#include "uplink.h"
#include "locks.h"
#include "memlog.h"
#include "sockhelper.h"
#include "image.h"
#include "helper.h"
#include "altservers.h"
#include "helper.h"
#include "protocol.h"
#include <pthread.h>
#include <sys/socket.h>
#include <string.h>
#include <sys/epoll.h>
#include <sys/errno.h>
#include <sys/eventfd.h>
#include <assert.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <inttypes.h>
#include <zlib.h>
#include <fcntl.h>
static void* uplink_mainloop(void *data);
static void uplink_send_requests(dnbd3_connection_t *link, int newOnly);
static void uplink_handle_receive(dnbd3_connection_t *link);
static int uplink_send_keepalive(const int fd);
static void uplink_addCrc32(dnbd3_connection_t *uplink);
static void uplink_sendReplicationRequest(dnbd3_connection_t *link);
// ############ uplink connection handling
/**
* Create and initialize an uplink instance for the given
* image. Uplinks run in their own thread.
* Locks on: _images[].lock
*/
int uplink_init(dnbd3_image_t *image, int sock, dnbd3_host_t *host)
{
if ( !_isProxy ) return FALSE;
dnbd3_connection_t *link = NULL;
assert( image != NULL );
spin_lock( &image->lock );
if ( image->uplink != NULL ) {
spin_unlock( &image->lock );
return TRUE;
}
if ( image->cache_map == NULL ) {
memlogf( "[WARNING] Uplink was requested for image %s, but it is already complete", image->lower_name );
goto failure;
}
link = image->uplink = calloc( 1, sizeof(dnbd3_connection_t) );
link->image = image;
link->queueLen = 0;
link->fd = -1;
link->signal = -1;
if ( sock >= 0 ) {
link->betterFd = sock;
link->betterServer = *host;
link->rttTestResult = RTT_DOCHANGE;
} else {
link->betterFd = -1;
link->rttTestResult = RTT_IDLE;
}
link->recvBufferLen = 0;
link->shutdown = FALSE;
spin_init( &link->queueLock, PTHREAD_PROCESS_PRIVATE );
if ( 0 != pthread_create( &(link->thread), NULL, &uplink_mainloop, (void *)(uintptr_t)link ) ) {
memlogf( "[ERROR] Could not start thread for new client." );
goto failure;
}
spin_unlock( &image->lock );
return TRUE;
failure: ;
if ( link != NULL ) free( link );
link = image->uplink = NULL;
spin_unlock( &image->lock );
return FALSE;
}
/**
* Locks on image.lock, uplink.lock
*/
void uplink_shutdown(dnbd3_image_t *image)
{
assert( image != NULL );
spin_lock( &image->lock );
if ( image->uplink == NULL || image->uplink->shutdown ) {
spin_unlock( &image->lock );
return;
}
dnbd3_connection_t * const uplink = image->uplink;
spin_lock( &uplink->queueLock );
if ( uplink->shutdown ) {
spin_unlock( &uplink->queueLock );
spin_unlock( &image->lock );
return;
}
image->uplink = NULL;
uplink->shutdown = TRUE;
spin_unlock( &uplink->queueLock );
spin_unlock( &image->lock );
if ( uplink->signal != -1 ) write( uplink->signal, "", 1 );
if ( uplink->image != NULL ) {
pthread_join( uplink->thread, NULL );
}
}
/**
* Remove given client from uplink request queue
* Locks on: uplink.queueLock, client.sendMutex
*/
void uplink_removeClient(dnbd3_connection_t *uplink, dnbd3_client_t *client)
{
spin_lock( &uplink->queueLock );
for (int i = uplink->queueLen - 1; i >= 0; --i) {
if ( uplink->queue[i].client == client ) {
uplink->queue[i].client = NULL;
uplink->queue[i].status = ULR_FREE;
if ( i > 20 && uplink->queueLen == i + 1 ) uplink->queueLen--;
}
}
spin_unlock( &uplink->queueLock );
}
/**
* Request a chunk of data through an uplink server
* Locks on: image.lock, uplink.queueLock
*/
int uplink_request(dnbd3_client_t *client, uint64_t handle, uint64_t start, uint32_t length)
{
if ( client == NULL || client->image == NULL ) return FALSE;
spin_lock( &client->image->lock );
if ( client->image->uplink == NULL ) {
spin_unlock( &client->image->lock );
printf( "[DEBUG] Uplink request for image with no uplink (%s)\n", client->image->lower_name );
return FALSE;
}
dnbd3_connection_t * const uplink = client->image->uplink;
