtnl_handle *rth, int family)
{
        struct {
                struct nlmsghdr nlh;
                struct fib_rule_hdr frh;
        } req = {
                .nlh.nlmsg_len = sizeof(req),
                .nlh.nlmsg_type = RTM_GETRULE,
                .nlh.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST,
                .nlh.nlmsg_seq = rth->dump = ++rth->seq,
                .frh.family = family
        };

        return send(rth->fd, &req, sizeof(req), 0);
}

int rtnl_neighdump_req(struct rtnl_handle *rth, int family)
{
        struct {
                struct nlmsghdr nlh;
                struct ndmsg ndm;
        } req = {
                .nlh.nlmsg_len = sizeof(req),
                .nlh.nlmsg_type = RTM_GETNEIGH,
                .nlh.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST,
                .nlh.nlmsg_seq = rth->dump = ++rth->seq,
                .ndm.ndm_family = family,
        };

        return send(rth->fd, &req, sizeof(req), 0);
}

int rtnl_neightbldump_req(struct rtnl_handle *rth, int family)
{
        struct {
                struct nlmsghdr nlh;
                struct ndtmsg ndtmsg;
        } req = {
                .nlh.nlmsg_len = sizeof(req),
                .nlh.nlmsg_type = RTM_GETNEIGHTBL,
                .nlh.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST,
                .nlh.nlmsg_seq = rth->dump = ++rth->seq,
                .ndtmsg.ndtm_family = family,
        };

        return send(rth->fd, &req, sizeof(req), 0);
}

int rtnl_mdbdump_req(struct rtnl_handle *rth, int family)
{
        struct {
                struct nlmsghdr nlh;
                struct br_port_msg bpm;
        } req = {
                .nlh.nlmsg_len = sizeof(req),
                .nlh.nlmsg_type = RTM_GETMDB,
                .nlh.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST,
                .nlh.nlmsg_seq = rth->dump = ++rth->seq,
                .bpm.family = family,
        };

        return send(rth->fd, &req, sizeof(req), 0);
}

int rtnl_netconfdump_req(struct rtnl_handle *rth, int family)
{
        struct {
                struct nlmsghdr nlh;
                struct netconfmsg ncm;
        } req = {
                .nlh.nlmsg_len = sizeof(req),
                .nlh.nlmsg_type = RTM_GETNETCONF,
                .nlh.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST,
                .nlh.nlmsg_seq = rth->dump = ++rth->seq,
                .ncm.ncm_family = family,
        };

        return send(rth->fd, &req, sizeof(req), 0);
}

int rtnl_nsiddump_req(struct rtnl_handle *rth, int family)
{
        struct {
                struct nlmsghdr nlh;
                struct rtgenmsg rtm;
        } req = {
                .nlh.nlmsg_len = sizeof(req),
                .nlh.nlmsg_type = RTM_GETNSID,
                .nlh.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST,
                .nlh.nlmsg_seq = rth->dump = ++rth->seq,
                .rtm.rtgen_family = family,
        };

        return send(rth->fd, &req, sizeof(req), 0);
}

int rtnl_linkdump_req(struct rtnl_handle *rth, int family)
{
        return rtnl_linkdump_req_filter(rth, family, RTEXT_FILTER_VF);
}

int rtnl_linkdump_req_filter(struct rtnl_handle *rth, int family,
                            __u32 filt_mask)
{
        struct {
                struct nlmsghdr nlh;
                struct ifinfomsg ifm;
                /* attribute has to be NLMSG aligned */
                struct rtattr ext_req __attribute__ ((aligned(NLMSG_ALIGNTO)));
                __u32 ext_filter_mask;
        } req = {
                .nlh.nlmsg_len = sizeof(req),
                .nlh.nlmsg_type = RTM_GETLINK,
                .nlh.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST,
                .nlh.nlmsg_seq = rth->dump = ++rth->seq,
                .ifm.ifi_family = family,
                .ext_req.rta_type = IFLA_EXT_MASK,
                .ext_req.rta_len = RTA_LENGTH(sizeof(__u32)),
                .ext_filter_mask = filt_mask,
        };

