196 lines · c
1// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)2 3/*4 * NETLINK Netlink attributes5 *6 * Copyright (c) 2003-2013 Thomas Graf <tgraf@suug.ch>7 */8 9#include <errno.h>10#include <string.h>11#include <stdio.h>12#include <linux/rtnetlink.h>13#include "nlattr.h"14#include "libbpf_internal.h"15 16static 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] = 0,23};24 25static struct nlattr *nla_next(const struct nlattr *nla, int *remaining)26{27 int totlen = NLA_ALIGN(nla->nla_len);28 29 *remaining -= totlen;30 return (struct nlattr *)((void *)nla + totlen);31}32 33static int nla_ok(const struct nlattr *nla, int remaining)34{35 return remaining >= (int)sizeof(*nla) &&36 nla->nla_len >= sizeof(*nla) &&37 nla->nla_len <= remaining;38}39 40static int nla_type(const struct nlattr *nla)41{42 return nla->nla_type & NLA_TYPE_MASK;43}44 45static int validate_nla(struct nlattr *nla, int maxtype,46 struct libbpf_nla_policy *policy)47{48 struct libbpf_nla_policy *pt;49 unsigned int minlen = 0;50 int type = nla_type(nla);51 52 if (type < 0 || type > maxtype)53 return 0;54 55 pt = &policy[type];56 57 if (pt->type > LIBBPF_NLA_TYPE_MAX)58 return 0;59 60 if (pt->minlen)61 minlen = pt->minlen;62 else if (pt->type != LIBBPF_NLA_UNSPEC)63 minlen = nla_attr_minlen[pt->type];64 65 if (libbpf_nla_len(nla) < minlen)66 return -1;67 68 if (pt->maxlen && libbpf_nla_len(nla) > pt->maxlen)69 return -1;70 71 if (pt->type == LIBBPF_NLA_STRING) {72 char *data = libbpf_nla_data(nla);73 74 if (data[libbpf_nla_len(nla) - 1] != '\0')75 return -1;76 }77 78 return 0;79}80 81static inline int nlmsg_len(const struct nlmsghdr *nlh)82{83 return nlh->nlmsg_len - NLMSG_HDRLEN;84}85 86/**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.93 *94 * Iterates over the stream of attributes and stores a pointer to each95 * attribute in the index array using the attribute type as index to96 * the array. Attribute with a type greater than the maximum type97 * specified will be silently ignored in order to maintain backwards98 * compatibility. If \a policy is not NULL, the attribute will be99 * validated using the specified policy.100 *101 * @see nla_validate102 * @return 0 on success or a negative error code.103 */104int libbpf_nla_parse(struct nlattr *tb[], int maxtype, struct nlattr *head,105 int len, struct libbpf_nla_policy *policy)106{107 struct nlattr *nla;108 int rem, err;109 110 memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));111 112 libbpf_nla_for_each_attr(nla, head, len, rem) {113 int type = nla_type(nla);114 115 if (type > maxtype)116 continue;117 118 if (policy) {119 err = validate_nla(nla, maxtype, policy);120 if (err < 0)121 goto errout;122 }123 124 if (tb[type])125 pr_warn("Attribute of type %#x found multiple times in message, "126 "previous attribute is being ignored.\n", type);127 128 tb[type] = nla;129 }130 131 err = 0;132errout:133 return err;134}135 136/**137 * Create attribute index based on nested attribute138 * @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.142 *143 * Feeds the stream of attributes nested into the specified attribute144 * to libbpf_nla_parse().145 *146 * @see libbpf_nla_parse147 * @return 0 on success or a negative error code.148 */149int libbpf_nla_parse_nested(struct nlattr *tb[], int maxtype,150 struct nlattr *nla,151 struct libbpf_nla_policy *policy)152{153 return libbpf_nla_parse(tb, maxtype, libbpf_nla_data(nla),154 libbpf_nla_len(nla), policy);155}156 157/* dump netlink extended ack error message */158int libbpf_nla_dump_errormsg(struct nlmsghdr *nlh)159{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 },163 };164 struct nlattr *tb[NLMSGERR_ATTR_MAX + 1], *attr;165 struct nlmsgerr *err;166 char *errmsg = NULL;167 int hlen, alen;168 169 /* no TLVs, nothing to do here */170 if (!(nlh->nlmsg_flags & NLM_F_ACK_TLVS))171 return 0;172 173 err = (struct nlmsgerr *)NLMSG_DATA(nlh);174 hlen = sizeof(*err);175 176 /* 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);179 180 attr = (struct nlattr *) ((void *) err + hlen);181 alen = (void *)nlh + nlh->nlmsg_len - (void *)attr;182 183 if (libbpf_nla_parse(tb, NLMSGERR_ATTR_MAX, attr, alen,184 extack_policy) != 0) {185 pr_warn("Failed to parse extended error attributes\n");186 return 0;187 }188 189 if (tb[NLMSGERR_ATTR_MSG])190 errmsg = (char *) libbpf_nla_data(tb[NLMSGERR_ATTR_MSG]);191 192 pr_warn("Kernel error message: %s\n", errmsg);193 194 return 0;195}196