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
nla_len(const struct nlattr * nla)29 static int nla_len(const struct nlattr *nla)
30 {
31 return nla->nla_len - NLA_HDRLEN;
32 }
33
nla_next(const struct nlattr * nla,int * remaining)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
nla_ok(const struct nlattr * nla,int remaining)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
nla_data(const struct nlattr * nla)49 static void *nla_data(const struct nlattr *nla)
50 {
51 return (char *) nla + NLA_HDRLEN;
52 }
53
nla_type(const struct nlattr * nla)54 static int nla_type(const struct nlattr *nla)
55 {
56 return nla->nla_type & NLA_TYPE_MASK;
57 }
58
validate_nla(struct nlattr * nla,int maxtype,struct nla_policy * policy)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
nlmsg_len(const struct nlmsghdr * nlh)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 */
nla_parse(struct nlattr * tb[],int maxtype,struct nlattr * head,int len,struct nla_policy * policy)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 */
nla_dump_errormsg(struct nlmsghdr * nlh)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 }
188
