/*
 * Network Block Device - server
 *
 * Copyright 1996-1998 Pavel Machek, distribute under GPL
 *  <pavel@atrey.karlin.mff.cuni.cz>
 * Copyright 2002 Anton Altaparmakov <aia21@cam.ac.uk>
 *
 * Version 1.0 - hopefully 64-bit-clean
 * Version 1.1 - merging enhancements from Josh Parsons, <josh@coombs.anu.edu.au>
 * Version 1.2 - autodetect size of block devices, thanx to Peter T. Breuer" <ptb@it.uc3m.es>
 * Version 1.5 - can compile on Unix systems that don't have 64 bit integer
 *	type, or don't have 64 bit file offsets by defining FS_32BIT
 *	in compile options for nbd-server *only*. This can be done
 *	with make FSCHOICE=-DFS_32BIT nbd-server. (I don't have the
 *	original autoconf input file, or I would make it a configure
 *	option.) Ken Yap <ken@nlc.net.au>.
 * Version 1.6 - fix autodetection of block device size and really make 64 bit
 * 	clean on 32 bit machines. Anton Altaparmakov <aia21@cam.ac.uk>
 * Version 2.0 - Version synchronised with client
 * Version 2.1 - Reap zombie client processes when they exit. Removed
 * 	(uncommented) the _IO magic, it's no longer necessary. Wouter
 * 	Verhelst <wouter@debian.org>
 * Version 2.2 - Auto switch to read-only mode (usefull for floppies).
 * Version 2.3 - Fixed code so that Large File Support works. This
 *	removes the FS_32BIT compile-time directive; define
 *	_FILE_OFFSET_BITS=64 and _LARGEFILE_SOURCE if you used to be
 *	using FS_32BIT. This will allow you to use files >2GB instead of
 *	having to use the -m option. Wouter Verhelst <wouter@debian.org>
 * Version 2.4 - Added code to keep track of children, so that we can
 * 	properly kill them from initscripts. Add a call to daemon(),
 * 	so that processes don't think they have to wait for us, which is
 * 	interesting for initscripts as well. Wouter Verhelst
 * 	<wouter@debian.org>
 * Version 2.5 - Bugfix release: forgot to reset child_arraysize to
 *      zero after fork()ing, resulting in nbd-server going berserk
 *      when it receives a signal with at least one child open. Wouter
 *      Verhelst <wouter@debian.org>
 * 10/10/2003 - Added socket option SO_KEEPALIVE (sf.net bug 819235);
 * 	rectified type of mainloop::size_host (sf.net bugs 814435 and
 * 	817385); close the PID file after writing to it, so that the
 * 	daemon can actually be found. Wouter Verhelst
 * 	<wouter@debian.org>
 */

#define VERSION PACKAGE_VERSION
#define GIGA (1*1024*1024*1024)

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/wait.h>		/* wait */
#include <signal.h>		/* sigaction */
#include <netinet/tcp.h>
#include <netinet/in.h>		/* sockaddr_in, htons, in_addr */
#include <netdb.h>		/* hostent, gethostby*, getservby* */
#include <syslog.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <arpa/inet.h>
#include <strings.h>

//#define _IO(a,b)
// #define ISSERVER
#define MY_NAME "nbd_server"

/* how much space for child PIDs we have by default. Dynamically
   allocated, and will be realloc()ed if out of space, so this should
   probably be fair for most situations. */
#define DEFAULT_CHILD_ARRAY 256

#include "cliserv.h"
//#undef _IO
/* Deep magic: ioctl.h defines _IO macro (at least on linux) */

/* Debugging macros, now nothing goes to syslog unless you say ISSERVER */
#ifdef ISSERVER
#define msg2(a,b) syslog(a,b)
#define msg3(a,b,c) syslog(a,b,c)
#define msg4(a,b,c,d) syslog(a,b,c,d)
#else
#define msg2(a,b) do { fprintf(stderr,b) ; fputs("\n",stderr) ; } while(0) 
#define msg3(a,b,c) do { fprintf(stderr,b,c); fputs("\n",stderr) ; } while(0) 
#define msg4(a,b,c,d) do { fprintf(stderr,b,c,d); fputs("\n",stderr) ; } while(0)
#endif

