1 /* SPDX-License-Identifier: LGPL-2.1-only */
2 /*
3 * Copyright (c) 2003-2012 Thomas Graf <[email protected]>
4 * Copyright (c) 2007 Philip Craig <[email protected]>
5 * Copyright (c) 2007 Secure Computing Corporation
6 */
7
8 /**
9 * @defgroup nfnl Netfilter Library (libnl-nf)
10 *
11 * @par Message Format
12 * @code
13 * <------- NLMSG_ALIGN(hlen) ------> <---- NLMSG_ALIGN(len) --->
14 * +----------------------------+- - -+- - - - - - - - - - -+- - -+
15 * | Header | Pad | Payload | Pad |
16 * | struct nlmsghdr | | | |
17 * +----------------------------+- - -+- - - - - - - - - - -+- - -+
18 * @endcode
19 * @code
20 * <-------- NFNL_HDRLEN --------->
21 * +--------------------------+- - -+------------+
22 * | Netfilter Netlink Header | Pad | Attributes |
23 * | struct nfgenmsg | | |
24 * +--------------------------+- - -+------------+
25 * nfnlmsg_attrdata(nfg, hdrlen)-----^
26 * @endcode
27 *
28 * @par 1) Creating a new netfilter netlink message
29 * @code
30 * struct nl_msg *msg;
31 *
32 * // Create a new empty netlink message
33 * msg = nlmsg_alloc();
34 *
35 * // Append the netlink and netfilter netlink message header
36 * hdr = nfnlmsg_put(msg, PID, SEQ, SUBSYS, TYPE, NLM_F_ECHO,
37 * FAMILY, RES_ID);
38 *
39 * // Append the attributes.
40 * nla_put_u32(msg, 1, 0x10);
41 *
42 * // Message is ready to be sent.
43 * nl_send_auto_complete(sk, msg);
44 *
45 * // All done? Free the message.
46 * nlmsg_free(msg);
47 * @endcode
48 *
49 * @par 2) Sending of trivial messages
50 * @code
51 * // For trivial messages not requiring any subsys specific header or
52 * // attributes, nfnl_send_simple() may be used to send messages directly.
53 * nfnl_send_simple(sk, SUBSYS, TYPE, 0, FAMILY, RES_ID);
54 * @endcode
55 * @{
56 */
57
58 #include "nl-default.h"
59
60 #include <linux/netfilter/nfnetlink.h>
61
62 #include <netlink/netlink.h>
63 #include <netlink/netfilter/nfnl.h>
64 #include <netlink/data.h>
65 #include <netlink/msg.h>
66
67 #include "nl-aux-core/nl-core.h"
68
69 /**
70 * @name Socket Creating
71 * @{
72 */
73
74 /**
75 * Create and connect netfilter netlink socket.
76 * @arg sk Netlink socket.
77 *
78 * Creates a NETLINK_NETFILTER netlink socket, binds the socket and
79 * issues a connection attempt.
80 *
81 * @see nl_connect()
82 *
83 * @return 0 on success or a negative error code.
84 */
nfnl_connect(struct nl_sock * sk)85 int nfnl_connect(struct nl_sock *sk)
86 {
87 return nl_connect(sk, NETLINK_NETFILTER);
88 }
89
90 /** @} */
91
92 /**
93 * @name Sending
94 * @{
95 */
96
97 /**
98 * Send trivial netfilter netlink message
99 * @arg sk Netlink socket.
100 * @arg subsys_id nfnetlink subsystem
101 * @arg type nfnetlink message type
102 * @arg flags message flags
103 * @arg family nfnetlink address family
104 * @arg res_id nfnetlink resource id
105 *
106 * @return 0 on success or a negative error code. Due to a bug, this function
107 * returns the number of bytes sent. Treat any non-negative number as success.
