1 /*
2 * lib/netfilter/nfnl.c Netfilter Netlink
3 *
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Lesser General Public
6 * License as published by the Free Software Foundation version 2.1
7 * of the License.
8 *
9 * Copyright (c) 2003-2008 Thomas Graf <tgraf@suug.ch>
10 * Copyright (c) 2007 Philip Craig <philipc@snapgear.com>
11 * Copyright (c) 2007 Secure Computing Corporation
12 */
13
14 /**
15 * @defgroup nfnl Netfilter Netlink
16 *
17 * @par Message Format
18 * @code
19 * <------- NLMSG_ALIGN(hlen) ------> <---- NLMSG_ALIGN(len) --->
20 * +----------------------------+- - -+- - - - - - - - - - -+- - -+
21 * | Header | Pad | Payload | Pad |
22 * | struct nlmsghdr | | | |
23 * +----------------------------+- - -+- - - - - - - - - - -+- - -+
24 * @endcode
25 * @code
26 * <-------- NFNL_HDRLEN --------->
27 * +--------------------------+- - -+------------+
28 * | Netfilter Netlink Header | Pad | Attributes |
29 * | struct nfgenmsg | | |
30 * +--------------------------+- - -+------------+
31 * nfnlmsg_attrdata(nfg, hdrlen)-----^
32 * @endcode
33 *
34 * @par 1) Creating a new netfilter netlink message
35 * @code
36 * struct nl_msg *msg;
37 *
38 * // Create a new empty netlink message
39 * msg = nlmsg_alloc();
40 *
41 * // Append the netlink and netfilter netlink message header
42 * hdr = nfnlmsg_put(msg, PID, SEQ, SUBSYS, TYPE, NLM_F_ECHO,
43 * FAMILY, RES_ID);
44 *
45 * // Append the attributes.
46 * nla_put_u32(msg, 1, 0x10);
47 *
48 * // Message is ready to be sent.
49 * nl_send_auto_complete(sk, msg);
50 *
51 * // All done? Free the message.
52 * nlmsg_free(msg);
53 * @endcode
54 *
55 * @par 2) Sending of trivial messages
56 * @code
57 * // For trivial messages not requiring any subsys specific header or
58 * // attributes, nfnl_send_simple() may be used to send messages directly.
59 * nfnl_send_simple(sk, SUBSYS, TYPE, 0, FAMILY, RES_ID);
60 * @endcode
61 * @{
62 */
63
64 #include <netlink-local.h>
65 #include <netlink/netlink.h>
66 #include <netlink/netfilter/nfnl.h>
67
68 /**
69 * @name Socket Creating
70 * @{
71 */
72
73 /**
74 * Create and connect netfilter netlink socket.
75 * @arg sk Netlink socket.
76 *
77 * Creates a NETLINK_NETFILTER netlink socket, binds the socket and
78 * issues a connection attempt.
79 *
80 * @see nl_connect()
81 *
82 * @return 0 on success or a negative error code.
83 */
nfnl_connect(struct nl_sock * sk)84 int nfnl_connect(struct nl_sock *sk)
85 {
86 return nl_connect(sk, NETLINK_NETFILTER);
87 }
88
89 /** @} */
90
91 /**
92 * @name Sending
93 * @{
94 */
95
96 /**
97 * Send trivial netfilter netlink message
98 * @arg sk Netlink socket.
99 * @arg subsys_id nfnetlink subsystem
100 * @arg type nfnetlink message type
101 * @arg flags message flags
102 * @arg family nfnetlink address family
103 * @arg res_id nfnetlink resource id
104 *
105 * @return Newly allocated netlink message or NULL.