#include <sys/ioctl.h>
#include <sys/mount.h>		/* For BLKGETSIZE */

//#define DODBG
#ifdef DODBG
#define DEBUG( a ) printf( a )
#define DEBUG2( a,b ) printf( a,b )
#define DEBUG3( a,b,c ) printf( a,b,c )
#else
#define DEBUG( a )
#define DEBUG2( a,b ) 
#define DEBUG3( a,b,c ) 
#endif

void serveconnection(int net);
void set_peername(int net,char *clientname);

#define LINELEN 256 
char difffilename[256];
unsigned int timeout = 0;
int autoreadonly = 0;
char *auth_file="nbd_server.allow";

int authorized_client(char *name)
/* 0 - authorization refused, 1 - OK 
  authorization file contains one line per machine, no wildcards
*/
{
	FILE *f ;
   
	char line[LINELEN] ; 

	if ((f=fopen(auth_file,"r"))==NULL) {
		msg4(LOG_INFO,"Can't open authorization file %s (%s).",
		     auth_file,strerror(errno)) ;
		return 1 ; 
	}
  
	while (fgets(line,LINELEN,f)!=NULL) {
		if (strncmp(line,name,strlen(name))==0) {
			fclose(f);
			return 1;
		}
	}
	fclose(f) ;
	return 0 ;
}

inline void readit(int f, void *buf, int len)
{
	int res;
	while (len > 0) {
		DEBUG("*");
		if ((res = read(f, buf, len)) <= 0)
			err("Read failed: %m");
		len -= res;
		buf += res;
	}
}

inline void writeit(int f, void *buf, int len)
{
	int res;
	while (len > 0) {
		DEBUG("+");
		if ((res = send(f, buf, len, 0)) <= 0)
			err("Send failed: %m");
		len -= res;
		buf += res;
	}
}

/* This is starting to get ugly. If someone knows a better way to find
 * the maximum value of a signed type *without* relying on overflow
 * (doing so breaks on 64bit architectures), that would be nice.
 */
#define OFFT_MAX (((((off_t)1)<<((sizeof(off_t)-1)*8))-1)<<7)+127
int port;			/* Port I'm listening at */
char *exportname;		/* File I'm exporting */
off_t exportsize = OFFT_MAX;	/* ...and its length */
off_t hunksize = OFFT_MAX;
int flags = 0;
int export[1024];
int difffile=-1 ;
u32 difffilelen=0 ; /* number of pages in difffile */
u32 *difmap=NULL ;
char clientname[256] ;
int child_arraysize=DEFAULT_CHILD_ARRAY;
pid_t *children;
char pidfname[256];

#define DIFFPAGESIZE 4096 /* diff file uses those chunks */

#define F_READONLY 1
#define F_MULTIFILE 2 
#define F_COPYONWRITE 4

void cmdline(int argc, char *argv[])
{
	int i;

	if (argc < 3) {
		printf("This is nbd-server version " VERSION "\n");	
		printf("Usage: port file_to_export [size][kKmM] [-r] [-m] [-c] [-a timeout_sec]\n"
		       "	-r read only\n"
		       "	-m multiple file\n"
		       "	-c copy on write\n"
		       "        -l file with list of hosts that are allowed to connect.\n"
		       "        -a maximum idle seconds, terminates when idle time exceeded\n"
		       "	if port is set to 0, stdin is used (for running from inetd)\n"
		       "	if file_to_export contains '%%s', it is substituted with IP\n"
		       "		address of machine trying to connect\n" );
		exit(0);
	}
	port = atoi(argv[1]);
	for (i = 3; i < argc; i++) {
		if (*argv[i] == '-') {
			switch (argv[i][1]) {
			case 'r':
				flags |= F_READONLY;
				break;
			case 'm':
				flags |= F_MULTIFILE;
				hunksize = 1*GIGA;
				break;
			case 'c': flags |=F_COPYONWRITE;
			        break;
			case 'l':
				free(auth_file);
				if (i+1<argc) {
					auth_file=argv[++i];
				} else {
					fprintf(stderr, "host list file requires an argument");
				}
				break;
			case 'a': 
				if (i+1<argc) {
					timeout = atoi(argv[i+1]);
					i++;
				} else {
					fprintf(stderr, "timeout requires argument\n");
					exit(1);
				}
			}
		} else {
			off_t es;
			int last = strlen(argv[i])-1;
			char suffix = argv[i][last];
			if (suffix == 'k' || suffix == 'K' ||
			    suffix == 'm' || suffix == 'M')
				argv[i][last] = '\0';
			es = (off_t)atol(argv[i]);
			switch (suffix) {
				case 'm':
				case 'M':  es <<= 10;
				case 'k':
				case 'K':  es <<= 10;
				default :  break;
			}
			exportsize = es;
		}
	}

