1 /***
2 This file is part of avahi.
3
4 avahi is free software; you can redistribute it and/or modify it
5 under the terms of the GNU Lesser General Public License as
6 published by the Free Software Foundation; either version 2.1 of the
7 License, or (at your option) any later version.
8
9 avahi is distributed in the hope that it will be useful, but WITHOUT
10 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
11 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General
12 Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with avahi; if not, write to the Free Software
16 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
17 USA.
18 ***/
19
20 #ifdef HAVE_CONFIG_H
21 #include <config.h>
22 #endif
23
24 #include <unistd.h>
25 #include <errno.h>
26 #include <string.h>
27 #include <sys/ioctl.h>
28 #include <assert.h>
29
30 #include "avahi-common/avahi-malloc.h"
31 #include "netlink.h"
32 #include "log.h"
33
34 struct AvahiNetlink {
35 int fd;
36 unsigned seq;
37 AvahiNetlinkCallback callback;
38 void* userdata;
39 uint8_t* buffer;
40 size_t buffer_length;
41
42 const AvahiPoll *poll_api;
43 AvahiWatch *watch;
44 };
45
avahi_netlink_work(AvahiNetlink * nl,int block)46 int avahi_netlink_work(AvahiNetlink *nl, int block) {
47 ssize_t bytes;
48 struct msghdr smsg;
49 struct cmsghdr *cmsg;
50 struct ucred *cred;
51 struct iovec iov;
52 struct nlmsghdr *p;
53 char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
54
55 assert(nl);
56
57 iov.iov_base = nl->buffer;
58 iov.iov_len = nl->buffer_length;
59
60 smsg.msg_name = NULL;
61 smsg.msg_namelen = 0;
62 smsg.msg_iov = &iov;
63 smsg.msg_iovlen = 1;
64 smsg.msg_control = cred_msg;
65 smsg.msg_controllen = sizeof(cred_msg);
66 smsg.msg_flags = (block ? 0 : MSG_DONTWAIT);
67
68 if ((bytes = recvmsg(nl->fd, &smsg, 0)) < 0) {
69 if (errno == EAGAIN || errno == EINTR)
70 return 0;
71
72 avahi_log_error(__FILE__": recvmsg() failed: %s", strerror(errno));
73 return -1;
74 }
75
76 cmsg = CMSG_FIRSTHDR(&smsg);
77
78 if (!cmsg || cmsg->cmsg_type != SCM_CREDENTIALS) {
79 avahi_log_warn("No sender credentials received, ignoring data.");
80 return -1;
81 }
82
83 cred = (struct ucred*) CMSG_DATA(cmsg);
84
85 if (cred->uid != 0)
86 return -1;
87
88 p = (struct nlmsghdr *) nl->buffer;
89
90 assert(nl->callback);
91
92 for (; bytes > 0; p = NLMSG_NEXT(p, bytes)) {
93 if (!NLMSG_OK(p, (size_t) bytes)) {
94 avahi_log_warn(__FILE__": packet truncated");
95 return -1;
96 }
97
98 nl->callback(nl, p, nl->userdata);
99 }
100
101 return 0;
102 }
103
socket_event(AvahiWatch * w,int fd,AVAHI_GCC_UNUSED AvahiWatchEvent event,void * userdata)104 static void socket_event(AvahiWatch *w, int fd, AVAHI_GCC_UNUSED AvahiWatchEvent event, void *userdata) {
105 AvahiNetlink *nl = userdata;
106
107 assert(w);
108 assert(nl);
109 assert(fd == nl->fd);
110
111 avahi_netlink_work(nl, 0);
112 }
113
avahi_netlink_new(const AvahiPoll * poll_api,uint32_t groups,void (* cb)(AvahiNetlink * nl,struct nlmsghdr * n,void * userdata),void * userdata)114 AvahiNetlink *avahi_netlink_new(const AvahiPoll *poll_api, uint32_t groups, void (*cb) (AvahiNetlink *nl, struct nlmsghdr *n, void* userdata), void* userdata) {
115 int fd = -1;
116 const int on = 1;
117 struct sockaddr_nl addr;
118 AvahiNetlink *nl = NULL;
119
120 assert(poll_api);
121 assert(cb);
122
123 if ((fd = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE)) < 0) {
124 avahi_log_error(__FILE__": socket(PF_NETLINK): %s", strerror(errno));
125 return NULL;
126 }
127
128 memset(&addr, 0, sizeof(addr));
129 addr.nl_family = AF_NETLINK;
130 addr.nl_groups = groups;
131 addr.nl_pid = getpid();
132
133 if (bind(fd, (struct sockaddr *) &addr, sizeof(addr)) < 0) {
134 avahi_log_error(__FILE__": bind(): %s", strerror(errno));
135 goto fail;
136 }
137
138 if (setsockopt(fd, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on)) < 0) {
139 avahi_log_error(__FILE__": SO_PASSCRED: %s", strerror(errno));
140 goto fail;
141 }
142
143 if (!(nl = avahi_new(AvahiNetlink, 1))) {
144 avahi_log_error(__FILE__": avahi_new() failed.");
145 goto fail;
146 }
147
148 nl->poll_api = poll_api;
149 nl->fd = fd;
150 nl->seq = 0;
151 nl->callback = cb;
152 nl->userdata = userdata;
153
154 if (!(nl->buffer = avahi_new(uint8_t, nl->buffer_length = 64*1024))) {
155 avahi_log_error(__FILE__": avahi_new() failed.");
156 goto fail;
157 }
158
159 if (!(nl->watch = poll_api->watch_new(poll_api, fd, AVAHI_WATCH_IN, socket_event, nl))) {
160 avahi_log_error(__FILE__": Failed to create watch.");
161 goto fail;
162 }
163
164 return nl;
165
166 fail:
167
168 if (fd >= 0)
169 close(fd);
170
171 if (nl) {
172 avahi_free(nl->buffer);
173 avahi_free(nl);
174 }
175
176 return NULL;
177 }
178
avahi_netlink_free(AvahiNetlink * nl)179 void avahi_netlink_free(AvahiNetlink *nl) {
180 assert(nl);
181
182 if (nl->watch)
183 nl->poll_api->watch_free(nl->watch);
184
185 if (nl->fd >= 0)
186 close(nl->fd);
187
188 avahi_free(nl->buffer);
189 avahi_free(nl);
190 }
191
avahi_netlink_send(AvahiNetlink * nl,struct nlmsghdr * m,unsigned * ret_seq)192 int avahi_netlink_send(AvahiNetlink *nl, struct nlmsghdr *m, unsigned *ret_seq) {
193 assert(nl);
194 assert(m);
195
196 m->nlmsg_seq = nl->seq++;
197 m->nlmsg_flags |= NLM_F_ACK;
198
199 if (send(nl->fd, m, m->nlmsg_len, 0) < 0) {
200 avahi_log_error(__FILE__": send(): %s", strerror(errno));
201 return -1;
202 }
203
204 if (ret_seq)
205 *ret_seq = m->nlmsg_seq;
206
207 return 0;
208 }
209