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 struct nlattr *nla_next(const struct nlattr *nla, int *remaining) 30 { 31 int totlen = NLA_ALIGN(nla->nla_len); 32 33 *remaining -= totlen; 34 return (struct nlattr *) ((char *) nla + totlen); 35 } 36 37 static int nla_ok(const struct nlattr *nla, int remaining) 38 { 39 return remaining >= sizeof(*nla) && 40 nla->nla_len >= sizeof(*nla) && 41 nla->nla_len <= remaining; 42 } 43 44 static int nla_type(const struct nlattr *nla) 45 { 46 return nla->nla_type & NLA_TYPE_MASK; 47 } 48 49 static int validate_nla(struct nlattr *nla, int maxtype, 50 struct nla_policy *policy) 51 { 52 struct nla_policy *pt; 53 unsigned int minlen = 0; 54 int type = nla_type(nla); 55 56 if (type < 0 || type > maxtype) 57 return 0; 58 59 pt = &policy[type]; 60 61 if (pt->type > NLA_TYPE_MAX) 62 return 0; 63 64 if (pt->minlen) 65 minlen = pt->minlen; 66 else if (pt->type != NLA_UNSPEC) 67 minlen = nla_attr_minlen[pt->type]; 68 69 if (nla_len(nla) < minlen) 70 return -1; 71 72 if (pt->maxlen && nla_len(nla) > pt->maxlen) 73 return -1; 74 75 if (pt->type == NLA_STRING) { 76 char *data = nla_data(nla); 77 if (data[nla_len(nla) - 1] != '\0') 78 return -1; 79 } 80 81 return 0; 82 } 83 84 static inline int nlmsg_len(const struct nlmsghdr *nlh) 85 { 86 return nlh->nlmsg_len - NLMSG_HDRLEN; 87 } 88 89 /** 90 * Create attribute index based on a stream of attributes. 91 * @arg tb Index array to be filled (maxtype+1 elements). 92 * @arg maxtype Maximum attribute type expected and accepted. 93 * @arg head Head of attribute stream. 94 * @arg len Length of attribute stream. 95 * @arg policy Attribute validation policy. 96 * 97 * Iterates over the stream of attributes and stores a pointer to each 98 * attribute in the index array using the attribute type as index to 99 * the array. Attribute with a type greater than the maximum type 100 * specified will be silently ignored in order to maintain backwards 101 * compatibility. If \a policy is not NULL, the attribute will be 102 * validated using the specified policy. 103 * 104 * @see nla_validate 105 * @return 0 on success or a negative error code. 106 */ 107 int nla_parse(struct nlattr *tb[], int maxtype, struct nlattr *head, int len, 108 struct nla_policy *policy) 109 { 110 struct nlattr *nla; 111 int rem, err; 112 113 memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1)); 114 115 nla_for_each_attr(nla, head, len, rem) { 116 int type = nla_type(nla); 117 118 if (type > maxtype) 119 continue; 120 121 if (policy) { 122 err = validate_nla(nla, maxtype, policy); 123 if (err < 0) 124 goto errout; 125 } 126 127 if (tb[type]) 128 fprintf(stderr, "Attribute of type %#x found multiple times in message, " 129 "previous attribute is being ignored.\n", type); 130 131 tb[type] = nla; 132 } 133 134 err = 0; 135 errout: 136 return err; 137 } 138 139 /** 140 * Create attribute index based on nested attribute 141 * @arg tb Index array to be filled (maxtype+1 elements). 142 * @arg maxtype Maximum attribute type expected and accepted. 143 * @arg nla Nested Attribute. 144 * @arg policy Attribute validation policy. 145 * 146 * Feeds the stream of attributes nested into the specified attribute 147 * to nla_parse(). 148 * 149 * @see nla_parse 150 * @return 0 on success or a negative error code. 151 */ 152 int nla_parse_nested(struct nlattr *tb[], int maxtype, struct nlattr *nla, 153 struct nla_policy *policy) 154 { 155 return nla_parse(tb, maxtype, nla_data(nla), nla_len(nla), policy); 156 } 157 158 /* dump netlink extended ack error message */ 159 int nla_dump_errormsg(struct nlmsghdr *nlh) 160 { 161 struct nla_policy extack_policy[NLMSGERR_ATTR_MAX + 1] = { 162 [NLMSGERR_ATTR_MSG] = { .type = NLA_STRING }, 163 [NLMSGERR_ATTR_OFFS] = { .type = NLA_U32 }, 164 }; 165 struct nlattr *tb[NLMSGERR_ATTR_MAX + 1], *attr; 166 struct nlmsgerr *err; 167 char *errmsg = NULL; 168 int hlen, alen; 169 170 /* no TLVs, nothing to do here */ 171 if (!(nlh->nlmsg_flags & NLM_F_ACK_TLVS)) 172 return 0; 173 174 err = (struct nlmsgerr *)NLMSG_DATA(nlh); 175 hlen = sizeof(*err); 176 177 /* if NLM_F_CAPPED is set then the inner err msg was capped */ 178 if (!(nlh->nlmsg_flags & NLM_F_CAPPED)) 179 hlen += nlmsg_len(&err->msg); 180 181 attr = (struct nlattr *) ((void *) err + hlen); 182 alen = nlh->nlmsg_len - hlen; 183 184 if (nla_parse(tb, NLMSGERR_ATTR_MAX, attr, alen, extack_policy) != 0) { 185 fprintf(stderr, 186 "Failed to parse extended error attributes\n"); 187 return 0; 188 } 189 190 if (tb[NLMSGERR_ATTR_MSG]) 191 errmsg = (char *) nla_data(tb[NLMSGERR_ATTR_MSG]); 192 193 fprintf(stderr, "Kernel error message: %s\n", errmsg); 194 195 return 0; 196 } 197