        return send(rth->fd, &req, sizeof(req), 0);
}

int rtnl_linkdump_req_filter_fn(struct rtnl_handle *rth, int family,
                                req_filter_fn_t filter_fn)
{
        struct {
                struct nlmsghdr nlh;
                struct ifinfomsg ifm;
                char buf[1024];
        } req = {
                .nlh.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg)),
                .nlh.nlmsg_type = RTM_GETLINK,
                .nlh.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST,
                .nlh.nlmsg_seq = rth->dump = ++rth->seq,
                .ifm.ifi_family = family,
        };
        int err;

        if (!filter_fn)
                return -EINVAL;

        err = filter_fn(&req.nlh, sizeof(req));
        if (err)
                return err;

        return send(rth->fd, &req, req.nlh.nlmsg_len, 0);
}

int rtnl_statsdump_req_filter(struct rtnl_handle *rth, int fam, __u32 filt_mask)
{
        struct {
                struct nlmsghdr nlh;
                struct if_stats_msg ifsm;
        } req;

        memset(&req, 0, sizeof(req));
        req.nlh.nlmsg_len = NLMSG_LENGTH(sizeof(struct if_stats_msg));
        req.nlh.nlmsg_type = RTM_GETSTATS;
        req.nlh.nlmsg_flags = NLM_F_DUMP|NLM_F_REQUEST;
        req.nlh.nlmsg_pid = 0;
        req.nlh.nlmsg_seq = rth->dump = ++rth->seq;
        req.ifsm.family = fam;
        req.ifsm.filter_mask = filt_mask;

        return send(rth->fd, &req, sizeof(req), 0);
}

int rtnl_send(struct rtnl_handle *rth, const void *buf, int len)
{
        return send(rth->fd, buf, len, 0);
}

int rtnl_send_check(struct rtnl_handle *rth, const void *buf, int len)
{
        struct nlmsghdr *h;
        int status;
        char resp[1024];

        status = send(rth->fd, buf, len, 0);
        if (status < 0)
                return status;

        /* Check for immediate errors */
        status = recv(rth->fd, resp, sizeof(resp), MSG_DONTWAIT|MSG_PEEK);
        if (status < 0) {
                if (errno == EAGAIN)
                        return 0;
                return -1;
        }

        for (h = (struct nlmsghdr *)resp; NLMSG_OK(h, status);
             h = NLMSG_NEXT(h, status)) {
                if (h->nlmsg_type == NLMSG_ERROR) {
                        struct nlmsgerr *err = (struct nlmsgerr *)NLMSG_DATA(h);

                        if (h->nlmsg_len < NLMSG_LENGTH(sizeof(struct nlmsgerr)))
                                fprintf(stderr, "ERROR truncated\n");
                        else
                                errno = -err->error;
                        return -1;
                }
        }

        return 0;
}

int rtnl_dump_request(struct rtnl_handle *rth, int type, void *req, int len)
{
        struct nlmsghdr nlh = {
                .nlmsg_len = NLMSG_LENGTH(len),
                .nlmsg_type = type,
                .nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST,
                .nlmsg_seq = rth->dump = ++rth->seq,
        };
        struct sockaddr_nl nladdr = { .nl_family = AF_NETLINK };
        struct iovec iov[2] = {
                { .iov_base = &nlh, .iov_len = sizeof(nlh) },
                { .iov_base = req, .iov_len = len }
        };
        struct msghdr msg = {
                .msg_name = &nladdr,
                .msg_namelen = sizeof(nladdr),
                .msg_iov = iov,
                .msg_iovlen = 2,
        };

        return sendmsg(rth->fd, &msg, 0);
}

int rtnl_dump_request_n(struct rtnl_handle *rth, struct nlmsghdr *n)
{
        struct sockaddr_nl nladdr = { .nl_family = AF_NETLINK };
        struct iovec iov = {
                .iov_base = n,
                .iov_len = n->nlmsg_len
        };
        struct msghdr msg = {
                .msg_name = &nladdr,
                .msg_namelen = sizeof(nladdr),
                .msg_iov = &iov,
                .msg_iovlen = 1,
        };

