406 lines
13 KiB
C
406 lines
13 KiB
C
/*
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* Copyright (C) 2009 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/* A simple implementation of PPTP Network Server (RFC 2637) which only
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* creates a single session. The following code only handles control packets.
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* Data packets are handled by PPPoPNS driver which can be found in Android
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* kernel tree. */
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <errno.h>
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <arpa/inet.h>
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#include <linux/netdevice.h>
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#include <linux/if_pppox.h>
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#include "mtpd.h"
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enum pptp_message {
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SCCRQ = 1,
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SCCRP = 2,
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STOPCCRQ = 3,
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STOPCCRP = 4,
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ECHORQ = 5,
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ECHORP = 6,
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OCRQ = 7,
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OCRP = 8,
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ICRQ = 9,
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ICRP = 10,
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ICCN = 11,
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CCRQ = 12,
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CDN = 13,
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WEN = 14,
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SLI = 15,
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MESSAGE_MAX = 15,
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};
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static char *messages[] = {
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NULL, "SCCRQ", "SCCRP", "STOPCCRQ", "STOPCCRP", "ECHORQ", "ECHORP",
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"OCRQ", "OCRP", "ICRQ", "ICRP", "ICCN", "CCRQ", "CDN", "WEN", "SLI",
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};
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static uint8_t lengths[] = {
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0, 156, 156, 16, 16, 16, 20, 168, 32, 220, 24, 28, 16, 148, 40, 24,
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};
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#define CONTROL_MESSAGE htons(1)
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#define MAGIC_COOKIE htonl(0x1A2B3C4D)
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#define PROTOCOL_VERSION htons(0x0100)
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#define RESULT_OK 1
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#define RESULT_ERROR 2
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/* Some implementation uses 0 instead of 1, so we allow both of them. */
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#define ESTABLISHED(result) (result <= 1)
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#define HEADER_SIZE 8
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#define MIN_MESSAGE_SIZE 10
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static uint16_t local;
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static uint16_t remote;
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static uint16_t state;
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#define MAX_PACKET_LENGTH 220
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/* We define all the fields we used in this structure. Type conversion and byte
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* alignment are solved in one place. Although it looks a little bit ugly, it
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* really makes life easier. */
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static struct packet {
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int length;
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int expect;
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union {
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uint8_t buffer[MAX_PACKET_LENGTH];
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struct {
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struct __attribute__((packed)) {
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uint16_t length;
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uint16_t type;
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uint32_t cookie;
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} header;
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uint16_t message;
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uint16_t reserved;
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union {
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struct __attribute__((packed)) {
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uint16_t protocol_version;
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uint8_t result;
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uint8_t error;
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uint32_t framing;
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uint32_t bearer;
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uint16_t channels;
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uint16_t firmware_revision;
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char host[64];
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} sccrp, sccrq;
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struct __attribute__((packed)) {
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uint16_t call;
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uint16_t serial;
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uint32_t minimum_speed;
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uint32_t maximum_speed;
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uint32_t bearer;
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uint32_t framing;
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uint16_t window_size;
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} ocrq;
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struct __attribute__((packed)) {
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uint16_t call;
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uint16_t peer;
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uint8_t result;
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} ocrp, icrp;
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struct __attribute__((packed)) {
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uint32_t identifier;
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uint8_t result;
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} echorq, echorp;
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struct __attribute__((packed)) {
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uint16_t call;
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} icrq, ccrq, cdn;
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};
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} __attribute__((packed));
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} __attribute__((aligned(4)));
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} incoming, outgoing;
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static void set_message(uint16_t message)
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{
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uint16_t length = lengths[message];
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memset(outgoing.buffer, 0, length);
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outgoing.length = length;
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outgoing.header.length = htons(length);
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outgoing.header.type = CONTROL_MESSAGE;
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outgoing.header.cookie = MAGIC_COOKIE;
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outgoing.message = htons(message);
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}
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static void send_packet()
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{
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send(the_socket, outgoing.buffer, outgoing.length, 0);
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}
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static int recv_packet()
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{
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int length;
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/* We are going to read a new message if incoming.expect is 0. */
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if (!incoming.expect) {
