getaddr.c revision a45056e35c1af2a0f0a6eed258fd5fdf4846a79f 
1/*
2 * Copyright 2012 Daniel Drown
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 * getaddr.c - get a locally configured address
17 */
18#include <netinet/in.h>
19#include <strings.h>
20#include <string.h>
21#include <net/if.h>
22
23#include <linux/rtnetlink.h>
24#include <netlink/handlers.h>
25#include <netlink/msg.h>
26
27#include "getaddr.h"
28#include "netlink_msg.h"
29#include "logging.h"
30
31// shared state between getinterface_ip and getaddr_cb
32struct target {
33  int family;
34  unsigned int ifindex;
35  union anyip ip;
36  int foundip;
37};
38
39/* function: getaddr_cb
40 * callback for getinterface_ip
41 * msg  - netlink message
42 * data - (struct target) info for which address we're looking for
43 */
44static int getaddr_cb(struct nl_msg *msg, void *data) {
45  struct ifaddrmsg *ifa_p;
46  struct rtattr *rta_p;
47  int rta_len;
48  struct target *targ_p = (struct target *)data;
49
50  ifa_p = (struct ifaddrmsg *)nlmsg_data(nlmsg_hdr(msg));
51  rta_p = (struct rtattr *)IFA_RTA(ifa_p);
52
53  if(ifa_p->ifa_index != targ_p->ifindex)
54    return NL_OK;
55
56  if(ifa_p->ifa_scope != RT_SCOPE_UNIVERSE)
57    return NL_OK;
58
59  rta_len = RTM_PAYLOAD(nlmsg_hdr(msg));
60  for (; RTA_OK(rta_p, rta_len); rta_p = RTA_NEXT(rta_p, rta_len)) {
61    switch(rta_p->rta_type) {
62      case IFA_ADDRESS:
63        if((targ_p->family == AF_INET6) && !(ifa_p->ifa_flags & IFA_F_SECONDARY)) {
64          memcpy(&targ_p->ip.ip6, RTA_DATA(rta_p), rta_p->rta_len - sizeof(struct rtattr));
65          targ_p->foundip = 1;
66          return NL_OK;
67        }
68        break;
69      case IFA_LOCAL:
70        if(targ_p->family == AF_INET) {
71          memcpy(&targ_p->ip.ip4, RTA_DATA(rta_p), rta_p->rta_len - sizeof(struct rtattr));
72          targ_p->foundip = 1;
73          return NL_OK;
74        }
75        break;
76    }
77  }
78
79  return NL_OK;
80}
81
82/* function: error_handler
83 * error callback for getinterface_ip
84 * nla  - source of the error message
85 * err  - netlink message
86 * arg  - (struct target) info for which address we're looking for
87 */
88static int error_handler(struct sockaddr_nl *nla, struct nlmsgerr *err, void *arg) {
89  return NL_OK;
90}
91
92/* function: getinterface_ip
93 * finds the first global non-privacy IP of the given family for the given interface, or returns NULL.  caller frees pointer
94 * interface - interface to look for
95 * family    - family
96 */
97union anyip *getinterface_ip(const char *interface, int family) {
98  struct ifaddrmsg ifa;
99  struct nl_cb *callbacks = NULL;
100  struct target targ;
101  union anyip *retval = NULL;
102
103  targ.family = family;
104  targ.foundip = 0;
105  targ.ifindex = if_nametoindex(interface);
106  if(targ.ifindex == 0) {
107    return NULL; // interface not found
108  }
109
110  memset(&ifa, 0, sizeof(ifa));
111  ifa.ifa_family = targ.family;
112
113  callbacks = nl_cb_alloc(NL_CB_DEFAULT);
114  if(!callbacks) {
115    goto cleanup;
116  }
117  nl_cb_set(callbacks, NL_CB_VALID, NL_CB_CUSTOM, getaddr_cb, &targ);
118  nl_cb_err(callbacks, NL_CB_CUSTOM, error_handler, &targ);
119
120  // sends message and waits for a response
121  send_ifaddrmsg(RTM_GETADDR, NLM_F_REQUEST | NLM_F_ROOT, &ifa, callbacks);
122
123  if(targ.foundip) {
124    retval = malloc(sizeof(union anyip));
125    if(!retval) {
126      logmsg(ANDROID_LOG_FATAL,"getinterface_ip/out of memory");
127      goto cleanup;
128    }
129    memcpy(retval, &targ.ip, sizeof(union anyip));
130  }
131
132cleanup:
133  if(callbacks)
134    nl_cb_put(callbacks);
135
136  return retval;
137}
138