ifaddrs-android.h revision 1dd42bb9da388c55191449b848f9d82dc4673229 
1/*
2 * Copyright (C) 2009 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#ifndef IFADDRS_ANDROID_H_included
18#define IFADDRS_ANDROID_H_included
19
20#include <cstring>
21#include <new>
22#include <sys/types.h>
23#include <sys/socket.h>
24#include <stdio.h>
25#include <linux/netlink.h>
26#include <linux/rtnetlink.h>
27
28#include "LocalArray.h"
29#include "ScopedFd.h"
30
31// Android (bionic) doesn't have getifaddrs(3)/freeifaddrs(3).
32// We fake it here, so java_net_NetworkInterface.cpp can use that API
33// with all the non-portable code being in this file.
34
35// Source-compatible subset of the BSD struct.
36struct ifaddrs {
37    // Pointer to next struct in list, or NULL at end.
38    ifaddrs* ifa_next;
39
40    // Interface name.
41    char* ifa_name;
42
43    // Interface flags.
44    unsigned int ifa_flags;
45
46    // Interface address.
47    sockaddr* ifa_addr;
48
49    ifaddrs(ifaddrs* next)
50    : ifa_next(next), ifa_name(NULL), ifa_flags(0), ifa_addr(NULL)
51    {
52    }
53
54    ~ifaddrs() {
55        delete ifa_next;
56        delete[] ifa_name;
57        delete ifa_addr;
58    }
59
60    // Sadly, we can't keep the interface index for portability with BSD.
61    // We'll have to keep the name instead, and re-query the index when
62    // we need it later.
63    bool setNameAndFlagsByIndex(int interfaceIndex) {
64        // Get the name.
65        char buf[IFNAMSIZ];
66        char* name = if_indextoname(interfaceIndex, buf);
67        if (name == NULL) {
68            return false;
69        }
70        ifa_name = new char[strlen(name) + 1];
71        strcpy(ifa_name, name);
72
73        // Get the flags.
74        ScopedFd fd(socket(AF_INET, SOCK_DGRAM, 0));
75        if (fd.get() == -1) {
76            return false;
77        }
78        ifreq ifr;
79        memset(&ifr, 0, sizeof(ifr));
80        strcpy(ifr.ifr_name, name);
81        int rc = ioctl(fd.get(), SIOCGIFFLAGS, &ifr);
82        if (rc == -1) {
83            return false;
84        }
85        ifa_flags = ifr.ifr_flags;
86        return true;
87    }
88
89    // Netlink gives us the address family in the header, and the
90    // sockaddr_in or sockaddr_in6 bytes as the payload. We need to
91    // stitch the two bits together into the sockaddr that's part of
92    // our portable interface.
93    void setAddress(int family, void* data, size_t byteCount) {
94        sockaddr_storage* ss = new sockaddr_storage;
95        ss->ss_family = family;
96        if (family == AF_INET) {
97            void* dst = &reinterpret_cast<sockaddr_in*>(ss)->sin_addr;
98            memcpy(dst, data, byteCount);
99        } else if (family == AF_INET6) {
100            void* dst = &reinterpret_cast<sockaddr_in6*>(ss)->sin6_addr;
101            memcpy(dst, data, byteCount);
102        }
103        ifa_addr = reinterpret_cast<sockaddr*>(ss);
104    }
105};
106
107// FIXME: use iovec instead.
108struct addrReq_struct {
109    nlmsghdr netlinkHeader;
110    ifaddrmsg msg;
111};
112
113inline bool sendNetlinkMessage(int fd, const void* data, size_t byteCount) {
114    ssize_t sentByteCount = TEMP_FAILURE_RETRY(send(fd, data, byteCount, 0));
115    return (sentByteCount == static_cast<ssize_t>(byteCount));
116}
117
118inline ssize_t recvNetlinkMessage(int fd, char* buf, size_t byteCount) {
119    return TEMP_FAILURE_RETRY(recv(fd, buf, byteCount, 0));
120}
121
122// Source-compatible with the BSD function.
123inline int getifaddrs(ifaddrs** result) {
124    // Simplify cleanup for callers.
125    *result = NULL;
126
127    // Create a netlink socket.
128    ScopedFd fd(socket(PF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE));
129    if (fd.get() < 0) {
130        return -1;
131    }
132
133    // Ask for the address information.
134    addrReq_struct addrRequest;
135    memset(&addrRequest, 0, sizeof(addrRequest));
136    addrRequest.netlinkHeader.nlmsg_flags = NLM_F_REQUEST | NLM_F_MATCH;
137    addrRequest.netlinkHeader.nlmsg_type = RTM_GETADDR;
138    addrRequest.netlinkHeader.nlmsg_len = NLMSG_ALIGN(NLMSG_LENGTH(sizeof(addrRequest)));
139    addrRequest.msg.ifa_family = AF_UNSPEC; // All families.
140    addrRequest.msg.ifa_index = 0; // All interfaces.
141    if (!sendNetlinkMessage(fd.get(), &addrRequest, addrRequest.netlinkHeader.nlmsg_len)) {
142        return -1;
143    }
144
145    // Read the responses.
146    LocalArray<0> buf(65536); // We don't necessarily have std::vector.
147    ssize_t bytesRead;
148    while ((bytesRead  = recvNetlinkMessage(fd.get(), &buf[0], buf.size())) > 0) {
149        nlmsghdr* hdr = reinterpret_cast<nlmsghdr*>(&buf[0]);
150        for (; NLMSG_OK(hdr, bytesRead); hdr = NLMSG_NEXT(hdr, bytesRead)) {
151            switch (hdr->nlmsg_type) {
152            case NLMSG_DONE:
153                return 0;
154            case NLMSG_ERROR:
155                return -1;
156            case RTM_NEWADDR:
157                {
158                    ifaddrmsg* address = reinterpret_cast<ifaddrmsg*>(NLMSG_DATA(hdr));
159                    rtattr* rta = IFA_RTA(address);
160                    size_t ifaPayloadLength = IFA_PAYLOAD(hdr);
161                    while (RTA_OK(rta, ifaPayloadLength)) {
162                        if (rta->rta_type == IFA_LOCAL) {
163                            int family = address->ifa_family;
164                            if (family == AF_INET || family == AF_INET6) {
165                                *result = new ifaddrs(*result);
166                                if (!(*result)->setNameAndFlagsByIndex(address->ifa_index)) {
167                                    return -1;
168                                }
169                                (*result)->setAddress(family, RTA_DATA(rta), RTA_PAYLOAD(rta));
170                            }
171                        }
172                        rta = RTA_NEXT(rta, ifaPayloadLength);
173                    }
174                }
175                break;
176            }
177        }
178    }
179    // We only get here if recv fails before we see a NLMSG_DONE.
180    return -1;
181}
182
183// Source-compatible with the BSD function.
184inline void freeifaddrs(ifaddrs* addresses) {
185    delete addresses;
186}
187
188#endif  // IFADDRS_ANDROID_H_included
189