/*
* Copyright 2019, The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#define LOG_TAG "NetworkStackUtils-JNI"
#include <errno.h>
#include <jni.h>
#include <linux/filter.h>
#include <linux/if_arp.h>
#include <net/if.h>
#include <netinet/ether.h>
#include <netinet/icmp6.h>
#include <netinet/ip.h>
#include <netinet/ip6.h>
#include <netinet/udp.h>
#include <stdlib.h>
#include <string>
#include <nativehelper/JNIHelp.h>
#include <android/log.h>
namespace android {
constexpr const char NETWORKSTACKUTILS_PKG_NAME[] = "android/net/util/NetworkStackUtils";
static const uint32_t kEtherTypeOffset = offsetof(ether_header, ether_type);
static const uint32_t kEtherHeaderLen = sizeof(ether_header);
static const uint32_t kIPv4Protocol = kEtherHeaderLen + offsetof(iphdr, protocol);
static const uint32_t kIPv4FlagsOffset = kEtherHeaderLen + offsetof(iphdr, frag_off);
static const uint32_t kIPv6NextHeader = kEtherHeaderLen + offsetof(ip6_hdr, ip6_nxt);
static const uint32_t kIPv6PayloadStart = kEtherHeaderLen + sizeof(ip6_hdr);
static const uint32_t kICMPv6TypeOffset = kIPv6PayloadStart + offsetof(icmp6_hdr, icmp6_type);
static const uint32_t kUDPSrcPortIndirectOffset = kEtherHeaderLen + offsetof(udphdr, source);
static const uint32_t kUDPDstPortIndirectOffset = kEtherHeaderLen + offsetof(udphdr, dest);
static const uint16_t kDhcpClientPort = 68;
static bool checkLenAndCopy(JNIEnv* env, const jbyteArray& addr, int len, void* dst) {
if (env->GetArrayLength(addr) != len) {
return false;
}
env->GetByteArrayRegion(addr, 0, len, reinterpret_cast<jbyte*>(dst));
return true;
}
static void network_stack_utils_addArpEntry(JNIEnv *env, jobject thiz, jbyteArray ethAddr,
jbyteArray ipv4Addr, jstring ifname, jobject javaFd) {
arpreq req = {};
sockaddr_in& netAddrStruct = *reinterpret_cast<sockaddr_in*>(&req.arp_pa);
sockaddr& ethAddrStruct = req.arp_ha;
ethAddrStruct.sa_family = ARPHRD_ETHER;
if (!checkLenAndCopy(env, ethAddr, ETH_ALEN, ethAddrStruct.sa_data)) {
jniThrowException(env, "java/io/IOException", "Invalid ethAddr length");
return;
}
netAddrStruct.sin_family = AF_INET;
if (!checkLenAndCopy(env, ipv4Addr, sizeof(in_addr), &netAddrStruct.sin_addr)) {
jniThrowException(env, "java/io/IOException", "Invalid ipv4Addr length");
return;
}
int ifLen = env->GetStringLength(ifname);
// IFNAMSIZ includes the terminating NULL character
if (ifLen >= IFNAMSIZ) {
jniThrowException(env, "java/io/IOException", "ifname too long");
return;
}
env->GetStringUTFRegion(ifname, 0, ifLen, req.arp_dev);
req.arp_flags = ATF_COM; // Completed entry (ha valid)
int fd = jniGetFDFromFileDescriptor(env, javaFd);
if (fd < 0) {
jniThrowExceptionFmt(env, "java/io/IOException", "Invalid file descriptor");
return;
}
// See also: man 7 arp
if (ioctl(fd, SIOCSARP, &req)) {
jniThrowExceptionFmt(env, "java/io/IOException", "ioctl error: %s", strerror(errno));
return;
}
}
static void network_stack_utils_attachDhcpFilter(JNIEnv *env, jobject clazz, jobject javaFd) {
static sock_filter filter_code[] = {
// Check the protocol is UDP.
BPF_STMT(BPF_LD | BPF_B | BPF_ABS, kIPv4Protocol),
BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, IPPROTO_UDP, 0, 6),
// Check this is not a fragment.
BPF_STMT(BPF_LD | BPF_H | BPF_ABS, kIPv4FlagsOffset),
BPF_JUMP(BPF_JMP | BPF_JSET | BPF_K, IP_OFFMASK, 4, 0),
// Get the IP header length.
BPF_STMT(BPF_LDX | BPF_B | BPF_MSH, kEtherHeaderLen),
// Check the destination port.
BPF_STMT(BPF_LD | BPF_H | BPF_IND, kUDPDstPortIndirectOffset),
BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, kDhcpClientPort, 0, 1),
// Accept or reject.
BPF_STMT(BPF_RET | BPF_K, 0xffff),
BPF_STMT(BPF_RET | BPF_K, 0)
};
static const sock_fprog filter = {
sizeof(filter_code) / sizeof(filter_code[0]),
filter_code,
};
int fd = jniGetFDFromFileDescriptor(env, javaFd);
if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter)) != 0) {
jniThrowExceptionFmt(env, "java/net/SocketException",
"setsockopt(SO_ATTACH_FILTER): %s", strerror(errno));
}
}
static void network_stack_utils_attachRaFilter(JNIEnv *env, jobject clazz, jobject javaFd,
jint hardwareAddressType) {
if (hardwareAddressType != ARPHRD_ETHER) {
jniThrowExceptionFmt(env, "java/net/SocketException",
"attachRaFilter only supports ARPHRD_ETHER");
return;
}
static sock_filter filter_code[] = {
// Check IPv6 Next Header is ICMPv6.
