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
16 static 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
25 static 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
33 static 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
40 static int nla_type(const struct nlattr *nla)
41 {
42 return nla->nla_type & NLA_TYPE_MASK;
43 }
44
45 static 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
81 static 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 */
104 int 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;
132 errout:
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 */
149 int 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 */
158 int 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
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