1// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
  2
  3/*
  4 * NETLINK      Netlink attributes
  5 *
  6 * Copyright (c) 2003-2013 Thomas Graf <tgraf@suug.ch>
  7 */
  8
  9#include <errno.h>
 10#include "nlattr.h"
 11#include "libbpf_internal.h"
 12#include <linux/rtnetlink.h>
 13#include <string.h>
 14#include <stdio.h>
 15
 16/* make sure libbpf doesn't use kernel-only integer typedefs */
 17#pragma GCC poison u8 u16 u32 u64 s8 s16 s32 s64
 18
 19static uint16_t nla_attr_minlen[LIBBPF_NLA_TYPE_MAX+1] = {
 20	[LIBBPF_NLA_U8]		= sizeof(uint8_t),
 21	[LIBBPF_NLA_U16]	= sizeof(uint16_t),
 22	[LIBBPF_NLA_U32]	= sizeof(uint32_t),
 23	[LIBBPF_NLA_U64]	= sizeof(uint64_t),
 24	[LIBBPF_NLA_STRING]	= 1,
 25	[LIBBPF_NLA_FLAG]	= 0,
 26};
 27
 28static struct nlattr *nla_next(const struct nlattr *nla, int *remaining)
 29{
 30	int totlen = NLA_ALIGN(nla->nla_len);
 31
 32	*remaining -= totlen;
 33	return (struct nlattr *) ((char *) nla + totlen);
 34}
 35
 36static int nla_ok(const struct nlattr *nla, int remaining)
 37{
 38	return remaining >= sizeof(*nla) &&
 39	       nla->nla_len >= sizeof(*nla) &&
 40	       nla->nla_len <= remaining;
 41}
 42
 43static int nla_type(const struct nlattr *nla)
 44{
 45	return nla->nla_type & NLA_TYPE_MASK;
 46}
 47
 48static int validate_nla(struct nlattr *nla, int maxtype,
 49			struct libbpf_nla_policy *policy)
 50{
 51	struct libbpf_nla_policy *pt;
 52	unsigned int minlen = 0;
 53	int type = nla_type(nla);
 54
 55	if (type < 0 || type > maxtype)
 56		return 0;
 57
 58	pt = &policy[type];
 59
 60	if (pt->type > LIBBPF_NLA_TYPE_MAX)
 61		return 0;
 62
 63	if (pt->minlen)
 64		minlen = pt->minlen;
 65	else if (pt->type != LIBBPF_NLA_UNSPEC)
 66		minlen = nla_attr_minlen[pt->type];
 67
 68	if (libbpf_nla_len(nla) < minlen)
 69		return -1;
 70
 71	if (pt->maxlen && libbpf_nla_len(nla) > pt->maxlen)
 72		return -1;
 73
 74	if (pt->type == LIBBPF_NLA_STRING) {
 75		char *data = libbpf_nla_data(nla);
 76
 77		if (data[libbpf_nla_len(nla) - 1] != '\0')
 78			return -1;
 79	}
 80
 81	return 0;
 82}
 83
 84static inline int nlmsg_len(const struct nlmsghdr *nlh)
 85{
 86	return nlh->nlmsg_len - NLMSG_HDRLEN;
 87}
 88
 89/**
 90 * Create attribute index based on a stream of attributes.
 91 * @arg tb		Index array to be filled (maxtype+1 elements).
 92 * @arg maxtype		Maximum attribute type expected and accepted.
 93 * @arg head		Head of attribute stream.
 94 * @arg len		Length of attribute stream.
 95 * @arg policy		Attribute validation policy.
 96 *
 97 * Iterates over the stream of attributes and stores a pointer to each
 98 * attribute in the index array using the attribute type as index to
 99 * the array. Attribute with a type greater than the maximum type
100 * specified will be silently ignored in order to maintain backwards
101 * compatibility. If \a policy is not NULL, the attribute will be
102 * validated using the specified policy.
103 *
104 * @see nla_validate
105 * @return 0 on success or a negative error code.
106 */
107int libbpf_nla_parse(struct nlattr *tb[], int maxtype, struct nlattr *head,
108		     int len, struct libbpf_nla_policy *policy)
109{
110	struct nlattr *nla;
111	int rem, err;
112
113	memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
114
115	libbpf_nla_for_each_attr(nla, head, len, rem) {
116		int type = nla_type(nla);
117
118		if (type > maxtype)
119			continue;
120
121		if (policy) {
122			err = validate_nla(nla, maxtype, policy);
123			if (err < 0)
124				goto errout;
125		}
126
127		if (tb[type])
128			pr_warn("Attribute of type %#x found multiple times in message, "
129				"previous attribute is being ignored.\n", type);
130
131		tb[type] = nla;
132	}
133
134	err = 0;
135errout:
136	return err;
137}
138
139/**
140 * Create attribute index based on nested attribute
141 * @arg tb              Index array to be filled (maxtype+1 elements).
142 * @arg maxtype         Maximum attribute type expected and accepted.
143 * @arg nla             Nested Attribute.
144 * @arg policy          Attribute validation policy.
145 *
146 * Feeds the stream of attributes nested into the specified attribute
147 * to libbpf_nla_parse().
148 *
149 * @see libbpf_nla_parse
150 * @return 0 on success or a negative error code.
151 */
152int libbpf_nla_parse_nested(struct nlattr *tb[], int maxtype,
153			    struct nlattr *nla,
154			    struct libbpf_nla_policy *policy)
155{
156	return libbpf_nla_parse(tb, maxtype, libbpf_nla_data(nla),
157				libbpf_nla_len(nla), policy);
158}
159
160/* dump netlink extended ack error message */
161int libbpf_nla_dump_errormsg(struct nlmsghdr *nlh)
162{
163	struct libbpf_nla_policy extack_policy[NLMSGERR_ATTR_MAX + 1] = {
164		[NLMSGERR_ATTR_MSG]	= { .type = LIBBPF_NLA_STRING },
165		[NLMSGERR_ATTR_OFFS]	= { .type = LIBBPF_NLA_U32 },
166	};
167	struct nlattr *tb[NLMSGERR_ATTR_MAX + 1], *attr;
168	struct nlmsgerr *err;
169	char *errmsg = NULL;
170	int hlen, alen;
171
172	/* no TLVs, nothing to do here */
173	if (!(nlh->nlmsg_flags & NLM_F_ACK_TLVS))
174		return 0;
175
176	err = (struct nlmsgerr *)NLMSG_DATA(nlh);
177	hlen = sizeof(*err);
178
179	/* if NLM_F_CAPPED is set then the inner err msg was capped */
180	if (!(nlh->nlmsg_flags & NLM_F_CAPPED))
181		hlen += nlmsg_len(&err->msg);
182
183	attr = (struct nlattr *) ((void *) err + hlen);
184	alen = nlh->nlmsg_len - hlen;
185
186	if (libbpf_nla_parse(tb, NLMSGERR_ATTR_MAX, attr, alen,
187			     extack_policy) != 0) {
188		pr_warn("Failed to parse extended error attributes\n");
189		return 0;
190	}
191
192	if (tb[NLMSGERR_ATTR_MSG])
193		errmsg = (char *) libbpf_nla_data(tb[NLMSGERR_ATTR_MSG]);
194
195	pr_warn("Kernel error message: %s\n", errmsg);
196
197	return 0;
198}