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1 | // SPDX-License-Identifier: LGPL-2.1 |
2 | ||
3 | /* | |
4 | * NETLINK Netlink attributes | |
5 | * | |
6 | * This library is free software; you can redistribute it and/or | |
7 | * modify it under the terms of the GNU Lesser General Public | |
8 | * License as published by the Free Software Foundation version 2.1 | |
9 | * of the License. | |
10 | * | |
11 | * Copyright (c) 2003-2013 Thomas Graf <tgraf@suug.ch> | |
12 | */ | |
13 | ||
14 | #include <errno.h> | |
15 | #include "nlattr.h" | |
16 | #include <linux/rtnetlink.h> | |
17 | #include <string.h> | |
18 | #include <stdio.h> | |
19 | ||
20 | static uint16_t nla_attr_minlen[NLA_TYPE_MAX+1] = { | |
21 | [NLA_U8] = sizeof(uint8_t), | |
22 | [NLA_U16] = sizeof(uint16_t), | |
23 | [NLA_U32] = sizeof(uint32_t), | |
24 | [NLA_U64] = sizeof(uint64_t), | |
25 | [NLA_STRING] = 1, | |
26 | [NLA_FLAG] = 0, | |
27 | }; | |
28 | ||
29 | static int nla_len(const struct nlattr *nla) | |
30 | { | |
31 | return nla->nla_len - NLA_HDRLEN; | |
32 | } | |
33 | ||
34 | static struct nlattr *nla_next(const struct nlattr *nla, int *remaining) | |
35 | { | |
36 | int totlen = NLA_ALIGN(nla->nla_len); | |
37 | ||
38 | *remaining -= totlen; | |
39 | return (struct nlattr *) ((char *) nla + totlen); | |
40 | } | |
41 | ||
42 | static int nla_ok(const struct nlattr *nla, int remaining) | |
43 | { | |
44 | return remaining >= sizeof(*nla) && | |
45 | nla->nla_len >= sizeof(*nla) && | |
46 | nla->nla_len <= remaining; | |
47 | } | |
48 | ||
49 | static void *nla_data(const struct nlattr *nla) | |
50 | { | |
51 | return (char *) nla + NLA_HDRLEN; | |
52 | } | |
53 | ||
54 | static int nla_type(const struct nlattr *nla) | |
55 | { | |
56 | return nla->nla_type & NLA_TYPE_MASK; | |
57 | } | |
58 | ||
59 | static int validate_nla(struct nlattr *nla, int maxtype, | |
60 | struct nla_policy *policy) | |
61 | { | |
62 | struct nla_policy *pt; | |
63 | unsigned int minlen = 0; | |
64 | int type = nla_type(nla); | |
65 | ||
66 | if (type < 0 || type > maxtype) | |
67 | return 0; | |
68 | ||
69 | pt = &policy[type]; | |
70 | ||
71 | if (pt->type > NLA_TYPE_MAX) | |
72 | return 0; | |
73 | ||
74 | if (pt->minlen) | |
75 | minlen = pt->minlen; | |
76 | else if (pt->type != NLA_UNSPEC) | |
77 | minlen = nla_attr_minlen[pt->type]; | |
78 | ||
79 | if (nla_len(nla) < minlen) | |
80 | return -1; | |
81 | ||
82 | if (pt->maxlen && nla_len(nla) > pt->maxlen) | |
83 | return -1; | |
84 | ||
85 | if (pt->type == NLA_STRING) { | |
86 | char *data = nla_data(nla); | |
87 | if (data[nla_len(nla) - 1] != '\0') | |
88 | return -1; | |
89 | } | |
90 | ||
91 | return 0; | |
92 | } | |
93 | ||
94 | static inline int nlmsg_len(const struct nlmsghdr *nlh) | |
95 | { | |
96 | return nlh->nlmsg_len - NLMSG_HDRLEN; | |
97 | } | |
98 | ||
99 | /** | |
100 | * Create attribute index based on a stream of attributes. | |
101 | * @arg tb Index array to be filled (maxtype+1 elements). | |