// Check if the client is the same host as the uplink. If so assume this is a circular proxy chain
if ( isSameAddress( &uplink->currentServer, &client->host ) ) {
spin_unlock( &client->image->lock );
printf( "[DEBUG] Proxy cycle detected.\n" );
return FALSE;
}
int foundExisting = -1; // Index of a pending request that is a superset of our range, -1 otherwise
int existingType = -1; // ULR_* type of existing request
int i;
int freeSlot = -1;
const uint64_t end = start + length;
spin_lock( &uplink->queueLock );
spin_unlock( &client->image->lock );
for (i = 0; i < uplink->queueLen; ++i) {
if ( freeSlot == -1 && uplink->queue[i].status == ULR_FREE ) freeSlot = i;
if ( uplink->queue[i].status != ULR_PENDING && uplink->queue[i].status != ULR_NEW ) continue;
if ( (foundExisting == -1 || existingType == ULR_PENDING) && uplink->queue[i].from <= start && uplink->queue[i].to >= end ) {
foundExisting = i;
existingType = uplink->queue[i].status;
break;
}
}
if ( freeSlot == -1 ) {
if ( uplink->queueLen >= SERVER_MAX_UPLINK_QUEUE ) {
spin_unlock( &uplink->queueLock );
memlogf( "[WARNING] Uplink queue is full, consider increasing SERVER_MAX_UPLINK_QUEUE. Dropping client..." );
return FALSE;
}
freeSlot = uplink->queueLen++;
}
// Do not send request to uplink server if we have a matching pending request AND the request either has the
// status ULR_NEW OR we found a free slot with LOWER index than the one we attach to. Otherwise
// explicitly send this request to the uplink server. The second condition mentioned here is to prevent
// a race condition where the reply for the outstanding request already arrived and the uplink thread
// is currently traversing the request queue. As it is processing the queue from highest to lowest index, it might
// already have passed the index of the free slot we determined, but not reached the existing request we just found above.
if ( foundExisting != -1 && existingType != ULR_NEW && freeSlot > foundExisting ) foundExisting = -1;
// Fill structure
uplink->queue[freeSlot].from = start;
uplink->queue[freeSlot].to = end;
uplink->queue[freeSlot].handle = handle;
uplink->queue[freeSlot].client = client;
uplink->queue[freeSlot].status = (foundExisting == -1 ? ULR_NEW : ULR_PENDING);
#ifdef _DEBUG
uplink->queue[freeSlot].entered = time( NULL );
#endif
const int signalFd = uplink->signal;
spin_unlock( &uplink->queueLock );
if ( foundExisting == -1 ) { // Only wake up uplink thread if the request needs to be relayed
static uint64_t counter = 1;
write( signalFd, &counter, sizeof(uint64_t) );
}
return TRUE;
}
/**
* Uplink thread.
* Locks are irrelevant as this is never called from another function
*/
static void* uplink_mainloop(void *data)
{
const int MAXEVENTS = 3;
struct epoll_event ev, events[MAXEVENTS];
dnbd3_connection_t *link = (dnbd3_connection_t*)data;
int fdEpoll = -1;
int numSocks, i, waitTime;
int altCheckInterval = SERVER_RTT_DELAY_INIT;
int discoverFailCount = 0;
time_t nextAltCheck = 0;
char buffer[200];
//
assert( link != NULL );
assert( link->queueLen == 0 );
setThreadName( "idle-uplink" );
blockNoncriticalSignals();
//
fdEpoll = epoll_create( 2 );
if ( fdEpoll == -1 ) {
memlogf( "[WARNING] epoll_create failed. Uplink unavailable." );
goto cleanup;
}
link->signal = eventfd( 0, EFD_NONBLOCK );
if ( link->signal < 0 ) {
memlogf( "[WARNING] error creating pipe. Uplink unavailable." );
goto cleanup;
}
memset( &ev, 0, sizeof(ev) );
ev.events = EPOLLIN;
ev.data.fd = link->signal;
if ( epoll_ctl( fdEpoll, EPOLL_CTL_ADD, link->signal, &ev ) < 0 ) {
memlogf( "[WARNING] adding eventfd to epoll set failed" );
goto cleanup;
}
while ( !_shutdown && !link->shutdown ) {
// Check if server switch is in order
if ( link->rttTestResult == RTT_DOCHANGE ) {
link->rttTestResult = RTT_IDLE;
discoverFailCount = 0;
// The rttTest worker thread has finished our request.