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incoming.length = 0;
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incoming.expect = HEADER_SIZE;
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}
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/* The longest message defined in RFC 2637 is 220 bytes, but the protocol
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* itself allows up to 65536 bytes. Therefore we always read a complete
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* message but only keep the first 220 bytes before passing up. */
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length = incoming.expect - incoming.length;
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if (incoming.length >= MAX_PACKET_LENGTH) {
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uint8_t buffer[length];
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length = recv(the_socket, buffer, length, 0);
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} else {
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if (incoming.expect > MAX_PACKET_LENGTH) {
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length = MAX_PACKET_LENGTH - incoming.length;
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}
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length = recv(the_socket, &incoming.buffer[incoming.length], length, 0);
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}
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if (length == -1) {
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if (errno == EINTR) {
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return 0;
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}
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log_print(FATAL, "Recv() %s", strerror(errno));
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exit(NETWORK_ERROR);
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}
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if (length == 0) {
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log_print(DEBUG, "Connection closed");
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log_print(INFO, "Remote server hung up");
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return -REMOTE_REQUESTED;
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}
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incoming.length += length;
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/* If incoming.header is valid, check cookie and update incoming.expect. */
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if (incoming.length == HEADER_SIZE && incoming.expect == HEADER_SIZE) {
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if (incoming.header.cookie != MAGIC_COOKIE) {
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log_print(DEBUG, "Loss of synchronization");
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log_print(ERROR, "Protocol error");
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return -PROTOCOL_ERROR;
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}
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incoming.expect = ntohs(incoming.header.length);
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if (incoming.expect < HEADER_SIZE) {
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log_print(DEBUG, "Invalid message length");
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log_print(ERROR, "Protocol error");
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return -PROTOCOL_ERROR;
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}
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}
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/* Now we have a complete message. Reset incoming.expect. */
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if (incoming.length == incoming.expect) {
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incoming.expect = 0;
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/* Return 1 if it is a control message. */
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if (incoming.header.type == CONTROL_MESSAGE) {
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return 1;
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}
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log_print(DEBUG, "Ignored non-control message (type = %d)",
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ntohs(incoming.header.type));
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}
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return 0;
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}
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static int pptp_connect(char **arguments)
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{
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create_socket(AF_UNSPEC, SOCK_STREAM, arguments[0], arguments[1]);
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log_print(DEBUG, "Sending SCCRQ");
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state = SCCRQ;
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set_message(SCCRQ);
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outgoing.sccrq.protocol_version = PROTOCOL_VERSION;
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outgoing.sccrq.framing = htonl(3);
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outgoing.sccrq.bearer = htonl(3);
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outgoing.sccrq.channels = htons(1);
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strcpy(outgoing.sccrq.host, "anonymous");
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send_packet();
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return 0;
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}
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static int create_pppox()
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{
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int pppox = socket(AF_PPPOX, SOCK_DGRAM, PX_PROTO_OPNS);
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log_print(INFO, "Creating PPPoX socket");
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if (pppox == -1) {
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log_print(FATAL, "Socket() %s", strerror(errno));
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exit(SYSTEM_ERROR);
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} else {
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struct sockaddr_pppopns address = {
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.sa_family = AF_PPPOX,
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.sa_protocol = PX_PROTO_OPNS,
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.tcp_socket = the_socket,
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.local = local,
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.remote = remote,
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};
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if (connect(pppox, (struct sockaddr *)&address, sizeof(address))) {
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log_print(FATAL, "Connect() %s", strerror(errno));
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exit(SYSTEM_ERROR);
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}
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}
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return pppox;
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}
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static int pptp_process()
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{
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int result = recv_packet();
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if (result <= 0) {
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return result;
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}
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if (incoming.length < MIN_MESSAGE_SIZE) {
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log_print(DEBUG, "Control message too short");
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return 0;
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}
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incoming.message = ntohs(incoming.message);
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if (incoming.message > MESSAGE_MAX || !messages[incoming.message]) {
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log_print(DEBUG, "Received UNKNOWN %d", incoming.message);
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return 0;
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}
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if (incoming.length < lengths[incoming.message]) {
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log_print(DEBUG, "Received %s with invalid length (length = %d)",
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messages[incoming.message], incoming.length);
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return 0;
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}
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switch(incoming.message) {
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case SCCRP:
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if (state == SCCRQ) {
