/* * Copyright (C) 2007 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 TRACE_TAG TRACE_TRANSPORT #include "sysdeps.h" #include "transport.h" #include <ctype.h> #include <errno.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <base/stringprintf.h> #include "adb.h" #include "adb_utils.h" static void transport_unref(atransport *t); static atransport transport_list = { .next = &transport_list, .prev = &transport_list, }; static atransport pending_list = { .next = &pending_list, .prev = &pending_list, }; ADB_MUTEX_DEFINE( transport_lock ); void kick_transport(atransport* t) { if (t && !t->kicked) { int kicked; adb_mutex_lock(&transport_lock); kicked = t->kicked; if (!kicked) t->kicked = 1; adb_mutex_unlock(&transport_lock); if (!kicked) t->kick(t); } } // Each atransport contains a list of adisconnects (t->disconnects). // An adisconnect contains a link to the next/prev adisconnect, a function // pointer to a disconnect callback which takes a void* piece of user data and // the atransport, and some user data for the callback (helpfully named // "opaque"). // // The list is circular. New items are added to the entry member of the list // (t->disconnects) by add_transport_disconnect. // // run_transport_disconnects invokes each function in the list. // // Gotchas: // * run_transport_disconnects assumes that t->disconnects is non-null, so // this can't be run on a zeroed atransport. // * The callbacks in this list are not removed when called, and this function // is not guarded against running more than once. As such, ensure that this // function is not called multiple times on the same atransport. // TODO(danalbert): Just fix this so that it is guarded once you have tests. void run_transport_disconnects(atransport* t) { adisconnect* dis = t->disconnects.next; D("%s: run_transport_disconnects\n", t->serial); while (dis != &t->disconnects) { adisconnect* next = dis->next; dis->func( dis->opaque, t ); dis = next; } } static void dump_packet(const char* name, const char* func, apacket* p) { unsigned command = p->msg.command; int len = p->msg.data_length; char cmd[9]; char arg0[12], arg1[12]; int n; for (n = 0; n < 4; n++) { int b = (command >> (n*8)) & 255; if (b < 32 || b >= 127) break; cmd[n] = (char)b; } if (n == 4) { cmd[4] = 0; } else { /* There is some non-ASCII name in the command, so dump * the hexadecimal value instead */ snprintf(cmd, sizeof cmd, "%08x", command); } if (p->msg.arg0 < 256U) snprintf(arg0, sizeof arg0, "%d", p->msg.arg0); else snprintf(arg0, sizeof arg0, "0x%x", p->msg.arg0); if (p->msg.arg1 < 256U) snprintf(arg1, sizeof arg1, "%d", p->msg.arg1); else snprintf(arg1, sizeof arg1, "0x%x", p->msg.arg1); D("%s: %s: [%s] arg0=%s arg1=%s (len=%d) ", name, func, cmd, arg0, arg1, len); dump_hex(p->data, len); } static int read_packet(int fd, const char* name, apacket** ppacket) { char *p = (char*)ppacket; /* really read a packet address */ int r; int len = sizeof(*ppacket); char buff[8]; if (!name) { snprintf(buff, sizeof buff, "fd=%d", fd); name = buff; } while(len > 0) { r = adb_read(fd, p, len); if(r > 0) { len -= r; p += r; } else { D("%s: read_packet (fd=%d), error ret=%d errno=%d: %s\n", name, fd, r, errno, strerror(errno)); if((r < 0) && (errno == EINTR)) continue; return -1; } } if (ADB_TRACING) { dump_packet(name, "from remote", *ppacket); } return 0; } static int write_packet(int fd, const char* name, apacket** ppacket) { char *p = (char*) ppacket; /* we really write the packet address */ int r, len = sizeof(ppacket); char buff[8]; if (!name) { snprintf(buff, sizeof buff, "fd=%d", fd); name = buff; } if (ADB_TRACING) { dump_packet(name, "to remote", *ppacket); } len = sizeof(ppacket); while(len > 0) { r = adb_write(fd, p, len); if(r > 0) { len -= r; p += r; } else { D("%s: write_packet (fd=%d) error ret=%d errno=%d: %s\n", name, fd, r, errno, strerror(errno)); if((r < 0) && (errno == EINTR)) continue; return -1; } } return 0; } static void transport_socket_events(int fd, unsigned events, void *_t) { atransport *t = reinterpret_cast<atransport*>(_t); D("transport_socket_events(fd=%d, events=%04x,...)