// And says it's better to switch to another server
const int fd = link->fd;
link->fd = link->betterFd;
if ( fd != -1 ) close( fd );
// If we don't have a crc32 list yet, see if the new server has one
if ( link->image->crc32 == NULL ) {
uplink_addCrc32( link );
}
// Re-send all pending requests
uplink_send_requests( link, FALSE );
link->betterFd = -1;
link->currentServer = link->betterServer;
link->image->working = TRUE;
buffer[0] = '@';
if ( host_to_string( &link->currentServer, buffer + 1, sizeof(buffer) - 1 ) ) {
printf( "[DEBUG] Now connected to %s\n", buffer + 1 );
setThreadName( buffer );
}
memset( &ev, 0, sizeof(ev) );
ev.events = EPOLLIN;
ev.data.fd = link->fd;
if ( epoll_ctl( fdEpoll, EPOLL_CTL_ADD, link->fd, &ev ) < 0 ) {
memlogf( "[WARNING] adding uplink to epoll set failed" );
goto cleanup;
}
nextAltCheck = time( NULL ) + altCheckInterval;
// The rtt worker already did the handshake for our image, so there's nothing
// more to do here
}
// epoll()
waitTime = (time( NULL ) - nextAltCheck) * 1000;
if ( waitTime < 1500 ) waitTime = 1500;
if ( waitTime > 5000 ) waitTime = 5000;
numSocks = epoll_wait( fdEpoll, events, MAXEVENTS, waitTime );
if ( _shutdown || link->shutdown ) goto cleanup;
if ( numSocks < 0 ) { // Error?
memlogf( "[DEBUG] epoll_wait() error %d", (int)errno);
usleep( 10000 );
continue;
}
// Check all events
for (i = 0; i < numSocks; ++i) {
// Check for errors....
if ( (events[i].events & (EPOLLERR | EPOLLHUP)) || !(events[i].events & EPOLLIN) ) {
if ( events[i].data.fd == link->signal ) {
memlogf( "[WARNING] epoll error on signal-pipe!" );
goto cleanup;
}
if ( events[i].data.fd == link->fd ) {
link->fd = -1;
close( events[i].data.fd );
printf( "[DEBUG] Uplink gone away, panic!\n" );
nextAltCheck = 0;
} else {
printf( "[DEBUG] Error on unknown FD in uplink epoll\n" );
close( events[i].data.fd );
}
continue;
}
// No error, handle normally
if ( events[i].data.fd == link->signal ) {
// Event on the signal fd -> a client requests data
int ret;
do {
ret = read( link->signal, buffer, sizeof buffer );
} while ( ret == sizeof buffer ); // Throw data away, this is just used for waking this thread up
if ( ret == 0 ) {
memlogf( "[WARNING] Eventfd of uplink for %s closed! Things will break!", link->image->lower_name );
}
if ( ret < 0 ) {
ret = errno;
if ( ret != EAGAIN && ret != EWOULDBLOCK && ret != EBUSY && ret != EINTR ) {
memlogf( "[WARNING] Errno %d on eventfd on uplink for %s! Things will break!", ret, link->image->lower_name );
}
}
if ( link->fd != -1 ) {
// Uplink seems fine, relay requests to it...
