// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)

/*
 * NETLINK      Netlink attributes
 *
 * Copyright (c) 2003-2013 Thomas Graf <tgraf@suug.ch>
 */

#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <linux/rtnetlink.h>
#include "nlattr.h"
#include "libbpf_internal.h"

static uint16_t nla_attr_minlen[LIBBPF_NLA_TYPE_MAX+1] = {
        [LIBBPF_NLA_U8]         = sizeof(uint8_t),
        [LIBBPF_NLA_U16]        = sizeof(uint16_t),
        [LIBBPF_NLA_U32]        = sizeof(uint32_t),
        [LIBBPF_NLA_U64]        = sizeof(uint64_t),
        [LIBBPF_NLA_STRING]     = 1,
        [LIBBPF_NLA_FLAG]       = 0,
};

static struct nlattr *nla_next(const struct nlattr *nla, int *remaining)
{
        int totlen = NLA_ALIGN(nla->nla_len);

        *remaining -= totlen;
        return (struct nlattr *)((void *)nla + totlen);
}

static int nla_ok(const struct nlattr *nla, int remaining)
{
        return remaining >= sizeof(*nla) &&
               nla->nla_len >= sizeof(*nla) &&
               nla->nla_len <= remaining;
}

static int nla_type(const struct nlattr *nla)
{
        return nla->nla_type & NLA_TYPE_MASK;
}

static int validate_nla(struct nlattr *nla, int maxtype,
                        struct libbpf_nla_policy *policy)
{
        struct libbpf_nla_policy *pt;
        unsigned int minlen = 0;
        int type = nla_type(nla);

        if (type < 0 || type > maxtype)
                return 0;

        pt = &policy[type];

        if (pt->type > LIBBPF_NLA_TYPE_MAX)
                return 0;

        if (pt->minlen)
                minlen = pt->minlen;
        else if (pt->type != LIBBPF_NLA_UNSPEC)
                minlen = nla_attr_minlen[pt->type];

        if (libbpf_nla_len(nla) < minlen)
                return -1;

        if (pt->maxlen && libbpf_nla_len(nla) > pt->maxlen)
                return -1;

        if (pt->type == LIBBPF_NLA_STRING) {
                char *data = libbpf_nla_data(nla);

                if (data[libbpf_nla_len(nla) - 1] != '\0')
                        return -1;
        }

        return 0;
}

static inline int nlmsg_len(const struct nlmsghdr *nlh)
{
        return nlh->nlmsg_len - NLMSG_HDRLEN;
}

/**
 * Create attribute index based on a stream of attributes.
 * @arg tb              Index array to be filled (maxtype+1 elements).
 * @arg maxtype         Maximum attribute type expected and accepted.
 * @arg head            Head of attribute stream.
 * @arg len             Length of attribute stream.
 * @arg policy          Attribute validation policy.
 *
 * Iterates over the stream of attributes and stores a pointer to each
 * attribute in the index array using the attribute type as index to
 * the array. Attribute with a type greater than the maximum type
 * specified will be silently ignored in order to maintain backwards
 * compatibility. If \a policy is not NULL, the attribute will be
 * validated using the specified policy.
 *
 * @see nla_validate
 * @return 0 on success or a negative error code.
 */
int libbpf_nla_parse(struct nlattr *tb[], int maxtype, struct nlattr *head,
                     int len, struct libbpf_nla_policy *policy)
{
        struct nlattr *nla;
        int rem, err;

        memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));

        libbpf_nla_for_each_attr(nla, head, len, rem) {
                int type = nla_type(nla);

                if (type > maxtype)
                        continue;

                if (policy) {
                        err = validate_nla(nla, maxtype, policy);
                        if (err < 0)
                                goto errout;
                }

                if (tb[type])
                        pr_warn("Attribute of type %#x found multiple times in message, "
                                "previous attribute is being ignored.\n", type);

                tb[type] = nla;
        }

        err = 0;
errout:
        return err;
}

/**
 * Create attribute index based on nested attribute
 * @arg tb              Index array to be filled (maxtype+1 elements).
 * @arg maxtype         Maximum attribute type expected and accepted.
 * @arg nla             Nested Attribute.
 * @arg policy          Attribute validation policy.
 *
 * Feeds the stream of attributes nested into the specified attribute
 * to libbpf_nla_parse().
 *
 * @see libbpf_nla_parse
 * @return 0 on success or a negative error code.
 */
int libbpf_nla_parse_nested(struct nlattr *tb[], int maxtype,
                            struct nlattr *nla,
                            struct libbpf_nla_policy *policy)
{
        return libbpf_nla_parse(tb, maxtype, libbpf_nla_data(nla),
                                libbpf_nla_len(nla), policy);
}

/* dump netlink extended ack error message */
int libbpf_nla_dump_errormsg(struct nlmsghdr *nlh)
{
        struct libbpf_nla_policy extack_policy[NLMSGERR_ATTR_MAX + 1] = {
                [NLMSGERR_ATTR_MSG]     = { .type = LIBBPF_NLA_STRING },
                [NLMSGERR_ATTR_OFFS]    = { .type = LIBBPF_NLA_U32 },
        };
        struct nlattr *tb[NLMSGERR_ATTR_MAX + 1], *attr;
        struct nlmsgerr *err;
        char *errmsg = NULL;
        int hlen, alen;

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

        err = (struct nlmsgerr *)NLMSG_DATA(nlh);
        hlen = sizeof(*err);

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

        attr = (struct nlattr *) ((void *) err + hlen);
        alen = nlh->nlmsg_len - hlen;

        if (libbpf_nla_parse(tb, NLMSGERR_ATTR_MAX, attr, alen,
                             extack_policy) != 0) {
                pr_warn("Failed to parse extended error attributes\n");
                return 0;
        }

        if (tb[NLMSGERR_ATTR_MSG])
                errmsg = (char *) libbpf_nla_data(tb[NLMSGERR_ATTR_MSG]);

        pr_warn("Kernel error message: %s\n", errmsg);

        return 0;
}