        n->nlmsg_flags = NLM_F_DUMP|NLM_F_REQUEST;
        n->nlmsg_pid = 0;
        n->nlmsg_seq = rth->dump = ++rth->seq;

        return sendmsg(rth->fd, &msg, 0);
}

static int rtnl_dump_done(struct nlmsghdr *h)
{
        int len = *(int *)NLMSG_DATA(h);

        if (h->nlmsg_len < NLMSG_LENGTH(sizeof(int))) {
                fprintf(stderr, "DONE truncated\n");
                return -1;
        }

        if (len < 0) {
                errno = -len;
                switch (errno) {
                case ENOENT:
                case EOPNOTSUPP:
                        return -1;
                case EMSGSIZE:
                        fprintf(stderr,
                                "Error: Buffer too small for object.\n");
                        break;
                default:
                        perror("RTNETLINK answers");
                }
                return len;
        }

        /* check for any messages returned from kernel */
        nl_dump_ext_ack(h, NULL);

        return 0;
}

static void rtnl_dump_error(const struct rtnl_handle *rth,
                            struct nlmsghdr *h)
{

        if (h->nlmsg_len < NLMSG_LENGTH(sizeof(struct nlmsgerr))) {
                fprintf(stderr, "ERROR truncated\n");
        } else {
                const struct nlmsgerr *err = (struct nlmsgerr *)NLMSG_DATA(h);

                errno = -err->error;
                if (rth->proto == NETLINK_SOCK_DIAG &&
                    (errno == ENOENT ||
                     errno == EOPNOTSUPP))
                        return;

                if (!(rth->flags & RTNL_HANDLE_F_SUPPRESS_NLERR))
                        perror("RTNETLINK answers");
        }
}

static int __rtnl_recvmsg(int fd, struct msghdr *msg, int flags)
{
        int len;

        do {
                len = recvmsg(fd, msg, flags);
        } while (len < 0 && (errno == EINTR || errno == EAGAIN));

        if (len < 0) {
                fprintf(stderr, "netlink receive error %s (%d)\n",
                        strerror(errno), errno);
                return -errno;
        }

        if (len == 0) {
                fprintf(stderr, "EOF on netlink\n");
                return -ENODATA;
        }

        return len;
}

static int rtnl_recvmsg(int fd, struct msghdr *msg, char **answer)
{
        struct iovec *iov = msg->msg_iov;
        char *buf;
        int len;

        iov->iov_base = NULL;
        iov->iov_len = 0;

        len = __rtnl_recvmsg(fd, msg, MSG_PEEK | MSG_TRUNC);
        if (len < 0)
                return len;

        buf = malloc(len);
        if (!buf) {
                fprintf(stderr, "malloc error: not enough buffer\n");
                return -ENOMEM;
        }

        iov->iov_base = buf;
        iov->iov_len = len;

        len = __rtnl_recvmsg(fd, msg, 0);
        if (len < 0) {
                free(buf);
                return len;
        }

        if (answer)
                *answer = buf;
        else
                free(buf);

        return len;
}

int rtnl_dump_filter_l(struct rtnl_handle *rth,
                       const struct rtnl_dump_filter_arg *arg)
{
        struct sockaddr_nl nladdr;
        struct iovec iov;
        struct msghdr msg = {
                .msg_name = &nladdr,
                .msg_namelen = sizeof(nladdr),
                .msg_iov = &iov,
                .msg_iovlen = 1,
        };
        char *buf;
        int dump_intr = 0;

        while (1) {
                int status;
                const struct rtnl_dump_filter_arg *a;
                int found_done = 0;
                int msglen = 0;

                status = rtnl_recvmsg(rth->fd, &msg, &buf);
                if (status < 0)
                        return status;

                if (rth->dump_fp)
                        fwrite(buf, 1, NLMSG_ALIGN(status), rth->dump_fp);

                for (a = arg; a->filter; a++) {
                        struct nlmsghdr *h = (struct nlmsghdr *)buf;