102 | * @arg maxtype Maximum attribute type expected and accepted. | |
103 | * @arg head Head of attribute stream. | |
104 | * @arg len Length of attribute stream. | |
105 | * @arg policy Attribute validation policy. | |
106 | * | |
107 | * Iterates over the stream of attributes and stores a pointer to each | |
108 | * attribute in the index array using the attribute type as index to | |
109 | * the array. Attribute with a type greater than the maximum type | |
110 | * specified will be silently ignored in order to maintain backwards | |
111 | * compatibility. If \a policy is not NULL, the attribute will be | |
112 | * validated using the specified policy. | |
113 | * | |
114 | * @see nla_validate | |
115 | * @return 0 on success or a negative error code. | |
116 | */ | |
117 | static int nla_parse(struct nlattr *tb[], int maxtype, struct nlattr *head, int len, | |
118 | struct nla_policy *policy) | |
119 | { | |
120 | struct nlattr *nla; | |
121 | int rem, err; | |
122 | ||
123 | memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1)); | |
124 | ||
125 | nla_for_each_attr(nla, head, len, rem) { | |
126 | int type = nla_type(nla); | |
127 | ||
128 | if (type > maxtype) | |
129 | continue; | |
130 | ||
131 | if (policy) { | |
132 | err = validate_nla(nla, maxtype, policy); | |
133 | if (err < 0) | |
134 | goto errout; | |
135 | } | |
136 | ||
137 | if (tb[type]) | |
138 | fprintf(stderr, "Attribute of type %#x found multiple times in message, " | |
139 | "previous attribute is being ignored.\n", type); | |
140 | ||
141 | tb[type] = nla; | |
142 | } | |
143 | ||
144 | err = 0; | |
145 | errout: | |
146 | return err; | |
147 | } | |
148 | ||
149 | /* dump netlink extended ack error message */ | |
150 | int nla_dump_errormsg(struct nlmsghdr *nlh) | |
151 | { | |
152 | struct nla_policy extack_policy[NLMSGERR_ATTR_MAX + 1] = { | |
153 | [NLMSGERR_ATTR_MSG] = { .type = NLA_STRING }, | |
154 | [NLMSGERR_ATTR_OFFS] = { .type = NLA_U32 }, | |
155 | }; | |
156 | struct nlattr *tb[NLMSGERR_ATTR_MAX + 1], *attr; | |
157 | struct nlmsgerr *err; | |
158 | char *errmsg = NULL; | |
159 | int hlen, alen; | |
160 | ||
161 | /* no TLVs, nothing to do here */ | |
162 | if (!(nlh->nlmsg_flags & NLM_F_ACK_TLVS)) | |
163 | return 0; | |
164 | ||
165 | err = (struct nlmsgerr *)NLMSG_DATA(nlh); | |
166 | hlen = sizeof(*err); | |
167 | ||
168 | /* if NLM_F_CAPPED is set then the inner err msg was capped */ | |
169 | if (!(nlh->nlmsg_flags & NLM_F_CAPPED)) | |
170 | hlen += nlmsg_len(&err->msg); | |
171 | ||
172 | attr = (struct nlattr *) ((void *) err + hlen); | |
173 | alen = nlh->nlmsg_len - hlen; | |
174 | ||
175 | if (nla_parse(tb, NLMSGERR_ATTR_MAX, attr, alen, extack_policy) != 0) { | |
176 | fprintf(stderr, | |
177 | "Failed to parse extended error attributes\n"); | |
178 | return 0; | |
179 | } | |
180 | ||
181 | if (tb[NLMSGERR_ATTR_MSG]) | |
182 | errmsg = (char *) nla_data(tb[NLMSGERR_ATTR_MSG]); | |
183 | ||
184 | fprintf(stderr, "Kernel error message: %s\n", errmsg); | |
185 | ||
186 | return 0; | |
187 | } |