	exportname = argv[2];
}

void sigchld_handler(int s)
{
        int* status=NULL;
	int i;
	pid_t pid;

	while((pid=wait(status)) > 0) {
		if(WIFEXITED(status)) {
			msg3(LOG_INFO, "Child exited with %d", WEXITSTATUS(status));
		}
		for(i=0;children[i]!=pid&&i<child_arraysize;i++);
		if(i>=child_arraysize) {
			msg3(LOG_INFO, "SIGCHLD received for an unknown child with PID %ld",(long) pid);
		} else {
			children[i]=(pid_t)0;
			DEBUG2("Removing %d from the list of children", pid);
		}
	}
}

/* If we are terminated, make sure our children are, too. */
void sigterm_handler(int s) {
	int i;
	int parent=0;

	for(i=0;i<child_arraysize;i++) {
		if(children[i]) {
			kill(children[i], s);
			parent=1;
		}
	}

	if(parent) {
		unlink(pidfname);
	}
		
	exit(0);
}

void connectme(int port)
{
	struct sockaddr_in addrin;
	struct sigaction sa;
	int addrinlen = sizeof(addrin);
	int net, sock, newpid, i;
#ifndef sun
	int yes=1;
#else
	char yes='1';
#endif /* sun */
#ifndef NODAEMON
#ifndef NOFORK
	FILE*pidf;

	if(port) {
		if(daemon(0,0)<0) {
			err("daemon");
		}
		snprintf(pidfname, sizeof(char)*255, "/var/run/nbd-server.%d.pid", port);
		pidf=fopen(pidfname, "w");
		if(pidf) {
			fprintf(pidf,"%d", (int)getpid());
			fclose(pidf);
		} else {
			perror("fopen");
			fprintf(stderr, "Not fatal; continuing");
		}
	}
#endif /* NOFORK */
#endif /* NODAEMON */

	if ((sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
		err("socket: %m");

	/* lose the pesky "Address already in use" error message */
	if (setsockopt(sock,SOL_SOCKET,SO_REUSEADDR,&yes,sizeof(int)) == -1) {
	        err("setsockopt SO_REUSEADDR");
	}
	if (setsockopt(sock,SOL_SOCKET,SO_KEEPALIVE,&yes,sizeof(int)) == -1) {
		err("setsockopt SO_KEEPALIVE");
	}

	DEBUG("Waiting for connections... bind, ");
	addrin.sin_family = AF_INET;
	addrin.sin_port = htons(port);
	addrin.sin_addr.s_addr = 0;
	if (bind(sock, (struct sockaddr *) &addrin, addrinlen) < 0)
		err("bind: %m");
	DEBUG("listen, ");
	if (listen(sock, 1) < 0)
		err("listen: %m");
	DEBUG("accept, ");
	sa.sa_handler = sigchld_handler;
	sigemptyset(&sa.sa_mask);
	sa.sa_flags = SA_RESTART;
	if(sigaction(SIGCHLD, &sa, NULL) == -1)
		err("sigaction: %m");
	sa.sa_handler = sigterm_handler;
	sigemptyset(&sa.sa_mask);
	sa.sa_flags = SA_RESTART;
	if(sigaction(SIGTERM, &sa, NULL) == -1)
		err("sigaction: %m");
	children=malloc(sizeof(pid_t)*child_arraysize);
	memset(children, 0, sizeof(pid_t)*DEFAULT_CHILD_ARRAY);
	for(;;) { /* infinite loop */
		if ((net = accept(sock, (struct sockaddr *) &addrin, &addrinlen)) < 0)
			err("accept: %m");
		