                        msglen = status;

                        while (NLMSG_OK(h, msglen)) {
                                int err = 0;

                                h->nlmsg_flags &= ~a->nc_flags;

                                if (nladdr.nl_pid != 0 ||
                                    h->nlmsg_pid != rth->local.nl_pid ||
                                    h->nlmsg_seq != rth->dump)
                                        goto skip_it;

                                if (h->nlmsg_flags & NLM_F_DUMP_INTR)
                                        dump_intr = 1;

                                if (h->nlmsg_type == NLMSG_DONE) {
                                        err = rtnl_dump_done(h);
                                        if (err < 0) {
                                                free(buf);
                                                return -1;
                                        }

                                        found_done = 1;
                                        break; /* process next filter */
                                }

                                if (h->nlmsg_type == NLMSG_ERROR) {
                                        rtnl_dump_error(rth, h);
                                        free(buf);
                                        return -1;
                                }

                                if (!rth->dump_fp) {
                                        err = a->filter(&nladdr, h, a->arg1);
                                        if (err < 0) {
                                                free(buf);
                                                return err;
                                        }
                                }

skip_it:
                                h = NLMSG_NEXT(h, msglen);
                        }
                }
                free(buf);

                if (found_done) {
                        if (dump_intr)
                                fprintf(stderr,
                                        "Dump was interrupted and may be inconsistent.\n");
                        return 0;
                }

                if (msg.msg_flags & MSG_TRUNC) {
                        fprintf(stderr, "Message truncated\n");
                        continue;
                }
                if (msglen) {
                        fprintf(stderr, "!!!Remnant of size %d\n", msglen);
                        exit(1);
                }
        }
}

int rtnl_dump_filter_nc(struct rtnl_handle *rth,
                     rtnl_filter_t filter,
                     void *arg1, __u16 nc_flags)
{
        const struct rtnl_dump_filter_arg a[2] = {
                { .filter = filter, .arg1 = arg1, .nc_flags = nc_flags, },
                { .filter = NULL,   .arg1 = NULL, .nc_flags = 0, },
        };

        return rtnl_dump_filter_l(rth, a);
}

static void rtnl_talk_error(struct nlmsghdr *h, struct nlmsgerr *err,
                            nl_ext_ack_fn_t errfn)
{
        if (nl_dump_ext_ack(h, errfn))
                return;

        fprintf(stderr, "RTNETLINK answers: %s\n",
                strerror(-err->error));
}


static int __rtnl_talk_iov(struct rtnl_handle *rtnl, struct iovec *iov,
                           size_t iovlen, struct nlmsghdr **answer,
                           bool show_rtnl_err, nl_ext_ack_fn_t errfn)
{
        struct sockaddr_nl nladdr = { .nl_family = AF_NETLINK };
        struct iovec riov;
        struct msghdr msg = {
                .msg_name = &nladdr,
                .msg_namelen = sizeof(nladdr),
                .msg_iov = iov,
                .msg_iovlen = iovlen,
        };
        unsigned int seq = 0;
        struct nlmsghdr *h;
        int i, status;
        char *buf;

        for (i = 0; i < iovlen; i++) {
                h = iov[i].iov_base;
                h->nlmsg_seq = seq = ++rtnl->seq;
                if (answer == NULL)
                        h->nlmsg_flags |= NLM_F_ACK;
        }

        status = sendmsg(rtnl->fd, &msg, 0);
        if (status < 0) {
                perror("Cannot talk to rtnetlink");
                return -1;
        }

        /* change msg to use the response iov */
        msg.msg_iov = &riov;
        msg.msg_iovlen = 1;
        i = 0;
        while (1) {
                status = rtnl_recvmsg(rtnl->fd, &msg, &buf);
                ++i;

                if (status < 0)
                        return status;

                if (msg.msg_namelen != sizeof(nladdr)) {
                        fprintf(stderr,
                                "sender address length == %d\n",
                                msg.msg_namelen);
                        exit(1);
                }
                for (h = (struct nlmsghdr *)buf; status >= sizeof(*h); ) {
                        int len = h->nlmsg_len;
                        int l = len - sizeof(*h);