uplink_send_requests( link, TRUE );
}
} else if ( events[i].data.fd == link->fd ) {
uplink_handle_receive( link );
if ( link->fd == -1 ) nextAltCheck = 0;
if ( _shutdown || link->shutdown ) goto cleanup;
} else {
printf( "[DEBUG] Sanity check: unknown FD ready on epoll! Closing...\n" );
close( events[i].data.fd );
}
}
// Done handling epoll sockets
// Replicate missing blocks from the image so the proxy will eventually have a full copy
uplink_sendReplicationRequest( link );
// See if we should trigger an RTT measurement
if ( link->rttTestResult == RTT_IDLE || link->rttTestResult == RTT_DONTCHANGE ) {
const time_t now = time( NULL );
if ( now + SERVER_RTT_DELAY_FAILED < nextAltCheck ) {
// This probably means the system time was changed - handle this case properly by capping the timeout
nextAltCheck = now + SERVER_RTT_DELAY_FAILED;
} else if ( now >= nextAltCheck ) {
// It seems it's time for a check
if ( image_isComplete( link->image ) ) {
// Quit work if image is complete
memlogf( "[INFO] Replication of %s complete.", link->image->lower_name );
if ( spin_trylock( &link->image->lock ) == 0 ) {
image_markComplete( link->image );
spin_lock( &link->queueLock );
if ( !link->shutdown ) {
link->image->uplink = NULL;
link->shutdown = TRUE;
pthread_detach( link->thread );
}
spin_unlock( &link->queueLock );
spin_unlock( &link->image->lock );
goto cleanup;
}
} else {
// Not complete - do measurement
altservers_findUplink( link ); // This will set RTT_INPROGRESS (synchronous)
// Also send a keepalive packet to the currently connected server
if ( link->fd != -1 ) {
if ( !uplink_send_keepalive( link->fd ) ) {
printf( "[DEBUG] Error sending keep-alive to uplink\n" );
altservers_serverFailed( &link->currentServer );
const int fd = link->fd;
link->fd = -1;
close( fd );
}
}
}
altCheckInterval = MIN(altCheckInterval + 1, SERVER_RTT_DELAY_MAX);
nextAltCheck = now + altCheckInterval;
}
} else if ( link->rttTestResult == RTT_NOT_REACHABLE ) {
link->rttTestResult = RTT_IDLE;
discoverFailCount++;
nextAltCheck = time( NULL ) + (discoverFailCount < 5 ? altCheckInterval : SERVER_RTT_DELAY_FAILED);
}
#ifdef _DEBUG
if ( link->fd != -1 && !link->shutdown ) {
time_t deadline = time( NULL ) - 10;
spin_lock( &link->queueLock );
for (i = 0; i < link->queueLen; ++i) {
if ( link->queue[i].status != ULR_FREE && link->queue[i].entered < deadline ) {
snprintf( buffer, sizeof(buffer), "[DEBUG WARNING] Starving request detected:\n"
"%s\n(from %" PRIu64 " to %" PRIu64 ", status: %d)\n", link->queue[i].client->image->lower_name,
link->queue[i].from, link->queue[i].to, link->queue[i].status );
spin_unlock( &link->queueLock );
printf("%s", buffer);
spin_lock( &link->queueLock );
}
}
spin_unlock( &link->queueLock );
}
#endif
}
cleanup: ;
spin_lock( &link->image->lock );
spin_lock( &link->queueLock );
if (link->image != NULL) link->image->uplink = NULL;
spin_unlock( &link->image->lock );
const int fd = link->fd;
const int signal = link->signal;
link->fd = -1;
link->signal = -1;
spin_unlock( &link->queueLock );
if ( fd != -1 ) close( fd );
if ( signal != -1 ) close( signal );
if ( fdEpoll != -1 ) close( fdEpoll );
// Wait for the RTT check to finish/fail if it's in progress
while ( link->rttTestResult == RTT_INPROGRESS )
usleep( 10000 );
if ( link->betterFd != -1 ) close( link->betterFd );
spin_destroy( &link->queueLock );
free( link->recvBuffer );
link->recvBuffer = NULL;
free( link );
return NULL ;
}
static void uplink_send_requests(dnbd3_connection_t *link, int newOnly)
{
// Scan for new requests
int j;
dnbd3_request_t request;
request.magic = dnbd3_packet_magic;
spin_lock( &link->queueLock );
for (j = 0; j < link->queueLen; ++j) {
if ( link->queue[j].status != ULR_NEW && (newOnly || link->queue[j].status != ULR_PENDING) ) continue;
link->queue[j].status = ULR_PENDING;
request.handle = link->queue[j].from; // HACK: Store offset in handle too, as it won't be included in the reply
request.cmd = CMD_GET_BLOCK;
request.offset = link->queue[j].from;
request.size = link->queue[j].to - link->queue[j].from;
spin_unlock( &link->queueLock );
fixup_request( request );
const int ret = send( link->fd, &request, sizeof request, MSG_NOSIGNAL );
if ( ret != sizeof(request) ) {
// Non-critical - if the connection dropped or the server was changed
// the thread will re-send this request as soon as the connection
// is reestablished.
