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