		set_peername(net,clientname) ;
		if (!authorized_client(clientname)) {
			msg2(LOG_INFO,"Unauthorized client") ;
			close(net) ;
			continue ;
		}
		msg2(LOG_INFO,"Authorized client") ;
		for(i=0;children[i]&&i<child_arraysize;i++);
		if(i>=child_arraysize) {
			realloc(children, sizeof(pid_t)*child_arraysize);
			memset(children+child_arraysize, 0, sizeof(pid_t)*DEFAULT_CHILD_ARRAY);
			i=child_arraysize+1;
			child_arraysize+=DEFAULT_CHILD_ARRAY;
		}
#ifndef NOFORK
		if ((children[i]=fork())<0) {
			msg3(LOG_INFO,"Could not fork (%s)",strerror(errno)) ;
			close(net) ;
			continue ;
		}
		if (children[i]>0) { /* parent */
			close(net) ; continue ; }
		/* child */
		realloc(children,0);
		child_arraysize=0;
		close(sock) ;
#endif // NOFORK
		msg2(LOG_INFO,"Starting to serve") ;
		serveconnection(net) ;        
	}
}

#define SEND writeit( net, &reply, sizeof( reply ));
#define ERROR { reply.error = htonl(-1); SEND; reply.error = 0; lastpoint = -1; }

off_t lastpoint = (off_t)-1;

void maybeseek(int handle, off_t a)
{
if (a > exportsize)
	err("Can not happen\n");
if (lastpoint != a) {
	if (lseek(handle, a, SEEK_SET) < 0)
		err("Can not seek locally!\n");
	lastpoint = a;
} else {
	DEBUG("@");
}
}

void myseek(int handle,off_t a)
{
	if (lseek(handle, a, SEEK_SET) < 0)
		err("Can not seek locally!\n");
}

char pagebuf[DIFFPAGESIZE];

int rawexpread(off_t a, char *buf, int len)
{
	maybeseek(export[a/hunksize], a%hunksize);
	return (read(export[a/hunksize], buf, len) != len);
}

int expread(off_t a, char *buf, int len)
{
	int rdlen, offset;
	off_t mapcnt, mapl, maph, pagestart;
 
	if (!(flags & F_COPYONWRITE))
		return rawexpread(a, buf, len);
	DEBUG3("Asked to read %d bytes at %Lu.\n", len, (unsigned long long)a);

	mapl=a/DIFFPAGESIZE; maph=(a+len-1)/DIFFPAGESIZE;

	for (mapcnt=mapl;mapcnt<=maph;mapcnt++) {
		pagestart=mapcnt*DIFFPAGESIZE;
		offset=a-pagestart;
		rdlen=(len<DIFFPAGESIZE-offset) ? len : DIFFPAGESIZE-offset;
		if (difmap[mapcnt]!=(u32)(-1)) { /* the block is already there */
			DEBUG3("Page %Lu is at %lu\n", (unsigned long long)mapcnt,
			       (unsigned long)difmap[mapcnt]);
			myseek(difffile, difmap[mapcnt]*DIFFPAGESIZE+offset);
			if (read(difffile, buf, rdlen) != rdlen) return -1;
		} else { /* the block is not there */
			DEBUG2("Page %Lu is not here, we read the original one\n",
			       (unsigned long long)mapcnt);
			return rawexpread(a, buf, rdlen);
		}
		len-=rdlen; a+=rdlen; buf+=rdlen;
	}
	return 0;
}

int rawexpwrite(off_t a, char *buf, int len)
{
	maybeseek(export[a/hunksize], a%hunksize);
	return (write(export[a/hunksize], buf, len) != len);
}


int expwrite(off_t a, char *buf, int len)
{
	u32 mapcnt,mapl,maph ; int wrlen,rdlen ; 
	off_t pagestart ; int offset ;

	if (!(flags & F_COPYONWRITE))
		return(rawexpwrite(a,buf,len)); 
	DEBUG3("Asked to write %d bytes at %Lu.\n", len, (unsigned long long)a);

	mapl=a/DIFFPAGESIZE ; maph=(a+len-1)/DIFFPAGESIZE ;

	for (mapcnt=mapl;mapcnt<=maph;mapcnt++) {
		pagestart=mapcnt*DIFFPAGESIZE ;
		offset=a-pagestart ;
		wrlen=(len<DIFFPAGESIZE-offset) ? len : DIFFPAGESIZE-offset ;

