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// 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;
}
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