BPF_STMT(BPF_LD | BPF_B | BPF_ABS, kIPv6NextHeader),
BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, IPPROTO_ICMPV6, 0, 3),
// Check ICMPv6 type is Router Advertisement.
BPF_STMT(BPF_LD | BPF_B | BPF_ABS, kICMPv6TypeOffset),
BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ND_ROUTER_ADVERT, 0, 1),
// Accept or reject.
BPF_STMT(BPF_RET | BPF_K, 0xffff),
BPF_STMT(BPF_RET | BPF_K, 0)
};
static const sock_fprog filter = {
sizeof(filter_code) / sizeof(filter_code[0]),
filter_code,
};
int fd = jniGetFDFromFileDescriptor(env, javaFd);
if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter)) != 0) {
jniThrowExceptionFmt(env, "java/net/SocketException",
"setsockopt(SO_ATTACH_FILTER): %s", strerror(errno));
}
}
// TODO: Move all this filter code into libnetutils.
static void network_stack_utils_attachControlPacketFilter(
JNIEnv *env, jobject clazz, jobject javaFd, jint hardwareAddressType) {
if (hardwareAddressType != ARPHRD_ETHER) {
jniThrowExceptionFmt(env, "java/net/SocketException",
"attachControlPacketFilter only supports ARPHRD_ETHER");
return;
}
// Capture all:
// - ARPs
// - DHCPv4 packets
// - Router Advertisements & Solicitations
// - Neighbor Advertisements & Solicitations
//
// tcpdump:
// arp or
// '(ip and udp port 68)' or
// '(icmp6 and ip6[40] >= 133 and ip6[40] <= 136)'
static sock_filter filter_code[] = {
// Load the link layer next payload field.
BPF_STMT(BPF_LD | BPF_H | BPF_ABS, kEtherTypeOffset),
// Accept all ARP.
// TODO: Figure out how to better filter ARPs on noisy networks.
BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ETHERTYPE_ARP, 16, 0),
// If IPv4:
BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ETHERTYPE_IP, 0, 9),
// Check the protocol is UDP.
BPF_STMT(BPF_LD | BPF_B | BPF_ABS, kIPv4Protocol),
BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, IPPROTO_UDP, 0, 14),
// Check this is not a fragment.
BPF_STMT(BPF_LD | BPF_H | BPF_ABS, kIPv4FlagsOffset),
BPF_JUMP(BPF_JMP | BPF_JSET | BPF_K, IP_OFFMASK, 12, 0),
// Get the IP header length.
BPF_STMT(BPF_LDX | BPF_B | BPF_MSH, kEtherHeaderLen),
// Check the source port.
BPF_STMT(BPF_LD | BPF_H | BPF_IND, kUDPSrcPortIndirectOffset),
BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, kDhcpClientPort, 8, 0),
// Check the destination port.
BPF_STMT(BPF_LD | BPF_H | BPF_IND, kUDPDstPortIndirectOffset),
BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, kDhcpClientPort, 6, 7),
// IPv6 ...
BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ETHERTYPE_IPV6, 0, 6),
// ... check IPv6 Next Header is ICMPv6 (ignore fragments), ...
BPF_STMT(BPF_LD | BPF_B | BPF_ABS, kIPv6NextHeader),
BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, IPPROTO_ICMPV6, 0, 4),
// ... and check the ICMPv6 type is one of RS/RA/NS/NA.
BPF_STMT(BPF_LD | BPF_B | BPF_ABS, kICMPv6TypeOffset),
BPF_JUMP(BPF_JMP | BPF_JGE | BPF_K, ND_ROUTER_SOLICIT, 0, 2),
BPF_JUMP(BPF_JMP | BPF_JGT | BPF_K, ND_NEIGHBOR_ADVERT, 1, 0),
// Accept or reject.
BPF_STMT(BPF_RET | BPF_K, 0xffff),
BPF_STMT(BPF_RET | BPF_K, 0)
};
static const sock_fprog filter = {
sizeof(filter_code) / sizeof(filter_code[0]),
filter_code,
};
int fd = jniGetFDFromFileDescriptor(env, javaFd);
if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter)) != 0) {
jniThrowExceptionFmt(env, "java/net/SocketException",
"setsockopt(SO_ATTACH_FILTER): %s", strerror(errno));
}
}
/*
* JNI registration.
*/
static const JNINativeMethod gNetworkStackUtilsMethods[] = {
/* name, signature, funcPtr */
{ "addArpEntry", "([B[BLjava/lang/String;Ljava/io/FileDescriptor;)V", (void*) network_stack_utils_addArpEntry },
{ "attachDhcpFilter", "(Ljava/io/FileDescriptor;)V", (void*) network_stack_utils_attachDhcpFilter },
{ "attachRaFilter", "(Ljava/io/FileDescriptor;I)V", (void*) network_stack_utils_attachRaFilter },
{ "attachControlPacketFilter", "(Ljava/io/FileDescriptor;I)V", (void*) network_stack_utils_attachControlPacketFilter },
};
extern "C" jint JNI_OnLoad(JavaVM* vm, void*) {
JNIEnv *env;
if (vm->GetEnv(reinterpret_cast<void**>(&env), JNI_VERSION_1_6) != JNI_OK) {
__android_log_print(ANDROID_LOG_ERROR, LOG_TAG, "ERROR: GetEnv failed");
return JNI_ERR;
}
if (jniRegisterNativeMethods(env, NETWORKSTACKUTILS_PKG_NAME,
gNetworkStackUtilsMethods, NELEM(gNetworkStackUtilsMethods)) < 0) {
return JNI_ERR;
}
return JNI_VERSION_1_6;
}
}; // namespace android