		if (difmap[mapcnt]!=(u32)(-1)) { /* the block is already there */
			DEBUG3("Page %Lu is at %lu\n", (unsigned long long)mapcnt,
			       (unsigned long)difmap[mapcnt]) ;
			myseek(difffile,difmap[mapcnt]*DIFFPAGESIZE+offset) ;
			if (write(difffile, buf, wrlen) != wrlen) return -1 ;
		} else { /* the block is not there */
			myseek(difffile,difffilelen*DIFFPAGESIZE) ;
			difmap[mapcnt]=difffilelen++ ;
			DEBUG3("Page %Lu is not here, we put it at %lu\n",
			       (unsigned long long)mapcnt,
			       (unsigned long)difmap[mapcnt]);
			rdlen=DIFFPAGESIZE ;
			if (rdlen+pagestart%hunksize>hunksize) 
				rdlen=hunksize-(pagestart%hunksize) ;
			if (rawexpread(pagestart,pagebuf,rdlen)) return -1 ;
			memcpy(pagebuf+offset,buf,wrlen) ;
			if (write(difffile,pagebuf,DIFFPAGESIZE)!=DIFFPAGESIZE) return -1 ;
		}						    
		len-=wrlen ; a+=wrlen ; buf+=wrlen ;
	}
	return 0;
}

int mainloop(int net)
{
	struct nbd_request request;
	struct nbd_reply reply;
	char zeros[300];
	int i = 0;
	u64 size_host;

	memset(zeros, 0, 290);
	if (write(net, INIT_PASSWD, 8) < 0)
		err("Negotiation failed: %m");
	cliserv_magic = htonll(cliserv_magic);
	if (write(net, &cliserv_magic, sizeof(cliserv_magic)) < 0)
		err("Negotiation failed: %m");
	size_host = htonll((u64)exportsize);
	if (write(net, &size_host, 8) < 0)
		err("Negotiation failed: %m");
	if (write(net, zeros, 128) < 0)
		err("Negotiation failed: %m");

	DEBUG("Entering request loop!\n");
	reply.magic = htonl(NBD_REPLY_MAGIC);
	reply.error = 0;
	while (1) {
#define BUFSIZE (1024*1024)
		char buf[BUFSIZE];
		int len;
#ifdef DODBG
		i++;
		printf("%d: ", i);
#endif

		if (timeout) 
			alarm(timeout);
		readit(net, &request, sizeof(request));
		request.from = ntohll(request.from);
		request.type = ntohl(request.type);

		if (request.type==2) { /* Disconnect request */
		  if (difmap) free(difmap) ;
                  if (difffile>=0) { 
                     close(difffile) ; unlink(difffilename) ; }
		  err("Disconnect request received.") ;
		}

		len = ntohl(request.len);

		if (request.magic != htonl(NBD_REQUEST_MAGIC))
			err("Not enough magic.");
		if (len > BUFSIZE)
			err("Request too big!");
#ifdef DODBG
		printf("%s from %Lu (%Lu) len %d, ", request.type ? "WRITE" :
				"READ", (unsigned long long)request.from,
				(unsigned long long)request.from / 512, len);
#endif
		memcpy(reply.handle, request.handle, sizeof(reply.handle));
		if ((request.from + len) > (OFFT_MAX)) {
		  DEBUG("[Number too large!]");
		  ERROR;
		  continue;
		}
		if ((((off_t)request.from + len) > exportsize) ||
		    ((flags & F_READONLY) && request.type)) {
			DEBUG("[RANGE!]");
			ERROR;
			continue;
		}
		if (request.type==1) {	/* WRITE */
			DEBUG("wr: net->buf, ");
			readit(net, buf, len);
			DEBUG("buf->exp, ");
			if ((autoreadonly == 1) || expwrite(request.from, buf, len)) {
				DEBUG("Write failed: %m" );
				ERROR;
				continue;
			}
			lastpoint += len;
			SEND;
			DEBUG("OK!\n");
			continue;
		}
		/* READ */