printf( "[DEBUG] Error forwarding request to uplink server!\n" );
altservers_serverFailed( &link->currentServer );
return;
}
spin_lock( &link->queueLock );
}
spin_unlock( &link->queueLock );
}
/**
* Sent a block request to an uplink server without really having
* any client that needs that data. This will be used for background replication
*/
static void uplink_sendReplicationRequest(dnbd3_connection_t *link)
{
if ( link == NULL || link->fd == -1 ) return;
dnbd3_image_t * const image = link->image;
if ( image == NULL || image->cache_map == NULL || image->filesize < DNBD3_BLOCK_SIZE ) return;
const time_t now = time( NULL );
if ( now <= link->lastReplication + 1 ) return;
link->lastReplication = now;
spin_lock( &image->lock );
if ( image == NULL || image->cache_map == NULL ) {
spin_unlock( &image->lock );
return;
}
dnbd3_request_t request;
request.magic = dnbd3_packet_magic;
int sent = 0;
const size_t len = IMGSIZE_TO_MAPBYTES( image->filesize ) - 1;
for (int i = 0; i <= len; ++i) {
if ( image->cache_map == NULL || link->fd == -1 || sent > 20 ) break;
if ( image->cache_map[i] == 0xff || (i == len && link->replicatedLastBlock) ) continue;
if ( i == len ) link->replicatedLastBlock = TRUE;
spin_unlock( &image->lock );
// Unlocked - do not break or continue here...
++sent;
request.cmd = CMD_GET_BLOCK;
request.offset = request.handle = (uint64_t)i * DNBD3_BLOCK_SIZE * (uint64_t)8;
request.size = DNBD3_BLOCK_SIZE * (uint64_t)8;
if ( request.offset + request.size > image->filesize ) {
request.size = image->filesize - request.offset;
}
fixup_request( request );
const int ret = send( link->fd, &request, sizeof request, MSG_NOSIGNAL );
if ( ret != sizeof(request) ) {
printf( "[DEBUG] Error sending background replication request to uplink server!\n" );
return;
}
// Lock again...
spin_lock( &image->lock );
}
spin_unlock( &image->lock );
}
/**
* Receive data from uplink server and process/dispatch
* Locks on: link.lock, indirectly on images[].lock
*/
static void uplink_handle_receive(dnbd3_connection_t *link)
{
dnbd3_reply_t inReply, outReply;
int ret, i;
for (;;) {
ret = recv( link->fd, &inReply, sizeof inReply, MSG_DONTWAIT | MSG_NOSIGNAL );
if ( ret < 0 ) {
const int err = errno;
if ( err == EAGAIN || err == EWOULDBLOCK || err == EINTR ) return; // OK cases
goto error_cleanup;
}
if ( ret == 0 ) {
memlogf( "[INFO] Uplink: Remote host hung up (%s)", link->image->path );
goto error_cleanup;
}
if ( ret != sizeof inReply ) ret += recv( link->fd, &inReply + ret, sizeof(inReply) - ret, MSG_WAITALL | MSG_NOSIGNAL );
if ( ret != sizeof inReply ) {
const int err = errno;
memlogf( "[INFO] Lost connection to uplink server for %s (header %d/%d, e=%d)", link->image->path, ret, (int)sizeof(inReply),
err );
goto error_cleanup;
}
fixup_reply( inReply );
if ( inReply.magic != dnbd3_packet_magic ) {
memlogf( "[WARNING] Uplink server's packet did not start with dnbd3_packet_magic (%s)", link->image->path );
goto error_cleanup;
}
if ( inReply.size > 9000000 ) {
memlogf( "[WARNING] Pure evil: Uplink server sent too much payload for %s", link->image->path );
goto error_cleanup;
}
if ( link->recvBufferLen < inReply.size ) {
if ( link->recvBuffer != NULL ) free( link->recvBuffer );
link->recvBufferLen = MIN(9000000, inReply.size + 8192);
link->recvBuffer = malloc( link->recvBufferLen );
}
uint32_t done = 0;
while ( done < inReply.size ) {
ret = recv( link->fd, link->recvBuffer + done, inReply.size - done, MSG_NOSIGNAL );
if ( ret <= 0 ) {
memlogf( "[INFO] Lost connection to uplink server of %s (payload)", link->image->path );
goto error_cleanup;
}
done += ret;
}
// Payload read completely