                        if (l < 0 || len > status) {
                                if (msg.msg_flags & MSG_TRUNC) {
                                        fprintf(stderr, "Truncated message\n");
                                        free(buf);
                                        return -1;
                                }
                                fprintf(stderr,
                                        "!!!malformed message: len=%d\n",
                                        len);
                                exit(1);
                        }

                        if (nladdr.nl_pid != 0 ||
                            h->nlmsg_pid != rtnl->local.nl_pid ||
                            h->nlmsg_seq > seq || h->nlmsg_seq < seq - iovlen) {
                                /* Don't forget to skip that message. */
                                status -= NLMSG_ALIGN(len);
                                h = (struct nlmsghdr *)((char *)h + NLMSG_ALIGN(len));
                                continue;
                        }

                        if (h->nlmsg_type == NLMSG_ERROR) {
                                struct nlmsgerr *err = (struct nlmsgerr *)NLMSG_DATA(h);
                                int error = err->error;

                                if (l < sizeof(struct nlmsgerr)) {
                                        fprintf(stderr, "ERROR truncated\n");
                                        free(buf);
                                        return -1;
                                }

                                if (!error) {
                                        /* check messages from kernel */
                                        nl_dump_ext_ack(h, errfn);
                                } else {
                                        errno = -error;

                                        if (rtnl->proto != NETLINK_SOCK_DIAG &&
                                            show_rtnl_err)
                                                rtnl_talk_error(h, err, errfn);
                                }

                                if (answer)
                                        *answer = (struct nlmsghdr *)buf;
                                else
                                        free(buf);

                                return error ? -i : 0;
                        }

                        if (answer) {
                                *answer = (struct nlmsghdr *)buf;
                                return 0;
                        }

                        fprintf(stderr, "Unexpected reply!!!\n");

                        status -= NLMSG_ALIGN(len);
                        h = (struct nlmsghdr *)((char *)h + NLMSG_ALIGN(len));
                }
                free(buf);

                if (msg.msg_flags & MSG_TRUNC) {
                        fprintf(stderr, "Message truncated\n");
                        continue;
                }

                if (status) {
                        fprintf(stderr, "!!!Remnant of size %d\n", status);
                        exit(1);
                }
        }
}

static int __rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
                       struct nlmsghdr **answer,
                       bool show_rtnl_err, nl_ext_ack_fn_t errfn)
{
        struct iovec iov = {
                .iov_base = n,
                .iov_len = n->nlmsg_len
        };

        return __rtnl_talk_iov(rtnl, &iov, 1, answer, show_rtnl_err, errfn);
}

int rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
              struct nlmsghdr **answer)
{
        return __rtnl_talk(rtnl, n, answer, true, NULL);
}

int rtnl_talk_iov(struct rtnl_handle *rtnl, struct iovec *iovec, size_t iovlen,
                  struct nlmsghdr **answer)
{
        return __rtnl_talk_iov(rtnl, iovec, iovlen, answer, true, NULL);
}

int rtnl_talk_extack(struct rtnl_handle *rtnl, struct nlmsghdr *n,
                     struct nlmsghdr **answer,
                     nl_ext_ack_fn_t errfn)
{
        return __rtnl_talk(rtnl, n, answer, true, errfn);
}

int rtnl_talk_suppress_rtnl_errmsg(struct rtnl_handle *rtnl, struct nlmsghdr *n,
                                   struct nlmsghdr **answer)
{
        return __rtnl_talk(rtnl, n, answer, false, NULL);
}

int rtnl_listen_all_nsid(struct rtnl_handle *rth)
{
        unsigned int on = 1;