		DEBUG("exp->buf, ");
		if (expread(request.from, buf + sizeof(struct nbd_reply), len)) {
		 	lastpoint = -1;
			DEBUG("Read failed: %m");
			ERROR;
			continue;
		}
		lastpoint += len;

		DEBUG("buf->net, ");
		memcpy(buf, &reply, sizeof(struct nbd_reply));
		writeit(net, buf, len + sizeof(struct nbd_reply));
		DEBUG("OK!\n");
	}
}

char exportname2[1024];

void set_peername(int net,char *clientname)
{
	struct sockaddr_in addrin;
	int addrinlen = sizeof( addrin );
	char *peername ;

	if (getpeername( net, (struct sockaddr *) &addrin, &addrinlen ) < 0)
		err("getsockname failed: %m");
	peername = inet_ntoa(addrin.sin_addr);
	sprintf(exportname2, exportname, peername);

	msg4(LOG_INFO, "connect from %s, assigned file is %s", peername, exportname2);
	strncpy(clientname,peername,255) ;
}

off_t size_autodetect(int export)
{
	off_t es;
	u32 es32;
	struct stat stat_buf;
	int error;
	
	DEBUG("looking for export size with lseek SEEK_END\n");
	es = lseek(export, (off_t)0, SEEK_END);
	if (es > ((off_t)0)) {
		return es;
        } else {
                DEBUG2("lseek failed: %d", errno==EBADF?1:(errno==ESPIPE?2:(errno==EINVAL?3:4)));
        }
	
	DEBUG("looking for export size with fstat\n");
	stat_buf.st_size = 0;
	error = fstat(export, &stat_buf);
	if (!error && stat_buf.st_size > 0) {
		return (off_t)stat_buf.st_size;
        } else {
                err("fstat failed: %m");
        }
	
#ifdef BLKGETSIZE
	DEBUG("looking for export size with ioctl BLKGETSIZE\n");
	if (!ioctl(export, BLKGETSIZE, &es32) && es32) {
		es = (off_t)es32 * (off_t)512;
		return es;
	}
#endif
	err("Could not find size of exported block device: %m");
	return OFFT_MAX;
}

int main(int argc, char *argv[])
{
	int net;
	off_t i;

	if (sizeof( struct nbd_request )!=28) {
		fprintf(stderr,"Bad size of structure. Alignment problems?\n");
		exit(-1) ;
	}
	logging();
	cmdline(argc, argv);
	
	if (!port) return 1 ;
	connectme(port); /* serve infinitely */
	return 0 ;
}


void serveconnection(int net) 
{   
	off_t i ;
	
	for (i=0; i<exportsize; i+=hunksize) {
		char exportname3[1024];
		
		sprintf(exportname3, exportname2, i/hunksize);
		printf( "Opening %s\n", exportname3 );
		if ((export[i/hunksize] = open(exportname3, (flags & F_READONLY) ? O_RDONLY : O_RDWR)) == -1) {
			/* Read WRITE ACCESS was requested by media is only read only */
			autoreadonly = 1;
			flags |= F_READONLY;
			if ((export[i/hunksize] = open(exportname3, O_RDONLY)) == -1) 
				err("Could not open exported file: %m");
		}
	}
	
	if (exportsize == (off_t)OFFT_MAX) {
		exportsize = size_autodetect(export[0]);
	}
	if (exportsize > (off_t)OFFT_MAX) {
		err("Size of exported file is too big\n");
	}
	else
		msg3(LOG_INFO, "size of exported file/device is %Lu",
		     (unsigned long long)exportsize);
	
	if (flags & F_COPYONWRITE) {
		sprintf(difffilename,"%s-%s-%d.diff",exportname2,clientname,
			(int)getpid()) ;
		msg3(LOG_INFO,"About to create map and diff file %s",difffilename) ;
		difffile=open(difffilename,O_RDWR | O_CREAT | O_TRUNC,0600) ;
		if (difffile<0) err("Could not create diff file (%m)") ;
		if ((difmap=calloc(exportsize/DIFFPAGESIZE,sizeof(u32)))==NULL)
			err("Could not allocate memory") ;
		for (i=0;i<exportsize/DIFFPAGESIZE;i++) difmap[i]=(u32)-1 ;	  
	}
	
	setmysockopt(net);
	
	mainloop(net);
}