lib/netlink.h

   1 /*
   2  * Copyright (c) 2008, 2009, 2010, 2011 Nicira Networks.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at:
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #ifndef NETLINK_H
  18 #define NETLINK_H 1
  19
  20 /* Netlink message helpers.
  21  *
  22  * Netlink is a datagram-based network protocol primarily for communication
  23  * between user processes and the kernel, and mainly on Linux.  Netlink is
  24  * specified in RFC 3549, "Linux Netlink as an IP Services Protocol".
  25  *
  26  * Netlink is not suitable for use in physical networks of heterogeneous
  27  * machines because host byte order is used throughout.
  28  *
  29  * This header file defines helper functions for working with Netlink messages.
  30  * For Netlink protocol definitions, see netlink-protocol.h.  For
  31  * Linux-specific definitions for Netlink sockets, see netlink-socket.h.
  32  */
  33
  34 #include <stdbool.h>
  35 #include <stddef.h>
  36 #include <stdint.h>
  37 #include "netlink-protocol.h"
  38 #include "openvswitch/types.h"
  39
  40 struct ofpbuf;
  41 struct nlattr;
  42
  43 /* Accessing headers and data. */
  44 struct nlmsghdr *nl_msg_nlmsghdr(const struct ofpbuf *);
  45 struct genlmsghdr *nl_msg_genlmsghdr(const struct ofpbuf *);
  46 bool nl_msg_nlmsgerr(const struct ofpbuf *, int *error);
  47 void nl_msg_reserve(struct ofpbuf *, size_t);
  48
  49 /* Appending headers and raw data. */
  50 void nl_msg_put_nlmsghdr(struct ofpbuf *, size_t expected_payload,
  51                          uint32_t type, uint32_t flags);
  52 void nl_msg_put_genlmsghdr(struct ofpbuf *, size_t expected_payload,
  53                            int family, uint32_t flags,
  54                            uint8_t cmd, uint8_t version);
  55 void nl_msg_put(struct ofpbuf *, const void *, size_t);
  56 void *nl_msg_put_uninit(struct ofpbuf *, size_t);
  57
  58 /* Appending attributes. */
  59 void *nl_msg_put_unspec_uninit(struct ofpbuf *, uint16_t type, size_t);
  60 void nl_msg_put_unspec(struct ofpbuf *, uint16_t type, const void *, size_t);
  61 void nl_msg_put_flag(struct ofpbuf *, uint16_t type);
  62 void nl_msg_put_u8(struct ofpbuf *, uint16_t type, uint8_t value);
  63 void nl_msg_put_u16(struct ofpbuf *, uint16_t type, uint16_t value);
  64 void nl_msg_put_u32(struct ofpbuf *, uint16_t type, uint32_t value);
  65 void nl_msg_put_u64(struct ofpbuf *, uint16_t type, uint64_t value);
  66 void nl_msg_put_be16(struct ofpbuf *, uint16_t type, ovs_be16 value);
  67 void nl_msg_put_be32(struct ofpbuf *, uint16_t type, ovs_be32 value);
  68 void nl_msg_put_be64(struct ofpbuf *, uint16_t type, ovs_be64 value);
  69 void nl_msg_put_string(struct ofpbuf *, uint16_t type, const char *value);
  70
  71 size_t nl_msg_start_nested(struct ofpbuf *, uint16_t type);
  72 void nl_msg_end_nested(struct ofpbuf *, size_t offset);
  73 void nl_msg_put_nested(struct ofpbuf *, uint16_t type,
  74                        const void *data, size_t size);
  75
  76 /* Separating buffers into individual messages. */
  77 struct nlmsghdr *nl_msg_next(struct ofpbuf *buffer, struct ofpbuf *msg);
  78 \f
  79 /* Netlink attribute types. */
  80 enum nl_attr_type
  81 {
  82     NL_A_NO_ATTR = 0,
  83     NL_A_UNSPEC,
  84     NL_A_U8,
  85     NL_A_U16,
  86     NL_A_BE16 = NL_A_U16,
  87     NL_A_U32,
  88     NL_A_BE32 = NL_A_U32,
  89     NL_A_U64,
  90     NL_A_BE64 = NL_A_U64,
  91     NL_A_STRING,
  92     NL_A_FLAG,
  93     NL_A_NESTED,
  94     N_NL_ATTR_TYPES
  95 };
  96
  97 /* Netlink attribute iteration. */