// Bail out if we're not interested
if ( inReply.cmd != CMD_GET_BLOCK ) return;
// Is a legit block reply
const uint64_t start = inReply.handle;
const uint64_t end = inReply.handle + inReply.size;
// 1) Write to cache file
assert( link->image->cacheFd != -1 );
if ( lseek( link->image->cacheFd, start, SEEK_SET ) != start ) {
memlogf( "[ERROR] lseek() failed when writing to cache for %s", link->image->path );
} else {
ret = (int)write( link->image->cacheFd, link->recvBuffer, inReply.size );
if ( ret > 0 ) image_updateCachemap( link->image, start, start + ret, TRUE );
}
// 2) Figure out which clients are interested in it
struct iovec iov[2];
spin_lock( &link->queueLock );
for (i = 0; i < link->queueLen; ++i) {
dnbd3_queued_request_t * const req = &link->queue[i];
assert( req->status != ULR_PROCESSING || req->status != ULR_NEW );
if ( req->status != ULR_PENDING ) continue;
if ( req->from >= start && req->to <= end ) { // Match :-)
req->status = ULR_PROCESSING;
}
}
// 3) Send to interested clients - iterate backwards so request collaboration works, and
// so we can decrease queueLen on the fly while iterating. Should you ever change this to start
// from 0, you also need to change the "attach to existing request"-logic in uplink_request()
outReply.magic = dnbd3_packet_magic;
for (i = link->queueLen - 1; i >= 0; --i) {
dnbd3_queued_request_t * const req = &link->queue[i];
if ( req->status != ULR_PROCESSING ) continue;
assert( req->from >= start && req->to <= end );
dnbd3_client_t * const client = req->client;
outReply.cmd = CMD_GET_BLOCK;
outReply.handle = req->handle;
outReply.size = req->to - req->from;
iov[0].iov_base = &outReply;
iov[0].iov_len = sizeof outReply;
iov[1].iov_base = link->recvBuffer + (req->from - start);
iov[1].iov_len = outReply.size;
fixup_reply( outReply );
req->status = ULR_FREE;
pthread_mutex_lock( &client->sendMutex );
spin_unlock( &link->queueLock );
writev( client->sock, iov, 2 );
pthread_mutex_unlock( &client->sendMutex );
spin_lock( &link->queueLock );
if ( i > 20 && i == link->queueLen - 1 ) link->queueLen--;
}
spin_unlock( &link->queueLock );
}
error_cleanup: ;
altservers_serverFailed( &link->currentServer );
const int fd = link->fd;
link->fd = -1;
if ( fd != -1 ) close( fd );
}
/**
* Send keep alive request to server
*/
static int uplink_send_keepalive(const int fd)
{
static dnbd3_request_t request = { 0, 0, 0, 0, 0 };
if ( request.magic == 0 ) {
request.magic = dnbd3_packet_magic;
request.cmd = CMD_KEEPALIVE;
fixup_request( request );
}
return send( fd, &request, sizeof(request), MSG_NOSIGNAL ) == sizeof(request);
}
static void uplink_addCrc32(dnbd3_connection_t *uplink)
{
dnbd3_image_t *image = uplink->image;
if ( image == NULL || image->filesize == 0 ) return;
size_t bytes = IMGSIZE_TO_HASHBLOCKS(image->filesize) * sizeof(uint32_t);
uint32_t masterCrc;
uint32_t *buffer = malloc( bytes );
if ( !dnbd3_get_crc32( uplink->fd, &masterCrc, buffer, &bytes ) || bytes == 0 ) {
free( buffer );
return;
}
uint32_t lists_crc = crc32( 0L, Z_NULL, 0 );
lists_crc = crc32( lists_crc, (Bytef*)buffer, bytes );
if ( lists_crc != masterCrc ) {
memlogf( "[WARNING] Received corrupted crc32 list from uplink server (%s)!", uplink->image->lower_name );
free( buffer );
return;
}
uplink->image->masterCrc32 = masterCrc;
uplink->image->crc32 = buffer;
const size_t len = strlen( uplink->image->path ) + 30;
char path[len];
snprintf( path, len, "%s.crc", uplink->image->path );
const int fd = open( path, O_WRONLY | O_CREAT, 0640 );
if ( fd >= 0 ) {
write( fd, &masterCrc, sizeof(uint32_t) );
write( fd, buffer, bytes );
close( fd );
}
}
