1 // SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
4 * NETLINK Netlink attributes
6 * Copyright (c) 2003-2013 Thomas Graf <tgraf@suug.ch>
12 #include <linux/rtnetlink.h>
14 #include "libbpf_internal.h"
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,
25 static struct nlattr *nla_next(const struct nlattr *nla, int *remaining)
27 int totlen = NLA_ALIGN(nla->nla_len);
30 return (struct nlattr *) ((char *) nla + totlen);
33 static int nla_ok(const struct nlattr *nla, int remaining)
35 return remaining >= sizeof(*nla) &&
36 nla->nla_len >= sizeof(*nla) &&
37 nla->nla_len <= remaining;
40 static int nla_type(const struct nlattr *nla)
42 return nla->nla_type & NLA_TYPE_MASK;
45 static int validate_nla(struct nlattr *nla, int maxtype,
46 struct libbpf_nla_policy *policy)
48 struct libbpf_nla_policy *pt;
49 unsigned int minlen = 0;
50 int type = nla_type(nla);
52 if (type < 0 || type > maxtype)
57 if (pt->type > LIBBPF_NLA_TYPE_MAX)
62 else if (pt->type != LIBBPF_NLA_UNSPEC)
63 minlen = nla_attr_minlen[pt->type];
65 if (libbpf_nla_len(nla) < minlen)
68 if (pt->maxlen && libbpf_nla_len(nla) > pt->maxlen)
71 if (pt->type == LIBBPF_NLA_STRING) {
72 char *data = libbpf_nla_data(nla);
74 if (data[libbpf_nla_len(nla) - 1] != '\0')
81 static inline int nlmsg_len(const struct nlmsghdr *nlh)
83 return nlh->nlmsg_len - NLMSG_HDRLEN;
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.
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.
102 * @return 0 on success or a negative error code.
104 int libbpf_nla_parse(struct nlattr *tb[], int maxtype, struct nlattr *head,
105 int len, struct libbpf_nla_policy *policy)
110 memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
112 libbpf_nla_for_each_attr(nla, head, len, rem) {
113 int type = nla_type(nla);
119 err = validate_nla(nla, maxtype, policy);
125 pr_warn("Attribute of type %#x found multiple times in message, "
126 "previous attribute is being ignored.\n", type);
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.
143 * Feeds the stream of attributes nested into the specified attribute
144 * to libbpf_nla_parse().
146 * @see libbpf_nla_parse
147 * @return 0 on success or a negative error code.
149 int libbpf_nla_parse_nested(struct nlattr *tb[], int maxtype,
151 struct libbpf_nla_policy *policy)
153 return libbpf_nla_parse(tb, maxtype, libbpf_nla_data(nla),
154 libbpf_nla_len(nla), policy);
157 /* dump netlink extended ack error message */
158 int libbpf_nla_dump_errormsg(struct nlmsghdr *nlh)
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 },
164 struct nlattr *tb[NLMSGERR_ATTR_MAX + 1], *attr;
165 struct nlmsgerr *err;
169 /* no TLVs, nothing to do here */
170 if (!(nlh->nlmsg_flags & NLM_F_ACK_TLVS))
173 err = (struct nlmsgerr *)NLMSG_DATA(nlh);
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);
180 attr = (struct nlattr *) ((void *) err + hlen);
181 alen = (void *)nlh + nlh->nlmsg_len - (void *)attr;
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");
189 if (tb[NLMSGERR_ATTR_MSG])
190 errmsg = (char *) libbpf_nla_data(tb[NLMSGERR_ATTR_MSG]);
192 pr_warn("Kernel error message: %s\n", errmsg);