\n", fd, events); if(events & FDE_READ){ apacket *p = 0; if(read_packet(fd, t->serial, &p)){ D("%s: failed to read packet from transport socket on fd %d\n", t->serial, fd); } else { handle_packet(p, (atransport *) _t); } } } void send_packet(apacket *p, atransport *t) { unsigned char *x; unsigned sum; unsigned count; p->msg.magic = p->msg.command ^ 0xffffffff; count = p->msg.data_length; x = (unsigned char *) p->data; sum = 0; while(count-- > 0){ sum += *x++; } p->msg.data_check = sum; print_packet("send", p); if (t == NULL) { D("Transport is null \n"); // Zap errno because print_packet() and other stuff have errno effect. errno = 0; fatal_errno("Transport is null"); } if(write_packet(t->transport_socket, t->serial, &p)){ fatal_errno("cannot enqueue packet on transport socket"); } } /* The transport is opened by transport_register_func before ** the input and output threads are started. ** ** The output thread issues a SYNC(1, token) message to let ** the input thread know to start things up. In the event ** of transport IO failure, the output thread will post a ** SYNC(0,0) message to ensure shutdown. ** ** The transport will not actually be closed until both ** threads exit, but the input thread will kick the transport ** on its way out to disconnect the underlying device. */ static void *output_thread(void *_t) { atransport *t = reinterpret_cast<atransport*>(_t); apacket *p; D("%s: starting transport output thread on fd %d, SYNC online (%d)\n", t->serial, t->fd, t->sync_token + 1); p = get_apacket(); p->msg.command = A_SYNC; p->msg.arg0 = 1; p->msg.arg1 = ++(t->sync_token); p->msg.magic = A_SYNC ^ 0xffffffff; if(write_packet(t->fd, t->serial, &p)) { put_apacket(p); D("%s: failed to write SYNC packet\n", t->serial); goto oops; } D("%s: data pump started\n", t->serial); for(;;) { p = get_apacket(); if(t->read_from_remote(p, t) == 0){ D("%s: received remote packet, sending to transport\n", t->serial); if(write_packet(t->fd, t->serial, &p)){ put_apacket(p); D("%s: failed to write apacket to transport\n", t->serial); goto oops; } } else { D("%s: remote read failed for transport\n", t->serial); put_apacket(p); break; } } D("%s: SYNC offline for transport\n", t->serial); p = get_apacket(); p->msg.command = A_SYNC; p->msg.arg0 = 0; p->msg.arg1 = 0; p->msg.magic = A_SYNC ^ 0xffffffff; if(write_packet(t->fd, t->serial, &p)) { put_apacket(p); D("%s: failed to write SYNC apacket to transport", t->serial); } oops: D("%s: transport output thread is exiting\n", t->serial); kick_transport(t); transport_unref(t); return 0; } static void *input_thread(void *_t) { atransport *t = reinterpret_cast<atransport*>(_t); apacket *p; int active = 0; D("%s: starting transport input thread, reading from fd %d\n", t->serial, t->fd); for(;;){ if(read_packet(t->fd, t->serial, &p)) { D("%s: failed to read apacket from transport on fd %d\n", t->serial, t->fd ); break; } if(p->msg.command == A_SYNC){ if(p->msg.arg0 == 0) { D("%s: transport SYNC offline\n", t->serial); put_apacket(p); break; } else { if(p->msg.arg1 == t->sync_token) { D("%s: transport SYNC online\n", t->serial); active = 1; } else { D("%s: transport ignoring SYNC %d != %d\n", t->serial, p->msg.arg1, t->sync_token); } } } else { if(active) { D("%s: transport got packet, sending to remote\n", t->serial); t->write_to_remote(p, t); } else { D("%s: transport ignoring packet while offline\n", t->serial); } } put_apacket(p); } // this is necessary to avoid a race condition that occured when a transport closes // while a client socket is still active. close_all_sockets(t); D("%s: transport input thread is exiting, fd %d\n", t->serial, t->fd); kick_transport(t); transport_unref(t); return 0; } static int transport_registration_send = -1; static int transport_registration_recv = -1; static fdevent transport_registration_fde; #if ADB_HOST /* this adds support required by the 'track-devices' service. * this