  98 static inline struct nlattr *
  99 nl_attr_next(const struct nlattr *nla)
 100 {
 101     return (void *) ((uint8_t *) nla + NLA_ALIGN(nla->nla_len));
 102 }
 103
 104 static inline bool
 105 nl_attr_is_valid(const struct nlattr *nla, size_t maxlen)
 106 {
 107     return (maxlen >= sizeof *nla
 108             && nla->nla_len >= sizeof *nla
 109             && NLA_ALIGN(nla->nla_len) <= maxlen);
 110 }
 111
 112 /* This macro is careful to check for attributes with bad lengths. */
 113 #define NL_ATTR_FOR_EACH(ITER, LEFT, ATTRS, ATTRS_LEN)                  \
 114     for ((ITER) = (ATTRS), (LEFT) = (ATTRS_LEN);                        \
 115          nl_attr_is_valid(ITER, LEFT);                                  \
 116          (LEFT) -= NLA_ALIGN((ITER)->nla_len), (ITER) = nl_attr_next(ITER))
 117
 118
 119 /* This macro does not check for attributes with bad lengths.  It should only
 120  * be used with messages from trusted sources or with messages that have
 121  * already been validated (e.g. with NL_ATTR_FOR_EACH).  */
 122 #define NL_ATTR_FOR_EACH_UNSAFE(ITER, LEFT, ATTRS, ATTRS_LEN)           \
 123     for ((ITER) = (ATTRS), (LEFT) = (ATTRS_LEN);                        \
 124          (LEFT) > 0;                                                    \
 125          (LEFT) -= NLA_ALIGN((ITER)->nla_len), (ITER) = nl_attr_next(ITER))
 126
 127 /* These variants are convenient for iterating nested attributes. */
 128 #define NL_NESTED_FOR_EACH(ITER, LEFT, A)                               \
 129     NL_ATTR_FOR_EACH(ITER, LEFT, nl_attr_get(A), nl_attr_get_size(A))
 130 #define NL_NESTED_FOR_EACH_UNSAFE(ITER, LEFT, A)                        \
 131     NL_ATTR_FOR_EACH_UNSAFE(ITER, LEFT, nl_attr_get(A), nl_attr_get_size(A))
 132
 133 /* Netlink attribute parsing. */
 134 int nl_attr_type(const struct nlattr *);
 135 const void *nl_attr_get(const struct nlattr *);
 136 size_t nl_attr_get_size(const struct nlattr *);
 137 const void *nl_attr_get_unspec(const struct nlattr *, size_t size);
 138 bool nl_attr_get_flag(const struct nlattr *);
 139 uint8_t nl_attr_get_u8(const struct nlattr *);
 140 uint16_t nl_attr_get_u16(const struct nlattr *);
 141 uint32_t nl_attr_get_u32(const struct nlattr *);
 142 uint64_t nl_attr_get_u64(const struct nlattr *);
 143 ovs_be16 nl_attr_get_be16(const struct nlattr *);
 144 ovs_be32 nl_attr_get_be32(const struct nlattr *);
 145 ovs_be64 nl_attr_get_be64(const struct nlattr *);
 146 const char *nl_attr_get_string(const struct nlattr *);
 147 void nl_attr_get_nested(const struct nlattr *, struct ofpbuf *);
 148
 149 /* Netlink attribute policy.
 150  *
 151  * Specifies how to parse a single attribute from a Netlink message payload.
 152  */
 153 struct nl_policy
 154 {
 155     enum nl_attr_type type;
 156     size_t min_len, max_len;
 157     bool optional;
 158 };
 159
 160 bool nl_policy_parse(const struct ofpbuf *, size_t offset,
 161                      const struct nl_policy[],
 162                      struct nlattr *[], size_t n_attrs);
 163 bool nl_parse_nested(const struct nlattr *, const struct nl_policy[],
 164                      struct nlattr *[], size_t n_attrs);
 165
 166 const struct nlattr *nl_attr_find(const struct ofpbuf *, size_t hdr_len,
 167                                   uint16_t type);
 168 const struct nlattr *nl_attr_find_nested(const struct nlattr *, uint16_t type);
 169 const struct nlattr *nl_attr_find__(const struct nlattr *attrs, size_t size,
 170                                     uint16_t type);
 171
 172 #endif /* netlink.h */