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/*
* Copyright 2008, 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.
*/
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/uio.h>
#include <linux/if_ether.h>
#include <linux/if_packet.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/udp.h>
#include <unistd.h>
#ifdef ANDROID
#define LOG_TAG "DHCP"
#include <android/log.h>
#else
#include <stdio.h>
#define ALOGD printf
#define ALOGW printf
#endif
#include "dhcpmsg.h"
int fatal();
int open_raw_socket(const char *ifname __attribute__((unused)), uint8_t *hwaddr, int if_index)
{
int s;
struct sockaddr_ll bindaddr;
if((s = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP))) < 0) {
return fatal("socket(PF_PACKET)");
}
memset(&bindaddr, 0, sizeof(bindaddr));
bindaddr.sll_family = AF_PACKET;
bindaddr.sll_protocol = htons(ETH_P_IP);
bindaddr.sll_halen = ETH_ALEN;
memcpy(bindaddr.sll_addr, hwaddr, ETH_ALEN);
bindaddr.sll_ifindex = if_index;
if (bind(s, (struct sockaddr *)&bindaddr, sizeof(bindaddr)) < 0) {
return fatal("Cannot bind raw socket to interface");
}
return s;
}
static uint32_t checksum(void *buffer, unsigned int count, uint32_t startsum)
{
uint16_t *up = (uint16_t *)buffer;
uint32_t sum = startsum;
uint32_t upper16;
while (count > 1) {
sum += *up++;
count -= 2;
}
if (count > 0) {
sum += (uint16_t) *(uint8_t *)up;
}
while ((upper16 = (sum >> 16)) != 0) {
sum = (sum & 0xffff) + upper16;
}
return sum;
}
static uint32_t finish_sum(uint32_t sum)
{
return ~sum & 0xffff;
}
int send_packet(int s, int if_index, struct dhcp_msg *msg, int size,
uint32_t saddr, uint32_t daddr, uint32_t sport, uint32_t dport)
{
struct iphdr ip;
struct udphdr udp;
struct iovec iov[3];
uint32_t udpsum;
uint16_t temp;
struct msghdr msghdr;
struct sockaddr_ll destaddr;
ip.version = IPVERSION;
ip.ihl = sizeof(ip) >> 2;
ip.tos = 0;
ip.tot_len = htons(sizeof(ip) + sizeof(udp) + size);
ip.id = 0;
ip.frag_off = 0;
ip.ttl = IPDEFTTL;
ip.protocol = IPPROTO_UDP;
ip.check = 0;
ip.saddr = saddr;
ip.daddr = daddr;
ip.check = finish_sum(checksum(&ip, sizeof(ip), 0));
udp.source = htons(sport);
udp.dest = htons(dport);
udp.len = htons(sizeof(udp) + size);
udp.check = 0;
/* Calculate checksum for pseudo header */
udpsum = checksum(&ip.saddr, sizeof(ip.saddr), 0);
udpsum = checksum(&ip.daddr, sizeof(ip.daddr), udpsum);
temp = htons(IPPROTO_UDP);
udpsum = checksum(&temp, sizeof(temp), udpsum);
temp = udp.len;
udpsum = checksum(&temp, sizeof(temp), udpsum);
/* Add in the checksum for the udp header */
udpsum = checksum(&udp, sizeof(udp), udpsum);
/* Add in the checksum for the data */
udpsum = checksum(msg, size, udpsum);
udp.check = finish_sum(udpsum);
iov[0].iov_base = (char *)&ip;
iov[0].iov_len = sizeof(ip);
iov[1].iov_base = (char *)&udp;
iov[1].iov_len = sizeof(udp);
iov[2].iov_base = (char *)msg;
iov[2].iov_len = size;
memset(&destaddr, 0, sizeof(destaddr));
destaddr.sll_family = AF_PACKET;
destaddr.sll_protocol = htons(ETH_P_IP);
destaddr.sll_ifindex = if_index;
destaddr.sll_halen = ETH_ALEN;
memcpy(destaddr.sll_addr, "\xff\xff\xff\xff\xff\xff", ETH_ALEN);
msghdr.msg_name = &destaddr;
msghdr.msg_namelen = sizeof(destaddr);
msghdr.msg_iov = iov;
msghdr.msg_iovlen = sizeof(iov) / sizeof(struct iovec);
msghdr.msg_flags = 0;
msghdr.msg_control = 0;
msghdr.msg_controllen = 0;
return sendmsg(s, &msghdr, 0);
}
int receive_packet(int s, struct dhcp_msg *msg)
{
int nread;
int is_valid;
struct dhcp_packet {
struct iphdr ip;
struct udphdr udp;
struct dhcp_msg dhcp;
} packet;
int dhcp_size;
uint32_t sum;
uint16_t temp;
uint32_t saddr, daddr;
nread = read(s, &packet, sizeof(packet));
if (nread < 0) {
return -1;
}
/*
* The raw packet interface gives us all packets received by the
* network interface. We need to filter out all packets that are
* not meant for us.
*/
is_valid = 0;
if (nread < (int)(sizeof(struct iphdr) + sizeof(struct udphdr))) {
#if VERBOSE
ALOGD("Packet is too small (%d) to be a UDP datagram", nread);
#endif
} else if (packet.ip.version != IPVERSION || packet.ip.ihl != (sizeof(packet.ip) >> 2)) {
#if VERBOSE
ALOGD("Not a valid IP packet");
#endif
} else if (nread < ntohs(packet.ip.tot_len)) {
#if VERBOSE
ALOGD("Packet was truncated (read %d, needed %d)", nread, ntohs(packet.ip.tot_len));
#endif
} else if (packet.ip.protocol != IPPROTO_UDP) {
#if VERBOSE
ALOGD("IP protocol (%d) is not UDP", packet.ip.protocol);
#endif
} else if (packet.udp.dest != htons(PORT_BOOTP_CLIENT)) {
#if VERBOSE
ALOGD("UDP dest port (%d) is not DHCP client", ntohs(packet.udp.dest));
#endif
} else {
is_valid = 1;
}
if (!is_valid) {
return -1;
}
/* Seems like it's probably a valid DHCP packet */
/* validate IP header checksum */
sum = finish_sum(checksum(&packet.ip, sizeof(packet.ip), 0));
if (sum != 0) {
ALOGW("IP header checksum failure (0x%x)", packet.ip.check);
return -1;
}
/*
* Validate the UDP checksum.
* Since we don't need the IP header anymore, we "borrow" it
* to construct the pseudo header used in the checksum calculation.
*/
dhcp_size = ntohs(packet.udp.len) - sizeof(packet.udp);
saddr = packet.ip.saddr;
daddr = packet.ip.daddr;
nread = ntohs(packet.ip.tot_len);
memset(&packet.ip, 0, sizeof(packet.ip));
packet.ip.saddr = saddr;
packet.ip.daddr = daddr;
packet.ip.protocol = IPPROTO_UDP;
packet.ip.tot_len = packet.udp.len;
temp = packet.udp.check;
packet.udp.check = 0;
sum = finish_sum(checksum(&packet, nread, 0));
packet.udp.check = temp;
if (!sum)
sum = finish_sum(sum);
if (temp != sum) {
ALOGW("UDP header checksum failure (0x%x should be 0x%x)", sum, temp);
return -1;
}
memcpy(msg, &packet.dhcp, dhcp_size);
return dhcp_size;
}
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