        if (setsockopt(rth->fd, SOL_NETLINK, NETLINK_LISTEN_ALL_NSID, &on,
                       sizeof(on)) < 0) {
                perror("NETLINK_LISTEN_ALL_NSID");
                return -1;
        }
        rth->flags |= RTNL_HANDLE_F_LISTEN_ALL_NSID;
        return 0;
}

int rtnl_listen(struct rtnl_handle *rtnl,
                rtnl_listen_filter_t handler,
                void *jarg)
{
        int status;
        struct nlmsghdr *h;
        struct sockaddr_nl nladdr = { .nl_family = AF_NETLINK };
        struct iovec iov;
        struct msghdr msg = {
                .msg_name = &nladdr,
                .msg_namelen = sizeof(nladdr),
                .msg_iov = &iov,
                .msg_iovlen = 1,
        };
        char   buf[16384];
        char   cmsgbuf[BUFSIZ];

        if (rtnl->flags & RTNL_HANDLE_F_LISTEN_ALL_NSID) {
                msg.msg_control = &cmsgbuf;
                msg.msg_controllen = sizeof(cmsgbuf);
        }

        iov.iov_base = buf;
        while (1) {
                struct rtnl_ctrl_data ctrl;
                struct cmsghdr *cmsg;

                iov.iov_len = sizeof(buf);
                status = recvmsg(rtnl->fd, &msg, 0);

                if (status < 0) {
                        if (errno == EINTR || errno == EAGAIN)
                                continue;
                        fprintf(stderr, "netlink receive error %s (%d)\n",
                                strerror(errno), errno);
                        if (errno == ENOBUFS)
                                continue;
                        return -1;
                }
                if (status == 0) {
                        fprintf(stderr, "EOF on netlink\n");
                        return -1;
                }
                if (msg.msg_namelen != sizeof(nladdr)) {
                        fprintf(stderr,
                                "Sender address length == %d\n",
                                msg.msg_namelen);
                        exit(1);
                }

                if (rtnl->flags & RTNL_HANDLE_F_LISTEN_ALL_NSID) {
                        memset(&ctrl, 0, sizeof(ctrl));
                        ctrl.nsid = -1;
                        for (cmsg = CMSG_FIRSTHDR(&msg); cmsg;
                             cmsg = CMSG_NXTHDR(&msg, cmsg))
                                if (cmsg->cmsg_level == SOL_NETLINK &&
                                    cmsg->cmsg_type == NETLINK_LISTEN_ALL_NSID &&
                                    cmsg->cmsg_len == CMSG_LEN(sizeof(int))) {
                                        int *data = (int *)CMSG_DATA(cmsg);

                                        ctrl.nsid = *data;
                                }
                }

                for (h = (struct nlmsghdr *)buf; status >= sizeof(*h); ) {
                        int err;
                        int len = h->nlmsg_len;
                        int l = len - sizeof(*h);

                        if (l < 0 || len > status) {
                                if (msg.msg_flags & MSG_TRUNC) {
                                        fprintf(stderr, "Truncated message\n");
                                        return -1;
                                }
                                fprintf(stderr,
                                        "!!!malformed message: len=%d\n",
                                        len);
                                exit(1);
                        }

                        err = handler(&nladdr, &ctrl, h, jarg);
                        if (err < 0)
                                return err;

                        status -= NLMSG_ALIGN(len);
                        h = (struct nlmsghdr *)((char *)h + NLMSG_ALIGN(len));
                }
                if (msg.msg_flags & MSG_TRUNC) {
                        fprintf(stderr, "Message truncated\n");
                        continue;
                }
                if (status) {
                        fprintf(stderr, "!!!Remnant of size %d\n", status);
                        exit(1);
                }
        }
}

int rtnl_from_file(FILE *rtnl, rtnl_listen_filter_t handler,
                   void *jarg)
{
        int status;
        struct sockaddr_nl nladdr = { .nl_family = AF_NETLINK };
        char buf[16384];
        struct nlmsghdr *h = (struct nlmsghdr *)buf;

        while (1) {
                int err, len;
                int l;

                status = fread(&buf, 1, sizeof(*h), rtnl);

