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/if_addr.h>
24#include <linux/rtnetlink.h>
25#include <netlink/handlers.h>
26#include <netlink/msg.h>
27
28#include "getaddr.h"
29#include "netlink_msg.h"
30#include "logging.h"
31
32// shared state between getinterface_ip and getaddr_cb
33struct target {
34  int family;
35  unsigned int ifindex;
36  union anyip ip;
37  int foundip;
38};
39
40/* function: getaddr_cb
41 * callback for getinterface_ip
42 * msg  - netlink message
43 * data - (struct target) info for which address we're looking for
44 */
45static int getaddr_cb(struct nl_msg *msg, void *data) {
46  struct ifaddrmsg *ifa_p;
47  struct rtattr *rta_p;
48  int rta_len;
49  struct target *targ_p = (struct target *)data;
50
51  ifa_p = (struct ifaddrmsg *)nlmsg_data(nlmsg_hdr(msg));
52  rta_p = (struct rtattr *)IFA_RTA(ifa_p);
53
54  if(ifa_p->ifa_index != targ_p->ifindex)
55    return NL_OK;
56
57  if(ifa_p->ifa_scope != RT_SCOPE_UNIVERSE)
58    return NL_OK;
59
60  rta_len = RTM_PAYLOAD(nlmsg_hdr(msg));
61  for (; RTA_OK(rta_p, rta_len); rta_p = RTA_NEXT(rta_p, rta_len)) {
62    switch(rta_p->rta_type) {
63      case IFA_ADDRESS:
64        if((targ_p->family == AF_INET6) && !(ifa_p->ifa_flags & IFA_F_SECONDARY)) {
65          memcpy(&targ_p->ip.ip6, RTA_DATA(rta_p), rta_p->rta_len - sizeof(struct rtattr));
66          targ_p->foundip = 1;
67          return NL_OK;
68        }
69        break;
70      case IFA_LOCAL:
71        if(targ_p->family == AF_INET) {
72          memcpy(&targ_p->ip.ip4, RTA_DATA(rta_p), rta_p->rta_len - sizeof(struct rtattr));
73          targ_p->foundip = 1;
74          return NL_OK;
75        }
76        break;
77    }
78  }
79
80  return NL_OK;
81}
82
83/* function: error_handler
84 * error callback for getinterface_ip
85 * nla  - source of the error message
86 * err  - netlink message
87 * arg  - (struct target) info for which address we're looking for
88 */
89static int error_handler(__attribute__((unused)) struct sockaddr_nl *nla,
90                         __attribute__((unused)) struct nlmsgerr *err,
91                         __attribute__((unused)) void *arg) {
92  return NL_OK;
93}
94
95/* function: getinterface_ip
96 * finds the first global non-privacy IP of the given family for the given interface, or returns NULL.  caller frees pointer
97 * interface - interface to look for
98 * family    - family
99 */
100union anyip *getinterface_ip(const char *interface, int family) {
101  struct ifaddrmsg ifa;
102  struct nl_cb *callbacks = NULL;
103  struct target targ;
104  union anyip *retval = NULL;
105
106  targ.family = family;
107  targ.foundip = 0;
108  targ.ifindex = if_nametoindex(interface);
109  if(targ.ifindex == 0) {
110    return NULL; // interface not found
111  }
112
113  memset(&ifa, 0, sizeof(ifa));
114  ifa.ifa_family = targ.family;
115
116  callbacks = nl_cb_alloc(NL_CB_DEFAULT);
117  if(!callbacks) {
118    goto cleanup;
119  }
120  nl_cb_set(callbacks, NL_CB_VALID, NL_CB_CUSTOM, getaddr_cb, &targ);
121  nl_cb_err(callbacks, NL_CB_CUSTOM, error_handler, &targ);
122
123  // sends message and waits for a response
124  send_ifaddrmsg(RTM_GETADDR, NLM_F_REQUEST | NLM_F_ROOT, &ifa, callbacks);
125
126  if(targ.foundip) {
127    retval = malloc(sizeof(union anyip));
128    if(!retval) {
129      logmsg(ANDROID_LOG_FATAL,"getinterface_ip/out of memory");
130      goto cleanup;
131    }
132    memcpy(retval, &targ.ip, sizeof(union anyip));
133  }
134
135cleanup:
136  if(callbacks)
137    nl_cb_put(callbacks);
138
139  return retval;
140}
141