is used to send the content of "list_transport" to any * number of client connections that want it through a single * live TCP connection */ struct device_tracker { asocket socket; int update_needed; device_tracker* next; }; /* linked list of all device trackers */ static device_tracker* device_tracker_list; static void device_tracker_remove( device_tracker* tracker ) { device_tracker** pnode = &device_tracker_list; device_tracker* node = *pnode; adb_mutex_lock( &transport_lock ); while (node) { if (node == tracker) { *pnode = node->next; break; } pnode = &node->next; node = *pnode; } adb_mutex_unlock( &transport_lock ); } static void device_tracker_close( asocket* socket ) { device_tracker* tracker = (device_tracker*) socket; asocket* peer = socket->peer; D( "device tracker %p removed\n", tracker); if (peer) { peer->peer = NULL; peer->close(peer); } device_tracker_remove(tracker); free(tracker); } static int device_tracker_enqueue( asocket* socket, apacket* p ) { /* you can't read from a device tracker, close immediately */ put_apacket(p); device_tracker_close(socket); return -1; } static int device_tracker_send(device_tracker* tracker, const std::string& string) { apacket* p = get_apacket(); asocket* peer = tracker->socket.peer; snprintf(reinterpret_cast<char*>(p->data), 5, "%04x", static_cast<int>(string.size())); memcpy(&p->data[4], string.data(), string.size()); p->len = 4 + string.size(); return peer->enqueue(peer, p); } static void device_tracker_ready(asocket* socket) { device_tracker* tracker = reinterpret_cast<device_tracker*>(socket); // We want to send the device list when the tracker connects // for the first time, even if no update occurred. if (tracker->update_needed > 0) { tracker->update_needed = 0; std::string transports = list_transports(false); device_tracker_send(tracker, transports); } } asocket* create_device_tracker(void) { device_tracker* tracker = reinterpret_cast<device_tracker*>(calloc(1, sizeof(*tracker))); if (tracker == nullptr) fatal("cannot allocate device tracker"); D( "device tracker %p created\n", tracker); tracker->socket.enqueue = device_tracker_enqueue; tracker->socket.ready = device_tracker_ready; tracker->socket.close = device_tracker_close; tracker->update_needed = 1; tracker->next = device_tracker_list; device_tracker_list = tracker; return &tracker->socket; } // Call this function each time the transport list has changed. void update_transports() { std::string transports = list_transports(false); device_tracker* tracker = device_tracker_list; while (tracker != nullptr) { device_tracker* next = tracker->next; // This may destroy the tracker if the connection is closed. device_tracker_send(tracker, transports); tracker = next; } } #else void update_transports() { // Nothing to do on the device side. } #endif // ADB_HOST struct tmsg { atransport *transport; int action; }; static int transport_read_action(int fd, struct tmsg* m) { char *p = (char*)m; int len = sizeof(*m); int r; while(len > 0) { r = adb_read(fd, p, len); if(r > 0) { len -= r; p += r; } else { if((r < 0) && (errno == EINTR)) continue; D("transport_read_action: on fd %d, error %d: %s\n", fd, errno, strerror(errno)); return -1; } } return 0; } static int transport_write_action(int fd, struct tmsg* m) { char *p = (char*)m; int len = sizeof(*m); int r; while(len > 0) { r = adb_write(fd, p, len); if(r > 0) { len -= r; p += r; } else { if((r < 0) && (errno == EINTR)) continue; D("transport_write_action: on fd %d, error %d: %s\n", fd, errno, strerror(errno)); return -1; } } return 0; } static void transport_registration_func(int _fd, unsigned ev, void *data) { tmsg m; adb_thread_t output_thread_ptr; adb_thread_t input_thread_ptr; int s[2]; atransport *t; if(!