                if (status < 0) {
                        if (errno == EINTR)
                                continue;
                        perror("rtnl_from_file: fread");
                        return -1;
                }
                if (status == 0)
                        return 0;

                len = h->nlmsg_len;
                l = len - sizeof(*h);

                if (l < 0 || len > sizeof(buf)) {
                        fprintf(stderr, "!!!malformed message: len=%d @%lu\n",
                                len, ftell(rtnl));
                        return -1;
                }

                status = fread(NLMSG_DATA(h), 1, NLMSG_ALIGN(l), rtnl);

                if (status < 0) {
                        perror("rtnl_from_file: fread");
                        return -1;
                }
                if (status < l) {
                        fprintf(stderr, "rtnl-from_file: truncated message\n");
                        return -1;
                }

                err = handler(&nladdr, NULL, h, jarg);
                if (err < 0)
                        return err;
        }
}

int addattr(struct nlmsghdr *n, int maxlen, int type)
{
        return addattr_l(n, maxlen, type, NULL, 0);
}

int addattr8(struct nlmsghdr *n, int maxlen, int type, __u8 data)
{
        return addattr_l(n, maxlen, type, &data, sizeof(__u8));
}

int addattr16(struct nlmsghdr *n, int maxlen, int type, __u16 data)
{
        return addattr_l(n, maxlen, type, &data, sizeof(__u16));
}

int addattr32(struct nlmsghdr *n, int maxlen, int type, __u32 data)
{
        return addattr_l(n, maxlen, type, &data, sizeof(__u32));
}

int addattr64(struct nlmsghdr *n, int maxlen, int type, __u64 data)
{
        return addattr_l(n, maxlen, type, &data, sizeof(__u64));
}

int addattrstrz(struct nlmsghdr *n, int maxlen, int type, const char *str)
{
        return addattr_l(n, maxlen, type, str, strlen(str)+1);
}

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

        if (NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len) > maxlen) {
                fprintf(stderr,
                        "addattr_l ERROR: message exceeded bound of %d\n",
                        maxlen);
                return -1;
        }
        rta = NLMSG_TAIL(n);
        rta->rta_type = type;
        rta->rta_len = len;
        if (alen)
                memcpy(RTA_DATA(rta), data, alen);
        n->nlmsg_len = NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len);
        return 0;
}

int addraw_l(struct nlmsghdr *n, int maxlen, const void *data, int len)
{
        if (NLMSG_ALIGN(n->nlmsg_len) + NLMSG_ALIGN(len) > maxlen) {
                fprintf(stderr,
                        "addraw_l ERROR: message exceeded bound of %d\n",
                        maxlen);
                return -1;
        }

        memcpy(NLMSG_TAIL(n), data, len);
        memset((void *) NLMSG_TAIL(n) + len, 0, NLMSG_ALIGN(len) - len);
        n->nlmsg_len = NLMSG_ALIGN(n->nlmsg_len) + NLMSG_ALIGN(len);
        return 0;
}

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 = (void *)NLMSG_TAIL(n) - (void *)nest;
        return n->nlmsg_len;
}

struct rtattr *addattr_nest_compat(struct nlmsghdr *n, int maxlen, int type,
                                   const void *data, int len)
{
        struct rtattr *start = NLMSG_TAIL(n);

        addattr_l(n, maxlen, type, data, len);
        addattr_nest(n, maxlen, type);
        return start;
}

int addattr_nest_compat_end(struct nlmsghdr *n, struct rtattr *start)
{
        struct rtattr *nest = (void *)start + NLMSG_ALIGN(start->rta_len);

        start->rta_len = (void *)NLMSG_TAIL(n) - (void *)start;
        addattr_nest_end(n, nest);
        return n->nlmsg_len;
}

int rta_addattr32(struct rtattr *rta, int maxlen, int type, __u32 data)
{
        int len = RTA_LENGTH(4);
        struct rtattr *subrta;

        if (RTA_ALIGN(rta->rta_len) + len > maxlen) {
                fprintf(stderr,
                        "rta_addattr32: Error! max allowed bound %d exceeded\n",
                        maxlen);
                return -1;
        }
        subrta = (struct rtattr *)(((char *)rta) + RTA_ALIGN(rta->rta_len));
        subrta->rta_type = type;
        subrta->rta_len = len;
        memcpy(RTA_DATA(subrta), &data, 4);
        rta->rta_len = NLMSG_ALIGN(rta->rta_len) + len;
        return 0;
}