108 */
nfnl_send_simple(struct nl_sock * sk,uint8_t subsys_id,uint8_t type,int flags,uint8_t family,uint16_t res_id)109 int nfnl_send_simple(struct nl_sock *sk, uint8_t subsys_id, uint8_t type,
110 int flags, uint8_t family, uint16_t res_id)
111 {
112 struct nfgenmsg hdr = {
113 .nfgen_family = family,
114 .version = NFNETLINK_V0,
115 .res_id = htons(res_id),
116 };
117
118 return nl_send_simple(sk, NFNLMSG_TYPE(subsys_id, type), flags,
119 &hdr, sizeof(hdr));
120 }
121
122 /** @} */
123
124 /**
125 * @name Message Parsing
126 * @{
127 */
128
129 /**
130 * Get netfilter subsystem id from message
131 * @arg nlh netlink messsage header
132 */
nfnlmsg_subsys(struct nlmsghdr * nlh)133 uint8_t nfnlmsg_subsys(struct nlmsghdr *nlh)
134 {
135 return NFNL_SUBSYS_ID(nlh->nlmsg_type);
136 }
137
138 /**
139 * Get netfilter message type from message
140 * @arg nlh netlink messsage header
141 */
nfnlmsg_subtype(struct nlmsghdr * nlh)142 uint8_t nfnlmsg_subtype(struct nlmsghdr *nlh)
143 {
144 return NFNL_MSG_TYPE(nlh->nlmsg_type);
145 }
146
147 /**
148 * Get netfilter family from message
149 * @arg nlh netlink messsage header
150 */
nfnlmsg_family(struct nlmsghdr * nlh)151 uint8_t nfnlmsg_family(struct nlmsghdr *nlh)
152 {
153 struct nfgenmsg *nfg = nlmsg_data(nlh);
154
155 return nfg->nfgen_family;
156 }
157
158 /**
159 * Get netfilter resource id from message
160 * @arg nlh netlink messsage header
161 */
nfnlmsg_res_id(struct nlmsghdr * nlh)162 uint16_t nfnlmsg_res_id(struct nlmsghdr *nlh)
163 {
164 struct nfgenmsg *nfg = nlmsg_data(nlh);
165
166 return ntohs(nfg->res_id);
167 }
168
169 /** @} */
170
171 /**
172 * @name Message Building
173 * @{
174 */
175
nfnlmsg_append(struct nl_msg * msg,uint8_t family,uint16_t res_id)176 static int nfnlmsg_append(struct nl_msg *msg, uint8_t family, uint16_t res_id)
177 {
178 struct nfgenmsg *nfg;
179
180 nfg = nlmsg_reserve(msg, sizeof(*nfg), NLMSG_ALIGNTO);
181 if (nfg == NULL)
182 return -NLE_NOMEM;
183
184 nfg->nfgen_family = family;
185 nfg->version = NFNETLINK_V0;
186 nfg->res_id = htons(res_id);
187 NL_DBG(2, "msg %p: Added nfnetlink header family=%d res_id=%d\n",
188 msg, family, res_id);
189 return 0;
190 }
191
192 /**
193 * Allocate a new netfilter netlink message
194 * @arg subsys_id nfnetlink subsystem
195 * @arg type nfnetlink message type
196 * @arg flags message flags
197 * @arg family nfnetlink address family
198 * @arg res_id nfnetlink resource id
199 *
200 * @return Newly allocated netlink message or NULL.
201 */
nfnlmsg_alloc_simple(uint8_t subsys_id,uint8_t type,int flags,uint8_t family,uint16_t res_id)202 struct nl_msg *nfnlmsg_alloc_simple(uint8_t subsys_id, uint8_t type, int flags,
203 uint8_t family, uint16_t res_id)
204 {
205 struct nl_msg *msg;
206
207 msg = nlmsg_alloc_simple(NFNLMSG_TYPE(subsys_id, type), flags);
208 if (msg == NULL)
209 return NULL;
210
211 if (nfnlmsg_append(msg, family, res_id) < 0)
212 goto nla_put_failure;
213
214 return msg;
215
216 nla_put_failure:
217 nlmsg_free(msg);
218 return NULL;
219 }
220
221 /**
222 * Add netlink and netfilter netlink headers to netlink message
223 * @arg msg netlink message
224 * @arg pid netlink process id
225 * @arg seq sequence number of message
226 * @arg subsys_id nfnetlink subsystem
227 * @arg type nfnetlink message type
228 * @arg flags message flags
229 * @arg family nfnetlink address family
230 * @arg res_id nfnetlink resource id
231 */
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)232 int nfnlmsg_put(struct nl_msg *msg, uint32_t pid, uint32_t seq,
233 uint8_t subsys_id, uint8_t type, int flags, uint8_t family,
234 uint16_t res_id)
235 {
236 struct nlmsghdr *nlh;
237
238 nlh = nlmsg_put(msg, pid, seq, NFNLMSG_TYPE(subsys_id, type), 0, flags);
239 if (nlh == NULL)
240 return -NLE_MSGSIZE;
241
242 return nfnlmsg_append(msg, family, res_id);
243 }
244
245 /** @} */
246
247 /** @} */
248