106 */
nfnl_send_simple(struct nl_sock * sk,uint8_t subsys_id,uint8_t type,int flags,uint8_t family,uint16_t res_id)107 int nfnl_send_simple(struct nl_sock *sk, uint8_t subsys_id, uint8_t type,
108 int flags, uint8_t family, uint16_t res_id)
109 {
110 struct nfgenmsg hdr = {
111 .nfgen_family = family,
112 .version = NFNETLINK_V0,
113 .res_id = htons(res_id),
114 };
115
116 return nl_send_simple(sk, NFNLMSG_TYPE(subsys_id, type), flags,
117 &hdr, sizeof(hdr));
118 }
119
120 /** @} */
121
122 /**
123 * @name Message Parsing
124 * @{
125 */
126
127 /**
128 * Get netfilter subsystem id from message
129 * @arg nlh netlink messsage header
130 */
nfnlmsg_subsys(struct nlmsghdr * nlh)131 uint8_t nfnlmsg_subsys(struct nlmsghdr *nlh)
132 {
133 return NFNL_SUBSYS_ID(nlh->nlmsg_type);
134 }
135
136 /**
137 * Get netfilter message type from message
138 * @arg nlh netlink messsage header
139 */
nfnlmsg_subtype(struct nlmsghdr * nlh)140 uint8_t nfnlmsg_subtype(struct nlmsghdr *nlh)
141 {
142 return NFNL_MSG_TYPE(nlh->nlmsg_type);
143 }
144
145 /**
146 * Get netfilter family from message
147 * @arg nlh netlink messsage header
148 */
nfnlmsg_family(struct nlmsghdr * nlh)149 uint8_t nfnlmsg_family(struct nlmsghdr *nlh)
150 {
151 struct nfgenmsg *nfg = nlmsg_data(nlh);
152
153 return nfg->nfgen_family;
154 }
155
156 /**
157 * Get netfilter resource id from message
158 * @arg nlh netlink messsage header
159 */
nfnlmsg_res_id(struct nlmsghdr * nlh)160 uint16_t nfnlmsg_res_id(struct nlmsghdr *nlh)
161 {
162 struct nfgenmsg *nfg = nlmsg_data(nlh);
163
164 return ntohs(nfg->res_id);
165 }
166
167 /** @} */
168
169 /**
170 * @name Message Building
171 * @{
172 */
173
nfnlmsg_append(struct nl_msg * msg,uint8_t family,uint16_t res_id)174 static int nfnlmsg_append(struct nl_msg *msg, uint8_t family, uint16_t res_id)
175 {
176 struct nfgenmsg *nfg;
177
178 nfg = nlmsg_reserve(msg, sizeof(*nfg), NLMSG_ALIGNTO);
179 if (nfg == NULL)
180 return -NLE_NOMEM;
181
182 nfg->nfgen_family = family;
183 nfg->version = NFNETLINK_V0;
184 nfg->res_id = htons(res_id);
185 NL_DBG(2, "msg %p: Added nfnetlink header family=%d res_id=%d\n",
186 msg, family, res_id);
187 return 0;
188 }
189
190 /**
191 * Allocate a new netfilter netlink message
192 * @arg subsys_id nfnetlink subsystem
193 * @arg type nfnetlink message type
194 * @arg flags message flags
195 * @arg family nfnetlink address family
196 * @arg res_id nfnetlink resource id
197 *
198 * @return Newly allocated netlink message or NULL.
199 */
nfnlmsg_alloc_simple(uint8_t subsys_id,uint8_t type,int flags,uint8_t family,uint16_t res_id)200 struct nl_msg *nfnlmsg_alloc_simple(uint8_t subsys_id, uint8_t type, int flags,
201 uint8_t family, uint16_t res_id)
202 {
203 struct nl_msg *msg;
204
205 msg = nlmsg_alloc_simple(NFNLMSG_TYPE(subsys_id, type), flags);
206 if (msg == NULL)
207 return NULL;
208
209 if (nfnlmsg_append(msg, family, res_id) < 0)
210 goto nla_put_failure;
211
212 return msg;
213
214 nla_put_failure:
215 nlmsg_free(msg);
216 return NULL;
217 }
218
219 /**
220 * Add netlink and netfilter netlink headers to netlink message
221 * @arg msg netlink message
222 * @arg pid netlink process id
223 * @arg seq sequence number of message
224 * @arg subsys_id nfnetlink subsystem
225 * @arg type nfnetlink message type
226 * @arg flags message flags
227 * @arg family nfnetlink address family
228 * @arg res_id nfnetlink resource id
229 */
nfnlmsg_put(struct nl_msg * msg,uint32_t pid,uint32_t seq,uint8_t subsys_id,uint8_t type,int flags,uint8_t family,uint16_t res_id)230 int nfnlmsg_put(struct nl_msg *msg, uint32_t pid, uint32_t seq,
231 uint8_t subsys_id, uint8_t type, int flags, uint8_t family,
232 uint16_t res_id)
233 {
234 struct nlmsghdr *nlh;
235
236 nlh = nlmsg_put(msg, pid, seq, NFNLMSG_TYPE(subsys_id, type), 0, flags);
237 if (nlh == NULL)
238 return -NLE_MSGSIZE;
239
240 return nfnlmsg_append(msg, family, res_id);
241 }
242
243 /** @} */
244
245 /** @} */
246