ifaddrs-android.h revision 5d26339aed33942ba82bfdb79e1b7e9a832c96a7 
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// NOTE: this in JNIHelp.h in later releases.
32const char* jniStrError(int errnum, char* buf, size_t buflen) {
33    // note: glibc has a nonstandard strerror_r that returns char* rather
34    // than POSIX's int.
35    // char *strerror_r(int errnum, char *buf, size_t n);
36    char* ret = (char*) strerror_r(errnum, buf, buflen);
37    if (((int)ret) == 0) {
38        //POSIX strerror_r, success
39        return buf;
40    } else if (((int)ret) == -1) {
41        //POSIX strerror_r, failure
42        // (Strictly, POSIX only guarantees a value other than 0. The safest
43        // way to implement this function is to use C++ and overload on the
44        // type of strerror_r to accurately distinguish GNU from POSIX. But
45        // realistic implementations will always return -1.)
46        snprintf(buf, buflen, "errno %d", errnum);
47        return buf;
48    } else {
49        //glibc strerror_r returning a string
50        return ret;
51    }
52}
53
54// NOTE: this in bionic's stdlib.h in later releases.
55#define TEMP_FAILURE_RETRY(exp) ({         \
56    typeof (exp) _rc;                      \
57    do {                                   \
58        _rc = (exp);                       \
59    } while (_rc == -1 && errno == EINTR); \
60    _rc; })
61
62// Android (bionic) doesn't have getifaddrs(3)/freeifaddrs(3).
63// We fake it here, so java_net_NetworkInterface.cpp can use that API
64// with all the non-portable code being in this file.
65
66// Source-compatible subset of the BSD struct.
67struct ifaddrs {
68    // Pointer to next struct in list, or NULL at end.
69    ifaddrs* ifa_next;
70
71    // Interface name.
72    char* ifa_name;
73
74    // Interface flags.
75    unsigned int ifa_flags;
76
77    // Interface address.
78    sockaddr* ifa_addr;
79
80    ifaddrs(ifaddrs* next)
81    : ifa_next(next), ifa_name(NULL), ifa_flags(0), ifa_addr(NULL)
82    {
83    }
84
85    ~ifaddrs() {
86        delete ifa_next;
87        delete[] ifa_name;
88        delete ifa_addr;
89    }
90
91    // Sadly, we can't keep the interface index for portability with BSD.
92    // We'll have to keep the name instead, and re-query the index when
93    // we need it later.
94    bool setNameAndFlagsByIndex(int interfaceIndex) {
95        // Get the name.
96        char buf[IFNAMSIZ];
97        char* name = if_indextoname(interfaceIndex, buf);
98        if (name == NULL) {
99            return false;
100        }
101        ifa_name = new char[strlen(name) + 1];
102        strcpy(ifa_name, name);
103
104        // Get the flags.
105        ScopedFd fd(socket(AF_INET, SOCK_DGRAM, 0));
106        if (fd.get() == -1) {
107            return false;
108        }
109        ifreq ifr;
110        memset(&ifr, 0, sizeof(ifr));
111        strcpy(ifr.ifr_name, name);
112        int rc = ioctl(fd.get(), SIOCGIFFLAGS, &ifr);
113        if (rc == -1) {
114            return false;
115        }
116        ifa_flags = ifr.ifr_flags;
117        return true;
118    }
119
120    // Netlink gives us the address family in the header, and the
121    // sockaddr_in or sockaddr_in6 bytes as the payload. We need to
122    // stitch the two bits together into the sockaddr that's part of
123    // our portable interface.
124    void setAddress(int family, void* data, size_t byteCount) {
125        sockaddr_storage* ss = new sockaddr_storage;
126        ss->ss_family = family;
127        if (family == AF_INET) {
128            void* dst = &reinterpret_cast<sockaddr_in*>(ss)->sin_addr;
129            memcpy(dst, data, byteCount);
130        } else if (family == AF_INET6) {
131            void* dst = &reinterpret_cast<sockaddr_in6*>(ss)->sin6_addr;
132            memcpy(dst, data, byteCount);
133        }
134        ifa_addr = reinterpret_cast<sockaddr*>(ss);
135    }
136};
137
138// FIXME: use iovec instead.
