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// SPDX-License-Identifier: LGPL-2.1
/*
* NETLINK Netlink attributes
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation version 2.1
* of the License.
*
* Copyright (c) 2003-2013 Thomas Graf <tgraf@suug.ch>
*/
#include <errno.h>
#include "nlattr.h"
#include <linux/rtnetlink.h>
#include <string.h>
#include <stdio.h>
static uint16_t nla_attr_minlen[NLA_TYPE_MAX+1] = {
[NLA_U8] = sizeof(uint8_t),
[NLA_U16] = sizeof(uint16_t),
[NLA_U32] = sizeof(uint32_t),
[NLA_U64] = sizeof(uint64_t),
[NLA_STRING] = 1,
[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 *) ((char *) 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 nla_policy *policy)
{
struct 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 > NLA_TYPE_MAX)
return 0;
if (pt->minlen)
minlen = pt->minlen;
else if (pt->type != NLA_UNSPEC)
minlen = nla_attr_minlen[pt->type];
if (nla_len(nla) < minlen)
return -1;
if (pt->maxlen && nla_len(nla) > pt->maxlen)
return -1;
if (pt->type == NLA_STRING) {
char *data = nla_data(nla);
if (data[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 nla_parse(struct nlattr *tb[], int maxtype, struct nlattr *head, int len,
struct nla_policy *policy)
{
struct nlattr *nla;
int rem, err;
memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
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])
fprintf(stderr, "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 nla_parse().
*
* @see nla_parse
* @return 0 on success or a negative error code.
*/
int nla_parse_nested(struct nlattr *tb[], int maxtype, struct nlattr *nla,
struct nla_policy *policy)
{
return nla_parse(tb, maxtype, nla_data(nla), nla_len(nla), policy);
}
/* dump netlink extended ack error message */
int nla_dump_errormsg(struct nlmsghdr *nlh)
{
struct nla_policy extack_policy[NLMSGERR_ATTR_MAX + 1] = {
[NLMSGERR_ATTR_MSG] = { .type = NLA_STRING },
[NLMSGERR_ATTR_OFFS] = { .type = 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 (nla_parse(tb, NLMSGERR_ATTR_MAX, attr, alen, extack_policy) != 0) {
fprintf(stderr,
"Failed to parse extended error attributes\n");
return 0;
}
if (tb[NLMSGERR_ATTR_MSG])
errmsg = (char *) nla_data(tb[NLMSGERR_ATTR_MSG]);
fprintf(stderr, "Kernel error message: %s\n", errmsg);
return 0;
}
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