(ev & FDE_READ)) { return; } if(transport_read_action(_fd, &m)) { fatal_errno("cannot read transport registration socket"); } t = m.transport; if(m.action == 0){ D("transport: %s removing and free'ing %d\n", t->serial, t->transport_socket); /* IMPORTANT: the remove closes one half of the ** socket pair. The close closes the other half. */ fdevent_remove(&(t->transport_fde)); adb_close(t->fd); adb_mutex_lock(&transport_lock); t->next->prev = t->prev; t->prev->next = t->next; adb_mutex_unlock(&transport_lock); run_transport_disconnects(t); if (t->product) free(t->product); if (t->serial) free(t->serial); if (t->model) free(t->model); if (t->device) free(t->device); if (t->devpath) free(t->devpath); memset(t,0xee,sizeof(atransport)); free(t); update_transports(); return; } /* don't create transport threads for inaccessible devices */ if (t->connection_state != CS_NOPERM) { /* initial references are the two threads */ t->ref_count = 2; if(adb_socketpair(s)) { fatal_errno("cannot open transport socketpair"); } D("transport: %s socketpair: (%d,%d) starting", t->serial, s[0], s[1]); t->transport_socket = s[0]; t->fd = s[1]; fdevent_install(&(t->transport_fde), t->transport_socket, transport_socket_events, t); fdevent_set(&(t->transport_fde), FDE_READ); if(adb_thread_create(&input_thread_ptr, input_thread, t)){ fatal_errno("cannot create input thread"); } if(adb_thread_create(&output_thread_ptr, output_thread, t)){ fatal_errno("cannot create output thread"); } } adb_mutex_lock(&transport_lock); /* remove from pending list */ t->next->prev = t->prev; t->prev->next = t->next; /* put us on the master device list */ t->next = &transport_list; t->prev = transport_list.prev; t->next->prev = t; t->prev->next = t; adb_mutex_unlock(&transport_lock); t->disconnects.next = t->disconnects.prev = &t->disconnects; update_transports(); } void init_transport_registration(void) { int s[2]; if(adb_socketpair(s)){ fatal_errno("cannot open transport registration socketpair"); } D("socketpair: (%d,%d)", s[0], s[1]); transport_registration_send = s[0]; transport_registration_recv = s[1]; fdevent_install(&transport_registration_fde, transport_registration_recv, transport_registration_func, 0); fdevent_set(&transport_registration_fde, FDE_READ); } /* the fdevent select pump is single threaded */ static void register_transport(atransport *transport) { tmsg m; m.transport = transport; m.action = 1; D("transport: %s registered\n", transport->serial); if(transport_write_action(transport_registration_send, &m)) { fatal_errno("cannot write transport registration socket\n"); } } static void remove_transport(atransport *transport) { tmsg m; m.transport = transport; m.action = 0; D("transport: %s removed\n", transport->serial); if(transport_write_action(transport_registration_send, &m)) { fatal_errno("cannot write transport registration socket\n"); } } static void transport_unref_locked(atransport *t) { t->ref_count--; if (t->ref_count == 0) { D("transport: %s unref (kicking and closing)\n", t->serial); if (!t->kicked) { t->kicked = 1; t->kick(t); } t->close(t); remove_transport(t); } else { D("transport: %s unref (count=%d)\n", t->serial, t->ref_count); } } static void transport_unref(atransport *t) { if (t) { adb_mutex_lock(&transport_lock); transport_unref_locked(t); adb_mutex_unlock(&transport_lock); } } void add_transport_disconnect(atransport* t, adisconnect* dis) { adb_mutex_lock(&transport_lock); dis->next = &t->disconnects; dis->prev = dis->next->prev; dis->prev->next = dis; dis->next->prev = dis; adb_mutex_unlock(&transport_lock); } void remove_transport_disconnect(atransport* t, adisconnect* dis) { dis->prev->next = dis->next; dis->next->prev = dis->prev; dis->next = dis->prev = dis; } static int qual_match(const char *to_test, const char *prefix, const char *qual, bool sanitize_qual) { if (!to_test || !*to_test) /* Return true if both the qual and to_test are null strings. */ return !qual || !*qual; if (!qual) return 0; if (prefix) { while (*prefix) { if (*prefix++ != *to_test++) return 0; } } while (*qual) { char ch = *qual++; if (sanitize_qual && !isalnum(ch)) ch = '_'; if (ch != *to_test++) return 0; } /* Everything matched so far. Return true if *to_test is a NUL. */ return !