1 /*
2 * Copyright (C) 2011 The Android Open Source Project
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 /* NOTICE: This is a clean room re-implementation of libnl */
18
19 #include <malloc.h>
20 #include <unistd.h>
21 #include <sys/socket.h>
22 #include <linux/netlink.h>
23 #include "netlink-types.h"
24
25 /* Allocate a new netlink message with the default maximum payload size. */
nlmsg_alloc(void)26 struct nl_msg *nlmsg_alloc(void)
27 {
28 /* Whole page will store nl_msg + nlmsghdr + genlmsghdr + payload */
29 const int page_sz = getpagesize();
30 struct nl_msg *nm;
31 struct nlmsghdr *nlh;
32
33 /* Netlink message */
34 nm = (struct nl_msg *) malloc(page_sz);
35 if (!nm)
36 goto fail;
37
38 /* Netlink message header pointer */
39 nlh = (struct nlmsghdr *) ((char *) nm + sizeof(struct nl_msg));
40
41 /* Initialize */
42 memset(nm, 0, page_sz);
43 nm->nm_size = page_sz;
44
45 nm->nm_src.nl_family = AF_NETLINK;
46 nm->nm_src.nl_pid = getpid();
47
48 nm->nm_dst.nl_family = AF_NETLINK;
49 nm->nm_dst.nl_pid = 0; /* Kernel */
50
51 /* Initialize and add to netlink message */
52 nlh->nlmsg_len = NLMSG_HDRLEN;
53 nm->nm_nlh = nlh;
54
55 /* Add to reference count and return nl_msg */
56 nlmsg_get(nm);
57 return nm;
58 fail:
59 return NULL;
60 }
61
62 /* Return pointer to message payload. */
nlmsg_data(const struct nlmsghdr * nlh)63 void *nlmsg_data(const struct nlmsghdr *nlh)
64 {
65 return (char *) nlh + NLMSG_HDRLEN;
66 }
67
68 /* Add reference count to nl_msg */
nlmsg_get(struct nl_msg * nm)69 void nlmsg_get(struct nl_msg *nm)
70 {
71 nm->nm_refcnt++;
72 }
73
74 /* Release a reference from an netlink message. */
nlmsg_free(struct nl_msg * nm)75 void nlmsg_free(struct nl_msg *nm)
76 {
77 if (nm) {
78 nm->nm_refcnt--;
79 if (nm->nm_refcnt <= 0)
80 free(nm);
81 }
82
83 }
84
85 /* Return actual netlink message. */
nlmsg_hdr(struct nl_msg * n)86 struct nlmsghdr *nlmsg_hdr(struct nl_msg *n)
87 {
88 return n->nm_nlh;
89 }
90
91 /* Return head of attributes data / payload section */
nlmsg_attrdata(const struct nlmsghdr * nlh,int hdrlen)92 struct nlattr *nlmsg_attrdata(const struct nlmsghdr *nlh, int hdrlen)
93 {
94 unsigned char *data = nlmsg_data(nlh);
95 return (struct nlattr *)(data + NLMSG_ALIGN(hdrlen));
96 }
97
98 /* Returns pointer to end of netlink message */
nlmsg_tail(const struct nlmsghdr * nlh)99 void *nlmsg_tail(const struct nlmsghdr *nlh)
100 {
101 return (void *)((char *)nlh + NLMSG_ALIGN(nlh->nlmsg_len));
102 }
103
104 /* Next netlink message in message stream */
nlmsg_next(struct nlmsghdr * nlh,int * remaining)105 struct nlmsghdr *nlmsg_next(struct nlmsghdr *nlh, int *remaining)
106 {
107 struct nlmsghdr *next_nlh = NULL;
108 int len = nlmsg_len(nlh);
109
110 len = NLMSG_ALIGN(len);
111 if (*remaining > 0 &&
112 len <= *remaining &&
113 len >= (int) sizeof(struct nlmsghdr)) {
114 next_nlh = (struct nlmsghdr *)((char *)nlh + len);
115 *remaining -= len;
116 }
117
118 return next_nlh;
119 }
120
nlmsg_datalen(const struct nlmsghdr * nlh)121 int nlmsg_datalen(const struct nlmsghdr *nlh)
122 {
123 return nlh->nlmsg_len - NLMSG_HDRLEN;
124 }
125
126 /* Length of attributes data */
nlmsg_attrlen(const struct nlmsghdr * nlh,int hdrlen)127 int nlmsg_attrlen(const struct nlmsghdr *nlh, int hdrlen)
128 {
129 return nlmsg_datalen(nlh) - NLMSG_ALIGN(hdrlen);
130 }
131
132 /* Length of netlink message */
nlmsg_len(const struct nlmsghdr * nlh)133 int nlmsg_len(const struct nlmsghdr *nlh)
134 {
135 return nlh->nlmsg_len;
136 }
137
138 /* Check if the netlink message fits into the remaining bytes */
nlmsg_ok(const struct nlmsghdr * nlh,int rem)139 int nlmsg_ok(const struct nlmsghdr *nlh, int rem)
140 {
141 return rem >= (int)sizeof(struct nlmsghdr) &&
142 rem >= nlmsg_len(nlh) &&
143 nlmsg_len(nlh) >= (int) sizeof(struct nlmsghdr) &&
144 nlmsg_len(nlh) <= (rem);
145 }
146
nlmsg_padlen(int payload)147 int nlmsg_padlen(int payload)
148 {
149 return NLMSG_ALIGN(payload) - payload;
150 }
151