139struct addrReq_struct {
140    nlmsghdr netlinkHeader;
141    ifaddrmsg msg;
142};
143
144inline bool sendNetlinkMessage(int fd, const void* data, size_t byteCount) {
145    ssize_t sentByteCount = TEMP_FAILURE_RETRY(send(fd, data, byteCount, 0));
146    return (sentByteCount == static_cast<ssize_t>(byteCount));
147}
148
149inline ssize_t recvNetlinkMessage(int fd, char* buf, size_t byteCount) {
150    return TEMP_FAILURE_RETRY(recv(fd, buf, byteCount, 0));
151}
152
153// Source-compatible with the BSD function.
154inline int getifaddrs(ifaddrs** result) {
155    // Simplify cleanup for callers.
156    *result = NULL;
157
158    // Create a netlink socket.
159    ScopedFd fd(socket(PF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE));
160    if (fd.get() < 0) {
161        return -1;
162    }
163
164    // Ask for the address information.
165    addrReq_struct addrRequest;
166    memset(&addrRequest, 0, sizeof(addrRequest));
167    addrRequest.netlinkHeader.nlmsg_flags = NLM_F_REQUEST | NLM_F_MATCH;
168    addrRequest.netlinkHeader.nlmsg_type = RTM_GETADDR;
169    addrRequest.netlinkHeader.nlmsg_len = NLMSG_ALIGN(NLMSG_LENGTH(sizeof(addrRequest)));
170    addrRequest.msg.ifa_family = AF_UNSPEC; // All families.
171    addrRequest.msg.ifa_index = 0; // All interfaces.
172    if (!sendNetlinkMessage(fd.get(), &addrRequest, addrRequest.netlinkHeader.nlmsg_len)) {
173        return -1;
174    }
175
176    // Read the responses.
177    LocalArray<0> buf(65536); // We don't necessarily have std::vector.
178    ssize_t bytesRead;
179    while ((bytesRead  = recvNetlinkMessage(fd.get(), &buf[0], buf.size())) > 0) {
180        nlmsghdr* hdr = reinterpret_cast<nlmsghdr*>(&buf[0]);
181        for (; NLMSG_OK(hdr, bytesRead); hdr = NLMSG_NEXT(hdr, bytesRead)) {
182            switch (hdr->nlmsg_type) {
183            case NLMSG_DONE:
184                return 0;
185            case NLMSG_ERROR:
186                return -1;
187            case RTM_NEWADDR:
188                {
189                    ifaddrmsg* address = reinterpret_cast<ifaddrmsg*>(NLMSG_DATA(hdr));
190                    rtattr* rta = IFA_RTA(address);
191                    size_t ifaPayloadLength = IFA_PAYLOAD(hdr);
192                    while (RTA_OK(rta, ifaPayloadLength)) {
193                        if (rta->rta_type == IFA_ADDRESS) {
194                            int family = address->ifa_family;
195                            if (family == AF_INET || family == AF_INET6) {
196                                *result = new ifaddrs(*result);
197                                if (!(*result)->setNameAndFlagsByIndex(address->ifa_index)) {
198                                    return -1;
199                                }
200                                (*result)->setAddress(family, RTA_DATA(rta), RTA_PAYLOAD(rta));
201                            }
202                        }
203                        rta = RTA_NEXT(rta, ifaPayloadLength);
204                    }
205                }
206                break;
207            }
208        }
209    }
210    // We only get here if recv fails before we see a NLMSG_DONE.
211    return -1;
212}
213
214// Source-compatible with the BSD function.
215inline void freeifaddrs(ifaddrs* addresses) {
216    delete addresses;
217}
218
219#endif  // IFADDRS_ANDROID_H_included
220