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if (incoming.sccrp.protocol_version == PROTOCOL_VERSION &&
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ESTABLISHED(incoming.sccrp.result)) {
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while (!local) {
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local = random();
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}
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log_print(DEBUG, "Received SCCRP -> Sending OCRQ "
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"(local = %d)", local);
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log_print(INFO, "Tunnel established");
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state = OCRQ;
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set_message(OCRQ);
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outgoing.ocrq.call = local;
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outgoing.ocrq.serial = random();
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outgoing.ocrq.minimum_speed = htonl(1000);
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outgoing.ocrq.maximum_speed = htonl(100000000);
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outgoing.ocrq.bearer = htonl(3);
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outgoing.ocrq.framing = htonl(3);
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outgoing.ocrq.window_size = htons(8192);
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send_packet();
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return 0;
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}
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log_print(DEBUG, "Received SCCRP (result = %d)",
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incoming.sccrq.result);
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log_print(INFO, "Remote server hung up");
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return -REMOTE_REQUESTED;
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}
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break;
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case OCRP:
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if (state == OCRQ && incoming.ocrp.peer == local) {
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if (ESTABLISHED(incoming.ocrp.result)) {
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remote = incoming.ocrp.call;
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log_print(DEBUG, "Received OCRQ (remote = %d)", remote);
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log_print(INFO, "Session established");
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state = OCRP;
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start_pppd(create_pppox());
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return 0;
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}
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log_print(DEBUG, "Received OCRP (result = %d)",
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incoming.ocrp.result);
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log_print(INFO, "Remote server hung up");
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return -REMOTE_REQUESTED;
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}
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break;
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case STOPCCRQ:
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log_print(DEBUG, "Received STOPCCRQ");
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log_print(INFO, "Remote server hung up");
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state = STOPCCRQ;
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return -REMOTE_REQUESTED;
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case CCRQ:
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/* According to RFC 2637 page 45, we should never receive CCRQ for
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* outgoing calls. However, some implementation only acts as PNS and
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* always uses CCRQ to clear a call, so here we still handle it. */
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if (state == OCRP && incoming.ccrq.call == remote) {
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log_print(DEBUG, "Received CCRQ (remote = %d)", remote);
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log_print(INFO, "Remote server hung up");
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return -REMOTE_REQUESTED;
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}
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break;
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case CDN:
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if (state == OCRP && incoming.cdn.call == remote) {
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log_print(DEBUG, "Received CDN (remote = %d)", remote);
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log_print(INFO, "Remote server hung up");
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return -REMOTE_REQUESTED;
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}
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break;
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case ECHORQ:
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log_print(DEBUG, "Received ECHORQ -> Sending ECHORP");
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set_message(ECHORP);
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outgoing.echorp.identifier = incoming.echorq.identifier;
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outgoing.echorp.result = RESULT_OK;
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send_packet();
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return 0;
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case WEN:
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case SLI:
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log_print(DEBUG, "Recevied %s", messages[incoming.message]);
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return 0;
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case ICRQ:
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log_print(DEBUG, "Received ICRQ (remote = %d) -> Sending ICRP "
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"with error", incoming.icrq.call);
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set_message(ICRP);
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outgoing.icrp.peer = incoming.icrq.call;
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outgoing.icrp.result = RESULT_ERROR;
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send_packet();
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return 0;
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case OCRQ:
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log_print(DEBUG, "Received OCRQ (remote = %d) -> Sending OCRP "
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"with error", incoming.ocrq.call);
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set_message(OCRP);
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outgoing.ocrp.peer = incoming.ocrq.call;
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outgoing.ocrp.result = RESULT_ERROR;
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send_packet();
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return 0;
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}
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/* We reach here if we got an unexpected message. Just log it. */
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log_print(DEBUG, "Received UNEXPECTED %s", messages[incoming.message]);
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return 0;
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}
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static int pptp_timeout()
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{
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return 0;
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}
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static void pptp_shutdown()
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{
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/* Normally we should send STOPCCRQ and wait for STOPCCRP, but this might
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* block for a long time. Here we simply take the shortcut: do nothing. */
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}
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struct protocol pptp = {
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.name = "pptp",
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.arguments = 2,
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.usage = "<server> <port>",
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.connect = pptp_connect,
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.process = pptp_process,
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.timeout = pptp_timeout,
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.shutdown = pptp_shutdown,
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};
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