*to_test; } atransport* acquire_one_transport(int state, transport_type ttype, const char* serial, std::string* error_out) { atransport *t; atransport *result = NULL; int ambiguous = 0; retry: if (error_out) *error_out = android::base::StringPrintf("device '%s' not found", serial); adb_mutex_lock(&transport_lock); for (t = transport_list.next; t != &transport_list; t = t->next) { if (t->connection_state == CS_NOPERM) { if (error_out) *error_out = "insufficient permissions for device"; continue; } /* check for matching serial number */ if (serial) { if ((t->serial && !strcmp(serial, t->serial)) || (t->devpath && !strcmp(serial, t->devpath)) || qual_match(serial, "product:", t->product, false) || qual_match(serial, "model:", t->model, true) || qual_match(serial, "device:", t->device, false)) { if (result) { if (error_out) *error_out = "more than one device"; ambiguous = 1; result = NULL; break; } result = t; } } else { if (ttype == kTransportUsb && t->type == kTransportUsb) { if (result) { if (error_out) *error_out = "more than one device"; ambiguous = 1; result = NULL; break; } result = t; } else if (ttype == kTransportLocal && t->type == kTransportLocal) { if (result) { if (error_out) *error_out = "more than one emulator"; ambiguous = 1; result = NULL; break; } result = t; } else if (ttype == kTransportAny) { if (result) { if (error_out) *error_out = "more than one device/emulator"; ambiguous = 1; result = NULL; break; } result = t; } } } adb_mutex_unlock(&transport_lock); if (result) { if (result->connection_state == CS_UNAUTHORIZED) { if (error_out) { *error_out = "device unauthorized.\n"; char* ADB_VENDOR_KEYS = getenv("ADB_VENDOR_KEYS"); *error_out += "This adbd's $ADB_VENDOR_KEYS is "; *error_out += ADB_VENDOR_KEYS ? ADB_VENDOR_KEYS : "not set"; *error_out += "; try 'adb kill-server' if that seems wrong.\n"; *error_out += "Otherwise check for a confirmation dialog on your device."; } result = NULL; } /* offline devices are ignored -- they are either being born or dying */ if (result && result->connection_state == CS_OFFLINE) { if (error_out) *error_out = "device offline"; result = NULL; } /* check for required connection state */ if (result && state != CS_ANY && result->connection_state != state) { if (error_out) *error_out = "invalid device state"; result = NULL; } } if (result) { /* found one that we can take */ if (error_out) *error_out = "success"; } else if (state != CS_ANY && (serial || !ambiguous)) { adb_sleep_ms(1000); goto retry; } return result; } const char* atransport::connection_state_name() const { switch (connection_state) { case CS_OFFLINE: return "offline"; case CS_BOOTLOADER: return "bootloader"; case CS_DEVICE: return "device"; case CS_HOST: return "host"; case CS_RECOVERY: return "recovery"; case CS_NOPERM: return "no permissions"; case CS_SIDELOAD: return "sideload"; case CS_UNAUTHORIZED: return "unauthorized"; default: return "unknown"; } } #if ADB_HOST static void append_transport_info(std::string* result, const char* key, const char* value, bool sanitize) { if (value == nullptr || *value == '\0') { return; } *result += ' '; *result += key; for (const char* p = value; *p; ++p) { result->push_back((!sanitize || isalnum(*p)) ? *p : '_'); } } static void append_transport(atransport* t, std::string* result, bool long_listing) { const char* serial = t->serial; if (!serial || !serial[0]) { serial = "(no serial number)"; } if (!long_listing) { *result += serial; *result += '\t'; *result += t->connection_state_name(); } else { android::base::StringAppendF(result, "%-22s %s", serial, t->connection_state_name()); append_transport_info(result, "", t->devpath, false); append_transport_info(result, "product:", t->product, false); append_transport_info(result, "model:", t->model, true); append_transport_info(result, "device:", t->device, false); } *result += '\n'; } std::string list_transports(bool long_listing) { std::string result; adb_mutex_lock(&transport_lock); for (atransport* t = transport_list.next; t != &transport_list; t = t->next) { append_transport(t, &result, long_listing); } adb_mutex_unlock(&transport_lock); return result; } /* hack for osx */ void close_usb_devices() { adb_mutex_lock(&transport_lock); for (atransport* t = transport_list.next; t != &transport_list; t = t->next) { if ( !t->kicked ) { t->kicked = 1; t->kick(t); } } adb_mutex_unlock(&transport_lock); } #endif // ADB_HOST int register_socket_transport(int s, const char *serial, int port, int local) { atransport *t = reinterpret_cast<atransport*>(calloc(1, sizeof(atransport))); if (t == nullptr) { return -1; } atransport *n; char buff[32]; if (!serial) { snprintf(buff, sizeof buff, "T-%p", t); serial = buff; } D("transport: %s init'ing for socket %d, on port %d\n", serial, s, port); if (init_socket_transport(t, s, port, local) < 0) { free(t); return -1; } adb_mutex_lock(&transport_lock); for (n = pending_list.next; n != &pending_list; n = n->next) { if (n->serial && !strcmp(serial, n->serial)) { adb_mutex_unlock(&transport_lock); free(t); return -1; } } for (n = transport_list.next; n != &transport_list; n = n->next) { if (n->serial && !strcmp(serial, n->serial)) { adb_mutex_unlock(&transport_lock); free(t); return -1; } } t->next = &pending_list; t->prev = pending_list.prev; t->next->prev = t; t->prev->next = t; t->serial = strdup(serial); adb_mutex_unlock(&transport_lock); register_transport(t); return 0; } #if ADB_HOST atransport *find_transport(const char *serial) { atransport *t; adb_mutex_lock(&transport_lock); for(t = transport_list.next; t != &transport_list; t = t->next) { if (t->serial && !strcmp(serial, t->serial)) { break; } } adb_mutex_unlock(&transport_lock); if (t != &transport_list) return t; else return 0; } void unregister_transport(atransport *t) { adb_mutex_lock(&transport_lock); t->next->prev = t->prev; t->prev->next = t->next; adb_mutex_unlock(&transport_lock); kick_transport(t); transport_unref(t); } // unregisters all non-emulator TCP transports void unregister_all_tcp_transports() { atransport *t, *next; adb_mutex_lock(&transport_lock); for (t = transport_list.next; t != &transport_list; t = next) { next = t->next; if (t->type == kTransportLocal && t->adb_port == 0) { t->next->prev = t->prev; t->prev->next = next; // we cannot call kick_transport when holding transport_lock if (!t->kicked) { t->kicked = 1; t->kick(t); } transport_unref_locked(t); } } adb_mutex_unlock(&transport_lock); } #endif void register_usb_transport(usb_handle *usb, const char *serial, const char *devpath, unsigned writeable) { atransport *t = reinterpret_cast<atransport*>(calloc(1, sizeof(atransport))); if (t == nullptr) fatal("cannot allocate USB atransport"); D("transport: %p init'ing for usb_handle %p (sn='%s')\n", t, usb, serial ? serial : ""); init_usb_transport(t, usb, (writeable ? CS_OFFLINE : CS_NOPERM)); if(serial) { t->serial = strdup(serial); } if(devpath) { t->devpath = strdup(devpath); } adb_mutex_lock(&transport_lock); t->next = &pending_list; t->prev = pending_list.prev; t->next->prev = t; t->prev->next = t; adb_mutex_unlock(&transport_lock); register_transport(t); } /* this should only be used for transports with connection_state == CS_NOPERM */ void unregister_usb_transport(usb_handle *usb) { atransport *t; adb_mutex_lock(&transport_lock); for(t = transport_list.next; t != &transport_list; t = t->next) { if (t->usb == usb && t->connection_state == CS_NOPERM) { t->next->prev = t->prev; t->prev->next = t->next; break; } } adb_mutex_unlock(&transport_lock); } #undef TRACE_TAG #define TRACE_TAG TRACE_RWX int check_header(apacket *p) { if(p->msg.magic != (p->msg.command ^ 0xffffffff)) { D("check_header(): invalid magic\n"); return -1; } if(p->msg.data_length > MAX_PAYLOAD) { D("check_header(): %d > MAX_PAYLOAD\n", p->msg.data_length); return -1; } return 0; } int check_data(apacket *p) { unsigned count, sum; unsigned char *x; count = p->msg.data_length; x = p->data; sum = 0; while(count-- > 0) { sum += *x++; } if(sum != p->msg.data_check) { return -1; } else { return 0; } }