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

        if (RTA_ALIGN(rta->rta_len) + RTA_ALIGN(len) > maxlen) {
                fprintf(stderr,
                        "rta_addattr_l: Error! max allowed bound %d exceeded\n",
                        maxlen);
                return -1;
        }
        subrta = (struct rtattr *)(((char *)rta) + RTA_ALIGN(rta->rta_len));
        subrta->rta_type = type;
        subrta->rta_len = len;
        if (alen)
                memcpy(RTA_DATA(subrta), data, alen);
        rta->rta_len = NLMSG_ALIGN(rta->rta_len) + RTA_ALIGN(len);
        return 0;
}

int rta_addattr8(struct rtattr *rta, int maxlen, int type, __u8 data)
{
        return rta_addattr_l(rta, maxlen, type, &data, sizeof(__u8));
}

int rta_addattr16(struct rtattr *rta, int maxlen, int type, __u16 data)
{
        return rta_addattr_l(rta, maxlen, type, &data, sizeof(__u16));
}

int rta_addattr64(struct rtattr *rta, int maxlen, int type, __u64 data)
{
        return rta_addattr_l(rta, maxlen, type, &data, sizeof(__u64));
}

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 = (void *)RTA_TAIL(rta) - (void *)nest;

        return rta->rta_len;
}

int parse_rtattr(struct rtattr *tb[], int max, struct rtattr *rta, int len)
{
        return parse_rtattr_flags(tb, max, rta, len, 0);
}

int parse_rtattr_flags(struct rtattr *tb[], int max, struct rtattr *rta,
                       int len, unsigned short flags)
{
        unsigned short type;

        memset(tb, 0, sizeof(struct rtattr *) * (max + 1));
        while (RTA_OK(rta, len)) {
                type = rta->rta_type & ~flags;
                if ((type <= max) && (!tb[type]))
                        tb[type] = rta;
                rta = RTA_NEXT(rta, len);
        }
        if (len)
                fprintf(stderr, "!!!Deficit %d, rta_len=%d\n",
                        len, rta->rta_len);
        return 0;
}

int parse_rtattr_byindex(struct rtattr *tb[], int max,
                         struct rtattr *rta, int len)
{
        int i = 0;

        memset(tb, 0, sizeof(struct rtattr *) * max);
        while (RTA_OK(rta, len)) {
                if (rta->rta_type <= max && i < max)
                        tb[i++] = rta;
                rta = RTA_NEXT(rta, len);
        }
        if (len)
                fprintf(stderr, "!!!Deficit %d, rta_len=%d\n",
                        len, rta->rta_len);
        return i;
}

struct rtattr *parse_rtattr_one(int type, struct rtattr *rta, int len)
{
        while (RTA_OK(rta, len)) {
                if (rta->rta_type == type)
                        return rta;
                rta = RTA_NEXT(rta, len);
        }

        if (len)
                fprintf(stderr, "!!!Deficit %d, rta_len=%d\n",
                        len, rta->rta_len);
        return NULL;
}

int __parse_rtattr_nested_compat(struct rtattr *tb[], int max,
                                 struct rtattr *rta,
                                 int len)
{
        if (RTA_PAYLOAD(rta) < len)
                return -1;
        if (RTA_PAYLOAD(rta) >= RTA_ALIGN(len) + sizeof(struct rtattr)) {
                rta = RTA_DATA(rta) + RTA_ALIGN(len);
                return parse_rtattr_nested(tb, max, rta);
        }
        memset(tb, 0, sizeof(struct rtattr *) * (max + 1));
        return 0;
}