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